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 Date: February 11, 2014
  7. Change Record
    1. Table of Contents
  8. The LSST Telescope and Site Subsystem Requirements
    1. Introduction and Scope
    2. Supporting Documents
    3. Definition of Terms:
  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. 4 Telescope and Site Operational Requirements
      1. 4.1 Telescope Safety Requirements
      2. 4.2 Telescope Security Requirements
      3. 4.3 Telescope Environment Compliance
      4. 4.4 Telescope and Site Lifetime
      5. 4.5 Telescope Summit-Base Network Loss
      6. 4.6 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. 5.3 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 Downtime
      7. 5.7 Telescope and Site Activity Support, Tracking and Reporting
    6. 6 Telescope and Site Standards
      1. 6.1 Telescope Time Reference
      2. 6.2 Electrical Standards
      3. 6.3 Building Codes

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
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.
1
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 Date: February 11, 2014
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.
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
i

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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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
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
Supporting
Documents
................................................................................................................................
iv
Definition
of
Terms:
.....................................................................................................................................
iv
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
...........................................................................................
18
2.4
Telescope and Site Monitoring and Diagnostics Requirements
........................................... 20
2.5
Telescope
Auxiliary
Requirements
.........................................................................................
22
3
Telescope and Site Calibration Requirements
............................................................................. 26
3.1
Telescope
Calibration
Screen
.................................................................................................
26
3.2
Telescope
and
Site
Auxiliary
Telescope
.................................................................................
29
3.3
Water
Vapor
Monitoring
System
...........................................................................................
31
4
Telescope
and
Site
Operational
Requirements
............................................................................
32
4.1
Telescope
Safety
Requirements
.............................................................................................
32
4.2
Telescope
Security
Requirements
..........................................................................................
33
4.3
Telescope
Environment
Compliance
......................................................................................
33
4.4
Telescope
and
Site
Lifetime
....................................................................................................
33
4.5
Telescope
Summit-Base
Network
Loss
..................................................................................
33
4.6
Base-Archive
Network
Loss
....................................................................................................
34
5
Telescope and Site Integration and Maintenance Requirements
............................................... 34
5.1
Integration
and
Test
...............................................................................................................
34
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
iii
5.2
Access and Removal of Major Subsystems
............................................................................ 34
5.3
Telescope
and
Site
Predictive
Maintenance
..........................................................................
34
5.4
Telescope
and
Site
Preventive
Maintenance
.........................................................................
35
5.5
Telescope and Site Baseline Performance Reporting Requirement
..................................... 35
5.6
Telescope
and
Site
Downtime
................................................................................................
35
5.7
Telescope and Site Activity Support, Tracking and Reporting
.............................................. 35
6
Telescope
and
Site
Standards
.......................................................................................................
36
6.1
Telescope
Time
Reference
......................................................................................................
36
6.2
Electrical
Standards
................................................................................................................
37
6.3
Building
Codes
.........................................................................................................................
37
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
iv

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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.
Supporting Documents
1. LSST Science Requirements Document (document LPM-17)
2. LSST System Requirements (document LSE-29)
3. LSST Observatory System Specifications (document LSE-30)
Definition 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.
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
1

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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;
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
2
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:
ID: TLS-REQ-0007
ID:
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
The operational summit elevation base of the telescope pier is
summitElevation.
2650
Meters
summitElevation
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
3
Description
Value
Unit
Name
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: 2/11/2014
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 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
The maximum temperature for normal operations at the summit
shall be
normTempMax
.
19.0
Celsius
normTempMax
The rate of change for design purposes shall be
normTempGrad.
0.7
C/Hour
normTempGrad
When design considerations require operational wind
specifications all summit based systems shall use the extreme
operational wind speed,
normWindMax
.
12
m/sec
normWindMax
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
normHumidityMea
n
When design considerations require barometric pressure
specifications all summit based systems shall use the mean
pressure
normBaroMean
.
750
mbar
normBaroMean
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
4
Description
Value
Unit
Name
The maximum barometric pressure for normal operations at the
summit shall be
normBaroMax
775
mbar
normBaroMax
The maximum barometric pressure for normal operations at the
summit shall be
normBaroMin
725
mbar
normBaroMin
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
marginaltempGradi
ent
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 windspeed 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
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
survivalWindExteri
or
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
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 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
survivalTemperatur
e
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
5
Description
Value
Unit
Name
The survival load on the Summit Facility due to snow shall be
snowLoading
(ref. Norma Chilena NCH 431).
200
kg/m^2
snowLoading
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
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 Cerro Pachón 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
The ambient temperature range or transportation to the summit
is
-15C to
+40C
Celsius
Temperature
Range
The relative humidity range is from 10% to 100% with
condensation for transportation to the summit
10% to
100%
Percent
Relative Humidity
Range
Wind speed may reach up to 45m/s during transportation to the
summit
45
m/sec
Wind Speed
Pressure will change during transportation to the summit from
1000mbar at sea level down to 750mbar at the summit
1000 to
750
milibar
Pressure
Containers have to be designed to limit water, dust, sand and
insect access during transportation
Contamination
Dirt roads will be used during transportation to the summit with
grades up to 16%
16
Percent
Roads
During transportation to the summit, some roads have vehicle
weight restrictions.
Gross Vehicle Weight GVW = TBD
Weight/axle = TBD
TBD
kg
GVW
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
1.2.3
Seismic Parameters for Design
ID: TLS-REQ-0143
Last Modified: 10/2/2013
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
6
1.2.3.1
Survival Seismic Parameters for Design
ID:
ID: TLS-REQ-0014
ID:
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 Cerro Pachón implies a set of constraints relating to the astro-
climate under which the survey performance requirements from the LSR must be met. These 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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
7
Specification
: The LSST shall meet the survey performance requirements under the constraint of the atmospheric
seeing on Cerro Pachón (El Peñón) 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
ArcsecFWH
M
seeing1stQuartile
The median of the seeing distribution shall be taken as
seeingMedian
0.69
ArcsecFWH
M
seeingMedian
The third quartile of the seeing distribution shall be taken as
seeing3rdQuartile
0.84
ArcsecFWH
M
seeing3rdQuartile
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.
https://www.lsstcorp.org/docushare/dsweb/Get/Document-3902
https://www.lsstcorp.org/docushare/dsweb/View/Collection-973
Description
Value
Unit
Name
1976 US standard STP sea level pressure is
seaLevelPressure
.
1013
milibar
seaLevelPressure
The standard relative humidity percentage is
stpRelHumidity
.
15
Percent
stpRelHumidity
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
8
Description
Value
Unit
Name
The standard typical Ozone level over northern Chile is
ozoneLevel
.
338
Dobson
ozoneLevel
Reference airmass for calculating the standard transmission
function is
stdAirmass
.
1.0
Airmass
stdAirmass
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 u-band.
22.92
mag/SqArc
sec
u_SkyBrightness
Integrated reference sky brightness in the g-band.
22.27
mag/SqArc
sec
g_SkyBrightness
Integrated reference sky brightness in the r-band.
21.20
mag/SqArc
sec
r_SkyBrightness
Integrated reference sky brightness in the i-band.
20.47
mag/SqArc
sec
i_SkyBrightness
Integrated reference sky brightness in the z-band.
19.59
mag/SqArc
sec
z_SkyBrightness
Integrated reference sky brightness in the y-band.
18.42
mag/SqArc
sec
y_SkyBrightness
1.2.4.5
Usable Observing Time
ID: TLS-REQ-0022
Last Modified: 7/27/2011
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.
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
9
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:
ID: TLS-REQ-0025
ID:
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
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: 7/27/2011
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
10
Description
Value
Unit
Name
The telescope shall achieve the Abs_Pointing accuracy
requirement for all elevation angles (measured on sky).
2
ArcsecRMS 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
ArcsecRMS
Offset_Point_Error
2.1.1.2
Telescope Tracking Requirements
ID: TLS-REQ-0027
Last Modified: 10/2/2013
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 have a tracking accuracy of Tel_Track_Error in
open loop over a 10min interval within the tracking range.
1
ArcsecRMS
Tel_Track_Error
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
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.
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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
11
Description
Value
Unit
Name
The telescope shall be able to reach the maximum velocity
Vel_Az_Max for the azimuth axis.
10.5
Degrees/se
c
Vel_Az_Max
The telescope shall be able to reach the maximum
acceleration/deceleration rate Acc_Az_Max for the azimuth axis
10.5
Degrees/se
c^2
Acc_Az_Max
Description
Value
Unit
Name
The telescope shall be able to reach the maximum velocity
Vel_El_Max for the elevation axis.
5.25
Degrees/se
c
Vel_El_Max
The telescope shall be able to reach the maximum
acceleration/deceleration rate Acc_El_Max for the elevation axis.
5.25
Degrees/se
c^2
Acc_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
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/se
c^2
Acc_Rot_Max
The rotator shall have at minimum this range of rotation.
±90
Degrees
Field_Rotation_Rang
e
The rotator shall be able to achieve this maximum velocity during
3.5
Degrees/se
Vel_Rot_Max
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
12
Description
Value
Unit
Name
slews of the telescope.
c
Time allocated to the telescope for aligning the filter changing
mechanism with gravity.
30
Seconds
Time_Change_Rot
The rotator shall have at maximum this absolute angle error.
0.01
Degrees
Rot_Abs_Error
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
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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
13
Description
Value
Unit
Name
The primary mirror outer clear aperture radius shall be at least
m1OuterCa.
4180.0
mm
m1OuterCa
The primary mirror inner clear aperture radius shall be no more
than m1InnerCa
.
2558.0
mm
m1InnerCa
The primary mirror radius of curvature shall be
-19835.0
mm
m1Radius
The primary mirror surface conic constant shall be
m1ConicConstant.
-1.2150
m1ConicConstant
The primary mirror surface 6th order aspheric coefficient shall be
m1_6thAsphere
1.381e-24 mm^-5
m1_6thAsphere
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 (m2) outer clear aperture radius shall be at
least
m2OuterCa.
1710.0
mm
m2OuterCa
The secondary mirror (m2) inner clear aperture radius shall be no
more than
m2InnerCa
900.0
mm
m2InnerCa
The secondary mirror surface radius of curvature shall be
m2Radius.
-6788.0
mm
m2Radius
The secondary mirror surface conic constant shall be
m2Conic.
-0.2220
m2Conic
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
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 outer clear aperture radius shall be at least
m3OuterCa.
2508.0
mm
m3OuterCa
The tertiary mirror inner clear aperture radius shall be at least
m3InnerCa.
550.0
mm
m3InnerCa
The tertiary mirror surface radius of curvature shall be
m3Radius.
-8344.5
mm
m3Radius
The tertiary mirror surface conic constant shall be
m3Conic.
0.1550
m3Connic
The tertiary mirror surface 6th order aspheric coefficient shall be
-4.500e-
mm^-5
m3_6thAsphere
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
14
Description
Value
Unit
Name
m3_6thAsphere.
22
The tertiary mirror surface 8th order aspheric coefficient shall be
m3_8thAsphere.
-8.150e-
30
mm^-7
m3_8thAsphere
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
-
6156.2006
mm
m1m2Spacing
The distance from the vertex of M2 to the vertex of M3 shal be
m2m3Spacing
6390.0006
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
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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
15
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
ArcsecFWH
M
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.
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: 7/27/2011
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_Angl
e
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_Dela
y
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
16
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
Mirror Reflectivity Performance
ID: TLS-REQ-0047
Last Modified: 7/27/2011
Specification
: After coating, the reflectivity of the telescope (3 mirrors) shall be equal or better than
t
elAveThroughput
for each filter.
Description
Value
Unit
Name
When averaged over the u-band filter the telescope throughput
shall be at least
67.6
Percent
telAveThroughput_u
When averaged over the g-band filter the telescope throughput
shall be at least
68.3
Percent
telAveThroughput_g
When averaged over the r-band filter the telescope throughput
shall be at least
65.9
Percent
telAveThroughput_r
When averaged over the i-band filter the telescope throughput
shall be at least
59.2
Percent
telAveThroughput_i
When averaged over the z-band filter the telescope throughput
shall be at least
59.0
Percent
telAveThroughput_z
When averaged over the y4-band filter the telescope throughput
shall be at least
68.6
Percent
telAveThroughput_y
4
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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
17
Description
Value
Unit
Name
This requirement defines the allowable percentage of reflectivity
loss before cleaning of the mirrors (TBR).
2
Percent
Reflectivity_Loss
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.
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
Maximum Telescope Clear Aperture Obscuration on-axis
2
Percent
Clear_Ap_Obscuratio
n
Maximum Telescope Clear Aperture Obscuration off-axis
3.5
Percent
Clear_Ap_Obscuratio
n_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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
18
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
ID: TLS-REQ-0055
Last Modified: 5/30/2013
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: 7/27/2011
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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
19
ID: TLS-REQ-0057
Last Modified: 5/23/2013
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: 7/27/2011
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 guide images received from the LSST Camera.
2.3.4
Wavefront Control
ID: TLS-REQ-0059
Last Modified: 7/27/2011
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: 7/27/2011
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: 7/27/2011
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;
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
20
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
ID: TLS-REQ-0063
Last Modified: 2/11/2014
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 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
Users at the Summit shall be able to view the image data on a
display with the Display-Size requirements.
TBD
int
Display-Size
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: 7/27/2011
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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
21
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.
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
Atmospheric Turbulence Structure
ID: TLS-REQ-0068
Last Modified: 7/27/2011
Specification:
the Telescope and Site shall provide the necessary instruments to measure the structure of the
atmospheric turbulence.
Discussion:
A Multi Aperture Scintillation Sensor (MASS) was selected for this purpose.
2.4.4.3
Cloud Mapping and Monitoring
ID: TLS-REQ-0069
Last Modified: 7/27/2011
Specification:
The Telescope and Site shall provide the necessary instruments to provide a 2-D map of the
extinction caused by cloud cover covering the visible sky centered on the Summit Site with a cadence equal to or
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
22
faster than that of the standard survey with a minimum pixel scale of TBD.
Discussion:
An all-sky IR camera was selected for the purpose of providing cloud mapping on Peñón for optimizing
the operation of the Observatory.
2.4.4.4
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.
2.4.4.5
Weather Monitoring
ID: TLS-REQ-0071
Last Modified: 7/27/2011
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
2.4.4.6
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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
23
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
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
Y Decenter Range
10
mm
Y-Decenter-Range
Z Axial Range
10
mm
Z-Axial-Range
X Tilt Range
0.1
Degrees
X-Tilt-Range
Y Tilt Range
0.1
int
Y-Tilt-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: 7/27/2011
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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
24
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
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.
A surrogate M1M3 substrate that integrates with the M1M3 cell and allows telescope elevation motion.
A surrogate LSST Camera mass that can be utilized with or without a surrogate integrating structure
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/se
c^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/se
c^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/se
c
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/se
c
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,
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
25
commissioning, operations, servicing and maintenance on the summit to the following minimum specifications.
2.5.6.1
Summit Facility Electrical Power
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: 7/27/2011
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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
26
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
ID: TLS-REQ-0094
Last Modified: 10/3/2013
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
27
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 minimum wavelength emitted by the broadband "white" light
continuum source.
320
nm
wlsLambdaMin
The maximum wavelength emitted by the broadband "white" light
continuum source.
1100
nm
wlsLambdaMax
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 maximum line width of the flux emitted by the
monochromatic light source.
1
nm
mlsLineWidth
The minimum tuning step for the flux emitted by the
monochromatic light source.
1
nm
mlsLineStep
3.1.3.2
Wavelength Accuracy
ID: TLS-REQ-0099
Last Modified: 10/3/2013
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
28
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 minimum wavelength of the range over which the
monochromatic light source can be tuned.
320
nm
mlsLambdaMin
The maximum wavelength of the range over which the
monochromatic light source can be tuned.
1125
nm
mlsLambdaMax
3.1.4
Telescope calibration Screen Flux Measurement
ID: TLS-REQ-0092
Last Modified: 10/3/2013
Specification:
The optical flux emitted from the screen per exposure must be known to a relative precision
specified by
screenFluxMeasure
over the full wavelength range.
Description
Value
Unit
Name
The percent RMS relative precision per exposure in the griz
passbands.
0.2
Percent
RMS
screenFlux_griz
The percent RMS relative precision per exposure in the uy
passbands.
0.3
Percent
RMS
screenFlux_uy
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.
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
29
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: 7/27/2011
Specification:
The Auxiliary Telescope shall have efficient operating throughput over a spectral range given in
atSpecRange.
Description
Value
Unit
Name
The minimum operating wavelength of the auxiliary telescope.
400
nm
atLambdaMin
The maximum operating wavelength of the auxiliary telescope.
1125
nm
atLambdaMax
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 minimum elevation angle that the AT must be able to conduct
normal observing.
20
Degrees
atElRangeMin
The maximum elevation angle that the AT must be able to conduct
normal observing.
86.5
Degrees
atElRangeMax
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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
30
3.2.4
Auxiliary Telescope Scheduling
ID: TLS-REQ-0106
Last Modified: 7/27/2011
Specification:
The Auxiliary Telescope shall follow a programmable observing schedule controllable by fixed
database entries. The Auxiliary Telescope scheduling program shall have access to the observing schedule of the
LSST main telescope.
3.2.5
Auxiliary Telescope Instrument
ID: TLS-REQ-0107
Last Modified: 7/27/2011
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
dependant absorption allowing through interpolation to estimate the transmission function any specific LSST visit.
3.2.5.1
Auxiliary Instrument Spectral Range
ID: TLS-REQ-0108
Last Modified: 10/3/2013
Specification:
The spectral rang of the auxiliary telescope spectrometer shall be
aux
I
nstSpecRange.
Description
Value
Unit
Name
The minimum wavelength of the spectrum obtained byt the
auxiliary instrument.
400
nm
auxInstLambdaMin
The maximum wavelength of the spectrum obtained byt the
auxiliary instrument.
1125
nm
auxInstLambdaMax
3.2.5.2
Auxiliary Instrument Spectral Resolution
ID: TLS-REQ-0109
Last Modified: 7/27/2011
Specification:
The spectral resolution of the Auxiliary Telescope spectrograph shall be at least
auxInstSpecRes
.
Discussion:
This requirement is referenced at a wavelength of 500nm for a resolution of at least 300.
Description
Value
Unit
Name
The minimum spectral resolution of the auxiliary instrument.
1.5
nm
auxInstRes
3.2.5.3
Auxiliary Instrument Wavelength Calibration
ID: TLS-REQ-0110
Last Modified: 10/3/2013
Specification:
The calibration of the wavelength scale of the Auxiliary Telescope spectrograph shall be performed
using arc lamps that cover the full spectral range.
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
31
3.2.5.4
Auxiliary Instrument Spectral Stability
ID: TLS-REQ-0145
Last Modified: 10/3/2013
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.
3.2.5.5
Integrated Spectral Signal to Noise Ratio (SNR)
ID: TLS-REQ-0111
Last Modified: 7/27/2011
Specification:
The SNR of the detected flux integrated over each of the LSST griz bands must be at least
auxSpecSNR_griz
for each acquired spectrum; this value must be at least
auxSpecSNR_uy
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
3.2.5.6
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 limiting r-band magnitude which the AT + Instrument is
required to meet the integrated SNR.
12
ABmag
auxSourceMagMin
The maximum r-band magnitude which the AT + Instrument is
required to meet the integrated SNR with out saturating.
8
ABmag
auxSourceMagMax
3.2.5.7
Auxiliary Instrument Detector Gain Stability
ID: TLS-REQ-0146
Last Modified: 10/3/2013
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: 10/3/2013
3.3.1
GPS Instrument
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
32
ID: TLS-REQ-0148
Last Modified: 10/3/2013
Specification:
A GPS instrument shall be installed to monitor the water vapor level in the atmosphere.
3.3.2
Microwave System
ID: TLS-REQ-0149
Last Modified: 10/3/2013
Specification:
A microwave system shall be installed and boresited with the LSST main telescope to monitor water
vapor in the atmosphere. The microwave radiometer shall measure the precipitable water
vapor along the LSST's line of sight with an accuracy of +/- 1mm.
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
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.
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
33
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:
ID: TLS-REQ-0122
ID:
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.
4.3.2
Radio Active Background
ID: TLS-REQ-0124
Last Modified: 10/2/2013
Specification:
The Telescope and Site shall verify that the Summit Facility does not generate measurable
radioactive background above the levels measured at the other telescope facilities located on Cerro Pachón.
4.4 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.
4.5 Telescope Summit-Base Network Loss
ID:
ID: TLS-REQ-0127
ID:
Last Modified: 5/23/2013
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
34
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.
4.6 Base-Archive Network Loss
ID:
ID: TLS-REQ-0128
ID:
Last Modified: 5/23/2013
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.
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:
ID: TLS-REQ-0130
ID:
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
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
35
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:
ID: TLS-REQ-0134
ID:
Last Modified: 5/23/2013
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 Downtime
ID: TLS-REQ-0135
Last Modified: 5/23/2013
Specification:
The Telescope and Site shall be able to execute planned maintenance and repair activities that
require to shutdown the telescope within a period equivalent to 14 days per year.
The Telescope and Site shall be designed to facilitate unplanned repair activities and adequate spare parts shall be
available. 21 days per year have been allocated to unplanned repairs.
Discussion:
The basis for allocating the unscheduled downtime uses "typical" observatory down time of 4% with
2% added to account for the single instrument of the LSST.
5.7 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).
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
36
Warehouse inventory and property control
Document control center
Analysis tools for supporting predictive maintenance.
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 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.
6.1.1
Time Absolute Accuracy and Relative Precision
ID: TLS-REQ-0139
Last Modified: 7/27/2011
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
6.1.2
Telescope Internal Time Standard
ID: TLS-REQ-0140
Last Modified: 7/27/2011
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

LSST Telescope and Site Subsystem Requirements
LSE-60
Latest Revision 2/11/2014
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
37
Specification:
The Telescope and Site internal time reporting standard shall be International Atomic Time (TAI).
6.2 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.
6.3 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.
Does NOT reflect changes approved but not yet
implemented in SysML model
(LCRs 193, 198, 199 & 200)

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