1. Large Synoptic Survey Telescope (LSST)
  2. Telescope and Site Subsystem
  3. Requirements
  4. Jacques Sebag and Victor Krabbendam
  5. LSE-60
  6. Latest Revision: August 10, 2016
  7. Change Record
    1. Table of Contents
  8. The LSST Telescope and Site Subsystem Requirements
    1. Introduction and Scope
    2. Acronyms and Definitions of Terms
    3. Verb Usage:
    4. Reference Documents
  9. The LSST Telescope and Site Subsystem Requirements
    1. 1 Telescope and Site Composition and Constraints
      1. 1.1 Composition
      2. 1.2 Summit Site Constraints
    2. 2 Telescope and Site Functional and Performance Requirements
      1. 2.1 Telescope Positioning and Rates Requirements
      2. 2.2 Telescope Optical Requirements
      3. 2.3 Telescope Control Requirements
      4. 2.4 Telescope and Site Monitoring and Diagnostics Requirements
      5. 2.5 Telescope Auxiliary Requirements
    3. 3 Telescope and Site Calibration Requirements
      1. 3.1 Telescope Calibration Screen
      2. 3.2 Telescope and Site Auxiliary Telescope
      3. 3.3 Water Vapor Monitoring System
      4. 3.4 Collimated Beam Projector
    4. 4 Telescope and Site Operational Requirements
      1. Telescope Safety Requirements
      2. 4.2 Telescope Security Requirements
      3. 4.3 Telescope Environment Compliance
      4. 4.4 Radio Active Background
      5. 4.5 Telescope and Site Lifetime
      6. 4.6 Telescope Summit-Base Network Loss
      7. 4.7 Base-Archive Network Loss
    5. 5 Telescope and Site Integration and Maintenance Requirements
      1. 5.1 Integration and Test
      2. 5.2 Access and Removal of Major Subsystems
      3. Telescope and Site Predictive Maintenance
      4. 5.4 Telescope and Site Preventive Maintenance
      5. 5.5 Telescope and Site Baseline Performance Reporting Requirement
      6. 5.6 Telescope and Site Scheduled Downtime
      7. 5.7 Telescope and Site Unscheduled Downtime
      8. 5.8 Telescope and Site Activity Support, Tracking and Reporting
    6. 6 Telescope and Site Standards
      1. 6.1 Components Standardization Goal
      2. 6.2 Telescope Time Reference
      3. 6.3 Electrical Standards
      4. 6.4 Building Codes

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval of the LSST Change Control Board.
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Large Synoptic Survey Telescope (LSST)

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Telescope and Site Subsystem

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Requirements

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Jacques Sebag and Victor Krabbendam

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LSE-60

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Latest Revision: August 10, 2016
This LSST document has been approved as a Content-Controlled Document. Its contents are subject to
configuration control and may not be changed, altered, or their provisions waived without prior
approval. If this document is changed or superseded, the new document will retain the Handle
designation shown above. The control is on the most recent digital document with this Handle in the
LSST digital archive and not printed versions.

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
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Change Record
Version
Date
Description
Owner name
1
7/27/20111
Initial release
J. Sebag & V.
Krabbendam
2
2/13/2013
LCR-74 approved changes
J. Sebag
3
10/4/2013
LCR-140 approved changes
J. Sebag
4
10/8/2013
LCR-146 approved changes (p16)
J. Sebag
5
2/5/2014
LCR-165 approved changes (p20)
J. Sebag
6
2/11/2014
LCR-168 approved changes (p3)
J. Sebag
7
2/1/2016
Incorporates LCRs 188 (adds a Components
Standardization Goal, updates to Scheduled and
Unscheduled Downtime Requirements, update to
Radioactive Background Requirement), 198
(Remove IR All Sky Camera Reference from T&S
Requirements), 199 (Add Collimated Beam Project
to Project Baseline), 200 (Auxilliary Telescope Blue
Wavelength Limit)
J. Sebag and Brian
Selvy
8
8/10/2016
Implementation of LCRs 359 and 581. LCR-359: TLS-
REQ-0047 documents to correct the flow down
from m5 limiting magnitude to system hardware
integrals and makes subsystem allocations for
throughput. LCR-581 TLS-REQ-0068, 0092, 0103,
0106, 0108, 0109, 0110, 0111, 0149 to provide
better hardware specifications definition to reflect
required knowledge to obtain precision
photometry.
Chuck Claver & Patrick
Ingraham (LCRs), B.
Selvy & Kathryn
Wesson (SysML),
Robert McKercher
(DocuShare)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
ii
Table of Contents
Change
Record
...............................................................................................................................................
i
Introduction
and
Scope
................................................................................................................................
iv
Acronyms and Definitions of Terms ............................................................................................................. iv
Verb
Usage:
..................................................................................................................................................
iv
Reference
Documents
...................................................................................................................................
v
1
Telescope and Site Composition and Constraints ........................................................................... 1
1.1
Composition
..............................................................................................................................
1
1.2
Summit Site Constraints ............................................................................................................ 2
2
Telescope and Site Functional and Performance Requirements ..................................................... 9
2.1
Telescope Positioning and Rates Requirements ....................................................................... 9
2.2
Telescope Optical Requirements ............................................................................................. 12
2.3
Telescope Control Requirements ............................................................................................ 19
2.4
Telescope and Site Monitoring and Diagnostics Requirements .............................................. 21
2.5
Telescope Auxiliary Requirements .......................................................................................... 24
3
Telescope and Site Calibration Requirements ............................................................................... 28
3.1
Telescope Calibration Screen .................................................................................................. 28
3.2
Telescope and Site Auxiliary Telescope ................................................................................... 31
3.3
Water Vapor Monitoring System ............................................................................................ 35
3.4
Collimated Beam Projector ..................................................................................................... 35
4
Telescope and Site Operational Requirements ............................................................................. 36
4.1
Telescope Safety Requirements .............................................................................................. 36
4.2
Telescope Security Requirements ........................................................................................... 37
4.3
Telescope Environment Compliance ....................................................................................... 37
4.4
Radio Active Background ......................................................................................................... 37
4.5
Telescope and Site Lifetime ..................................................................................................... 38
4.6
Telescope Summit-Base Network Loss .................................................................................... 38

LSST Telescope and Site Subsystem Requirements
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iii
4.7
Base-Archive Network Loss ..................................................................................................... 38
5
Telescope and Site Integration and Maintenance Requirements ................................................. 38
5.1
Integration and Test ................................................................................................................ 39
5.2
Access and Removal of Major Subsystems ............................................................................. 39
5.3
Telescope and Site Predictive Maintenance ........................................................................... 39
5.4
Telescope and Site Preventive Maintenance .......................................................................... 39
5.5
Telescope and Site Baseline Performance Reporting Requirement ....................................... 39
5.6
Telescope and Site Scheduled Downtime ............................................................................... 40
5.7
Telescope and Site Unscheduled Downtime ........................................................................... 40
5.8
Telescope and Site Activity Support, Tracking and Reporting ................................................ 40
6
Telescope and Site Standards ........................................................................................................ 41
6.1
Components Standardization Goal ......................................................................................... 41
6.2
Telescope Time Reference ...................................................................................................... 41
6.3
Electrical Standards ................................................................................................................. 42
6.4
Building Codes ......................................................................................................................... 42

LSST Telescope and Site Subsystem Requirements
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The LSST Telescope and Site Subsystem Requirements
Introduction and Scope
This document describes the functional and performance requirements, tolerances and allocations for
the Telescope and Site portion of the LSST as allocated from the LSST Observatory System Specifications
(LSE-30). The requirements in this document, combined with those of the other LSST subsystems satisfy
the full functionality and performance for the LSST system.
Acronyms and Definitions of Terms
In this document a
requirement
refers to a declaration of a specified function or quantitative
performance that the delivered system or subsystem must meet. It is a statement that identifies a
necessary attribute, capability, characteristic, or quality of a system in order for the delivered system or
subsystem to meet a derived or higher requirement, constraint, or function.
This document uses the term
specification(s)
to mean one or more performance parameter(s) being
established by a requirement that the delivered system or subsystem must meet.
An
attribute
specifies a quantitative performance
parameter
in the context of the SysML based SysArch
model used to generate this document.
A
constraint
is used to refer to an external limitation imposed on a delivered item under which it must
meet its requirements (e.g., the survey performance must be met under the constraint of the historical
weather pattern of the chosen site). A constraint in not a characteristic the system or subsystem itself
possesses.
Glossary of Abbreviations
(
Document-11921
)
Glossary of Definitions
(
Document-14412
)
Verb Usage:
Statements of need, requirements, and constraints are written using one of three verbs that have a
specific meaning with respect to verification. All statements in this specification that convey operational,
functional, or performance needs, requirements, constraints, or goals on the LSST system will contain
one of these three verbs.
Will
A statement of fact. Will statements document something that will occur through the course of
normal design practice, project process, etc. These statements do not get formally verified.
Should
A goal. Should statements document a stretch goal. A should statement is typically partnered
with a shall statement. Should statements do not get formally verified.
Shall -
A requirement that gets formally verified. Shall statements document critical requirements that
must be verified through inspection, demonstration, analysis, or test during the verification phase of the

LSST Telescope and Site Subsystem Requirements
LSE-60
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waived without prior approval.
v
project to ensure objectively that the as-built design meets the requirement.
Reference Documents
LSST Document Tree (LSE-39)
LSST System Requirements Document (LSR, LSE-29)
Observatory System Specifications (OSS, LSE-30)
Science Requirements Document (LPM-17)

LSST Telescope and Site Subsystem Requirements
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Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
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The LSST Telescope and Site Subsystem Requirements
1
Telescope and Site Composition and Constraints
The Telescope and Site system will consist of facilities constructed at several sites in Chile. In this section
we enumerate the facilities and their functions that shall be provided by the Telescope and Site group.
The LSST summit site selection process resulted in the choice of Cerro Pachón in Chile for the location of
the observatory itself. The weather, astro-climate (seeing and cloud cover), and local infrastructure of
Cerro Pachón provide system constraints under which the survey design requirements must be met and
the under which the telescope and site must be constructed.
1.1
Composition
ID: TLS-REQ-0002
Last Modified: 5/23/2013
Specification:
The Telescope and Site shall provide two facilities; Summit Facility and Base Facility,
These facilities shall be designed and constructed for delivery with the entire system at Engineering First
Light. These buildings shall adhere to the local building codes, environmental conditions and
requirements as defined in this document. These facilities are described below.
1.1.1 Summit Facility
ID: TLS-REQ-0003
Last Modified: 5/23/2013
Specification:
The Telescope and Site shall provide a "Summit Facility" on the El Peñón peak atop Cerro
Pachón, in Chile. The summit facility shall host the following functions and their associated maintenance
activities:
Collection of the science and engineering data for the survey;
Collection of additional data required for photometric calibration; and
Control of the Observatory for safe and efficient operation that includes local and remote aspects
of control and data collection.
Discussion:
The Summit Facility includes the main telescope and its enclosure, camera service areas,
mirror coating systems, the auxiliary telescope and its enclosure, utility equipment, and all other
infrastructure necessary to safely execute all the functions above and secure all LSST assets located on
the summit. Summit Facility also must provide the space and functional equipment to safely maintain all
the system assets operating on the site. The LSST Project conducted an international search for the site
to locate the telescope. In April 2006 the site on AURA property in Chile was chosen.
1.1.2 Base Facility
ID: TLS-REQ-0004
Last Modified: 10/2/2013
Specification:
The Telescope and Site shall provide a "Base Facility" to host the following functions and
their associated maintenance activities:
The Primary Remote Observing facility to assist in the control of the Observatory;
Survey planning and performance monitoring;
Data quality analysis for newly acquired science and calibration data;

LSST Telescope and Site Subsystem Requirements
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Collection of newly acquired data for transfer to the LSST data archive;
Backup of all data - raw, engineering, and derived products;
Host Country Data Access Center, as defined below; and
Control of Data Management operations (secondary location).
Discussion:
The Base Facility may be a single structure or a series of co-located buildings that provides
the personnel offices, computer equipment, and other specialized infrastructure necessary to safely
execute all the functions above and to secure all LSST assets located at the Base.
1.1.3 Hardware Deliverables
ID: TLS-REQ-0005
Last Modified: 7/27/2011
Specification:
The telescope and site system shall provide the hardware, equipment, and facilities to
collect light from the night sky and direct it through the optical system to the LSST camera. It shall provide
the reflective optics and the telescope structure to support, point, and align the optical system while
maintaining specified image quality, throughput and stray light performance. The deliverable hardware
also includes the calibration equipment, interior and exterior monitoring equipment, safety systems, and
personnel support equipment necessary to support the construction, commissioning, and operation of the
LSST on the summit and at the base. Telescope & Site shall deliver all the hardware necessary to meet
the requirements articulated in this document.
1.1.4 Software Deliverables
ID: TLS-REQ-0006
Last Modified: 7/27/2011
Specification:
The Telescope & Site shall deliver all the software, and data systems necessary to meet
the requirements articulated in this document. This includes the software to safely operate all the
hardware systems, to store all the required data, to operate the facility at the duty cycles defined, and to
maintain the facility as necessary to operate efficiently to the specified levels.
1.2
Summit Site Constraints
ID: TLS-REQ-0007
Last Modified: 5/23/2013
Specification:
All functions of the Summit Facility shall be compatible with the defined geographic,
weather, access, seismic and other site conditions provided below.
1.2.1 Summit Geographic Definitions
ID: TLS-REQ-0008
Last Modified: 7/27/2011
Specifications:
All hardware and software developed by the Telescope & Site for operation at the
Summit Facility shall be located and compatible with the following definitions for elevation, latitude, and
longitude:
Description
Value
Unit
Name

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3
Description
Value
Unit
Name
The operational summit elevation base of the telescope pier is
summitElevation.
2650
Meters
summitElevation
The operational site latitude at the center of the telescope pier
is
summit Latitude.
-30.2444 Degrees
summitLatitude
The operational summit longitude at the center of the
telescope pier is
summitLongitude.
-70.7494 Degrees
summitLongitude
1.2.2 Summit Environment
ID: TLS-REQ-0009
Last Modified: 7/27/2011
Specification:
All Telescope & Site systems operating at the Summit Facility shall meet all their
functional and performance specifications for the Normal site conditions, shall operate in defined
degraded modes under the Marginal conditions, and withstand without damage the non-operational
Survival conditions provided below. Methods to protect equipment and systems for the exterior
environmental conditions shall be provided as appropriate to their functional use.
Discussion:
Items on the telescope, for example, are subject to wind loading after attenuation from the
dome and systems within the facility benefit from its weather protection to the extent provided
1.2.2.1 Normal Operating Conditions
ID: TLS-REQ-0010
Last Modified: 7/27/2011
Specification:
The equipment and systems at the Summit Facilities shall meet all of their functional,
performance, and operational specifications under the normal exterior environmental conditions specified
in the table below.
Discussion:
These conditions correspond to the ~90% to 95% values of the weather distribution.
Description
Value
Unit
Name
The maximum barometric pressure for normal operations at
the summit shall be
normBaroMax
.
775
milibar
normBaroMax
When design considerations require barometric pressure
specifications all summit based systems shall use the mean
pressure
normBaroMean
.
750
milibar
normBaroMean
The maximum barometric pressure for normal operations at
the summit shall be
normBaroMin
725
milibar
normBaroMin
When design considerations require humidity specifications all
summit based systems shall use the normal maximal
operational relative humidity (non-condensing)
normHumidityMax
90
Percent
normHumidityMax
When design considerations require humidity specifications all
summit based systems shall use the normal mean operational
relative humidity (non-condensing)
normHumidityMean.
40
Percent
normHumidityMean
The rate of change for design purposes shall be
normTempGrad.
0.7
C/Hour
normTempGrad
The maximum temperature for normal operations at the
19.0
Celsius
normTempMax

LSST Telescope and Site Subsystem Requirements
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Description
Value
Unit
Name
summit shall be
normTempMax
.
The mean temperature for normal operations at the summit
shall be
normTempMean
.
11.5
Celsius
normTempMean
The minimum temperature for normal operations at the
summit shall be
normTempMin
.
-3.0
Celsius
normTempMin
When design considerations require operational wind
specifications all summit based systems shall use the extreme
operational wind speed,
normWindMax
.
12
m/sec
normWindMax
1.2.2.2 Marginal Operating Conditions
ID: TLS-REQ-0011
Last Modified: 7/27/2011
Specification:
The equipment and systems at the Summit Facility shall be operable (not necessarily
meeting all performance and functional requirements) over the range of marginal exterior environmental
conditions specified in the table below.
Discussion:
These conditions correspond to the ~99% values of the weather distribution.
Description
Value
Unit
Name
The temperature rate of change for degraded operations is
marginalTempGradient
2.0
C/Hour
marginaltempGradie
nt
The maximum temperature for degraded operations at the
summit shall be
marginalTempMax
.
30
Celsius
marginalTempMax
The minimum temperature for degraded operations at the
summit shall be
marginalTempMin
.
-5
Celsius
marginalTempMin
The maximum free air wind speed for degraded operations at
the summit shall be
marginalWind
.
20
m/sec
marginalWind
1.2.2.3 Survival Conditions
ID: TLS-REQ-0012
Last Modified: 7/27/2011
Specification:
The equipment and systems at the Summit Facility shall survive (without needing to meet
functional and operational requirements) over the range of survival environmental conditions specified in
the table below.
Description
Value
Unit
Name
The survival load on the Summit Facility for ice on vertical
surfaces shall be
iceLoading
(ref. Norma Chilena NCH 431)
22
kg/m^2
iceLoading
The survival load on the Summit Facility due to snow shall be
snowLoading
(ref. Norma Chilena NCH 431).
200
kg/m^2
snowLoading
All equipment at the Summit Facility must be capable of
surviving a maximum non-condensing humidity of
survivalHumidity
without damage.
100
Percent
survivalHumidity
All equipment located at the Summit Facility must be capable
of surviving an ambient air temperature of
survivalTemperature.
-10
Celsius
survivalTemperature

LSST Telescope and Site Subsystem Requirements
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Description
Value
Unit
Name
The equipment in the interior of the Summit Facility must be
capable of surviving a constant wind speed of
survivalWind.
20
m/sec
survivalWind
All hardware permanently located on the exterior of the
Summit Facility shall be capable of surviving a constant wind
speed of
survivalWindExterior.
54
m/sec
survivalWindExterior
The equipment in the interior of the Summit Facility must be
capable of surviving an exterior 10-second wind gust speed of
survivalWindGust.
25
m/sec
survivalWindGust
1.2.2.4 Transportation/Shipping Environment
ID: TLS-REQ-0013
Last Modified: 7/27/2011
Specification:
Components of the LSST Observatory that are transported to Chile shall survive the
shipping conditions described below.
Discussion:
The shipping environment includes the general conditions when equipment is shipped to the
summit. The equipment must remain undamaged after repeated shipments. Delivery is expected to be by
plane or boat to Chile and then by road to the summit.
There is a tunnel on the road between the town of La Serena and the summit site on CerroPachón called
the Puclaro Tunnel. Any equipment will have to pass through that tunnel. Its overall dimensions are given
below.
Description
Value
Unit
Name
During transportation, the effective altitude can change
between sea level and 3000m.
Sea level
to 2700m
Meters
Altitude
Containers have to be designed to limit water, dust, sand and
insect access during transportation
Contamination
During transportation to the summit, some roads have vehicle
weight restrictions.
Gross Vehicle Weight GVW = TBD
Weight/axle = TBD
TBD
kg
GVW
Pressure will change during transportation to the summit from
1000mbar at sea level down to 750mbar at the summit
1000 to
750
milibar
Pressure
The relative humidity range is from 10% to 100% with
condensation for transportation to the summit
10% to
100%
Percent
Relative Humidity
Range
Dirt roads will be used during transportation to the summit
with grades up to 16%
16
Percent
Roads
The ambient temperature range or transportation to the
summit is
-15C to
+40C
Celsius
Temperature Range
The container dimensions are limited by the Puclaro Dam
tunnel (see figure 7) located on the road between La Serena
and the summit.
9
Meters
Tunnel
Wind speed may reach up to 45m/s during transportation to
the summit
45
m/sec
Wind Speed
1.2.3 Seismic Parameters for Design

LSST Telescope and Site Subsystem Requirements
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ID: TLS-REQ-0143
Last Modified: 10/2/2013
1.2.3.1 Survival Seismic Parameters for Design
ID: TLS-REQ-0014
Last Modified: 10/2/2013
Specification:
All systems and/or components permanently located at the Summit or Base Facilities shall
be designed to withstand the loads resulting from an earthquake up to the levels a 300-year return period
seismic event and stay intact such that catastrophic failure is prevented and the hazards to personnel
safety are either eliminated or reduced. The levels of a 300-year return period earthquake have a 9.5%
probability of being exceeded in 30 years. The ground acceleration values corresponding to a 300-year
return period earthquake are defined in the standards established in TLS-REQ-0142. "Catastrophic
failure” shall be defined as fracture or rupture that allows a significant element to separate and fall, or
produces the possibility of personnel injury.
Discussion:
The return of the Summit or Base Facilities and their contents to "normal" operations
following a "Survival" event will be assessed based on actual damage incurred.
https://www.lsstcorp.org/docushare/dsweb/Get/Document-3717
1.2.3.2 Recoverable Seismic Parameters for Design
ID: TLS-REQ-0015
Last Modified: 10/2/2013
Specification:
All systems and/or components permanently located at the Summit or Base Facilities shall
be designed to operate without any permanent damage following a seismic event equivalent to a 20%
probability of return over the specified design lifetime of the system and/or component.
"Permanent damage” shall be defined as any damage to optical elements, any yielding of primary
structural components, damage where capital repair costs are in excess of $10M (TBR) or repair times
longer than 6 months after access and damage assessment.
1.2.3.3 Operable Seismic Parameters for Design
ID: TLS-REQ-0016
Last Modified: 10/2/2013
Specification:
All systems and/or components permanently located at the Summit or Base Facilities shall
be designed to operate without any significant damage following a seismic event with a return period
equivalent to specified design lifetime of the system and/or component.
"Significant damage" shall be defined as any damage that cannot be repaired within the statistical
allocation of the unscheduled down time defined in TLS-REQ-0135
1.2.4 Astro-Climate
ID: TLS-REQ-0017
Last Modified: 7/27/2011
Discussion:
The selection of the summit site on CerroPachón implies a set of constraints relating to the
astro-climate under which the survey performance requirements from the LSR must be met. These

LSST Telescope and Site Subsystem Requirements
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7
include atmospheric seeing, usable fraction of nights and cloud cover fraction, standard dark sky
brightness, and standard atmospheric transparency.
1.2.4.1 Atmospheric Seeing
ID: TLS-REQ-0018
Last Modified: 7/27/2011
Specification
: The LSST shall meet the survey performance requirements under the constraint of the
atmospheric seeing on Cerro Pachón (ElPeñón) as specified in the table below.
Discussion:
The values included here are direct DIMM measurements referenced to a wavelength of
500 nm. They do not represent the integrated delivered seeing over an 8.4m aperture or include affects
from the outer scale.
Description
Value
Unit
Name
The first quartile of the seeing distribution shall be taken as
seeing1stQuartile
0.58
ArcsecFW
HM
seeing1stQuartile
The third quartile of the seeing distribution shall be taken as
seeing3rdQuartile
0.84
ArcsecFW
HM
seeing3rdQuartile
The median of the seeing distribution shall be taken as
seeingMedian
0.69
ArcsecFW
HM
seeingMedian
1.2.4.2 Cloud Coverage
ID: TLS-REQ-0019
Last Modified: 7/27/2011
Specification:
The LSST Observatory shall meet the survey specifications under the assumed weather
conditions recorded at Cerro Tololo Observatory from 1975 to 2005 for cloud cover and fraction of
photometric and usable nights as defined in the table below.
Description
Value
Unit
Name
The historically monthly mean available time fraction that is
considered "photometric" (i.e. cloudless) shall be taken as
photTimeFrac
53
Percent
photTimeFrac
The historically monthly mean available time fraction that is
considered usable (i.e. with clouds but observable, also called
"spectroscopic") shall be taken as
usableTimeFrac
85
Percent
usableTimeFrac
1.2.4.3 Standard Atmospheric Transmission
ID: TLS-REQ-0020
Last Modified: 7/27/2011
Specification:
For the purpose of evaluating the system performance and the flow down of subsystem
requirements the standard atmospheric transmission shall be calculated from the USAF MODTRAN
model using the reference atmospheric parameters given in the table below.
Discussion:
While the reference airmass is X=1, Collection-973 contains data files for other airmass
values up to x=2.5. Document-3902 contains details on using MODTRAN to calculate the atmospheric
transmission functions.

LSST Telescope and Site Subsystem Requirements
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The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
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8
https://www.lsstcorp.org/docushare/dsweb/Get/Document-3902
https://www.lsstcorp.org/docushare/dsweb/View/Collection-973
Description
Value
Unit
Name
The standard typical Ozone level over northern Chile is
ozoneLevel
.
338
Dobson
ozoneLevel
1976 US standard STP sea level pressure is
seaLevelPressure
.
1013
milibar
seaLevelPressure
Reference airmass for calculating the standard transmission
function is
stdAirmass
.
1.0
Airmass
stdAirmass
The standard relative humidity percentage is
stpRelHumidity
.
15
Percent
stpRelHumidity
1.2.4.4 Standard Dark Sky Emission
ID: TLS-REQ-0021
Last Modified: 7/27/2011
Specification:
For the purpose of evaluating the system performance and the flow down of subsystem
requirements the assumed sky brightness in each filter shall be as defined in the
darkSkyBrightness
table below.
Discussion:
The details of the sky brightness model and assumptions used are given in Document-8857.
The data file containing the assumed sky spectrum is found in Document-8817.
The value for the y-band is for the adopted baseline y4 filter.
The intense sky emission at the extreme red end of the LSST system response means this value could
change significantly should a different y-band definition be adopted later.
https://www.lsstcorp.org/docushare/dsweb/Get/Document-8817
https://www.lsstcorp.org/docushare/dsweb/Get/Document-8857
Description
Value
Unit
Name
Integrated reference sky brightness in the g-band.
22.27
mag/SqArc
sec
g_SkyBrightness
Integrated reference sky brightness in the i-band.
20.47
mag/SqArc
sec
i_SkyBrightness
Integrated reference sky brightness in the r-band.
21.20
mag/SqArc
sec
r_SkyBrightness
Integrated reference sky brightness in the u-band.
22.92
mag/SqArc
sec
u_SkyBrightness
Integrated reference sky brightness in the y-band.
18.42
mag/SqArc
sec
y_SkyBrightness
Integrated reference sky brightness in the z-band.
19.59
mag/SqArc
sec
z_SkyBrightness
1.2.4.5 Usable Observing Time
ID: TLS-REQ-0022
Last Modified: 7/27/2011

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
9
Specification:
The LSST system shall be designed for the expected average number of usable
observing hours at the site,
nightDurationAvg
, the winter maximum,
nightDurationMax
, and the
summer minimum,
nightDurationMin
.
Discussion:
These values have been defined with reference to Nautical (12-degree) twilight and do not
include the effects of weather.
These specifications are required for the design of the peak and average capacities of data collection
systems.
They also provide constraints for the definition of the non-observing-time budget for observing
preparation, calibration, and maintenance activities together. During the period around winter solstice the
scheduled maintenance and calibration activities will be defined such that they can be accommodated in
short non-observing hours.
Description
Value
Unit
Name
The mean useable length of a night shall be taken as
nightDurationAvg.
10
Hour
nightDurationAvg
The maximum useable length of a winter night shall be taken
as
nightDurationMax
.
12
Hour
nightDurationMax
The minimum useable length of a summer night shall be taken
as
nightDurationMin
.
8
Hour
nightDurationMin
2
Telescope and Site Functional and Performance Requirements
This section provides the functional capability, performance requirements, and tolerances for the system.
The requirements in this section shall be met for all "Normal” environmental conditions defined for the
observatory.
2.1
Telescope Positioning and Rates Requirements
ID: TLS-REQ-0024
Last Modified: 5/23/2013
Specification
: The telescope shall be an altitude over azimuth configuration with a camera de-rotator to
point the optical system at the specified range of azimuth and zenith angles. These requirements define
the necessary articulation to support general positioning of the telescope and maintenance activities as
well as the operational observing. The requirements below define the pointing range, rates, accuracies
and the slew and settle time.
2.1.1 Telescope Pointing and Tracking Requirements
ID: TLS-REQ-0025
Last Modified: 7/27/2011
Specification
:The telescope shall achieve an on sky pointing request for observing in the ranges
El_Point_Range
and
Az_Point_Range
within the tolerance of
Abs_Pointing
as measured on sky. The
telescope shall follow sidereal objects, and maintain a fixed sky orientation on the focal plane (camera de-
rotation) throughout this range to within
Tel_Track_Error
. The telescope shall meet off set pointing
requirements up to
Tel_Point_Offset
, within
SlewSettle_Time
seconds with an on-sky angular position
error of less than or equal to
Offset_Point_Error
. The pointing is considered completed when

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
10
Tel_Track_Error
is being achieved. These requirements shall be met after mount model corrections that
are developed without impact on observing time.
2.1.1.1 Pointing Requirements
ID: TLS-REQ-0026
Last Modified: 8/10/2016
Specification:
The Telescope shall achieve the azimuth and elevation pointing ranges with the accuracy
and error specified in the table below.
Description
Value
Unit
Name
The telescope shall achieve the Abs_Pointing accuracy
requirement for all elevation angles (measured on sky).
2
ArcsecRM
S
Abs_Pointing
The telescope shall be able to point to any azimuth angle in
the Az_Point_Range range.
± 270
Degrees
Az_Point_Range
The telescope shall be able to point to any elevation angle in
the El_Point_Range range.
90
Degrees
El_Point_Range
The LSST shall be capable of relative offset pointing within a
single 3.5deg field-of-view with a precision of no more than
offset_Pointing_Error (measured on sky).
0.2
ArcsecRM
S
Offset_Point_Error
2.1.1.2 Telescope Tracking Requirements
ID: TLS-REQ-0027
Last Modified: 8/10/2016
Specification:
The telescope shall be capable of tracking in azimuth and elevation angular ranges with
the accuracy specified in the table below.
Discussion
: The major structural elements of the dome should enable a lower low elevation angle limit
(15 degrees) with a different wind/light screen potentially implemented later
Description
Value
Unit
Name
The telescope shall be able to track in azimuth over the
angular range of Az_Track_Range.
± 270
Degrees
Az_Track_Range
Minimum high elevation limit where sidereal tracking is to be
maintained El_Track_Range_High
86.5
Degrees
El_Track_Range_Hi
gh
Minimum low elevation limit where sidereal tracking is to be
maintained El_Track_Range_Low
20
Degrees
El_Track_Range_Lo
w
The telescope shall have a tracking accuracy of
Tel_Track_Error in open loop over a 10min interval within the
tracking range.
1
ArcsecRM
S
Tel_Track_Error
2.1.2 Telescope Slewing Requirements
ID: TLS-REQ-0028
Last Modified: 5/23/2013
Specification
: The telescope shall be able to reposition the pointing vector using the axis velocities and
accelerations and settling times defined here.

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
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11
2.1.2.1 Telescope Slewing Rate Requirements
ID: TLS-REQ-0029
Last Modified: 7/27/2011
Specification
:The telescope shall be able to position the optical axis pointing vector in azimuth and
elevation at the following rates and accelerations over the full positioning range specified. Azimuth rates
and accelerations shall be
Vel_Az_Max
and
Acc_Az_Max
. Elevation rates and accelerations shall be
Vel_El_Max
and
Acc_El_Max
. The elevation positioning tolerance within the Tracking range is further
defined below.
Discussion:
The telescope slewing requirement analysis is located in documents document-2454 and
document-8384.
https://www.lsstcorp.org/docushare/dsweb/Get/Document-2454
https://www.lsstcorp.org/docushare/dsweb/Get/Document-8384
Description
Value
Unit
Name
The telescope shall be able to reach the maximum
acceleration/deceleration rate Acc_Az_Max for the azimuth
axis
10.5
Degrees/s
ec^2
Acc_Az_Max
The telescope shall be able to reach the maximum velocity
Vel_Az_Max for the azimuth axis.
10.5
Degrees/s
ec
Vel_Az_Max
Description
Value
Unit
Name
The telescope shall be able to reach the maximum
acceleration/deceleration rate Acc_El_Max for the elevation
axis.
5.25
Degrees/s
ec^2
Acc_El_Max
The telescope shall be able to reach the maximum velocity
Vel_El_Max for the elevation axis.
5.25
Degrees/s
ec
Vel_El_Max
2.1.2.2 Slew and Settle Time Requirement
ID: TLS-REQ-0030
Last Modified: 7/27/2011
Specification:
The telescope shall achieve a settling time from a repositioning slew motion of
SlewSettle_Time
. This time is measured from the end of one exposure through the repositioning of the
telescope pointing vector to an adjacent field that is 3.5 degrees (on sky), to the start of the next
exposure. This is for moves between fields with a zenith angle equal or higher than 30 degrees and
includes the time to achieve tracking and optical requirements at the new position.
Description
Value
Unit
Name
The telescope shall achieve a slew and settle time duration
SlewSettle_Time between visits.
5
Seconds
SlewSettle_Time
2.1.3 Telescope Rotator Requirements
ID: TLS-REQ-0031
Last Modified: 7/27/2011
Specification
:The telescope shall be able to angularly position the camera, about the pointing axis of the
telescope over the angular range of
Field_Rotation_Range
with an absolute angle accuracy of

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
12
Rot_Abs_Error
. This range should be reachable without overriding safety limits. Field rotation rates and
accelerations shall be within
Vel_Rot_Max
and
Acc_Rot_Max
. The azimuth positioning tolerance within
the Tracking range is further defined below.
The rotator shall align the filter changing mechanism with gravity within the time allocated
Time_Change_Rot
.
Discussion:
The rotation range is wide enough to cover most of the sky positions for deep drilling
tracking for one hour without reaching the limits. The OCS will select the time of observation to ensure
validity with the range to avoid having to de-rotate.
Description
Value
Unit
Name
The rotator shall be able to achieve this maximum
acceleration during slews of the telescope.
1
Degrees/s
ec^2
Acc_Rot_Max
The rotator shall have at minimum this range of rotation.
±90
Degrees
Field_Rotation_Ran
ge
The rotator shall have at maximum this absolute angle error.
0.01
Degrees
Rot_Abs_Error
Time allocated to the telescope for aligning the filter changing
mechanism with gravity.
30
Seconds
Time_Change_Rot
The rotator shall be able to achieve this maximum velocity
during slews of the telescope.
3.5
Degrees/s
ec
Vel_Rot_Max
2.1.4 Telescope Guiding Requirements
ID: TLS-REQ-0032
Last Modified: 7/27/2011
Specification:
Within the Slew and Settle time requirement, the telescope shall achieve the pointing and
tracking requirements without feedback from the camera guider system within a period of
Open_Loop_Time
.
Discussion:
The tracking requirements may benefit from guider signals developed from 8 sensors in the
Camera Focal Plane.The system is constrained by the sensor locations being behind the Camera shutter.
Complete definition shall be captured in the telescope and camera interface definition.
Description
Value
Unit
Name
The time allowed for the open loop (e.g. look-up table driven)
active optics target values to be met after pointing the
telescope shall be no more than Open_Loop_Time per 3.5
degrees offset
.
1.0
Seconds
Open_Loop_Time
2.2
Telescope Optical Requirements
ID: TLS-REQ-0033
Last Modified: 5/23/2013
[Composite Requirement]
2.2.1 Optical Prescription Requirements
ID: TLS-REQ-0034
Last Modified: 7/27/2011

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
13
Specification:
The Telescope and Site shall provide the three reflective mirrors in the optical design
defined here. These mirrors shall include the support systems necessary to safely mount them in the
telescope, to operate the telescope throughout its pointing and tracking requirements, to meet the stated
quality requirements during nightly operations, and to remain operational and safe through the full range
of telescope pointings.
Discussion:
The reference optical prescription is given in document LSE-11. All parameters follow the
sign conventions used by Zemax.
https://www.lsstcorp.org/docushare/dsweb/Get/LSE-11
2.2.1.1 M1 Prescription
ID: TLS-REQ-0035
Last Modified: 7/27/2011
Specification:
The surface prescription of the primary mirror (M1) shall be defined by the table of
parameters below:
Description
Value
Unit
Name
The primary mirror surface 6th order aspheric coefficient shall
be
m1_6thAsphere
1.381e-24
mm^-5
m1_6thAsphere
The primary mirror surface conic constant shall be
m1ConicConstant.
-1.2150
m1ConicConstant
The primary mirror inner clear aperture radius shall be no
more than
m1InnerCa.
2558.0
mm
m1InnerCa
The primary mirror outer clear aperture radius shall be at least
m1OuterCa.
4180.0
mm
m1OuterCa
The primary mirror radius of curvature shall be
-19835.0
mm
m1Radius
2.2.1.2 M2 Prescription
ID: TLS-REQ-0036
Last Modified: 7/27/2011
Specification:
The surface prescription of the secondary mirror (M2) shall be defined by the table of
parameters below:
Description
Value
Unit
Name
The secondary mirror surface 6th order aspheric coefficient
shall be
m2_6thAsphere.
-1.274e-
20
mm^-5
m2_6thAsphere
The secondary mirror surface 8th order aspheric coefficient
shall be
m2_8thAsphere.
-9.680e-
28
mm^-7
m2_8thAsphere
The secondary mirror surface conic constant shall be
m2Conic.
-0.2220
m2Conic
The secondary mirror (m2) inner clear aperture radius shall be
no more than
m2InnerCa
900.0
mm
m2InnerCa
The secondary mirror (m2) outer clear aperture radius shall be
at least
m2OuterCa.
1710.0
mm
m2OuterCa
The secondary mirror surface radius of curvature shall be
m2Radius.
-6788.0
mm
m2Radius

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
14
2.2.1.3 M3 Prescription
ID: TLS-REQ-0037
Last Modified: 7/27/2011
Specification:
The surface prescription of the tertiary mirror (M3) shall be defined by the table of
parameters below:
Description
Value
Unit
Name
The tertiary mirror surface 6th order aspheric coefficient shall
be
m3_6thAsphere.
-4.500e-
22
mm^-5
m3_6thAsphere
The tertiary mirror surface 8th order aspheric coefficient shall
be
m3_8thAsphere.
-8.150e-
30
mm^-7
m3_8thAsphere
The tertiary mirror surface conic constant shall be
m3Conic.
0.1550
m3Connic
The tertiary mirror inner clear aperture radius shall be at least
m3InnerCa.
550.0
mm
m3InnerCa
The tertiary mirror outer clear aperture radius shall be at least
m3OuterCa.
2508.0
mm
m3OuterCa
The tertiary mirror surface radius of curvature shall be
m3Radius.
-8344.5
mm
m3Radius
2.2.1.4 Mirror Spacings
ID: TLS-REQ-0038
Last Modified: 7/27/2011
Specification:
The prescription for the separation of the successive mirror surfaces and the next optical
element in the system shall be defined by the parameters in table below:
Description
Value
Unit
Name
The distance from the vertex of M1 to the vertex of M2 shall
be m1m2Spacing
-
6156.200
6
mm
m1m2Spacing
The distance from the vertex of M2 to the vertex of M3 shal be
m2m3Spacing
6390.000
6
mm
m2m3Spacing
The distance from the vertex of M3 to the vertex of the first
surface of L1 shall be m2l1Spacing for the R band
-3631.273
mm
m3l1Spacing
2.2.1.5 Telescope Field of View
ID: TLS-REQ-0039
Last Modified: 7/27/2011
Specification:
The telescope shall provide the optical system to achieve a minimum unvignetted field of
view (FOV) of
Tel_Field_of_View
.
Description
Value
Unit
Name
The telescope shall provide this minimum unvignetted Field of
View.
3.5
Degrees
Tel_Field_of_View
2.2.2 Telescope Image Quality

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
15
ID: TLS-REQ-0040
Last Modified: 7/27/2011
Specification
: The telescope shall provide and maintain the required delivered image quality for all
sidereal objects observed within the defined tracking range. This value is referenced at Zenith pointing
and can degrade as defined by a function of Zenith angle. The telescope delivered image quality shall be
met for all normal operating environmental conditions and include the error contributions of
manufacturing, mirror supports, mirror and camera system spacing, active controls, dome environment,
and telescope pointing and tracking. The control of image quality can include input from deployed sensors
for feedback to active controls, the 8 guide sensors in the Camera, and 4 wavefront sensors in the
camera with additional feedback requirements as defined in the Active Optics Requirements
2.2.2.1 Telescope Delivered Image Quality Requirement
ID: TLS-REQ-0041
Last Modified: 10/3/2013
Specification
: The total telescope image quality degradation shall not exceed the telescope system
image quality allocation value
Tel_DIQ
defined at zenith.
Discussion
: The OSS allocates 0.25"FWHM to the telescope median delivered PSF.
Description
Value
Unit
Name
The telescope shall deliver this image quality contribution.
0.25
ArcsecFW
HM
Tel_DIQ
2.2.2.2 Off Zenith Image Degradation
ID: TLS-REQ-0042
Last Modified: 7/27/2011
Specification:
The system image quality is allowed to degrade as a function of Zenith Distance (angle)
as sec(ZD)
0.6
.
Discussion:
The design specification for the image quality requires that, for the median atmospheric
seeing, the system contribution to the delivered image quality never exceeds 15%. This requirement
should be fulfilled irrespective of the airmass, which limits the seeing degradation due to hardware away
from the zenith (e.g. due to gravity load). Assuming that the atmospheric seeing increases with airmass,
X, as X^0.6 , the design specification for the allowed error budget due to system is 0.52 arcsec at airmass
of 2 and for the median seeing conditions (0.42 arcsec for X=1.4).
2.2.3 Telescope Active Optics Requirements
ID: TLS-REQ-0043
Last Modified: 7/27/2011
Specification:
The telescope shall provide all the necessary equipment to support the optics and Camera
within the full pointing range and to maintain the alignment and mirror figures to achieve the image quality
requirements throughout the tracking range. This system shall function with optical feedback but the open
loop active optics corrections must occur within the
Open_Loop_Time
after a telescope slew is
completed. This system shall also function with optical feedback from wavefront sensors in the Camera
focal plane that can provide data within the full focal plane exposure limitations.

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
16
The Telescope shall maintain the image quality for any repointing of less than or equal to the
Closed_Loop_Angle
. For slews greater than the
Closed_Loop_Angle
, the telescope shall have the
time defined by
Closed_Loop_Delay
to correct the optical system to within image quality specifications.
2.2.3.1 Closed Loop Active Optics
ID: TLS-REQ-0044
Last Modified: 8/8/2016
Specification
: The Telescope and Site's active optics system shall only require corrections to achieve
image quality specifications for slews more than
Closed_Loop_Angle
, and the time allowed to establish
and apply its target values after a move more than
Closed_Loop_Angle
shall be no more than
Closed_Loop_Dela
y.
Description
Value
Unit
Name
The active optics corrections from wavefront data shall only
be needed to achieve image quality specifications for slews of
more than Closed_Loop_Angle
.
9
Degrees
Closed_Loop_Angle
The time allowed for the closed loop active optics to establish
and to apply its target values after a move to a field pointing
more than Closed_Loop_Angle shall be no more than
Closed_Loop_Delay
.
.
20
Seconds
Closed_Loop_Delay
2.2.3.2 Telescope Wavefront Sensing Requirements
ID: TLS-REQ-0045
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall process camera supplied wavefront images from 4 sets of
wavefront sensors to independently evaluate the quality of the image quality. The wavefront values shall
be determined for every exposure taken and shall be expressed in annular Zernike terms for each sensor
set. The results shall be made available to the Facility Database. The details of the wavefront sensors
and the interface with the Camera shall be enumerated in the Telescope to Camera ICD.
The Telescope and Site shall be able to reconstruct the equivalent of up to the first 22 Zernike modes of
wavefront error at the telescope pupil.
2.2.4 Telescope Throughput
ID: TLS-REQ-0046
Last Modified: 7/27/2011
Specification
: The telescope shall maintain the required throughput for the three mirror system for all
telescope observations taken within the tracking range under normal operating conditions.
2.2.4.1 Total Telescope Optical Hardware Throughput
ID: TLS-REQ-0047
Last Modified: 8/4/2016

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
17
Specification:
The total telescope optical hardware throughput integrals between the upperRed and
upperBlue wavelength limits in each filter band (OSS-REQ-240 through OSS-REQ-245) shall exceed the
allocations given in the table below for
S_tel(u)
through
S_tel(y)
.
Discussion:
The wavelength limits used for defining the integration boundaries are defined by the upper
envelope specifications for the filters as defined in OSS-REQ-240 through OSS-REQ-245. Because these
values do not expressly flow to the telescope requirements, they (upperBlue-upperRed) are proivided
here for reference: u-band: 305.5 - 408.5; g-band: 386.6 - 562.0; r-band: 537.0 - 706.0; i-band: 676.0 -
833.0; z-band: 803.0 - 938.0; y-band: 908.5 - 1100.0.
For the purpose of flowdown to individual surfaces and/or compoinents the Telescope & Site subsystem
may use the implied mean fractional thorughput for each filter band. These are ferived from the hardware
integrals given in LTS-REQ-0047, the implied mean throughput for each filter band as measured between
the referenced upperBlue and upperRed limits shall be at least
thruTel(u)
through
thruTel(y)
.
Technical memo LSE-240 outlines a method of approximation that allows the combination of component
throughput integrals using a simple algebraic expression. Using this method the total system throughput
integral, S_sys, through given filter, f, can be estimated by S_sys(f) ~ [S_tel(f) * S_cam(f)]/W(f), where
W(f) is the "window" integral of unity response, S_tel is the telescope integral and S_cam is the camera
integral between the red and blue wavelength limits of the filter. The limits for each filter are taken as the
upperBlue and upperRed wavelengths defined in OSS-REQ-0240 - OSS-REQ-0245, giving window
integral values of 0.291, 0.374, 0.274, 0.209, 0.155 and 0.191 for the u, g, r, i, z and y-band filters
respectively.
The implied mean fractional throughput for each filter, f, is derived by thruTel(f) = S_Tel(f)/W(f). Note: The
mean fractional throughput for the Telescope is calculated for each filter between the upper envelope
wavelength limits, upperBlue and upperRed, defined in OSS-REQ-240 - OSS-REQ-245. These limits
include the effects of the tapered filter band edges where the nominal response drops to near zero at
upperBlue and upperRed envelope wavelength limits, hence the apparently low values.
Because the telescope system is simpler, having three optical surface impacting system throughput, it's
expected performance has been used to guide the allocation ratio between the camera and telescope
subsystems. The telescope throughput integrals are based on coating M2 with protected silver, coating
M1M 3 with protected aluminum, 3% surface losses and a 3% overall margin.
Description
Value
Unit
Name
The allocated minimum integrated g-band throughput for the
Telescope is:
0.254
S_tel(g)
The allocated minimum integrated i-band throughput for the
Telescope is:
0.137
S_tel(i)
The allocated minimum integrated r-band throughput for the
Telescope is:
0.189
S_tel(r)
The allocated minimum integrated u-band throughput for the
Telescope is:
0.129
S_tel(u)
The allocated minimum integrated y-band throughput for the
Telescope is:
0.138
S_tel(y)
The allocated minimum integrated z-band throughput for the
Telescope is:
0.102
S_tel(z)
Description
Value
Unit
Name

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 8/10/2016
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
18
Description
Value
Unit
Name
The implied mean fractional Telescope throughput in the g-
band is:
68.0
Percent
thruTel(g)
The implied mean fractional Telescope throughput in the i-
band is:
65.5
Percent
thruTel(i)
The implied mean fractional Telescope throughput in the r-
band is:
69.1
Percent
thruTel(r)
The implied mean fractional Telescope throughput in the u-
band is:
44.2
Percent
thruTel(u)
The implied mean fractional Telescope throughput in the y-
band is:
72.2
Percent
thruTel(y)
The implied mean fractional Telescope throughput in the z-
band is:
64.8
Percent
thruTel(z)
Mirror Reflectivity Maintenance
ID: TLS-REQ-0048
Last Modified: 7/27/2011
Specification:
The Telescope and site shall provide the equipment and procedures necessary to
measure the reflectivity of the mirrors during operation on a routine weekly basis. The systems shall be
provided to allow on telescope CO2 and wet washing of the optical surfaces in a single operations shift.
The reflectivity shall be maintained with the
Reflectivity_Loss
value as averaged over each filter band
with the in-situ cleaning systems for a minimum of two years
Mirror Coating on the summit
ID: TLS-REQ-0049
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall provide the necessary facilities, equipment, and procedures
to restore the reflective coatings to the
telAveThroughput
levels. This shall include the equipment to
safely strip the coatings, prepare the surfaces and coat the surfaces using appropriate solvent recovery
and personnel safety systems
Discussion:
The process to recoat either the primary or the secondary shall be designed to be
accomplished with one 14 day scheduled maintenance period.
Description
Value
Unit
Name
This requirement defines the allowable percentage of
reflectivity loss before cleaning of the mirrors (TBR).
2
Percent
Reflectivity_Loss
2.2.4.2 Clear Aperture Obscuration
ID: TLS-REQ-0050
Last Modified: 10/2/2013
Specification:
The telescope shall limit the on-axis obscuration of the telescope clear aperture to less
than
Clear_Ap_Obscuration
and
Clear_Ap_Obscuration_OffAxis
off-axis
.
Description
Value
Unit
Name

LSST Telescope and Site Subsystem Requirements
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19
Description
Value
Unit
Name
Maximum Telescope Clear Aperture Obscuration on-axis
2
Percent
Clear_Ap_Obscurati
on
Maximum Telescope Clear Aperture Obscuration off-axis
3.5
Percent
Clear_Ap_Obscurati
on_OffAxis
2.2.5 Telescope Stray light Requirements
ID: TLS-REQ-0051
Last Modified: 7/27/2011
Specification:
The telescope and site shall be designed to reduce the image degrading stray light to the
minimum practical level.
2.2.5.1 Stray Light Point Source Transmittance
ID: TLS-REQ-0052
Last Modified: 7/27/2011
Specification:
The out-of-field Point Source Transmittance (PST) of stray light versus elevation angle
shall be at least four orders of magnitude (TBR) below the field of view PST amplitude.
Discussion:
This requirement quantifies the out-of-field stray light. In addition, the PST Is expected to be
smoothly declining with out-of-field angle to indicate a well baffled system.
2.2.5.2 Light Baffles
ID: TLS-REQ-0053
Last Modified: 7/27/2011
Specification:
The telescope and dome design shall incorporate light baffles and vanes where
appropriate to reduce stray and scattered light. The baffles shall be located as to not vignette a field of
view equal to
Baffle_FOV
with a tolerance of
Baffle_FOV_tol.
Discussion:
The
Baffle_FOV
is larger than the telescope FOV because of the camera focal plane layout
Description
Value
Unit
Name
The baffles shall be located as to not vignette a field of view
equal to Baffle_FOV
3.9
Degrees
Baffle_FOV
Tolerance for the positioning of the baffles relative to the
Baffle_FOV.
0.1
Degrees
Baffle_FOV_Tol
2.2.5.3 Stray light during Daytime
ID: TLS-REQ-0054
Last Modified: 7/27/2011
Specification:
Stray light shall be minimized during daytime to allow start of the calibration process in the
afternoon.
2.3
Telescope Control Requirements

LSST Telescope and Site Subsystem Requirements
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20
ID: TLS-REQ-0055
Last Modified: 4/14/2014
Specification:
The Telescope and Site shall include a Telescope Control System (TCS), ensemble of
computer hardware and software responsible for the safe control of the telescope assembly and
associated hardware. It shall be the central coordination facility that controls the delivery of high quality
images to the camera, providing continuous set-points for the relevant hardware devices and provides the
operator with the necessary feedback to efficiently and safely monitor the system operation.
Discussion:
The TCS achieves its tasks by coordinating and controlling the activities of the telescope
subsystems, such as the Mount Control System, the Active Optics Control System and the Enclosure
Control System.
The TCS control model is based on a supervisory control strategy. Under this model, a supervisor agent
computes the set-point to be applied to a controllable device. The time critical loops are closed locally at
the device level, and the device makes status information available for monitoring purposes.
2.3.1 Access Control
ID: TLS-REQ-0056
Last Modified: 4/14/2014
Specification
:The TCS shall connect to the observatory access system, handled by the Observatory
Control System, to support local and remote user interaction with the summit based telescope and site
systems. The TCS shall be controlled either directly by a telescope operator, or commanded by the
Observatory Control System using the observatory access system. The TCS shall report the telemetry of
the Telescope and Site subsystem, enabling the monitoring and the maintenance support.
Discussion
: The TCS is the entry point to the Telescope and Site subsystem. The OCS can command
the T&S subsystem through this TCS interface, exercising the hierarchical control architecture.
2.3.2 Acquire Target
ID: TLS-REQ-0057
Last Modified: 4/14/2014
Specification
: The TCS is responsible for the precise pointing and tracking calculations necessary to
observe a certain field.The TCS shall support the precise pointing requirements through the use of
pointing models, as necessary, and shall include the tools to develop the pointing models without impact
on observing time.
Discussion
:The TCS shall accept a target position in Raw, Alt-Az or RA-DEC coordinate system, and
point the telescope to the target position.
The high efficiency specified for the LSST system implies that most of the observations will need to be
acquired in blind pointing mode. In that mode, the TCS relies on the accuracy of its pointing model to
point the telescope at the correct position without any optical feedback from the sky.
2.3.3 Track Target
ID: TLS-REQ-0058
Last Modified: 4/14/2014

LSST Telescope and Site Subsystem Requirements
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waived without prior approval.
21
Specification
: The TCS shall control the tracking/guiding function of the Telescope within the
performance specified for the Tracking requirements.The TCS shall provide any necessary supervisory
and algorithmic support for the use of guideimages received from the LSST Camera.
2.3.4 Wavefront Control
ID: TLS-REQ-0059
Last Modified: 4/14/2014
Specification
:The TCS shall be responsible for controlling the flow of wavefront information between the
LSST camera and the telescope and site subsystems. To the extent required to maintain the image
quality specifications the TCS shall manage the wavefront image processing and mirror control pipelines.
2.3.5 Support for Remote Observing
ID: TLS-REQ-0060
Last Modified: 4/14/2014
Specification:
The TCS shall be designed to support remote observing. This mode of operation will have
the necessary minimum operator staff on the summit and science and engineering supervisory staff
located remotely off the summit. A minimum of three primary off site remote operations centers shall be
supported: one at the base, one at the LSST headquarters, and one at the archive center
2.3.6 Telescope Control System Operational States
ID: TLS-REQ-0061
Last Modified: 4/14/2014
Specification:
The telescope control system shall be designed and constructed to support the following
operational states:
Fully automated observing - used for most of the survey observing;
Calibration - used for special observing modes needed to calibration either the science data or
other technical aspects of the observatory;
Manual observing - used for specific non-scheduler drive observing to support system verification
and testing or specialized science programs;
Engineering and Maintenance
Discussion:
The systems shall continue to operate in a variety of degraded states to full and / or
specified reduced performance levels.
2.4
Telescope and Site Monitoring and Diagnostics Requirements
ID: TLS-REQ-0062
Last Modified: 5/23/2013
Specification:
In addition to any equipment and sensing systems necessary to meet the stated functional
and performance requirements for all the operational modes of the system, the Telescope and Site shall
deliver the following monitoring and diagnostic capabilities.
2.4.1 Telescope and Site Image Visualization

LSST Telescope and Site Subsystem Requirements
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22
ID: TLS-REQ-0063
Last Modified: 2/5/2014
Specification:
An image display shall be available at the Summit Facility with the latency performances
indicated below.
Description
Value
Unit
Name
Users at the Summit shall be able to view the image data from
the most recent exposure within
displayLatency
after the
shutter has closed.
10
Seconds
Display-Latency
Users at the Summit shall be able to view the image data on a
display with the
Display-Size
requirements.
TBD
int
Display-Size
Users shall be able to cycle through predefined views of the
full image (e.g. bright or faint star optimized binned, bias map,
noise map, etc.) within
View-Cycle-Time
between each.
2
Seconds
View-Cycle-Time
2.4.2 Telescope and Site Engineering Data Visualization
ID: TLS-REQ-0064
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall provide tools for the access and visualization of all data
published to the Engineering and Facility Database including monitoring and diagnostic data. The tools
and visualization of the data shall include:
Statistical, including histograms, correlation plots, and basic statistical data reductions on
selected data
Temporal, showing time histories of selected parameters and of statistical properties of acquired
data
Spatial, displaying data overlaid on associated images
2.4.3 Telescope and Site Telemetry Requirements
ID: TLS-REQ-0065
Last Modified: 8/8/2016
Specification:
The Telescope and Site shall publish telemetry using the Observatory specified protocol
(Document-2233) containing time stamped structures of all command-response pairs and all technical
data streams including hardware health, and status information.
The telemetry shall include all required information (metadata) needed for the scientific analysis of the
survey data as well as, at a minimum, the following:
Changes in the internal state of the system,
Health and status of operating systems, and
Temperature, rate, pressure, loads, status, and conditions at all sensed system components.
Discussion:
Hardware health and status information includes data regarding the correct functionality of
all major internal components and sub-subsystems are to be stored in the facility database to support day
to day service, maintenance and operation of the LSST as well as future investigation into the state and
status of the facility during any part of operation. Future correlation of the observed data with observing
conditions is enabled with the storage and persistence of this data.

LSST Telescope and Site Subsystem Requirements
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23
2.4.4 Telescope and Site Environmental Monitoring Requirements
ID: TLS-REQ-0066
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall monitor the local observing environment so that delivered
data performances can be assessed against the state of the environment at the time the data were
obtained. The monitoring shall include all natural elements that impact the image data quality and at a
minimum shall include the following as detailed below.
2.4.4.1 Atmospheric Seeing
ID: TLS-REQ-0067
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall provide the necessary instruments to measure the
atmospheric seeing independently from the main observing system.
Discussion:
A Differential Image Motion Monitor (DIMM) was selected for this purpose. It will be located
outside on its own tower (~5m above ground). It will use a 25cm Meade telescope with an SBIG ST7
camera to form a compact instrument.
2.4.4.2 Cloud Mapping and Monitoring
ID: TLS-REQ-0069
Last Modified: 2/3/2015
Specification:
The Telescope and Site shall provided the necessary hardware-software system to
provide a quantified 2-D map of the atmospheric extinction over the visible sky centered on the Summit
site with a cadence equal to or faster than the nominal visit duration and with a spatial resolution of at
least 0.5 degrees.
Discussion:
A spatial resolution of 0.5 degrees provides 7 resolution elements over the LSST's 3.5
degree FOV and should be sufficient for observing optimization and cloud avoidance. A visible all sky
camera providing bright star photometric measurements in the LSST filter bands scaled to IR all sky
images would satisfy this requirement.
2.4.4.3 Seismic Monitoring
ID: TLS-REQ-0070
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall provide a measurement system and real time monitoring of
local summit seismic activity and a near real-time feedback on nearby seismic events to the local
operators at the summit and base facilities. The monitoring system shall allow operator or automatic
toggle between local measurement data and a feed from regional networks. The minimum sensitivity of
measurements shall be TBD.
2.4.4.4 Weather Monitoring
ID: TLS-REQ-0071
Last Modified: 7/27/2011

LSST Telescope and Site Subsystem Requirements
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24
Specification:
The Telescope and Site shall provide local weather conditions on the summit. Sensing
shall include both exterior and interior to the dome measurements of the following parameters:
Wind speed and direction
Air temperature
Humidity
2.4.4.5 Facility Monitoring
ID: TLS-REQ-0072
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall provide remote sensing capability on all operationally critical
doors, windows, and hatches that provide facility state indication to the operators in the control room. This
shall, as a minimum, include all exterior doors.
2.5
Telescope Auxiliary Requirements
ID: TLS-REQ-0073
Last Modified: 5/23/2013
Specification:
In addition to the equipment, software, systems and functional capabilities specified, the
Telescope and Site shall provide additional capability and functionality as defined in this section.
2.5.1 Telescope Alignment and Compensation
ID: TLS-REQ-0074
Last Modified: 7/27/2011
Specification:
The telescope shall be provided with additional articulation and functional capability, as
defined in this section, to support alignment, testing, servicing and maintenance functions for the
observatory.
2.5.1.1 Telescope M2 Hexapod
ID: TLS-REQ-0075
Last Modified: 7/27/2011
Specification:
The telescope shall be composed of a hexapod to adjust the position of the secondary
mirror in the telescope. The secondary mirror cell shall be supported by this hexapod for automated
adjustment of its position relative to the primary mirror in at least five degrees of freedom.
2.5.1.2 Telescope Camera Hexapod
ID: TLS-REQ-0076
Last Modified: 7/27/2011
Specification:
The telescope shall be composed of a hexapod to adjust the position of the camera in the
telescope. The camera shall be supported by this hexapod for automated adjustment of its position
relative to the primary mirror in at least five degrees of freedom.
2.5.1.3 Telescope Hexapods Range

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25
ID: TLS-REQ-0077
Last Modified: 7/27/2011
Specification:
The M2 and Camera hexapod design ranges shall be sufficient to meet the functional and
performance requirements for the telescope to compensate for filter changes, for thermally induced
deformations, for gravity induced deformations, for creep and for construction tolerances and shall, at a
minimum, have the following range and resolution.
Description
Value
Unit
Name
X Decenter Range
10
mm
X-Decenter-Range
X Tilt Range
0.1
Degrees
X-Tilt-Range
Y Decenter Range
10
mm
Y-Decenter-Range
Y Tilt Range
0.1
int
Y-Tilt-Range
Z Axial Range
10
mm
Z-Axial-Range
2.5.2 Telescope and Site Thermal Requirements
ID: TLS-REQ-0078
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall be designed to reduce and to control thermal effects during
operation, providing air flow and cooling where needed under the summit environment operating
conditions. The ambient air temperature in the dome shall be controlled during the day to match the
expected temperature for the beginning of the night to within TBD degrees to maintain all optical and
structural components at a thermal soak.
2.5.3 Telescope Mount Balance System
ID: TLS-REQ-0079
Last Modified: 10/11/2013
Specification:
The Telescope and Site shall provide a remotely articulated mount balancing system to
adjust the telescope balance during operations. This system shall account for the variations in subsystem
centers of gravity (CG), including the camera CG tolerance specified in the Telescope to Camera ICD
(LSE-80).
In addition, the mount shall have the provisions for static adjustment of system balance as needed for
Telescope and Site manufacturing tolerances as well as a minimum of 100 times the remotely articulated
values
Discussion:
During operations, filters swap in the camera will generate change of balance. In addition,
the use of dummy weights for balancing the telescope during integration and maintenance operation will
change the balance of the mount.
2.5.4 Telescope Mount Surrogate Mass Elements
ID: TLS-REQ-0080
Last Modified: 7/27/2011

LSST Telescope and Site Subsystem Requirements
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The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
26
Specification:
The Telescope and Site shall provide, at a minimum, the following surrogate mass
elements to allow the operations team to efficiently service and maintain the system. The surrogate mass
elements shall provide telescope balance in the absence of the principal element for the activities defined.
1. A surrogate M1M3 substrate that integrates with the M1M3 cell and allows telescope elevation
motion.
2. A surrogate LSST Camera mass that can be utilized with or without a surrogate integrating
structure
3. A surrogate integrating structure that can be used with the surrogate camera to balance the
telescope in the elevation axis.
A surrogate Secondary mirror that can be used separately with the LSST Camera, or in
combination with the surrogate camera and integrating structure to balance the telescope in
elevation.
2.5.5 Telescope and Site Dome Requirements
ID: TLS-REQ-0081
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall incorporate a dome to protect the telescope from the
weather and to provide a suitable environment for calibration and observing. The dome shall support the
functional and performance requirements provided for the overall system and, at a minimum, meet the
following:
Description
Value
Unit
Name
The dome shall be able to reach the maximum
acceleration/deceleration rate acc_azdome_max for the
azimuth rotational axis.
0.75
Degrees/s
ec^2
acc_azdome_max
The dome shall be able to reach the maximum
acceleration/deceleration rate acc_eldome_max for the
elevation axis.
0.875
Degrees/s
ec^2
acc_eldome_max
The dome shall be able to close its shutter doors and vents in
shutter_close seconds to protect the telescope against a
sudden weather change.
90
Seconds
Shutter_close
The dome shall be able to reach the maximum velocity
vel_azdome_max for the azimuth rotational axis during slews.
1.5
Degrees/s
ec
vel_azdome_max
The dome light/wind screen shall be able to reach the
maximum velocity vel_eldome_max during slews of the
telescope.
1.75
Degrees/s
ec
vel_eldome_max
2.5.6 Telescope and Site Electrical Requirements
ID: TLS-REQ-0082
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall provide the electrical power necessary to support all LSST
construction, commissioning, operations, servicing and maintenance on the summit to the following
minimum specifications.
2.5.6.1 Summit Facility Electrical Power

LSST Telescope and Site Subsystem Requirements
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27
ID: TLS-REQ-0083
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall provide 380/220V primary power, 3Ø Wye connection,
grounded neutral for the Summit Facility. The frequency shall be 50Hz (Chilean Standard). The site shall
provide UPS power to critical components except for heavy loads. The site shall provide 120V UPS
courtesy power with limited distribution.The electrical system shall follow the NFPA-70 code.The system
shall also provide facility wide protection of individual phase drop.
2.5.6.2 Summit Facility Back-up Power
ID: TLS-REQ-0084
Last Modified: 10/11/2013
Specification:
A local generator shall be available on site to provide enough power for operation in case
of power grid failure.
Discussion:
The telescope is required to operate normally for a minimum duration of 2 days while on
generator.
2.5.6.3 Electrical Overcurrent Protection
ID: TLS-REQ-0085
Last Modified: 7/27/2011
Specification:
The Summit Electrical system shall include the equipment for the protection of all summit
subsystems from electrical surge, either generated within the facility or arriving from the power grid. All
stationary and large portable loads within the facility shall have local overcurrent protection
(thermomagnetic breakers, fuses, lightning arresters, surge protection, etc.) that meet the referenced
National Electric code.
2.5.6.4 Electromagnetic Emissions
ID: TLS-REQ-0086
Last Modified: 10/2/2013
Specification:
The telescope shall not emit electromagnetic radiation that significantly interferes with
itself (as defined by meeting its performance specifications) or the operation of other observatory
subsystems. Off-the-shelf electronics devices shall be compliant with FCC part 15 Class B standards or
shall have shielding or other mitigation. Custom designed electronics shall take advantage of all
reasonable good practices in design and fabrication to minimize interference.
2.5.6.5 Electromagnetic Susceptibility
ID: TLS-REQ-0144
Last Modified: 10/2/2013
Specification:
The telescope shall not be susceptible to electromagnetic emissions from itself or other
elements in the observatory. Off-the-shelf electronics devices shall be compliant with FCC part 15 Class
A standards or shall have shielding or other mitigation. Custom designed electronics shall take advantage
of all reasonable good practices in design and fabrication to minimize susceptibility.
2.5.6.6 Shielding and Grounding

LSST Telescope and Site Subsystem Requirements
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28
ID: TLS-REQ-0087
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall provide facility wide common grounding system that
minimizes system ground loop potential. Electrical connectors, cabling, and tubing shall be consistent
with high reliability operation and EMC constraints. Power and signal cables shall be shielded for low and
high frequency interference. Whenever possible, power and signal wires shall be routed separately. The
cabling design shall avoid ground loops.
2.5.6.7 Telescope and Site Lightning Protection
ID: TLS-REQ-0088
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall include all necessary equipment for lightning protection
according to NFPA 780 "Standard for the Installation of Lightning protection Systems".
3
Telescope and Site Calibration Requirements
Specification:
The Telescope and Site shall provide a calibration screen system for the instrument
calibration, an auxiliary telescope (also called calibration telescope) and water vapor monitoring system
for the atmospheric characterization.
3.1
Telescope Calibration Screen
ID: TLS-REQ-0090
Last Modified: 10/3/2013
Specification:
A calibration screen located in the telescope dome shall be provided for the purpose of
measuring the relative throughput efficiency of the LSST Optical system as a function of wavelength.
Discussion:
The function of the Calibration Screen is to measure the relative throughput of the LSST
instrumental system from the input pupil of the telescope to the digitization of charge in the camera
electronics. This includes the reflectivity of the mirrors, transmission of the refractive optics and filters, the
quantum efficiency of the sensors in the camera, and the gain and linearity of the sensor read-out
electronics. Spatial, temporal, and chromatic variations of the throughput must be determined up to a
single overall normalization for the accumulated LSST survey.
3.1.1 Telescope Calibration Screen Flux Uniformity
ID: TLS-REQ-0091
Last Modified: 10/3/2013
Specification:
The calibration screen shall have a spatial uniformity as specified below throughout the
specified range of wavelengths
.
Description
Value
Unit
Name
The maximum spatial variation in the calibration screen
illumination
10
Percent
dsSpatialUniformity
3.1.2 Telescope Calibration White Light Source

LSST Telescope and Site Subsystem Requirements
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29
ID: TLS-REQ-0094
Last Modified: 10/3/2013
Specification:
The calibration screen shall be capable of emitting broadband "white" light with a known
spectral energy distribution meeting the following functional and performance specification.
Discussion:
The white light spectral energy distribution is to be measured every time the white light is
used. A 1% RMS relative accuracy per exposure is expected for this measurement.
3.1.2.1 White Light Wavelength Range
ID: TLS-REQ-0095
Last Modified: 10/3/2013
Specification:
The broadband "white" light source shall span a wavelength range of
wlsWavelengthRange
with no discontinuities.
Description
Value
Unit
Name
The maximum wavelength emitted by the broadband "white"
light continuum source.
1100
nm
wlsLambdaMax
The minimum wavelength emitted by the broadband "white"
light continuum source.
320
nm
wlsLambdaMin
3.1.2.2 White Light Spectral Radiance
ID: TLS-REQ-0096
Last Modified: 10/3/2013
Specification:
The intensity of the broadband "white" light emitted by the calibration screen shall be
sufficient to produce a spectral radiance of at least 3 milli-Jansky per arcsec^2..
3.1.3 Telescope Monochromatic Light Source
ID: TLS-REQ-0097
Last Modified: 7/27/2011
Specification:
The calibration screen shall be capable of emitting tunable monochromatic light meeting
the following functional and performance specification.
3.1.3.1 Monochromatic Line Width
ID: TLS-REQ-0098
Last Modified: 7/27/2011
Specification:
The optical band emitted from the screen during each calibration exposure must be no
wider than
mlsLineWidth
and it must be possible to step the optical band in
mlsLineStep
increments.
Description
Value
Unit
Name
The minimum tuning step for the flux emitted by the
monochromatic light source.
1
nm
mlsLineStep
The maximum line width of the flux emitted by the
monochromatic light source.
1
nm
mlsLineWidth

LSST Telescope and Site Subsystem Requirements
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30
3.1.3.2 Wavelength Accuracy
ID: TLS-REQ-0099
Last Modified: 10/3/2013
Specification:
The wavelength of the center of the optical band emitted from the monochromatic light
source during each calibration exposure must be known to a maximum uncertainty (1-sigma) specified by
mlsWavelengthAccuracy.
Description
Value
Unit
Name
Maximum allowable uncertainty in knowing the center
wavelength of the monochromatic light source across the griz
passbands.
1
nm
mlsLambdaErr_griz
Maximum allowable uncertainty in knowing the center
wavelength of the monochromatic light source across the u
and y passbands.
1
nm
mlsLambdaErr_uy
3.1.3.3 Wavelength Range
ID: TLS-REQ-0100
Last Modified: 7/27/2011
Specification:
The wavelength of the monochromatic light emitted from the screen shall be tunable
across the LSST bandpass from
mlsWavelengthRange.
Description
Value
Unit
Name
The maximum wavelength of the range over which the
monochromatic light source can be tuned.
1125
nm
mlsLambdaMax
The minimum wavelength of the range over which the
monochromatic light source can be tuned.
320
nm
mlsLambdaMin
3.1.4 Telescope Calibration Screen Flux Measurement
ID: TLS-REQ-0092
Last Modified: 8/8/2016
Specification:
The optical flux reflected from the screen per exposure must be known to a relative
precision specified by
screenFluxMeasure
over the full wavelength range, for an interval specified by
screen_FluxInterval
.
Discussion:
This specification is to ensure any incident light variation on the screen is measurable over
the time it takes to perform a flat-fielding sequence. The maximum amount of time to perform a flat-
fielding sequence is 4 hours (TLS-REQ-0101).
Description
Value
Unit
Name
The percent RMS relative precision per exposure in the griz
passbands.
0.2
Percent
RMS
screenFlux_griz
The time interval over which screenFlux_griz and
screenFlux_uy must be valid:
4
Hour
screenFlux_interval
The percent RMS relative precision per exposure in the uy
passbands.
0.3
Percent
RMS
screenFlux_uy

LSST Telescope and Site Subsystem Requirements
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31
3.1.5 Telescope Calibration Screen Operations
ID: TLS-REQ-0101
Last Modified: 10/3/2013
Specification:
The screen shall be usable during the hour just before evening twilight and the hour just
after morning twilight of each night’s observing; Further, the calibration screen shall be usable during the
afternoon to permit long bandpass scan calibrations using the monochromatic light source. The dome
shall be dark enough to not exceed 1% (TBR) of the broadband white light calibration screen illumination.
It shall be possible to set up the screen and begin taking calibration data within 30(TBR) minutes of
command to do so. It shall be possible to change the wavelength of the narrow band light source within
5(TBR) seconds. It shall be possible to scan a filter in 4 hours.
3.2
Telescope and Site Auxiliary Telescope
ID: TLS-REQ-0102
Last Modified: 5/23/2013
Specification:
An auxiliary telescope shall be provided for the purpose of calibrating the atmospheric
transmission function.
Discussion:
The primary function of the Auxiliary Telescope (AT) is to measure spectra of stars with
sufficiently fine sampling in spatial coordinates and time to determine the wavelength dependence of
optical transmission of light from the top of the atmosphere to the input pupil of the telescope for each
LSST image.
3.2.1 Auxiliary Telescope Spectral Range
ID: TLS-REQ-0103
Last Modified: 2/3/2015
Specification:
The Auxiliary Telescope shall have efficient operating throughput over a spectral range
given by
atLambdaMin
and
atLambdaMax
.
Description
Value
Unit
Name
The maximum operating wavelength of the auxiliary
telescope.
1000
nm
atLambdaMax
The minimum operating wavelength of the auxiliary telescope.
320
nm
atLambdaMin
3.2.2 Auxiliary Telescope Observing Range
ID: TLS-REQ-0104
Last Modified: 7/27/2011
Specification:
The Auxiliary Telescope shall be capable of observing over an elevation rang defined by
atElRange
over 360 degrees of azimuth.
Description
Value
Unit
Name
The maximum elevation angle that the AT must be able to
conduct normal observing.
86.5
Degrees
atElRangeMax
The minimum elevation angle that the AT must be able to
conduct normal observing.
20
Degrees
atElRangeMin

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32
3.2.3 Auxiliary Telescope Observing Cadence
ID: TLS-REQ-0105
Last Modified: 7/27/2011
Specification:
The Auxiliary Telescope shall track a star to take the specified spectra, transmit the data,
and retarget to the next star, anywhere in the Observation Area, within
atObsCadence
.
Discussion:
The Auxiliary Telescope is expected to be operated as a robotic telescope or remotely in an
automatic mode from the main LSST telescope.
Description
Value
Unit
Name
The time interval over which the aux. telescope must be able
to obtain an observation over the current nightly survey area.
5
Minute
atObsCadence
3.2.4 Auxiliary Telescope Scheduling
ID: TLS-REQ-0106
Last Modified: 8/3/2016
Specification:
The Auxiliary Telescope shall follow a schedule determined by an Auxiliary Telescope
Scheduler. The Scheduler shall optimize the Auxiliary Telescope observations via a cost function that
shall include the previous history of LSST observations combined with the predicted future visits to
determine to determine which targets to observe. The targets shall be a list of pre-selected stars.
Discussion:
The Auxiliary Telescope Scheduler will be a very simplified version of the main telescope
scheduler.
3.2.5 Auxiliary Telescope Instrument
ID: TLS-REQ-0107
Last Modified: 8/10/2016
Specification:
The auxiliary telescope shall be instrumented with an imaging spectrometer having the
following functional and performance specifications.
Discussion:
The approach adopted by the LSST project for estimating the atmospheric transmission
function relies on using spectra of reference stars to back illuminate the atmosphere. These spectra are
fitted using catalogue reference spectra and a model atmosphere using MODTRAN. The resulting fit
provides coefficients as a function of time and sky coordinates for the constituent components of the
atmosphere responsible for the wavelength dependent absorption allowing through interpolation to
estimate the transmission function any specific LSST visit.
3.2.5.1 Beam Projector Coordinate Relationship
ID: TLS-REQ-0157
Last Modified: 8/10/2016
Specification:
A coordinate system transformation system shall be developed to relate collimated beam
projector position, telescope pupil position, to illumination position on the telescope optical elements and
focal plane position.

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Discussion:
This is necessary to facilitate the data acquisition and reduction. The user will be able to
specify an LSST pupil and focal plane position for a given spot, then have the CBP and telescope offset
accordingly. Similarly, the spot positions should be predictable based on the CBP and telescope position.
3.2.5.2 Beam Projector Pupil Pivot Capability
ID: TLS-REQ-0158
Last Modified: 8/9/2016
Specification:
The collimated Beam Projector shall pivot about a common pupil position.
Discussion:
Holding the pupil location fixed ensures the projection of light from any desired location on
the CBP mask onto the same location in the focal plane, using a common trajectory through the LSST
optical train. This is used to determine the relative emittance of the different pinholes in the mask that is a
required correction in the determination of the relative response across the LSST focal plane.
3.2.5.3 Auxiliary Instrument Spectral Range
ID: TLS-REQ-0108
Last Modified: 2/3/2015
Specification:
The spectral range of the auxiliary telescope spectrometer shall be
aux
I
nstLambdaMin
through
auxInstLambdaMax.
Description
Value
Unit
Name
The maximum wavelength of the spectrum obtained by the
auxiliary instrument.
The redwavelength limit is set by water feature ranging from
900980 nm. The spectrograph must have a wavelength range
to sample the redside of this feature to measure the
continuum for accurate fitting.
1000
nm
auxInstLambdaMax
The minimum wavelength of the spectrum obtained by the
auxiliary instrument.
320
nm
auxInstLambdaMin
3.2.5.4 Auxiliary Instrument Spectral Resolution
ID: TLS-REQ-0109
Last Modified: 8/9/2016
Specification:
The spectral resolution of the Auxiliary Telescope Spectrograph shall be at least
auxInstSpecRes
(TBR) for wavelengths longer than
auxInstSpecResWave
(TBR).
Discussion:
This requirement corresponds to a spectral resolution of R=150, which is required to
properly characterize the water absorption feature at 900-980 nm.
This specification is being left as TBR as further on-sky measurements and tests are required to finalize
this number.
Description
Value
Unit
Name
The minimum spectral resolution of the auxiliary instrument at
6.0
nm
auxInstSpecRes

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34
Description
Value
Unit
Name
the reference wavelength.
The reference wavelength for the spectral resolution.
900
nm
auxInstSpecResWa
ve
3.2.5.5 Auxiliary Instrument Wavelength Calibration
ID: TLS-REQ-0110
Last Modified: 8/3/2016
Specification:
Calibration of the instrumental dispersion function of the Auxiliary Telescope spectrograph
shall be achievable with on-sky observations.
3.2.5.6 Auxiliary Instrument Spectral Stability
ID: TLS-REQ-0145
Last Modified: 10/4/2013
Specification:
After determining the wavelength calibration of the spectrograph from the arc lamp, the
wavelength calibration shall be predictable to within 1nm over the next 10 hours.
Discussion:
The prediction model may utilize any quantities that are included in the Engineering and
Facilities Database, for example, instrument temperature, to achieve the requirement.
3.2.5.7 Integrated Spectral Signal to Noise Ratio (SNR)
ID: TLS-REQ-0111
Last Modified: 8/3/2016
Specification:
The SNR of the detected flux integrated over each of the LSST griz bands must be at
least
auxSpecSNR_griz
(TBR) for each acquired spectrum; this value must be at least
auxSpecSNR_uy
(TBR) for u and y bands.
Description
Value
Unit
Name
The minimum SNR integrated over the griz passbands
required for determining the atmospheric transmission
function.
500
auxSpecSNR_griz
The minimum SNR integrated over the u and y passbands
required for determining the atmospheric transmission
function.
300
auxSpecSNR_uy
3.2.5.8 Target Brightness
ID: TLS-REQ-0112
Last Modified: 10/3/2013
Specification:
The Auxiliary Telescope + Instrument shall achieve the integrated spectral SNR
requirements on source targets over a brightness range defined by
auxInstSourceMag.
Description
Value
Unit
Name
The maximum r-band magnitude which the AT + Instrument is
required to meet the integrated SNR with out saturating.
8
ABmag
auxSourceMagMax

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35
Description
Value
Unit
Name
The limiting r-band magnitude which the AT + Instrument is
required to meet the integrated SNR.
12
ABmag
auxSourceMagMin
3.2.5.9 Auxiliary Instrument Detector Gain Stability
ID: TLS-REQ-0146
Last Modified: 10/11/2013
Specification:
The gain of the detector auxiliary instrument (electrons per ADU) shall be stable to 2%
over a period of 10 hours.
3.3
Water Vapor Monitoring System
ID: TLS-REQ-0147
Last Modified: 1/28/2015
3.3.1 GPS Instrument
ID: TLS-REQ-0148
Last Modified: 10/11/2013
Specification:
A GPS instrument shall be installed to monitor the water vapor level in the atmosphere.
3.4
Collimated Beam Projector
ID: TLS-REQ-0151
Last Modified: 1/28/2015
Specification:
An optical system capable of projecting a collimated beam onto the telescope entrance
pupil shall be installed inside the dome enclosure for the purpose of in-situ measurement and
characterization of the camera crosstalk coefficients and instrumental throughput.
3.4.1 Beam Projector Etendue Sampling Range
ID: TLS-REQ-0152
Last Modified: 1/28/2015
Specification
: The collimated beam projector shall be capable of sampling the entire range of field
angles and pupil aperture encompassed by the LSST optical system.
Discussion
: It is assumed that the collimated beam projector diameter is much smaller (i.e. 20-40cm)
than the LSST pupil diameter (8.4m). The LSST's etendue can be fully sampled by a combination of
telescope movements in elevation and azimuth and articulating small offsets in the launch angle from the
collimated beam projector.
3.4.2 Beam Projector Light Sources
ID: TLS-REQ-0153
Last Modified: 1/28/2015

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36
Specification:
The collimated beam projector shall be capable of using the same light sources as used
for the calibration screen as specified by TLS-REQ-0091, TLS-REQ-0094 and TLS-REQ-0095 for the
"white light" source and by TLS-REQ-0097, TLS-REQ-0098 and TLS-REQ-0099 for the monochromatic
source.
3.4.3 Beam Projector Spot Size
ID: TLS-REQ-0154
Last Modified: 1/28/2015
Specification:
The collimated beam projector shall be capable of projecting a spot of <
BeamProjectorSpotSize
in diameter at the Camera's detector surface.
Discussion:
The magnification factor for the collimated beam projector is the ratio of the LSST focal
length and that of the projector. The LSST focal length is ~10369 mm. A 5 micron pinhole at the projector
would require a magnification factor of <20 to meet this specification, implying a projector focal length no
shorter than 520 mm.
Description
Value
Unit
Name
Beam Projector Spot Size Diameter
100
Microns
BeamProjectorSpot
Size
3.4.4 Beam Projector Spacial Patterns
ID: TLS-REQ-0155
Last Modified: 1/28/2015
Specification:
The collimated beam projector shall cary at least 5 selectable projection patterns that can
be deployed at anytime during operation.
4
Telescope and Site Operational Requirements
The Telescope and Site shall provide the facilities, subsystems and control software required for safe
operations to meet the specified functional and performance requirements at the summit and at the base.
These facilities shall include all necessary utilities and services that are safe for personnel and
equipment.
4.1
Telescope Safety Requirements
ID: TLS-REQ-0116
Last Modified: 5/23/2013
Specification:
Safety during operation and maintenance shall be provided by design, and the telescope
shall include all equipment and procedures necessary to ensure protection of components and personnel.
Radio communication devices shall be provided to support the personnel necessary to be on the summit
site. This equipment shall be consistent with Summit radio infrastructure already in place.
4.1.1 Personnel Safety
ID: TLS-REQ-0117
Last Modified: 7/27/2011

LSST Telescope and Site Subsystem Requirements
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37
Specification:
Safety during operation and maintenance shall be provided by design, and the telescope
shall include all equipment and procedures necessary to ensure protection of personnel.
4.1.2 Hardware Safety
ID: TLS-REQ-0118
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall include brakes, dampened hard stops, stow pins to lock the
telescope at horizon and zenith position (with telescope balanced or out of balance), emergency stops,
safety interlocks and any other systems necessary to ensure protection of components.
4.1.3 Telescope and Site Earthquake Display
ID: TLS-REQ-0119
Last Modified: 7/27/2011
Specification:
The Telescope and Site summit facility and base shall include a comfort display to present
summit personnel with information on seismic activity down to a level of 3 on the Richter scale.
4.2
Telescope Security Requirements
ID: TLS-REQ-0121
Last Modified: 5/23/2013
Specification:
The Telescope and Site shall provide a secure environment for personnel, equipment, and
data.
4.3
Telescope Environment Compliance
ID: TLS-REQ-0122
Last Modified: 5/23/2013
Specification:
The LSST shall be developed and operated in compliance with all applicable local
environmental, cultural, and permitting regulations for each relevant LSST site and location of work. All
LSST development and operation shall comply with the LSST Environmental and Cultural Sensitivity Plan
(Document-TBD) that describes in detail the LSST Policy and Procedure for adhering to local permitting
requirements and other US Federal guidelines for extraterritorial projects. In addition to these local and
international standards the LSST shall also comply with the following environmental parameters.
4.3.1 Night Light Emission
ID: TLS-REQ-0123
Last Modified: 7/27/2011
Specification:
During normal night time operation the LSST Summit Facility shall not generate detectable
light pollution.
Discussion:
The requirement is meant to both protect the scientific integrity of the LSST survey and also
minimize the LSST's impact on neighboring observatories.
4.4
Radio Active Background

LSST Telescope and Site Subsystem Requirements
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38
ID: TLS-REQ-0124
Last Modified: 1/28/2015
Specification:
The Telescope & Site subsystem shall have a project-reviewed radioactive material test
plan.
Discussion:
The Telescope must develop a radioactive material test plan that defines testing
approaches that are reasonable such that the camera subsystem can achieve a radiation level that is "As
Low as Reasonably Achievable" (ALARA). The test plan must specify testing of critical components and
subsystems assemblies to ensure that their contributions are well below the level of artifacts caused by
cosmic radiation. Critical components and sub-assemblies, as well as test success criteria, will be
determined by the T&S subsystem team taking into consideration the distance between the components
and sensors, shielding, component mass, and primary material of the component. A project-reviewed
radioactive material test plan means that the T&S subsystem test plan must be placed under the T&S
subsystem's change control; initial baselining and any subsequent updates must include review and input
from the LSST Project Systems Engineering (PSE) office.
4.5
Telescope and Site Lifetime
ID: TLS-REQ-0125
Last Modified: 5/23/2013
Specification:
The Telescope and Site shall be designed for a minimum lifetime of 15 years
.
Discussion:
The minimum design lifetime includes the time from assembly during construction, 2 years
of commissioning, and 10 years of survey operations.
4.6
Telescope Summit-Base Network Loss
ID: TLS-REQ-0127
Last Modified: 5/23/2013
Specification:
The telescope summit facility shall be designed to support normal operations in the event
of a network connectivity loss for a minimum of 2 days between the summit and the base facility.
4.7
Base-Archive Network Loss
ID: TLS-REQ-0128
Last Modified: 10/11/2013
Specification:
The telescope base facility shall be designed to support normal operations in the event of
a connectivity network loss for a minimum of 2 days between the base facility and the archive center.
Discussion:
A data buffer shall be provided at the base to archive the data during such loss. The
maximum recovery time for the network link between the base facility and the archive center is required to
be limited to 24h.
5
Telescope and Site Integration and Maintenance Requirements
The Telescope and Site shall provide all the typical telescope subsystems that are necessary for its
integration and maintenance.

LSST Telescope and Site Subsystem Requirements
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39
The Telescope and Site shall maintain up to date all the parameters necessary for the telescope
operation (including the look-up tables for the active optics control). Automatic and manual procedures
shall be implemented and supported.
5.1
Integration and Test
ID: TLS-REQ-0130
Last Modified: 5/23/2013
Specification:
The Telescope and Site shall provide for all the equipment necessary for its integration
and test before reception of the Camera.
Discussion:
The Telescope and Site is responsible for the equipment necessary for testing the mirrors
before installation of the camera.
5.2
Access and Removal of Major Subsystems
ID: TLS-REQ-0131
Last Modified: 5/23/2013
Specification:
The Telescope and Site shall be designed to allow for access and removal/installation of
major optical subsystems for maintenance.
Discussion:
The Telescope and Site is responsible for the equipment necessary for installation/removal
of the Camera from the Telescope.
5.3
Telescope and Site Predictive Maintenance
ID: TLS-REQ-0132
Last Modified: 5/23/2013
Specification:
The Telescope and Site shall implement and maintain a comprehensive predictive
maintenance program based on regular inspection and/or condition monitoring of all major sub-systems.
Discussion:
The goal is to detect and correct performance degradation and/or potential failures before
these problems cause lost science time or significantly reduce system efficiency. The OCS predictive
maintenance plan shall support this activity.
5.4
Telescope and Site Preventive Maintenance
ID: TLS-REQ-0133
Last Modified: 5/23/2013
Specification:
The Telescope and Site shall implement and maintain a comprehensive preventive
maintenance program for each subsystem component, based on vendor recommendations.
Discussion:
This program shall cover all major technical sub-systems including enclosure, mount,.... The
goal is to maintain system efficiency within specified ranges and maximize the time between failures.
5.5
Telescope and Site Baseline Performance Reporting Requirement
ID: TLS-REQ-0134
Last Modified: 5/23/2013

LSST Telescope and Site Subsystem Requirements
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40
Specification:
The Telescope and Site shall provide the initial baseline performance and trend analysis
specific to its design using the provided toolkit.
Discussion:
The baseline analysis is a deliverable of the telescope system and will be part of the
acceptance process.
5.6
Telescope and Site Scheduled Downtime
ID: TLS-REQ-0135
Last Modified: 1/27/2015
Specification:
The Telescope and Site shall be able to execute planned maintenance and repair
activities that require the shutdown of the telescope within the scheduled
ObservatorySchedDowntime
days per year.
Discussion:
The scheduled downtime will be scheduled in advance by Observatory management. All
Telescope and Site planned maintenance and repairs that require the shutdown of the telescope must
occur during this scheduled time.
Description
Value
Unit
Name
Scheduled downtime for the observatory for the year.
14
Days
ObservatorySchedD
owntime
5.7
Telescope and Site Unscheduled Downtime
ID: TLS-REQ-0150
Last Modified: 1/27/2015
Specification:
The Telescope and Site subsystem shall be designed to facilitate unplanned repair
activities expected not to exceed
TSUnSchDowntime
days per year.
Discussion:
This requirement does not invoke the need to verify by reliability analysis. Verification is by
analysis that identifies likely hardware failures and identifies mitigations to minimize downtime caused by
those failures.
Description
Value
Unit
Name
Unplanned downtime per year
10
Days
TSUnSchDowntime
5.8
Telescope and Site Activity Support, Tracking and Reporting
ID: TLS-REQ-0136
Last Modified: 5/23/2013
Specification:
The Telescope and Site shall implement the following systems:
Comprehensive problem reporting, tracking, and management system
Work order driven preventive maintenance support system (usually known as CMMS for
Computerized Maintenance Management System).
Warehouse inventory and property control
Document control center
Analysis tools for supporting predictive maintenance.

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41
The Telescope and Site shall maintain a permanent record of the description and time required to recover
from all maintenance events.
A set of automatic reports based on engineering telemetry shall be generated on a daily basis.
NOTE: This requirement corresponds mostly to the OCS domain. T&S shall provide the necessary
information to OCS for the maintenance management.
6
Telescope and Site Standards
Specification:
The LSST shall be designed to meet the site based component and procedure
standardization captured in the LSST System Standards document, LSE-XX. This document defines the
component standards to be followed to ensure a minimum dispersion of final design elements across the
LSST system, in particular at a single facility/site.
Discussion
: The objective is to minimize the support equipment and specialized training necessary to
maintain and operate different types of electronics, to minimize the types of tooling to service otherwise
similar hardware, etc...
6.1
Components Standardization Goal
Goal:
The Telescope and Site subsystem should be designed to standardize components within the
subsystem and with other subsystems when component functional, performance, and operational
requirements define overlapping solution spaces.
Discussion:
While it is desired to standardize component selection, it is realized that imposing this as a
strict requirement is not practical due to a variety of factors, including component requirements that may
require selection of unique hardware. However, standardizing components, where practical, supports
many project operational goals, including standardization of operational and maintenance procedures.
Additionally, standardization reduces the number of unique spares that must be stocked, helping reduce
maintenance costs during commissioning and operations. To support the goal of component
standardization, it is recommended that the Telescope and Site subsystem exchange information with the
other subsystems on an ongoing basis on their component selection to enable choices to be made
informed by what components are already in use. Note: this is a "goal" statement that does not require
verification.
6.2
Telescope Time Reference
ID: TLS-REQ-0138
Last Modified: 5/23/2013
Specification:
The Telescope and Site system shall provide a standard time reference to be used by all
for absolute and external time reference.
6.2.1 Time Absolute Accuracy and Relative Precision
ID: TLS-REQ-0139
Last Modified: 7/27/2011

LSST Telescope and Site Subsystem Requirements
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42
Specification:
All time tagged events reported both internally and externally by the Telescope and Site
shall be done with the timing absolute accuracy and relative precision given in the table below
.
Description
Value
Unit
Name
All time tagged events reported both internally and externally
shall be done with an accuracy of
Absolute_Accuracy
.
0.010
Seconds
Absolute_Accuracy
All internal events shall be recorded with a precision relative
to the master clock of
Relative_Precision
.
0.001
Seconds
Relative_Precision
6.2.2 Telescope Internal Time Standard
ID: TLS-REQ-0140
Last Modified: 7/27/2011
Specification:
The Telescope and Site internal time reporting standard shall be International Atomic
Time (TAI).
6.3
Electrical Standards
ID: TLS-REQ-0141
Last Modified: 5/23/2013
Specification:
The Telescope and Site shall develop and document standards for the following:
Control Panels
Electrical and Electromagnetic Compatibility
Controllers and associated software
Utility Connection
Grounding
Discussion:
The objective of these standards is to support efficient operations and minimize the
dispersion of final design elements across the summit support facility and the base facility.
6.4
Building Codes
ID: TLS-REQ-0142
Last Modified: 10/2/2013
Specification:
All LSST facilities shall comply with the 2006 International Building Code and the
accompanying 2006 International Mechanical/Plumbing Codes for the design of the Summit Support
Facility. These codes shall also apply to the LSST Base facility in Chile and the design of all U.S.-based
facilities.
In addition, all LSST Facilities in Chile shall comply with the applicable Norma Chilena:
NCH-431: "Earthquake resistant design of buildings";
NCH-433: "Earthquake resistant design of buildings";
NCH-2369: "Seismic design of industrial structures and installations"; and
with other related regulations regarding seismic design. In cases of conflicting requirements, the most
stringent code shall govern.

LSST Telescope and Site Subsystem Requirements
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