1. Large Synoptic Survey Telescope (LSST)
  2. LSST System Requirements
    1. Charles F. Claver and the LSST Systems Engineering Integrated Project Team
  3. LSE-29
  4. Latest Revision Date: March 11, 2015
  5. Change Record
    1. Table of Contents
  6. The LSST System Requirements
    1. Project Background
    2. Document Scope
    3. Acronyms and Definitions of Terms
    4. Reference Documents
  7. The LSST System Requirements
    1. 1 Survey Design Specifications
      1. 1.1 Filter Set Characteristics
      2. 1.2 Single Image Performance
      3. 1.3 Full Survey Performance
      4. 1.4 Data Processing and Management
    2. 2 System Capabilities
      1. 2.1 Optical Configuration
      2. 2.2 Observatory Control Capabilities
      3. 2.3 Data Collection
      4. 2.4 Data Products and Processing
      5. 2.5 Data Archiving & Services
    3. 3 Survey Operation & Administration
      1. 3.1 Operational Safety
      2. 3.2 Science Priorities and Survey Monitoring
      3. 3.3 Overall Operational Efficiency
      4. 3.4 LSST Broader Impacts

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
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)

Back to top


LSST System Requirements
Charles F. Claver and the LSST Systems Engineering Integrated Project Team

Back to top


LSE-29

Back to top


Latest Revision Date: March 11, 2015
This LSST document has been approved as a Content-Controlled Document. Its contents are subject to
configuration control and may not be changed, altered, or their provisions waived without prior
approval. If this document is changed or superseded, the new document will retain the Handle
designation shown above. The control is on the most recent digital document with this Handle in the
LSST digital archive and not printed versions.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
i

Back to top


Change Record
Version
Date
Description
Owner name
1
5/18/2010
Initial Version
Charles F. Claver and
the
LSST
Systems
Engineering Group
1.4
3/23/2011
Initial version placed under change control by CCB.
This is baselined as version 1.4 in the SysArch
model
Charles F. Claver and
the
LSST
Systems
Engineering Group
2.0
10/08/2013
Incorporates LCR-148, LCR-153 (amended by the
10/08/2013 CCB meeting minutes), and LCR-144
(amended by the 10/02/2013 meeting minutes)
Brian Selvy and the
LSST
Systems
Engineering Integrated
Product Team
3
3/11/2015
Incorporates LCRs 141, 182, and 253. LCR-141 flows
down SRD text edit to clarify the intent of
photometry
requirements.
LCR-182
adds
a
minimum exposure time specification. Changes
related to LCR-253 provide consistency throughout
throughput flowdown chain.
C. Claver and the LSST
Systems
Engineering
Integrated
Product
Team

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
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
Project
Background
.......................................................................................................................................
v
Document
Scope
...........................................................................................................................................
v
Acronyms and Definitions of Terms .............................................................................................................. v
Reference
Documents
..................................................................................................................................
vi
1
Survey Design Specifications ................................................................................................................. 1
1.1 Filter Set Characteristics .................................................................................................................. 1
1.1.1 Filter Complement .................................................................................................................... 1
1.1.2 Filter Complement Swap Time .................................................................................................. 1
1.1.3 Night Filter Availability .............................................................................................................. 2
1.1.4 Filter Bandpass Performance .................................................................................................... 2
1.1.5 Filter Temporal Stability ............................................................................................................ 3
1.2 Single Image Performance ............................................................................................................... 3
1.2.1 Delivered Image Quality ........................................................................................................... 3
1.2.2 Delivered Image Ellipticity ........................................................................................................ 6
1.2.3 Filter Depths .............................................................................................................................. 6
1.2.4 Photometric Performance ........................................................................................................ 8
1.2.5 Astrometric Performance ......................................................................................................... 9
1.2.6 Bright Sources ......................................................................................................................... 10
1.3 Full Survey Performance ................................................................................................................ 11
1.3.1 Ellipticity Correlations ............................................................................................................. 11
1.3.2 Sky Coverage ........................................................................................................................... 12
1.3.3 Integrated Astrometric Performance ..................................................................................... 12
1.4 Data Processing and Management ................................................................................................ 13
1.4.1 Data Processing for Single Visits and Transients .................................................................... 13
1.4.2 Data Release Processing ......................................................................................................... 13

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
iii
2
System Capabilities ............................................................................................................................. 14
2.1 Optical Configuration ..................................................................................................................... 14
2.1.1 Effective Aperture ................................................................................................................... 15
2.1.2 Field Of View ........................................................................................................................... 15
2.1.3 Effective Etendue .................................................................................................................... 15
2.1.4 Atmospheric Dispersion Correction ........................................................................................ 16
2.1.5 Stray and Scattered Light ........................................................................................................ 16
2.1.6 Science Instrument ................................................................................................................. 16
2.2 Observatory Control Capabilities ................................................................................................... 16
2.2.1 Central Administration ............................................................................................................ 17
2.2.2 Autonomous Operation .......................................................................................................... 17
2.2.3 Survey Scheduling ................................................................................................................... 17
2.2.4 Scientific Oversight During Data Collection ............................................................................ 17
2.2.5 Process Command and Control .............................................................................................. 17
2.3 Data Collection ............................................................................................................................... 18
2.3.1 Science Data ............................................................................................................................ 18
2.3.2 Photometric Calibration Data ................................................................................................. 19
2.3.3 Engineering Data ..................................................................................................................... 19
2.3.4 Ancillary Data .......................................................................................................................... 19
2.4 Data Products and Processing ....................................................................................................... 19
2.4.1 Calibrated Image Production .................................................................................................. 20
2.4.2 Catalog Production ................................................................................................................. 20
2.4.3 Calibration Data Products ....................................................................................................... 20
2.4.4 Optical Transient Alert Production ......................................................................................... 20
2.4.5 Science Data Products ............................................................................................................ 22
2.5 Data Archiving & Services .............................................................................................................. 27
2.5.1 Raw Image Data Archiving ...................................................................................................... 27

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
iv
2.5.2 Meta Data Archiving ............................................................................................................... 27
2.5.3 Data Product Archiving ........................................................................................................... 27
2.5.4 Engineering and Environmental Data Archiving ..................................................................... 28
2.5.5 Public Data Release ................................................................................................................. 28
2.5.6 Community Computing Services ............................................................................................. 29
2.5.7 Data Curation .......................................................................................................................... 29
3
Survey Operation & Administration.................................................................................................... 30
3.1 Operational Safety ......................................................................................................................... 30
3.2 Science Priorities and Survey Monitoring ...................................................................................... 30
3.2.1 Science Objectives Definition ................................................................................................. 30
3.2.2 Adjustment of Survey Priorities .............................................................................................. 30
3.2.3 Survey Performance Reviews ................................................................................................. 30
3.2.4 Survey Performance Evaluation .............................................................................................. 31
3.3 Overall Operational Efficiency ....................................................................................................... 31
3.3.1 Survey Time Allocation ........................................................................................................... 31
3.3.2 System Operational Lifetime .................................................................................................. 31
3.3.3 Graceful Degradation .............................................................................................................. 31
3.4 LSST Broader Impacts ..................................................................................................................... 32
3.4.1 EPO Users ................................................................................................................................ 32
3.4.2 EPO Products, Tools, and Interfaces ....................................................................................... 32
3.4.3 EPO User Impacts .................................................................................................................... 33
3.4.4 EPO Longevity ......................................................................................................................... 33
3.4.5 EPO Fully Integrated ............................................................................................................... 33

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
v

Back to top


The LSST System Requirements
Project Background
The LSST is a large-aperture, wide-field, ground-based telescope that will survey the visible sky every
few nights in six photometric bands. The 10-year survey will produce a database suitable for answering a
wide range of pressing questions in astrophysics, cosmology, and fundamental physics. LSST is designed
to be a public facility. The images, alerts, and resulting catalogs will be made available to a broad
community with no proprietary period. A sophisticated data management system will provide easy
access to these data, enabling simple queries from individual users (both professionals and laypersons),
as well as computationally intensive scientific investigations that utilize the entire dataset.
Document Scope
This LSST System Requirements (LSR) document provides a comprehensive definition of the highest level
of LSST Observatory system requirements. Contents of the document are generated out of the SysML
based LSST System Architecture model (see Claver et al, 2010). It is derived from the LSST Science
Requirements Document [LSST LPM-17] that describes the scientific motivations for the project, the
survey capabilities and the reference science missions used to develop detailed scientific specifications
for the LSST survey. This document builds on those to fully describe the specific nature of the LSST
survey, final data products, and derived system functions and specifications that must be met in the
execution of the LSST project.
These requirements cover the following areas:
Adopted survey performance parameters from the SRD table and Technical requirements
extracted from the SRD text,
Required system capabilities for
1. Optical configuration
2. Data collection functions and performance
3. Data processing functions and performance
4. Archiving and services functions and performance
Survey operation and administration functions
Acronyms and Definitions of Terms
In this document a
requirement
refers to a declaration of a specified function or quantitative
performance that the delivered system or subsystem must meet. It is a statement that identifies a
necessary attribute, capability, characteristic, or quality of a system in order for the delivered system or
subsystem to meet a derived or higher requirement, constraint, or function.
This document uses the term
specification(s)
to mean one or more performance parameter(s) being
established by a requirement that the delivered system or subsystem must meet.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
vi
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 chose site). A constraint in not a characteristic of the system or subsystem itself
possesses.
Glossary of Abbreviations
(
Document-11921
)
Glossary of Definitions
(
Document-14412
)
Reference Documents
The LSST Science Requirements Document (LPM-17)
The Observatory System Specifications (LSE-30)

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
1

Back to top


The LSST System Requirements
1 Survey Design Specifications
ID: LSR-REQ-0080
Last Modified: 1/27/2015
Requirement:
The LSST system shall be designed such that the system achieves a survey with the following
scientific and performance requirements.
Discussion:
The LSST SRD specifies a suite of requirements for the scientific performance of the survey with
minimum, design, and stretch goals. For the purpose of establishing the system design and flow down to lower level
requirements a single value for each parameter for these requirements is defined here. The requirements that follow
establish which specific value for each of the SRD performance parameters has been adopted, from within the SRD-
defined ranges for the system design.
Further additional requirements and parameters have been pulled out of the body text in the SRD as identified
requirements.
In nearly all cases the SRD design specification has been adopted for each parameter. It is explicitly noted where the
design specification has not been adopted.
1.1 Filter Set Characteristics
ID: LSR-REQ-0081
Last Modified: 1/27/2015
Requirement:
The LSST survey shall provide imaging in 6 spectral bandpasses that are defined in the following
requirements for the
Filter Complement
and the
Filter Bandpass Performance
.
1.1.1 Filter Complement
ID: LSR-REQ-0082
Last Modified: 3/16/2011
Requirement:
The filter set to be used during the lifetime of the survey shall comprise a complement of least 6
filters,
FC
, providing uniform sampling across the optical spectrum. The active complement shall be changeable
within
TDFMax
hours.
1.1.1.1 filterComplement
ID:
Last Modified: 7/14/2010
Description
Value
Unit
Name
The ugrizy filter set is based on the filters from the SDSS with the
addition of the y-band. These provide roughly uniform sampling of
the optical spectrum from 320-1000nm.
ugrizy
FC
1.1.2 Filter Complement Swap Time
ID: LSR-REQ-0103
Last Modified: 1/27/2015

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
2
Requirement:
The active complement shall be changeable within
TDFMax
hours.
1.1.2.1 maxFiltSwapTime
ID:
Last Modified: 3/15/2011
Description
Value
Unit
Name
This is the time allowed for swapping out any filter in the internal
complement of
nFilters
filters (those available on a nightly basis)
for another filter from the full complement
FC
.
8
Hour
TDFmax
1.1.3 Night Filter Availability
ID: LSR-REQ-0083
Last Modified: 3/16/2011
Requirement:
The number of filters available for use in the course of a night shall be at least
NFilters
, with no
more than
TFMax
seconds required to change the active filter.
1.1.3.1 nightlyFilters
ID:
Last Modified: 7/14/2010
Description
Value
Unit
Name
The number of filters available on a nightly basis within the required
change time.
5
int
NFilters
The total time allowed to change the selected internal filter. This
time includes any time needed to configure the LSST hardware to
execute the change and then return to normal operations.
120
Seconds
TFMax
1.1.4 Filter Bandpass Performance
ID: LSR-REQ-0084
Last Modified: 1/27/2015
Requirement:
The filter bandpasses shall have a maximum out of band leakage in an any 10nm interval of no more
than FLeak relative to the peak filter response more than one FWHM from the filter center wavelength, with the
total integrated leak outside the first 0.1% response points no more than FLeakTot relative to the total transmission.
Discussion:
The rationale is that this form of a requirement moves the max out of band leakage out to beyond the
foot of the filter response, and avoids the computational problem with the original spec. Furthermore this form does
not leave a gap between the 0.1% response and the FWHM point since the integrated out-of-band is maintained to
the first 0.1%, which controls the overall foot.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
3
Issue:
This requirement deviates from what is in the SRD. It is not possible to meet the requirement as stated in the
SRD. A change request to the SRD is pending to rectify the differences here.
1.1.4.1 bandpassPerformance
ID:
Last Modified: 7/14/2010
Description
Value
Unit
Name
The maximum out of band leakage in any 10nm interval relative to
the peak filter response outside first instance of reaching 0.1%
relative response..
0.01
Percent
FLeak
The integrated leak is measured from 300-1200nm.
0.05
Percent
FLeakTot
1.1.5 Filter Temporal Stability
ID: LSR-REQ-0085
Last Modified: 3/16/2011
Requirement:
The temporal stability of the filter bandpasses shall be sufficiently small such that the required
photometric calibration repeatability requirements can be met.
1.2 Single Image Performance
ID: LSR-REQ-0086
Last Modified: 1/27/2015
Requirement:
The LSST shall meet the following requirements for a
single standard visit
(defined by LSR-REQ-
0016) performance:
1. Delivered Image Quality
2. Photometric Performance
3. Astrometric Performance
4. Image Depth
Discussion:
The SRD defines a "single image" as the coaddition of the two exposures in a standard visit (see SRD
sections 3.2 and 3.3.2).
1.2.1 Delivered Image Quality
ID: LSR-REQ-0007
Last Modified: 1/27/2015
Requirement:
The design requirement for the image quality requires that, for the median atmospheric seeing, the
system contribution to the delivered image quality never exceeds 15% and have the properties specified in the table
imageQuality
.
Discussion:
The design point specified here deviates from the SRD design requirement due to the conflict between
image quality and charge spreading in the thick detectors, needed to achieve the desired z-band and y-band
sensitivities. Nevertheless, the adopted base system image quality of 0.4 arcsec FWHM remains within the allowed
value set by the SRD minimum specifications. Similarly the minimum specifications for encircled energy have also
been adopted.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
4
1.2.1.1 imageQuality
ID:
Last Modified: 2/22/2011
Description
Value
Unit
Name
The minimum number of pixels across the FWHM of the delivered
PSF under median atmospheric conditions (0.6 arcsec FWHM) shall
be
3
Pixels
PSFSample
Median system delivered image quality in atmospheric seeing of
0.44 arcseconds in the r and i filters.
0.59
ArcsecFWH
M
S1_0.44
Median system delivered image quality in atmospheric seeing of
0.60 arcsec in the r and i filters.
0.72
ArcsecFWH
M
S1_0.60
Median system delivered image quality in atmospheric seeing of
0.80 arcseconds in the r and i filters.
0.89
ArcsecFWH
M
S1_0.80
The maximum fraction of the images that can exceed the delivered
image size by a factor of
SX
.
10
Percent
SF1
The maximum radius of the PSF spatial profile containing 80
percent encircled energy.
0.80
Arcsec
SR1
The maximum radius of the PSF spatial profile containing 90
percent encircled energy.
1.31
Arcsec
SR2
The maximum radius of the PSF spatial profile containing 95
percent encircled energy.
1.81
Arcsec
SR3
Delivered image quality increase factor allowed over
SF1
fraction of
images.
1.1
float
SX
The maximum RSS contribution from the LSST system to the
atmospheric seeing referenced at zenith or airmass (sec(ZD)) = 1.
0.40
ArcsecFWH
M
SysIm_0
1.2.1.2 Variation Over FOV
ID: LSR-REQ-0008
Last Modified: 3/29/2011
Requirement:
The image degradation due to all system components (not including the atmosphere) over the field of
view shall be smooth and small compared to the atmospheric seeing such that no more than 10 percent of the field of
view shall be allowed to exceed a total RSS system image blur budget of
10%outlierBudget_0.44
in first quartile atmospheric seeing
10%outlierBudget_0.60
in median atmospheric seeing
10%outlierBudget_0.80
in third quartile atmospheric seeing

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
5
Discussion:
The specified budget allocations are consistent with the base system budget,
medianRMSBudget,
being
invariant with atmospheric conditions.
1.2.1.2.1 imageBudgetVariation
ID:
Last Modified: 2/17/2010
Description
Value
Unit
Name
The limiting RSS image blur that can be exceeded by 10% of the
field of view in the first quartile (0.44 arcsec FWHM) atmospheric
seeing conditions.
0.43
ArcsecFWH
M
10%outlierBudget_
0.44
The limiting RSS image blur that can be exceeded by 10% of the
field of view in the median (0.60 arcsec FWHM) atmospheric seeing
conditions.
0.46
ArcsecFWH
M
10%outlierBudget_
0.60
The limiting RSS image blur that can be exceeded by 10% of the
field of view in the third quartile (0.80 arcsec FWHM) atmospheric
seeing conditions.
0.52
ArcsecFWH
M
10%outlierBudget_
0.80
1.2.1.3 Off Zenith Degradation
ID: LSR-REQ-0087
Last Modified: 3/16/2011
Requirement
:
The system image quality is allowed to degrade as a function of Zenith Distance (angle) at the same
rate as the atmospheric turbulent seeing. The canonical dependence on zenith distance is given as sec(ZD)
ImFunc
.
Discussion:
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^I
mFunc
, the design specification for the allowed image quality budget due to the system is
0.60 arcsec at airmass of 2 and for the median seeing conditions (0.49 arcsec for X=1.4) as defined by the attributes
SysIm_60
(equivalent to
SXE
in SRD) and
SysIm_45
respectively.
1.2.1.3.1 offZenithImageQuality
ID:
Last Modified: 2/14/2011
Description
Value
Unit
Name
The system image budget is allowed to degrade through the three
reference zenith distances (ZD) as sec(ZD)
ImFunc
.
0.6
ImFunc
The maximum RSS contribution from the LSST system to the
atmospheric seeing referenced at zenith distance of 45 degrees or
airmass (sec(ZD)) = 1.4.
0.49
ArcsecFWH
M
SysIm_45
The maximum RSS contribution from the LSST system to the
atmospheric seeing referenced at zenith distance of 60 degrees or
airmass (sec(ZD)) = 2.0.
0.60
ArcsecFWH
M
SysIm_60

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
6
1.2.2 Delivered Image Ellipticity
ID: LSR-REQ-0092
Last Modified: 3/29/2011
Requirement:
The Point spread function ellipticity for bright isolated unresolved sources in images from a single
visit shall have the properties specified in the table
imageEllipticity
below.
1.2.2.1 imageEllipticity
ID:
Last Modified: 7/14/2010
Description
Value
Unit
Name
The fraction of PSF ellipticity measurements allowed to exceed the
ellipticity outlier limit for bright isolated non-saturated stars.
5
Percent
EF1
The maximum median raw PSF ellipticity over the full field of view
in a single 15 second exposure for bright isolated non-saturated
stars.
0.04
Ellipticity
SE1
The maximum PSF raw ellipticity outlier limit.
0.07
Ellipticity
SE2
1.2.3 Filter Depths
ID: LSR-REQ-0090
Last Modified: 10/4/2013
Requirement:
The single visit depth for unresolved point sources in each of the 6 LSST filters shall meet the
specifications in the following table, assuming the reference conditions specified in LSR-REQ-0089 scaled
appropriately for each filter.
Discussion:
A detailed description of the assumed inputs and methods used to calculate the 5-sigma limiting
magnitudes are given in Document-8857.
https://www.lsstcorp.org/docushare/dsweb/Get/Document-8857
1.2.3.1 filterDepths
ID:
Last Modified: 7/14/2010
Description
Value
Unit
Name
g-band point source 5-sigma detection depth median
24.8
ABmag
DB1g
i-band point source 5-sigma detection depth median
23.9
ABmag
DB1i
r-band point source 5-sigma detection depth median
24.4
ABmag
DB1r
u-band point source 5-sigma detection depth median
23.5
ABmag
DB1u
y-band point source 5-sigma detection depth median
22.1
ABmag
DB1y

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
7
z-band point source 5-sigma detection depth median
23.3
ABmag
DB1z
1.2.3.2 r-band Reference Depth
ID: LSR-REQ-0089
Last Modified: 1/27/2015
Requirement:
The single visit median depth in the r-band for unresolved point sources shall meet the specifications
in the following table, assuming the reference conditions specified therein.
Discussion:
The SNR v1.2 (Document-8857) calculation assumes optimal extraction even for sources near the noise
limit. Optimal extraction is applicable to time series photometry, and this is extrapolated to the background limited
extreme in all bands but u.
https://www.lsstcorp.org/docushare/dsweb/Get/Document-8857
1.2.3.2.1 r-bandRefDepth
ID:
Last Modified: 7/14/2010
Description
Value
Unit
Name
Given the median detection depth for a visit as MVD(i), the
distribution of MVD(i) shall have a median r-band 5-sigma limiting
magnitude no brighter than
D1
for unresolved point sources.
24.7
ABmag
D1
The fraction of the images with a median 5-sigma point source
detection depth (MVD(i)) brighter than the depth outlier limit (
Z1
)
shall be no more than
DF1.
10
Percent
DF1
The reference airmass under which the depth specifications shall be
met is
refAirmass.
1.0
Airmass
refAirmass
The reference exposure time for which the single image depth
specifications shall be met is
refExposureTime.
30
Seconds
refExposureTime
The reference atmospheric seeing for which the depth specifications
shall be met is
refSeeing
as measured in the r-band.
0.7
ArcsecFWH
M
refSeeing
The reference sky surface brightness for which the depth
specifications shall be met is
refSkyBrightness
as measured in the
r-band.
21
mag/SqArcs
ec
refSkyBrightness
The outlier limit for 5-sigma point source detection depth is
Z1
.
24.4
ABmag
Z1
1.2.3.3 Depth Variation Over FOV
ID: LSR-REQ-0109
Last Modified: 3/11/2015
Requirement:
An image meeting the median depth defined by the requirement
Filter Depths
(LSR-REQ-0090)
shall meet the specification for depth distribution given in
depthVarFOV
below.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
8
Discussion:
The variations in depth allowed for in this requirement are less stringent than those implied by the
variation in image quality. This requirement is meant to allow for variations in sensor sensitivity and effects of
vignetting. The intent of this requirement is to restrict using low QE sensors in the focal plane array is met by
requiring the camera detectors meet their minimum QE specifications (see OSS-REQ-0256 in the flow down).
1.2.3.3.1 depthVarFOV
ID:
Last Modified: 3/16/2011
Description
Value
Unit
Name
The maximum area over the 3.5 degree field-of-view with a 5-sigma
point source detection brighter than
Z2
above the median limiting
magnitude for that visit shall be no greater than
DF2
.
15%
Percent
DF2
The allowed 5-sigma detection outlier limit is Z2..
0.2
ABmag
Z2
1.2.4 Photometric Performance
ID: LSR-REQ-0093
Last Modified: 3/11/2015
Requirement:
The photometric quality of images from a single visit shall meet the specifications listed in the table
photometricPerformance
below.
Discussion:
The specifications for photometric repeatability, PA1, PA2 and PF1, applies to the cataloged LSST
magnitudes, m
std
(catalog) (see SRD eq. 8), for appropriately chosen main sequence stars (e.g. non-variable stars
color-selected from the main stellar locus).
1.2.4.1 photometricPerformance
ID:
Last Modified: 3/11/2015
Description
Value
Unit
Name
Percentage of image area that can have ghosts with surface
brightness gradient amplitude of more than 1/3 of the sky noise over
1 arcsec.
1
Percent
GhostAF
The RMS photometric repeatability of bright non-saturated
unresolved point sources in the
g
,
r,
and
i
filters.
5
mili-Mag
PA1gri
The RMS photometric repeatability of bright non-saturated
unresolved point sources in the
u
,
z
, and
y
filters.
7.5
mili-Mag
PA1uzy
Repeatability outlier limit for isolated bright non-saturated point
sources in the
g
,
r
, and
i
filters.
15
mili-Mag
PA2gri
Repeatability outlier limit for isolated bright non-saturated point
sources in the
u
,
z
, and
y
filters.
22.5
mili-Mag
PA2uzy

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
9
RMS width of internal photometric zero-point (precision of system
uniformity across the sky) for all bands except u-band.
10
mili-Mag
PA3
RMS width of internal photometric zero-point (precision of system
uniformity across the sky) in the u-band.
20
mili-Mag
PA3u
Accuracy of absolute band-to-band color zero-point for all colors
constructed from any filter pair, excluding the u-band.
5
mili-Mag
PA5
Accuracy of absolute band-to-band color zero-point for colors
constructed using the u-band.
10
mili-Mag
PA5u
Accuracy of the transformation of the internal LSST photometry to a
physical scale (e.g. AB magnitudes).
10
mili-Mag
PA6
The maximum fraction of isolated non-saturated point source
measurements exceeding the outlier limit.
10
Percent
PF1
Fraction of zeropoint errors that can exceed the zero point error
outlier limit.
10
Percent
PF2
The zero point error outlier limit.
15
mili-Mag
PF4
The maximum fraction of pixels scientifically unusable per sensor
out of the total allowable fraction of sensors meeting this
performance.
1
Percent
PixFrac
Maximum RMS of the ratio of the error in integrated flux
measurement between bright, isolated, resolved sources less than 10
arcsec in diameter and bright, isolated unresolved point sources.
2
ResSource
The maximum error in the precision of the sky brightness
determination.
1
Percent
SBPrec
The maximum allowable fraction of sensors with
PixFrac
scientifically unusable pixels.
15
Percent
SensorFraction
The maximum local significance integrated over the PSF of
imperfect crosstalk corrections.
3
Sigma
Xtalk
1.2.5 Astrometric Performance
ID: LSR-REQ-0094
Last Modified: 1/27/2015
Requirement:
The astrometric quality of images from a single visit shall meet the specifications listed in the table
astrometricPerformance
below.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
10
1.2.5.1 astrometricPerformance
ID:
Last Modified: 7/14/2010
Description
Value
Unit
Name
Median error in absolute position for each axis, RA & DEC, shall be
less than
AA1
.
50
mili-Arcsec
AA1
RMS difference between separations measured in the r-band and
those measured in any other filter.
10
mili-Arcsec
AB1
The color difference outlier limit for separations measured relative
the r-band filter in any other filter.
20
mili-Arcsec
AB2
Fraction of separations measured relative to the r-band that can
exceed the color difference outlier limit.
10
Percent
ABF1
5 arcminute outlier limit.
20
mili-Arcsec
AD1
20 arcminute outlier limit.
20
mili-Arcsec
AD2
200 arcminute outlier limit.
30
mili-Arcsec
AD3
The maximum fraction of relative astrometric measurements on 5
arcminute scales to exceed 5 arcminute outlier limit.
10
Percent
AF1
The maximum fraction of relative astrometric measurements on 20
arcminute scales to exceed 20 arcminute outlier limit.
10
Percent
AF2
Fraction of relative astrometric measurements on 200 arcminute
scales to exceed 200 arcminute outlier limit.
10
Percent
AF3
Median relative astrometric measurement error on 5 arcminute
scales shall be less than
AM1
.
10
mili-Arcsec
AM1
Median relative astrometric measurement error on 20 arcminute
scales.
10
mili-Arcsec
AM2
Median relative astrometric measurement error on 200 arcminute
scales.
15
mili-Arcsec
AM3
1.2.6 Bright Sources
ID: LSR-REQ-0095
Last Modified: 10/3/2013
Requirement:
The LSST shall be capable of unsaturated measurements of sources brighter than the nominal 15-
second saturation limit by at least
brightSource.
Discussion:
This is not a requirement on the ability to measure saturated sources in standard visits. It is largely a

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
11
requirement on the capability of the system to acquire and process visits of such duration that an object
brightSource
brighter than the nominal saturation limit would not be saturated (e.g., to support overlaps with
brighter external catalogs).
1.2.6.1 brightSources
ID:
Last Modified: 7/14/2010
Description
Value
Unit
Name
The LSST shall be capable of unsaturated measurements of sources
brighter than the nominal 15-second saturation limit by at least
brightSource.
1.0
ABmag
brightSource
1.3 Full Survey Performance
ID: LSR-REQ-0096
Last Modified: 3/16/2011
Requirement:
Integrated over all survey observations made over a 10 year period the LSST shall meet all
specifications for
skyCoverage
and
overallEllipticityCorrelations
.
1.3.1 Ellipticity Correlations
ID: LSR-REQ-0097
Last Modified: 10/3/2013
Requirement:
Using the full survey data, the E1 and E2 (see SRD for definitions) distributions averaged over an
arbitrary FOV shall have medians less than
TE1
for theta ~ 1 arcmin, and less than
TE3
for theta < 5 arcmin. No
more than
TEF
% of images shall have these medians for E1 and E2 larger than
TE2
for theta ~ 1 arcmin, or larger
than
TE4
for theta < 5 arcmin.
Discussion:
The requirements specified here require the full survey data set to exist before they can be met. Thus
these are intended to ensure that the LSST system design enables that these requirements can be met after the 10-
year survey. Prior to survey start, they will be verified to the extent possible using simulations incorporating the as-
built telescope and camera performance characteristics.
1.3.1.1 overallEllipticityCorrelations
ID:
Last Modified: 6/29/2010
Description
Value
Unit
Name
Median residual PSF ellipticity correlations averaged over an
arbitrary field of view for separations less than 1 arcmin shall be no
greater than
2.0e-5
TE1
Median residual PSF ellipticity correlations averaged over an
arbitrary field of view for separations between 1 and 5 arcmin shall
be no greater than
1.0e-7
TE2
The outlier limit on the PSF ellipticity correlation residuals on 1
4.0e-5
TE3

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
12
arcminute scales shall be no more than
The outlier limit on the PSF ellipticity correlation residuals on 5
arcminute scales shall be no more than
2.0e-7
TE4
The fraction of PSF ellipticity correlation residuals that can exceed
the outlier limits on 1 and 5 arcminutes scales, over an arbitrary
field, of view shall be no more than
15
Percent
TEF
1.3.2 Sky Coverage
ID: LSR-REQ-0098
Last Modified: 3/16/2011
Requirement:
Integrated over all survey observations made over a 10 year period the LSST shall meet all
specifications for
skyCoverage.
1.3.2.1 skyCoverage
ID:
Last Modified: 6/29/2010
Description
Value
Unit
Name
The total area of sky covered by the median number of visits shall
be no less than
18000
SquareDegr
ees
Asky
Upper limit of time intervals for the required "fast revisit" range, for
the fraction of sky specified by
RVA1
.
1800
Seconds
fastRevisitMax
Lower limit of time intervals for the required "fast revisit" range, for
the fraction of sky specified by
RVA1
.
40
Seconds
fastRevisitMin
The median number of visits for each place of the sky within the
main survey area shall be at least
825
Visits
Nv1Sum
The minimum area of sky covered at nearly uniformly sampled
revisit time scales between
fastRevisitMin
and
fastRevisitMax
.
2000
SquareDegr
ees
RVA1
1.3.3 Integrated Astrometric Performance
ID: LSR-REQ-0099
Last Modified: 3/16/2011
Requirement:
For all observations of unresolved point sources having r<24, after 10 years the astrometric
performance shall meet the specifications in the table
astrometricPerf
below.
Discussion:
These requirements constrain the distribution in time over 10 years such that the parallax factor is even
sampled and that the time baseline is sufficient to meet the proper motion performance specification.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
13
1.3.3.1 astrometricPerformance
ID:
Last Modified: 11/19/2010
Description
Value
Unit
Name
The median parallax uncertainty (sigma) for sources with r=24 or
brighter shall be no more than
SiGpar
.
3.0
mili-Arcsec
SIGpar
The median parallax uncertainty (sigma) in the y-band shall be no
more than
SiGparRed
.
6.0
mili-Arcsec
SIGparRed
The median proper motion accuracy per coordinate across the main
survey area for sources brighter than r=24 must be at least SIGpm.
1.0
mili-Arcsec
SIGpm
1.4 Data Processing and Management
ID: LSR-REQ-0100
Last Modified: 2/22/2011
1.4.1 Data Processing for Single Visits and Transients
ID: LSR-REQ-0101
Last Modified: 3/16/2011
Requirement:
The LSST shall meet the following specification for reporting of data on optical transients detected
in single-visit data:
OTT1
,
transN
, and
transSNR
.
Discussion:
It is unclear whether the SRD specification of
transN
refers to the number of alerts that can be
generated for a single visit (i.e. an instantaneous limit), or the number per visit averaged over time.
1.4.1.1 visitProcessing
ID:
Last Modified: 11/18/2010
Description
Value
Unit
Name
The latency of reporting optical transients following the completion
of readout of the last image of a visit
1
Minute
OTT1
The minimum number of optical transients for which data can be
reported per visit
1.0e4
int
transN
The signal-to-noise ratio in single-visit difference images above
which all optical transients are to be reported.
5
float
transSNR
1.4.2 Data Release Processing
ID: LSR-REQ-0102
Last Modified: 3/16/2011

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
14
Requirement:
Specific, fixed "snapshots" of the data (
data releases
) of the data shall be released to the public
periodically, at least every
DRT1
years.
Discussion:
The project is planning on at least two Data Releases in the first year of opperations.
1.4.2.1 dataReleaseInterval
ID:
Last Modified: 7/19/2010
Description
Value
Unit
Name
The minimum interval between standard Data Releases
1
Years
DRT1
2 System Capabilities
ID: LSR-REQ-0001
Last Modified: 5/24/2011
Requirement:
In order to perform a survey as defined above and present the data in a scientifically useful manner
the LSST Observatory shall be a complete system that:
1. obtains survey data in the form of digital images,
2. processes, calibrates, and archives the images,
3. generates source and object catalogs, and
4. makes all data and data products available to a wide range of users.
Discussion:
The requirements that define the system capabilities have been organized into 4 groupings that
characterize the high level performance and functional requirements that must be met. The 4 groupings include:
1.
The Optical Configuration:
These requirements specify the type of optical design, field of view, effective
aperture, and overall system throughput that are derived from the SRD.
2.
Observatory Control Capabilities:
These requirements specify the overall control and administration
functions needed to conduct the survey and ensure that the LSST is responsive to the scientific community of its
lifetime.
3.
Data Collection:
These requirements specify in broad terms the data collection functions the LSST system
must have in order to conduct the specified survey, optimize its operation, and record knowledge of its physical
state during routine operation.
4.
Data Products & Processing:
These requirements specify the high-level definition of the LSST data and data
quality products to be delivered to the user community and what process must occur to create these products.
5.
Data Archiving and Services:
These requirements define the high-level archiving and data delivery functions
that are needed to deliver the LSST data and Data Products to its intended user base. Also included are the
definitions of other data processing services that will be provided by the LSST system
2.1 Optical Configuration
ID: LSR-REQ-0002
Last Modified: 3/16/2011
Requirement:
The LSST optical configuration shall be from the anastigmatic class of optical designs meeting the
specification given below.
Discussion:
The anastigmatic design class eliminates 3rd order astigmatism across the field of view.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
15
2.1.1 Effective Aperture
ID: LSR-REQ-0003
Last Modified: 3/16/2011
Requirement:
The on-axis effective light collecting area of the LSST shall be equivalent to a clear unobstructed
circular aperture of at least
effAperture
.
2.1.1.1 effectiveAperture
ID:
Last Modified: 10/27/2009
Description
Value
Unit
Name
The on-axis effective aperture diameter - equivalent to 33.2 square
meters of collecting area.
6.5
Meters
effAperture
2.1.2 Field Of View
ID: LSR-REQ-0004
Last Modified: 3/16/2011
Requirement:
The field of view of the LSST optical system shall be at least an angle
fieldOfView
in diameter.
Discussion:
The FOV defined here is not meant to be the final effective FOV recorded by the LSST camera. This is
meant to be a nominal optical configuration requirement from which the optical design is derived.
2.1.2.1 fieldOfView
ID:
Last Modified: 10/27/2009
Description
Value
Unit
Name
The diameter of the field of view - equivalent to 9.6 square degrees
of sky coverage.
3.5
Degrees
fieldOfView
2.1.3 Effective Etendue
ID: LSR-REQ-0005
Last Modified: 3/16/2011
Requirement:
The LSST optical system shall have an effective etendue (effective collecting
x
area of sky recorded
in each image integrated over the
fieldOfView
) of at least
etendueRec
.
Discussion:
The specified value is less than the product of
effAperture
and
fieldOfView
because of vignetting and
focal plane fill factor.
2.1.3.1 etendueRec
ID:
Last Modified: 2/17/2010
Description
Value
Unit
Name

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
16
The effective collecting area integrated over the field of view * field
of view area recorded in each image.
280
Etendue
etendueRec
2.1.4 Atmospheric Dispersion Correction
ID: LSR-REQ-0006
Last Modified: 3/16/2011
Requirement:
An atmospheric dispersion corrector (ADC) is not required in the LSST system design.
Discussion:
The project undertook a detailed trade study during the early conceptual phase of the project to
determine if an ADC is needed and if it was even feasible to design and build an ADC large enough to accommodate
the LSST field of view. This trade study concluded that an ADC was feasible but was not necessary provided that
the survey observations were kept below 1.4 airmasses for that science needing the most control of the PSF shape.
The minimum survey area is achievable while staying below 1.4 airmasses. (Documentation relating to this study is
contained in Collection-894 on the LSST Document Archive).
https://www.lsstcorp.org/docushare/dsweb/View/Collection-894
2.1.5 Stray and Scattered Light
ID: LSR-REQ-0009
Last Modified: 3/16/2011
Requirement:
The LSST design shall control the effects of stray and scattered light to the extent necessary to meet
the performance in the Survey Specifications.
Discussion:
Stray and scattered light is defined as any light that is not part of the ideal image and includes:
diffuse scattered light,
secondary ghost images,
diffraction, and
structured glints.
2.1.5.1 Baffling
ID: LSR-REQ-0011
Last Modified: 3/16/2011
Requirement:
The LSST optical system shall be baffled as required to ensure that no unwanted specular path can
put light onto the LSST focal plane.
2.1.6 Science Instrument
ID: LSR-REQ-0012
Last Modified: 3/16/2011
Requirement:
The LSST system shall contain a single science instrument - the Camera.
Discussion:
By the very nature of conducting a consistent well calibrated survey the LSST will not need to support
the multiple instruments often found on classical telescope systems.
2.2 Observatory Control Capabilities
ID: LSR-REQ-0067
Last Modified: 3/16/2011

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
17
Requirement:
The observatory shall be developed with the necessary control centers to achieve the LSST
objectives. This shall include, as a minimum, the capabilities defined here.
2.2.1 Central Administration
ID: LSR-REQ-0068
Last Modified: 3/16/2011
Requirement:
A central location shall serve as Project Headquarters for operational coordination and project
interfaces to supporting agencies.
Discussion:
The LSST Observatory will be a distributed set of assets functioning for the specific objectives of
executing the survey and serving the raw data and its data products to the public.
2.2.2 Autonomous Operation
ID: LSR-REQ-0072
Last Modified: 3/16/2011
Requirement:
The LSST system shall operate in a locally supervised autonomous mode during routine survey data
collection and processing, with little human intervention required.
Discussion:
It is not practical to expect human driven observations to keep pace with the observing cadence dictated
by the LSST survey requirements.
2.2.3 Survey Scheduling
ID: LSR-REQ-0062
Last Modified: 3/16/2011
Requirement:
The Observatory shall include a dynamic scheduler sufficient to achieve the survey requirements in
the presence of changing observing conditions, nightly technical performance, and previous survey performance.
2.2.4 Scientific Oversight During Data Collection
ID: LSR-REQ-0071
Last Modified: 3/16/2011
Requirement:
The LSST Observatory shall be developed to allow an observing scientist to have oversight of the
Data Collection process. This interaction shall be enabled either locally on the summit or at remote locations. The
data provided shall include all observing condition data, telemetry data to assess telescope conditions, and science
data quality metrics for evaluation of the data collection process.
Discussion:
The objective this requirement is to enable the observing scientist to be directly involved in the
observing process. Under normal circumstances the observing scientist will not intervene with the autonomous
operations (LSR-REQ-0072), but should be allowed to override if anomalous behavior occurs.
2.2.5 Process Command and Control
ID: LSR-REQ-0069
Last Modified: 3/16/2011
Requirement:
In addition to the connectivity required for the science data, the observatory shall include the
necessary capability to command and control the process from multiple centers and to adjust for changing
environmental, technical, and scientific conditions.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
18
2.3 Data Collection
ID: LSR-REQ-0013
Last Modified: 3/16/2011
Requirement:
The LSST shall provide a Data Collection system that is capable of providing all necessary data to
meet the SRD survey specifications including science image data and all ancillary data needed to calibrate the
survey and to optimize operations.
2.3.1 Science Data
ID: LSR-REQ-0014
Last Modified: 3/16/2011
Requirement:
The observatory shall collect science images as a series of "visits", sequenced by an automated
system that optimizes the scientific return of the survey according to established priorities, taking into account
environmental and sky conditions in the course of each night.
2.3.1.1 Standard Visit
ID: LSR-REQ-0016
Last Modified: 3/16/2011
Requirement:
The bulk of the survey shall be performed as a sequences of "standard Visits", defined as
nVisitexp
back to back exposures in one of the system spectral bands, each having an exposure time of
visitExpTime
.
2.3.1.1.1 visitParameters
ID:
Last Modified: 3/11/2015
Description
Value
Unit
Name
The number of exposures,
nVisitExp
, in a standard visit shall be
2
int
nVisitExp
The exposure time,
visitExpTime
, for single images in a standard
visit shall be
15
Seconds
visitExpTime
2.3.1.2 Non-Standard Visit
ID: LSR-REQ-0111
Last Modified: 3/11/2015
Requirement:
The LSST shall be capable of obtaining and processing exposure not taken in a standard visit mode
including those with minimum exposure time of
minExpTime
.
Discussion:
Non-standard visits are defined as having a number of exposures per visit and visit exposure time
different from the values of
nVisitExp
and
visitExpTime
respectively, specified in
LSR-REQ-0016
. Non-standard
visit exposures may possibly be degraded in some aspects of performance (e.g. cosmic ray rejection on visits
consisting of a single exposure).
2.3.1.2.1 minimumExposureTime
ID:
Last Modified: 3/11/2015

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
19
Description
Value
Unit
Name
The maximum shortest exposure time of a single exposure is
minExpTime
.
1
Seconds
minExpTime
The goal for the shortest exposure time of a single exposure is
minExpTimeGoal
.
0.1
Seconds
minExpTimeGoal
2.3.1.3 Data Format
ID: LSR-REQ-0015
Last Modified: 3/16/2011
Requirement:
The LSST survey data shall be collected in the form of pixel addressable digital images that preserve
the full information content of the LSST instrument.
2.3.2 Photometric Calibration Data
ID: LSR-REQ-0017
Last Modified: 3/23/2011
Requirement:
The LSST shall measure and record data relating to instrumental and atmospheric transmission as
necessary to photometrically calibrate the science data, referenced to the top of the Earth's atmosphere.
2.3.3 Engineering Data
ID: LSR-REQ-0018
Last Modified: 3/16/2011
Requirement:
The LSST data collection system shall collect engineering and environmental data necessary to
capture the physical state of the observatory, its components, and surrounding environment, during all modes of
operation.
2.3.4 Ancillary Data
ID: LSR-REQ-0019
Last Modified: 3/16/2011
Requirement:
The LSST system shall measure and record the data required as input to the optimization of the
acquisition of survey data as well as record the environmental conditions that existed during each exposure. These
data shall include but are not limited to:
1. atmospheric seeing;
2. cloud cover; and
3. meteorological information (temperatures, wind, humidity etc..)
2.4 Data Products and Processing
ID: LSR-REQ-0020
Last Modified: 3/16/2011
Requirement:
The system shall process the raw image data from the camera to produce calibrated images, analyze
them to generate source and object catalogs, detect and generate alerts for transient phenomena, and record the
quality of the data collected and its processing provenance.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
20
Discussion:
The Observatory is expected to process and calibrate the data from the entire focal plane. While the
SRD requirements on image quality and depth are specified as applying only within the nominal 3.5-degree field of
view, the data processing is nevertheless expected to strive to maximize the scientific usability of the data outside
the nominal field.
2.4.1 Calibrated Image Production
ID: LSR-REQ-0021
Last Modified: 10/3/2013
Requirement:
The LSST data processing system shall process raw image data to produce photometrically and
astrometrically calibrated images, both from single visits and from deep coadds.
Discussion:
The single-visit and deep-coadd image-level calibrations are a subset of the final catalog-level
calibrations, which will be done in later stages of the processing flow (LSR-REQ-0029).
2.4.2 Catalog Production
ID: LSR-REQ-0029
Last Modified: 10/3/2013
Requirement:
The data processing system shall process calibrated image data to produce catalogs with
photometrically and astrometrically calibrated sources and objects.
Discussion:
"Sources" refer to measured properties from an astrophysical event or object in a single individual visit,
where as "Objects" refer to the inferred properties of the underlying astrophysical phenomenon, given information
collected from all visits to date.
2.4.3 Calibration Data Products
ID: LSR-REQ-0030
Last Modified: 3/16/2011
Requirement:
The data processing system shall, from time to time, generate Calibration Data Products, including
bias frames and flat fields, as required by the other processing functions.
Discussion:
These will typically appear at time scales intermediate to those of the Level 1 and Level 2 Data
Products as described below. The Alert Production will require calibration data products of sufficient timeliness and
quality to permit instrument signature removal prior to transient detection. These must be updated as often as
necessary to meet this need. Data Release Production will require higher-quality calibrations, but the production of
these may be done as part of the preparations for each new Data Release, i.e., annually.
2.4.4 Optical Transient Alert Production
ID: LSR-REQ-0022
Last Modified: 3/16/2011
Requirement:
The LSST data processing system shall process raw image data to detect optical transients and
generate alerts to the astronomical community based on these detections.
2.4.4.1 Optical Transi
e
nt Event Detection
ID: LSR-REQ-0023
Last Modified: 3/16/2011
Requirement:
Transient events above one or more thresholds shall be detected in acquired raw images, and their
detection and associated parameters shall be archived and made available for future transient classification.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
21
Discussion:
SRD flow down for transient detection is described in LSR-REQ-101.
2.4.4.2 Optical Transient Event Classification
ID: LSR-REQ-0024
Last Modified: 3/16/2011
Requirement:
The data processing for Optical Transient Alert production shall differentiate between moving
objects and other types of optical transients and shall reject cosmic rays and other non-astrophysical sources of
transients, to the extent practicable. Cosmic-ray rejection will primarily be based on the use of exposure pairs. If a
detected transient can be associated with a previously observed object, the processing shall include a calculation of
the probability that the object is variable, based on prior observations.
Discussion:
It is not possible to differentiate between moving objects and other types of optical transients in all
cases. For slowly moving objects, we can do so only to the extent that the catalog of moving objects is complete,
and this will never be 100%. At the beginning of the survey, it will be very incomplete, unless we are able to
initialize it based on a precursor survey.
2.4.4.3 Optical Transient Alert Generation
ID: LSR-REQ-0027
Last Modified: 3/16/2011
Requirement:
Transient alerts shall be generated based on detected transients, and made available to external
consumers. Alerts shall
include measurements of position, flux, size and shape, using appropriate weighting
functions, as well as prior variability information and data from the same night, if available. Prior variability
information shall include, at minimum, low-order light- curve moments and the above assessment of the probability
that the object is variable.
Discussion:
Alerts should ideally include the full light curves in all available bands as well.
2.4.4.3.1 Transient Filtering
ID: LSR-REQ-0025
Last Modified: 3/16/2011
Requirement:
Given an alert-detection algorithm chosen to meet LSR-REQ-0027, the algorithm shall be applied
and the alert transmitted within the specified latency for at least a fraction
OTR1
of instances where the image data
contains a transient detectable by the algorithm. The remaining transients so detectable must still be identified and
recorded at the next processing opportunity.
Discussion:
This requirement is on the production system given a particular algorithm and covers both detection and
latency. This requirement constrains the reliability and timeliness of application of the algorithm and the alert
publication. It does not constrain either the completeness or purity of the transient identifications themselves. It is
unspecified whether the "next processing opportunity" is a fault-tolerance fallback or the daily reprocessing at the
Archive.
2.4.4.3.1.1 alertReliability
ID:
Last Modified: 10/3/2013

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
22
Description
Value
Unit
Name
Fraction of detectable alerts for which an alert is actually transmitted
within latency
OTT1
(see LSR-REQ-0101).
98
Percent
OTR1
2.4.4.3.1.2 Predefined Transient Filters
ID: LSR-REQ-0026
Last Modified: 3/16/2011
Requirement:
Pre-defined filters optimized for traditionally popular transients shall be made available. It shall be
possible for the project to add new pre-defined filters as the survey progresses.
Discussion:
The list of pre-defined filters, by way of example, should include ones for supernovae and microlensed
sources.
2.4.5 Science Data Products
ID: LSR-REQ-0031
Last Modified: 3/15/2011
Discussion:
The requirements that follow govern the content and organization of the data products to be delivered
by the LSST Observatory and the need to support the 4 primary science missions of the LSST.
2.4.5.1 Organization of Data Products
ID: LSR-REQ-0032
Last Modified: 3/16/2011
Requirement:
The LSST data processing system shall provide the means for organizing the production of three
classes of science data products: Level 1 (nightly cadence), Level 2 (data release cadence), and Level 3 (user-
specified).
2.4.5.1.1 Level 1 Data Products
ID: LSR-REQ-0033
Last Modified: 10/3/2013
Requirement:
The LSST Observatory shall produce Level 1 Data Products as the result of processing of the stream
of image data from the Data Collection system during the course of normal observing.
Discussion:
Level 1 data products are intended to enable time-domain science use cases requiring timely alerting
and follow-up.
2.4.5.1.1.1 Level 1 Scientific Content
ID: LSR-REQ-0110
Last Modified: 10/3/2013
Requirement:
The Level 1 data products shall include:
Raw Science Images
Calibrated Science Images (trimmed, de-biased, flattened, etc.)
Difference Images
Image Metadata/Catalog

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
23
DIA Source Catalog
DIA Forced Source Catalog
DIA Object Catalog
Solar System Orbit Catalog
Transient Alerts
Nightly Data Quality Summary Report
Nightly Data Management System Performance Report
Discussion:
Level 1 products are generated by pipeline processing the stream of data from the camera system during
normal observing. Level 1 data products are therefore continuously generated and / or updated every observing
night. This process is of necessity highly automated, and must proceed with absolutely minimal human interaction.
In addition to science data products, a number of Level 1 SDQA data products are generated to assess quality and to
provide feedback to the Observatory Control System. The abbreviation "DIA" stands for "Difference Imaging
Analysis".
2.4.5.1.1.2 Level 1 Data Product Availability
ID: LSR-REQ-0104
Last Modified: 10/4/2013
Requirement:
All Level 1 Data Products except Transient Alerts & Solar System Objects shall be produced and
made publicly available within time
L1PublicT
of the acquisition of the corresponding raw images.
Discussion:
The exceptions for Transient Alerts and Solar System Objects are defined in requirements LSR-REQ-
0117 and LSR-REQ-0118, respectively.
2.4.5.1.1.2.1 L1PublicT
ID:
Last Modified: 3/15/2011
Description
Value
Unit
Name
Maximum time from the acquisition of science data to the public
release of associated Level 1 Data Products (except alerts)
24
Hour
L1PublicT
2.4.5.1.1.2.2 Level 1 Data Product Availability for Solar System Objects
ID:
ID: LSR-REQ-0118
ID:
Last Modified: 10/8/2013
Requirement:
Solar System Objects shall be made publicly available within
L1PublicT
of successful moving
source linkage and orbit computation.
Discussion:
It takes multiple visits to the same Solar System Object in order to successfully link moving sources
and compute their orbital parameters. As such, the time in which Solar System Objects can be made publicly
available is dependent upon the time it takes to obtain these multiple visit images.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
24
2.4.5.1.1.2.3 Level 1 Data Product Availability for Transient Alerts
ID:
ID: LSR-REQ-0117
ID:
Last Modified: 10/4/2013
Requirement:
Transient Alerts shall be produced and made publicly available within time
OTT1
of the acquisition
of the corresponding raw images.
Discussion:
OTT1 is the SRD (LPM-17) latency requirement and is defined in SRD section 3.4. LSR requirement
LSR-REQ-0101 defines the design value to be used for design purposes.
2.4.5.1.1.3 Calibration, Engineering, Ancillary, and Provenance Data
ID: LSR-REQ-0034
Last Modified: 3/16/2011
Requirement:
The Level 1 Data Products shall include all collected calibration, engineering, and ancillary data, and
all processing history and provenance, required to make sense of the science data.
2.4.5.1.1.4 Science Data Quality Monitoring
ID: LSR-REQ-0035
Last Modified: 3/16/2011
Requirement:
Level 1 Data Product production shall include the production of sufficient Science Data Quality
Assessment (SDQA) data, in a manner which supports feedback of observatory and observing conditions to the
Observatory Control System, and alerts to observatory operators when poor quality data are detected.
2.4.5.1.1.5 Science Data Quality Archiving
ID: LSR-REQ-0105
Last Modified: 3/16/2011
Requirement:
SDQA data produced shall be archived in association with the corresponding raw image data.
2.4.5.1.2 Level 2 Data Products
ID: LSR-REQ-0036
Last Modified: 3/16/2011
Requirement:
The LSST shall produce a set of Level 2 Data Products as the result of periodic processing of the
entire archive of raw image data from the Data Collection system.
2.4.5.1.2.1 Level 2 Scientific Content
ID: LSR-REQ-0037
Last Modified: 10/4/2013
Requirement:
The Level 2 Data Products in a Data Release shall include:
images, corrected for instrumental artifacts and photometrically and astrometrically calibrated,
measurements of the properties (positions, fluxes, shapes, motions) of all detected objects, including those
below single visit sensitivity limit;
astrometric and photometric calibration of the object catalog,

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
25
photometrically calibrated light curves for all detected objects,
orbital parameters for Solar System Objects (see discussion in LSR-REQ-0024),
limited classification of objects based on their static properties and time-domain behavior, and
deep co-added images of the full survey area on the sky.
Discussion:
The determination of motions for objects below the single-visit sensitivity limit will be constrained by
the data and by computational limits, and may have limited precision or be possible only in a limited part of
parameter space. The intent is to provide sufficient capability to support the planned TNO/KBO science.
Note that the requirement to provide light curves for "all" detected objects implies the provision of forced
photometry, for the evaluation of light curves below the single-visit sensitivity limit.
Examples of limited classification include star-galaxy separation, or assessment whether an object is variable or not
(see section 3.5 of the SRD).
2.4.5.1.2.2 Production in Data Releases
ID: LSR-REQ-0038
Last Modified: 3/16/2011
Requirement:
All Level 2 Data Products shall be produced in the context of Data Releases.
These Data Releases shall be produced at intervals no less than the Survey Specification for standardized data
release interval -
DRT1
(see LSR-REQ-0102).
Discussion:
Data Releases will be performed more frequently during the first year of the survey.
2.4.5.1.2.3 Calibration, Engineering, Ancillary, and Provenance Data
ID: LSR-REQ-0039
Last Modified: 10/4/2013
Requirement:
A release of Level 2 Data Products shall include a consistent set of all necessary calibration,
engineering, and ancillary data, and all processing history and provenance, required to understand how Level 2 data
products were generated, and allow their reproduction from the raw input data.
2.4.5.1.2.4 Data Quality Monitoring
ID: LSR-REQ-0040
Last Modified: 3/16/2011
Requirement:
Level 2 Data Product production shall include the production and publication of sufficient SDQA
data to allow the determination of the scientific usability of the data products and the assessment of the large-scale
progress of the survey.
2.4.5.1.3 Level 3 Data Products
ID: LSR-REQ-0041
Last Modified: 3/15/2011
Specification:
The LSST Observatory shall support Level 3 Data Products that are the result of processing based on
Level 1 and Level 2 Data Products, of a nature specified by users (by the provision of code and/or processing
configuration data).

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
26
2.4.5.1.3.1 Level 3 Data Processing
ID: LSR-REQ-0106
Last Modified: 10/4/2013
Specification:
The LSST Observatory shall provide software, services, and hardware resources to enable the
production and storage of Level 3 Data Products. It shall be possible to produce Level 3 Data Products using LSST
computing resources or elsewhere, and bring them into federation with Level 1 and 2 Data Products at the LSST
data center.
Discussion:
Level 3 Data Products are the result of processing that utilizes Level 1 and Level 2 Data Products, of a
nature specified by users (by the provision of code and/or processing configuration data).
2.4.5.1.3.2 Level 3 Data Product Federation
ID: LSR-REQ-0107
Last Modified: 3/15/2011
Specification:
The manner of production of Level 3 Data Products shall facilitate their federation with related Level
1 and Level 2 Data Products, when archived.
Discussion:
The LSST project may, over time, promote selected Level 3 Data Products and their production to
Level 2 or Level 1, subject to scientific justification and the availability of resources, and with the agreement of their
originators.
2.4.5.2 Science Flowdown
ID: LSR-REQ-0042
Last Modified: 3/23/2011
Requirement:
The LSST Observatory shall produce the data products necessary to support the 4 primary science
missions listed below.
Discussion:
The 4 key science drivers listed below are meant to exercise the extremes of capability phase space ,
thereby enabling a broad range of parallel scientific research. Additionally, the repeating of these key science drivers
from the SRD support the traceability of more detailed requirements at the OSS level.
2.4.5.2.1 Data Products for Dark Energy/Matter Science
ID: LSR-REQ-0043
Last Modified: 3/23/2011
Requirement:
The LSST Observatory shall provide the necessary data products to support the
Constraining Dark
Energy and Dark Matter
science as described in the LSST SRD.
2.4.5.2.2 Data Products for Solar System Science
ID: LSR-REQ-0044
Last Modified: 3/16/2011
Requirement:
The LSST Observatory shall produce the necessary data products to support the
Taking an
Inventory of the Solar System
science case described in the LSST SRD.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
27
2.4.5.2.2.1.1 Data Products for the Transient Sky
ID: LSR-REQ-0045
Last Modified: 3/16/2011
Requirement:
The LSST Observatory shall produce the necessary data products to support the
Exploring the
Transient Sky
science case described in the LSST SRD.
2.4.5.2.3 Data Products for Milky Way Science
ID: LSR-REQ-0046
Last Modified: 3/16/2011
Requirement:
The LSST observatory shall produce the necessary data products needed to support the
Mapping the
Milky Way
science case described in the LSST SRD.
2.5 Data Archiving & Services
ID: LSR-REQ-0047
Last Modified: 3/16/2011
Requirement:
The LSST shall archive all image, catalog, engineering, calibration, and environmental data collected
during the course of the survey, and shall make this data available for analysis and distribution.
2.5.1 Raw Image Data Archiving
ID: LSR-REQ-0048
Last Modified: 3/16/2011
Requirement:
The LSST system shall archive all raw science and calibration image data, collected in the course of
the survey as well as data collected during engineering and calibration operations, as well as all wavefront sensor
data. It shall also permit the archiving of such diagnostic image data as may be needed to support the commissioni
2.5.2 Meta Data Archiving
ID: LSR-REQ-0108
Last Modified: 10/4/2013
Requirement:
The LSST system shall archive sufficient information to permit the reliable and reproducible
retrieval of calibrated image data.
Discussion:
Calibrated image data must be available to retrieve, but may be reconstructed on demand as an
alternative to its direct archiving (see LSR-REQ-0049).
2.5.3 Data Product Archiving
ID: LSR-REQ-0049
Last Modified: 10/4/2013
Requirement:
The LSST system shall archive all generated Level 1, Level 2, and Calibration Data Products, or
provide services to reconstruct any given data product on demand. When regenerated on-demand, the Data Products
shall be scientifically equivalent
i.e. at a level of precision sufficient to reproduce the primary and derived
attributes well within their formal uncertainties.
Discussion:
Floating-point operations can return slightly different results on different hardware and guaranteeing
absolute bitwise reproducibility across generations of hardware platforms is infeasible. These differences are
typically in the least significant bit(s) that are already dominated by numerical or measurement noise. Thus the

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
28
scientific impact is minimal, if at all existent.
Nevertheless, whenever viable algorithmic alternatives exist they will be preferred to those that are potentially
hardware dependent, indeterministic, or numerically unstable.
2.5.3.1 Level 3 Data Product Archiving
ID: LSR-REQ-0050
Last Modified: 2/22/2011
Specification:
Level 3 Data Products shall be archived, subject to project approval, based on user applications. An
administrative mechanism shall be established to allocate a certain fraction of project resources for this purpose and
to allocate that fraction to approved user requests based on their assessed usefulness to the project and the
achievement of its science goals, and their value to the LSST user community.
2.5.4 Engineering and Environmental Data Archiving
ID: LSR-REQ-0051
Last Modified: 3/16/2011
Requirement:
The LSST system shall archive all ancillary (e.g. engineering and environmental) data collected by
the observatory.
2.5.5 Public Data Release
ID: LSR-REQ-0052
Last Modified: 3/16/2011
Requirement:
The LSST System shall provide open access to all LSST Level 1 and Level 2 Data Products, in
accordance with LSST Corporation Board approved policies. This shall include access to all engineering,
environmental, and ancillary data required for scientific interpretation of the Data Products.
Discussion:
Level 3 Data Products may or may not be available for open access, depending on agreements with
their creator. Whether the creator is willing to accept open access is a criterion that may be used to determine how
the project's resources for Level 3 Data Product archiving and service are allocated.
The LSST Corporation reserves the right to retain confidential business records, proposals, personnel files, medical
records, or other confidential documents, obtained from others.
2.5.5.1 No Proprietary Period
ID: LSR-REQ-0059
Last Modified: 10/4/2013
Requirement:
The raw survey data and processed data products shall be shall be released as Open Data and Open
Source to the US, Chile, and foreign partners without any proprietary period (via MOU as per LSST Board policy).
Discussion:
A necessary step in releasing the processed data is to perform Science Data Quality Analysis (SDQA).
If intermediate data products or products that have not undergone quality assessment are made available, they will
be clearly marked and documented as such
2.5.5.2 Data Distribution
ID: LSR-REQ-0053
Last Modified: 10/4/2013
Requirement:
The LSST shall permit and facilitate the bulk distribution of its public data to remote sites or users
wishing to consume or host it, subject to the availability of resources and the data access policy from LSR-REQ-

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
29
0052.
Discussion:
This requirement is not intended to create an open-ended obligation to add bandwidth for data
distribution. In cases where remote sites wish to host a large amount of LSST public data, it is anticipated that some
cost-recovery arrangement may be needed to support the installation of additional data distribution capacity.
2.5.5.3 Data Product Access Interface
ID: LSR-REQ-0
Last Modified: 10/4/2013
Requirement:
The LSST shall provide access to all its public data products through an interface that utilizes, to the
maximum practicable extent, community-based standards such as those for pixel-based images (e.g. FITS), as well
as those being developed by the Virtual Observatory (VO) community, and that facilitates user data analysis and the
production of Level 3 and other user-defined data products at LSST-provided facilities and at remote sites.
2.5.6 Community Computing Services
ID: LSR-REQ-0055
Last Modified: 3/16/2011
Requirement:
The LSST shall provide and maintain an amount of computing capacity equivalent to at least
userComputingFraction
of the total LSST data processing capacity (computing and storage) for the purpose of
scientific analysis of LSST data and the production of Level 3 Data Products by external users.
Discussion:
The detailed scope of this service is to be determined based on a representative set of system queries
and analyses assembled from community input and based on MOUs with other organizations willing to serve part of
the public access distribution.
The fraction set by this requirement refers only to project funded resources. The LSST Observatory expects and will
facilitate community use of grid, peta-scale computing centers, etrc...
2.5.6.1 userComputingFraction
ID:
Last Modified: 11/17/2010
Description
Value
Unit
Name
Fraction of total computing capacity dedicated to user-defined
processing and storage
10
Percent
userComputingFract
ion
2.5.7 Data Curation
ID: LSR-REQ-0056
Last Modified: 3/16/2011
Requirement:
The LSST Observatory shall develop a data curation plan that is consistent with developing
community standards (e.g. Open Archival Information System - OAIS, or the NSF DataNet Initiative) to the extenct
allowed by project budgets and schedules.
Discussion:
It is important that all archival data products generated by the LSST Observatory be managed to ensure
their long-term usability. This includes not only the preservation of the data itself, but the additional information
required to make it understandable by scientific users.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
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 Survey Operation & Administration
ID: LSR-REQ-0057
Last Modified: 5/24/2011
Requirement:
The Observatory shall be designed and developed to efficiently manage the execution of the survey.
Discussion:
The LSST Observatory will be a comprehensive project to capture, process, archive, and serve data.
3.1 Operational Safety
ID: LSR-REQ-0058
Last Modified: 3/16/2011
Requirement:
The LSST shall be designed, constructed, and operated so that the safety of personnel, followed by
safety of equipment, and then the integrity of the data are preserved.
Discussion:
The detailed safety requirements and applicable external codes are documented in the
Observatory
System Specifications Document
.
3.2 Science Priorities and Survey Monitoring
ID: LSR-REQ-0070
Last Modified: 3/16/2011
Requirement:
The LSST project shall monitor the scientific and technical progress of the survey, communicate
with the scientific user community and establish survey priorities, and adjust the survey design as needed to
accomplish its goals given these priorities and achieved performance.
3.2.1 Science Objectives Definition
ID: LSR-REQ-0063
Last Modified: 3/16/2011
Requirement:
The Observatory system shall provide the ability to define a set of scientific objectives and
associated performance metrics, which shall be used to assess and control the sequence of observations to optimally
satisfy these objectives.
Discussion:
The reference survey can be accomplished with many different observing cadences or sequences that
impact the scientific reach of the accumulated data.
3.2.2 Adjustment of Survey Priorities
ID: LSR-REQ-0064
Last Modified: 3/16/2011
Requirement:
The operation of the LSST Observatory shall allow for periodic adjustment of the survey priorities
based on community input.
Discussion:
This requirement is intended to ensure that the survey priorities and scheduling can be adapted to
address any changes in the scientific landscape that can occur on a 10-year timescale. It is intended that these
adjustments be assessed on relatively long time scales (e.g. every 6 months).
3.2.3 Survey Performance Reviews
ID: LSR-REQ-0065
Last Modified: 3/16/2011

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
31
Requirement:
The Observatory shall have the ability to provide periodic status reports on the progress of the survey
to allow both operations staff and the community to assess the survey progress.
3.2.4 Survey Performance Evaluation
ID: LSR-REQ-0066
Last Modified: 3/16/2011
Requirement:
The Project shall create the necessary survey performance evaluation tools to predict the final results
of the ten year survey based on the actual survey completed to date, assess the impacts of survey strategy changes
resulting from changes in scientific priorities, and support the planning of the survey on a variety of time scales,
from nightly through the entire 10 year duration.
3.3 Overall Operational Efficiency
ID: LSR-REQ-0073
Last Modified: 3/16/2011
Requirement:
The LSST system shall meet the Survey Design Specifications for number of visits and area
coverage, including the constraints of weather, system dynamics, scheduled maintenance, and unscheduled down
time.
Discussion:
The specifications for the allowed allocations to each of the terms for non-observable time are
contained in the companion document
the Observatory System Specifications
(document LSE-30).
3.3.1 Survey Time Allocation
ID: LSR-REQ-0075
Last Modified: 3/16/2011
Requirement:
The LSST Survey performance requirements shall be met utilizing approximately 90% of the
historically available observing time, leaving the remaining time available for yet to be defined special programs
(e.g. targeted deep drilling programs).
3.3.2 System Operational Lifetime
ID: LSR-REQ-0076
Last Modified: 3/16/2011
Requirement:
The LSST system shall meet all its requirements and specifications over the full duration of the 10
year survey.
3.3.2.1 Preventive Maintenance
ID: LSR-REQ-0077
Last Modified: 3/16/2011
Requirement:
The LSST system shall prepare a maintenance and reliability plan to ensure LSR-REQ-0076 (above)
is met with an optimum balance between preventive maintenance and replacement strategies.
Discussion:
Preventive maintenance implies servicing, repairing, and replacing components and subsystems based
on their expected lifetime, as opposed to their failure.
3.3.3 Graceful Degradation
ID: LSR-REQ-0074
Last Modified: 3/16/2011

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
32
Requirement:
The LSST system will be designed so that its performance degrades gracefully in the presence of
adverse environmental and/or operating conditions.
3.4 LSST Broader Impacts
ID: LSR-REQ-0061
Last Modified: 10/7/2013
Specification:
The LSST Observatory shall include an Education and Public Outreach program that supports
Federal "Broader Impacts" requirements encompassing "the potential to benefit society and contribute to the
achievement of specific, desired societal outcomes".
Discussion:
The National Science Foundation supports programs based both on intellectual merit and broader
impacts. The National Science Board strives for all American citizens to have the basic scientific, technological, and
mathematical knowledge to make informed personal choices, to be educated voters, and to thrive in the increasingly
technological global marketplace. The National Research Council, through its development of Science Education
standards, addresses the critical issues of STEM Education, U.S. competitiveness and workforce preparation.
3.4.1 EPO Users
ID:
ID: LSR-REQ-0112
ID:
Last Modified: 10/7/2013
Specification:
LSST-EPO shall be user-centered, building learning experiences to meet the needs of specific
audiences while proactively engaging diverse learners and those who are traditionally underrepresented in STEM
fields.
Discussion:
The audience for LSST EPO is potentially quite large, being any non-science user with an internet
connection. It is necessary to prioritize and target specific settings and user groups to maximize the impact of the
system. Increasing diversity in the STEM workforce is essential to sustained national prosperity. The specific
audiences are defined in the derived OSS requirements (OSS-REQ-0356, OSS-REQ-0357, OSS-REQ-0358).
3.4.2 EPO Products, Tools, and Interfaces
ID:
ID: LSR-REQ-0113
ID:
Last Modified: 10/3/2013
Specification:
LSST EPO shall provide access to LSST data through tools, interfaces, and learning experiences that
are designed to engage communities with different levels of knowledge, experience and skills.
Discussion:
Astronomy is known to be an entryway to science for everyone, not just those who end up in STEM
careers. Engaging learners in authentic science experiences is the best way for them to learn and gain an
understanding of science topics and the research process. Boundaries between learning environments are becoming
less defined, as learners become more self-directed and lifelong learning is recognized for its value. LSST EPO
products, tools, and interfaces, which are to be innovative and user-friendly, can be used in multiple settings; for
example, citizen science projects can take place online, incorporated into classroom settings, and introduced in
informal science settings through a kiosk or interactive planetarium show.

LSST System Requirements
LSE-29
Latest Revision 3/11/2015
The contents of this document are subject to configuration control and may not be changed, altered, or their provisions
waived without prior approval.
33
3.4.3 EPO User Impacts
ID:
ID: LSR-REQ-0114
ID:
Last Modified: 10/3/2013
Specification:
LSST EPO shall conduct an evidence-based evaluation program that measures (user-centered)
performance metrics as well as outcomes defined as demonstrated changes in understanding, appreciation, skills,
knowledge, or awareness.
Discussion:
It is important to use, identify, and share evidence based approaches to program development and
evaluation for maximum impact as described in the OMB STEM Strategic Plan.
3.4.4 EPO Longevity
ID:
ID: LSR-REQ-0115
ID:
Last Modified: 10/3/2013
Specification:
The LSST EPO plan shall be agile and remain relevant and effective for the full survey duration,
making adjustments that reflect technology trends and educational priorities.
Discussion:
In addition to using flexible interface designs and elastic computing resources, it will be necessary to
build strong partnerships with external organizations to maximize the longevity of the system.
3.4.5 EPO Fully Integrated
ID:
ID: LSR-REQ-0116
ID:
Last Modified: 10/3/2013
Specification:
LSST EPO shall be fully integrated into the design of LSST so that effort can be shared and
leveraged during construction. Additionally, Citizen Science results that extend the science goals of LSST shall be
made available to science users during operations.
Discussion
: The LSST EPO subsystem is not an add-on to the observatory conceptually or functionally. The science
and education goals have been developed in tandem as has the implementation of the system to support those goals.
Big Understandings of the EPO learning activities are aligned with the LSST science mission and the DM/EPO
interface allows for both transfer of data to the EPO system and the return of EPO-generated results that can be
integrated with science data products for the community. In this way the education and science from LSST are
collaboratively maximized.

Back to top