1. Large Synoptic Survey Telescope (LSST)
  2. System Requirements
  3. Charles F. Claver and the LSST Systems Engineering Integrated Project
  4. Team
  5. LSE-29
  6. Latest Revision: August 4, 2016
  7. Change Record
    1. Table of Contents
  8. The LSST System Requirements
    1. Project Background
    2. Document Scope
    3. Acronyms and Definitions of Terms
    4. Reference Documents
  9. 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

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Large Synoptic Survey Telescope (LSST)

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System Requirements

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Charles F. Claver and the LSST Systems Engineering Integrated Project

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Team

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LSE-29

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Latest Revision: August 4, 2016
This LSST document has been approved as a Content-Controlled Document. Its contents are subject to
configuration control and may not be changed, altered, or their provisions waived without prior
approval. If this document is changed or superseded, the new document will retain the Handle
designation shown above. The control is on the most recent digital document with this Handle in the
LSST digital archive and not printed versions.

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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
3.1
8/4/2016
Implementation of LCR-584. Add requirements that
provide the flow down logic for advanced
publication of the expected scheduler.
C. Claver (LCR), B.
Selvy (SysML), Robert
McKercher
(DocuShare)

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Table of Contents
Change
Record
...............................................................................................................................................
i
Project
Background
......................................................................................................................................
iii
Document
Scope
..........................................................................................................................................
iii
Acronyms and Definitions of Terms ............................................................................................................. iii
Reference
Documents
..................................................................................................................................
iv
1
Survey Design Specifications ............................................................................................................ 1
1.1
Filter Set Characteristics ............................................................................................................ 1
1.2
Single Image Performance ........................................................................................................ 3
1.3
Full Survey Performance ........................................................................................................... 9
1.4
Data Processing and Management ......................................................................................... 10
2
System Capabilities ........................................................................................................................ 11
2.1
Optical Configuration .............................................................................................................. 12
2.2
Observatory Control Capabilities ............................................................................................ 14
2.3
Data Collection ........................................................................................................................ 15
2.4
Data Products and Processing ................................................................................................. 17
2.5
Data Archiving & Services ........................................................................................................ 24
3
Survey Operation & Administration .............................................................................................. 27
3.1
Operational Safety ................................................................................................................... 27
3.2
Science Priorities and Survey Monitoring ............................................................................... 27
3.3
Overall Operational Efficiency ................................................................................................. 28
3.4
LSST Broader Impacts .............................................................................................................. 29

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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

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established by a requirement that the delivered system or subsystem must meet.
An
attribute
specifies a quantitative performance
parameter
in the context of the SysML based SysArch
model used to generate this document.
A
constraint
is used to refer to a 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
Science Requirements Document (v5.1.3), (SRD) (LPM-17)
Observatory System Specifications, (OSS) (LSE-30)

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The LSST System Requirements
1 Survey Design Specifications
ID: LSR-REQ-0080
Last Modified: 8/3/2016
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: 8/3/2016
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: 8/3/2016
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.
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: 8/3/2016
Requirement:
The active complement shall be changeable within
TDFMax
hours.

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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: 8/3/2016
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.
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: 8/3/2016
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.
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.
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: 8/3/2016

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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: 8/3/2016
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: 8/3/2016
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.
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
ArcsecFW
HM
S1_0.44
Median system delivered image quality in atmospheric seeing
of 0.60 arcsec in the r and i filters.
0.72
ArcsecFW
HM
S1_0.60
Median system delivered image quality in atmospheric seeing
of 0.80 arcseconds in the r and i filters.
0.89
ArcsecFW
HM
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

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Description
Value
Unit
Name
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
ArcsecFW
HM
SysIm_0
1.2.1.1 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
Discussion:
The specified budget allocations are consistent with the base system budget,
medianRMSBudget,
being invariant with atmospheric conditions.
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
ArcsecFW
HM
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
ArcsecFW
HM
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
ArcsecFW
HM
10%outlierBudget_0
.80
1.2.1.2 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.
Description
Value
Unit
Name

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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
ArcsecFW
HM
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
ArcsecFW
HM
SysIm_60
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.
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: 8/3/2016
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
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
z-band point source 5-sigma detection depth median
23.3
ABmag
DB1z

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1.2.3.1 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
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
ArcsecFW
HM
refSeeing
The reference sky surface brightness for which the depth
specifications shall be met is
refSkyBrightness
as measured
in the r-band.
21
mag/SqArc
sec
refSkyBrightness
The outlier limit for 5-sigma point source detection depth is
Z1
.
24.4
ABmag
Z1
1.2.3.2 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.
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).
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
15%
Percent
DF2

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Description
Value
Unit
Name
median limiting magnitude for that visit shall be no greater
than
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: 8/3/2016
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).
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
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
2
ResSource

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Description
Value
Unit
Name
point sources.
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: 8/3/2016
Requirement:
The astrometric quality of images from a single visit shall meet the specifications listed in
the table
astrometricPerformance
below.
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: 8/3/2016
Requirement:
The LSST shall be capable of unsaturated measurements of sources brighter than the
nominal 15-second saturation limit by at least
brightSource.

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9
Discussion:
This is not a requirement on the ability to measure saturated sources in standard visits. It is
largely a 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).
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: 8/3/2016
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.
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
arcminute scales shall be no more than
4.0e-5
TE3
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

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Requirement:
Integrated over all survey observations made over a 10 year period the LSST shall meet
all specifications for
skyCoverage.
Description
Value
Unit
Name
The total area of sky covered by the median number of visits
shall be no less than
18000 SquareDeg
rees
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
SquareDeg
rees
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.
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
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.

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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
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.
Description
Value
Unit
Name
The minimum interval between standard Data Releases
1
Years
DRT1
2 System Capabilities
ID: LSR-REQ-0001
Last Modified: 8/3/2016
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.

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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.
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
.
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.
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.

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Description
Value
Unit
Name
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.

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2.2
Observatory Control Capabilities
ID: LSR-REQ-0067
Last Modified: 3/16/2011
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: 8/3/2016
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 External Observatory Co-Observing Capability
ID: LSR-REQ-0119
Last Modified: 8/3/2016
Specification:
LSST Observatory shall enable "co-observing", where an external observatory can
anticipate where future observations will be made with reasonable likelihood.
2.2.5 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

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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.
2.2.6 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.
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
.
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

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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 vist and vist exposure time different from the values of
nVisitExp
and
visitExpTime
respectively,
speficied 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).
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;

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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.
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

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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 Transient 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.
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: 8/3/2016
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: 8/3/2016
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.
Transient Filtering

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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.
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
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).
Level 1 Data Products
ID: LSR-REQ-0033
Last Modified: 10/3/2013

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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.
Level 1 Scientific Content
ID: LSR-REQ-0110
Last Modified: 8/3/2016
Requirement:
The Level 1 data products shall include:
Raw Science Images
Calibrated Science Images (trimmed, de-biased, flattened, etc.)
Difference Images
Image Metadata/Catalog
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".
Level 1 Data Product Availability
ID: LSR-REQ-0104
Last Modified: 8/3/2016
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.
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
Level 1 Data Product Availability for Solar System Objects

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ID: LSR-REQ-0118
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.
Level 1 Data Product Availability for Transient Alerts
ID: LSR-REQ-0117
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.
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.
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.
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.
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.

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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,
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).
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.
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.
Data Quality Monitoring
ID: LSR-REQ-0040
Last Modified: 3/16/2011

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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.
Level 3 Data Products
ID: LSR-REQ-0041
Last Modified: 8/3/2016
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).
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).
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.
Data Products for Dark Energy/Matter Science

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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.
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.
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.
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 commissioning, calibration, and maintenance of the observatory.
2.5.2 Meta Data Archiving
ID: LSR-REQ-0108
Last Modified: 10/4/2013

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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 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.

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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-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-0054
Last Modified: 8/3/2016
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

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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...
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.
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

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ID: LSR-REQ-0070
Last Modified: 8/3/2016
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: 8/3/2016
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
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

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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
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".

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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: LSR-REQ-0112
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: LSR-REQ-0113
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.
3.4.3 EPO User Impacts
ID: LSR-REQ-0114
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.

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3.4.4 EPO Longevity
ID: LSR-REQ-0115
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: LSR-REQ-0116
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.

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