1. Large Synoptic Survey Telescope (LSST)
  2. Scope Options
  3. Victor L. Krabbendam
  4. LPM-72
  5. Latest Revision Date: August 27, 2015
  6. Change Record
    1. Table of Contents
  7. LSST Scope Options
    1. Acronyms and Definitions of Terms
    2. Referenced Documents
  8. LSST Scope Options
    1. 1 Introduction
    2. 2 Review of Budget and Schedule Contingency
    3. 3 Scope Contingency
      1. 3.1 Scope Reduction Summary
      2. 3.2 Scope Opportunity Summary
    4. 4 Scope Option Timeline
    5. - Scope Potential in $K
    6. Fiscal Year
    7. Scope Potential in $K
    8. Fiscal Year
    9. Potential Opportunities by Fiscal Year
    10. 5 Scope Option Conclusion

LSST Scope Options
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Large Synoptic Survey Telescope (LSST)

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Scope Options

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Victor L. Krabbendam

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LPM-72

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Latest Revision Date: August 27, 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 If this document is changed or superseded, the new document will retain the Handle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.

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Change Record
Version
Date
Description
Owner name
1.0
7/25/2011
Initial publication
D. Sweeney
1.1
8/3/2011
Format and content update
D. Sweeney
1.2
8/5/2011
Increased content
D. Sweeney
1.3
9/30/2013
Pre-FDR consistency check; correction of formatting
and typos. Correction of LSSTC to AURA. Approved
under LCR-154
R. McKercher
1.4
10/8/2013
Revised dates, Added Level 1 descope to DM
options, updated cost potentials
C. Claver
2.0
1/13/2014
Revised to match FDR baseline plan
V. Krabbendam
3.0
4/30/2015
Revised to incorporate tracking workbook and
Scope Opportunity Summary
V. Krabbendam
6/4/2015
Proofread and edited for consistency with the Cost
Estimating Plan, Risk & Opportunity Management
Plan, and Contingency Management Plan.
R. McKercher
8/27/2015
Implementation of LCR-423
R. McKercher

LSST Scope Options
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ii
Table of Contents
Change
Record
...............................................................................................................................................
i
Acronyms and Definitions of Terms ............................................................................................................. iii
Referenced
Documents
...............................................................................................................................
iii
1
Introduction
..........................................................................................................................................
1
2
Review of Budget and Schedule Contingency....................................................................................... 1
3
Scope Contingency ................................................................................................................................ 1
3.1
Scope Reduction Summary ........................................................................................................... 2
3.2
Scope Opportunity Summary ........................................................................................................ 7
4
Scope Option Timeline ........................................................................................................................ 10
5
Scope Option Conclusion .................................................................................................................... 11

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LSST Scope Options
Acronyms and Definitions of Terms
Glossary of Abbreviations
(
Document-11921
)
Glossary of Definitions
(
Document-14412
)
Referenced Documents
Cost Baseline:
https://project.lsst.org/costbaseline/
Cost Estimating Plan (LPM-81)
Contingency Management Plan (LPM-61)
LSST System Requirements (LSE-29)
Observatory System Specifications (LSE-30)
Project Execution Plan (LPM-54)
Risk & Opportunity Management Plan (LPM-20)
Science Requirements Document (LPM-17)
Scope Option Registry (Document-17914)

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LSST Scope Options
1 Introduction
The LSST project plan includes contingency reserves for budget, schedule and scope. This document
presents the LSST scope options for the NSF MREFC portion of the Project. The goal of the document is
to identify and prioritize a compliment of options to the project scope that can be implemented if the
LSST project is faced with a substantial shortfall of funding or schedule. The scope plan provides a list of
reductions that equal a minimum of 10% of the remaining planned budget. The document also includes
a summary of scope opportunities. All scope options will be evaluated for cost, schedule and
performance impact. The guiding rationale for proposed scope reductions is to minimize the impact of
reductions to the LSST system requirements, to minimize the impact to the science performance, and
also to avoid non-recoverable reductions in scope. All increased scope opportunities are still consistent
with the approved LSST scope, objectives, and performance. These opportunities primarily address the
technical approach to the LSST MREFC development and the performance goals provided in the LSST
Science Requirements Document (LPM-17). All options are identified with trigger dates to support the
management of the scope item. Any consideration of a scope change implementation would be made
only with the approval of the NSF per the CSA requirements.
The project scope options are defined and maintained in a separate spreadsheet and summarized in
this document. This document and all scope options are reviewed in a yearly update cycle to remain
current and consistent with the ongoing activities of the program.
The use of contingency is managed by the LSST Project Manager in conjunction with the Change
Control Board, LSST Director, and the funding agencies. The processes and approval thresholds for each
type of contingency allocation are described in the LSST Contingency Management Plan (LPM-61).
2 Review of Budget and Schedule Contingency
The LSST Project Office (LSSTPO) has completed an analysis of the cost and schedule contingency using
the process and applicable terms and conditions described in the LSST Contingency Management Plan
(LPM-61). As described there, this process uses the Baseline Plan and combines it with Technical, Cost,
and Schedule uncertainty factors and multipliers along with specific items in the LSST Risk Register to
run a Monte Carlo simulation on the plan in order to determine a statistical distribution of the likely
cost and schedule duration of the project. The established cost and schedule contingency values were
developed and approved under the basis that the project also have scope options identified that value
at least 10% of the remaining cost to complete the project.
3 Scope Contingency
This section summarizes options for overall scientific and technical scope of the LSST observatory. These
reductions in scope would be made if the LSST project is faced with substantial shortfall from the
allocation of planned funding, or if total project costs exceed the ability of the project to deal with

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unexpected costs and schedule delays using budget and schedule contingency. Reductions in scope
would be made only with the approval of the NSF. The scope increase opportunities would be
implemented if total project funding is healthy and the opportunity advantage is both a) within the
overall approved program scope and b) is evaluated as a positive net benefit to the program.
The system requirements for LSST that provide a framework for analysis of reductions in scientific scope
are specified in the Science Requirements Document (LPM-17), the LSST System Requirements (LSE-29)
and the Observatory System Specifications (LSE-30). These documents identify minimum and stretch
requirements between which the baseline design requirements are derived and scope options can be
considered.
The details for each scope option are captured in Document-17914, the scope option registry. In the
options registry, the scientific, technical, cost and schedule impacts are identified and the trigger dates
and status are maintained.
3.1 Scope Reduction Summary
The guiding rationale for identified scope reductions is to minimize the impact of reductions to the LSST
system requirements, to minimize the impact to the science performance, and also to avoid reductions
to the program plan that are not recoverable. The scope for the construction of the LSST can be reduced
in two fundamentally different ways: (1) reductions in the scientific or educational scope or (2)
reductions in engineering implementation.
The primary type of scope reduction is a change in the scientific reach of the project. If large cuts to the
construction budget are realized, this is the most likely pathway. Such scope reductions reduce the
quantity and quality of data products that can be developed by the LSST survey.
Another pathway is to make adjustments to the engineering implementation that supports the project
scientific scope. Engineering changes may a) affect data product quality, e.g. a reduction in resolution,
precision, or availability; b) reduce construction costs by causing higher costs in operations, e.g. building
cheaper infrastructure that will require more frequent or more costly maintenance; c) result in less
efficient and more costly operations cost, e.g. spares/backups not embedded within system, which
requires additional downtime if these instances occur; or d) increase the risk to the successful on-time
and on-budget execution of the baseline plan.
Table 3-1 identifies the scope reduction options along with a summary impact and cost saving estimate.
The descopes are in the relative order of priority that the Project would suggest implementation. The
exact order will depend on the necessary level of financial reduction and the timing of the change. The
list is current at the time each version of this document is published but will be reviewed when
descoping is necessary and prior to recommending any scope changes. Any changes in scope are
pursued within the authority levels and approval structure outlined in the Project Execution Plan (LPM-
54).
The project has identified 16 scope reduction items with a total financial value of $65.5M. The first 15
items total $40.2M, which is more than 10% of the current cost to complete the baseline plan.

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Table 3-1: LSST Scope Reduction Summary Table
Scope
ID
Title
Technical Impact
Value
Potential
($K)
Profile
(flat or
tapered)
Early
Date
(value
decline
starts)
Latest
Date
(value=0)
TS4
Change
Coating
Chamber From
Magnetron
Sputtering to
Vapor
Deposition
Technology
This descope will add complexity in the
design to support both the evaporative
and magnetron based coating systems.
The chamber will only be supplied and
tested in the evaporative configuration
with limited verification of the
magnetron upgrade.
2300
Flat
2016
DM4
Reduce Data
Release
Hardware by
10% (DR 1)
There is a higher risk to the schedule of
processing the first data release. The
time required for processing the first
data release will cause a 10% delay in
DR1 and a corresponding offset to
subsequent releases.
1800
Tapered
2018
2021
DM6
Remove Multi-
fit Hardware
and Test
Processing in
DR1 and DR2
This would eliminate a portion of the
infrastructure needed for the first 18
months of operations, as compute-
intensive measurements would not be
made in Data Releases 1 and 2.
2800
Tapered
2020
2021
DM5
Reduce
Development
and
Integration
Hardware
DM Integration hardware is built up
over 4 years to support the DM
development and testing work (FY15 to
FY18.) The initial 2 years of hardware
acquisition will remain as planned and
if this descope is pursued, the last two
years of that development will not be
continued. Development and testing
will continue at half the intended
capacity (10% full volume) for the
duration of the construction period.
5000
Tapered
2017
2021
TS1
Reduced
Summit
Facility
Functionality
The Summit Facility Design
requirements are driven primarily by
safe and efficient construction and
operation. The LSST team has
completed the design work with the
Architecture Firm and has the 100%
design package. Design functionality is
typically not recoverable as it is
designed into or out of the main
construction. Reduction in equipment
or ancillary aspects can be restored
with later upgrades.
230
Taper
2015
2016

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TS2
Reduced Base
Facility
Functionality
The Base Facility scope is derived from
the use cases and operating models to
support the Operations Phase as well
as the support of the construction and
commissioning efforts in building the
facility. The detailed design of the
facility is scheduled to begin in 2015
and removing functionality could be
assessed at that time. The impact will
depend on the exact descope.
340
Taper
2016
2018
TS6
Eliminate
Summit
Lodging
Expansion
The element includes the construction
of the summit lodging facilities to
support LSST integration,
commissioning, and operations teams.
The facility will be an addition to the
recently completed Pachón lodging and
dining building and is included in the
scope of work to be performed by the
summit facility general contractor.
These facilities are needed to support
the operations team and the large
teams of engineers, scientists, and
workers who will be performing time-
critical integration, assembly, test,
commissioning activities. Utilization of
facilities on the adjacent summit are
significant safety concerns and will
require additional travel resources, and
increased wear on roads and
equipment.
507
Flat
2017
TS7
Eliminate 6-12
Dome Vents
The LSST dome design must provide
adequate flushing of the enclosed
volume to mitigate thermal seeing
effects on overall telescope
performance. The baseline design
includes many adjustable vents that
regulate air flow through the building.
The current configuration has been
assessed via computational fluid
dynamics to determine wind flow and
air exchange rates.
Reduction of the number of dome
vents will reduce the precision of
thermal control within the enclosure.
Removing vents reduces the ventilation
area 15
31% The first 9% was area
margin, while the remaining will
increase dome seeing. A new
125
Tapered
2015
2016

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computational fluid dynamic analysis
will be required to determine the vents
with least impact.
TS9
Eliminate
M1M3 Trial
Assembly and
Test
The current plan includes trial assembly
and factory test of the M1M3 mirror
and mirror cell assembly in Tucson
prior to shipment to Chile. This
contracted effort with the University of
Arizona will confirm the performance
of the active optics control system.
The impact of descope of this activity
will be increased schedule on the
summit to confirm integration of the
systems and increased risk since
several support system tests are also
performed in this factory testing.
400
Flat
2017
DM3
Eliminate
Forced Source
Catalog
This descope would eliminate
infrastructure for performing forced
source measurement and storage of
the catalog.
4800
Tapered
2015
2018
SY2
Reduce System
Process and
Storage to SRD
Minimum
Specifications
This descope is the reduction of the
data management capacity to process
and store data coming off the
telescope. The reduction of data
volume is the result of either fewer
images, fewer sensors or, dropped
data. The visits per unit area of sky
design point is 825 (SRD design spec)
and the minimum is 750 (SRD minimum
spec). Reducing the number of visits to
the minimum spec reduces the data
volume. The data volume may be
reduced by either eliminating 20
sensors from the focal plane array or, if
there are no changes to the focal plane
or cadence, 10% of the data coming off
the telescope is not stored or
processed.
This descope is a 10% reduction in the
DM hardware to process and store
data. Less equipment will be purchased
and setup to provide the savings. To
preserve full recovery, the network
bandwidth is maintained.
1200
Flat
2019
2020

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SY4
Eliminate
Component
Spares
This de-scope eliminates component
spares from DM and T&S.
Eliminating such spares increases the
risk of schedule overruns during
commissioning should a component
suffer early life failure and will impact
system up-time requirements.
1061
Taper
2017
2020
DM2
Eliminate
Level-3 Data
Products
Support
This would eliminate the Level 3
infrastructure for the Data Access
Centers. It might also require a re-
negotiation of at least the intent, if not
the letter, of the AURA-Chile
agreement regarding LSST, since while
that agreement only calls for a copy of
a portion of the data to reside in Chile,
there have been communications and
expectations of a Data Access Center in
Chile.
2240
Tapered
2015
2019
TS5
Eliminate the
Calibration
Telescope
The 1.2m diameter Calibration
telescope is independent of the main
telescope in a separate building on the
site. This telescope is a key part of the
full calibration plan and also serves as
the initial test bed for the telescope
control and observatory control
software.
This instrument also serves as a test
bed for the development of the TCS
and OCS. Without it the commissioning
of the full facility will have higher risk
of schedule delay.
5400
Tapered
2015
2018
SY3
Reduce EPO
System
Capability and
Reach
This descope eliminates the technical
infrastructure planned for dedicated
EPO data center and citizen science
programs.
12000
Taper
2016
2021
DM1
Eliminate
Level-1 Data
Products
This descope would eliminate the
infrastructure for the alert production
processing, distribution, and archiving.
It would also reduce the Base to
Archive network bandwidth
requirements to roughly 5 Gbps.
25300
Tapered
2015
2020

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3.2 Scope Opportunity Summary
The scope opportunities developed for the project are primarily for specific risk reduction to accomplish
the construction project but also includes items that will address the stretch goals identified in the
Science requirements document.
There are 13 identified areas where the baseline plan can be extended at a total cost of $14.5M. Table
3-2 below provides a summary of the opportunity items in order of the decision date, earliest to latest.
Scope
ID
Title
Technical Impact
Cost
Potential
Profile
(flat or
tapered)
Latest Date
(when value=0)
TS1-U
Linear Drives for
the Dome
This option would be to upgrade the
current dome drive system to a magnetic
direct drive system. This upgrade would
improve the commissioning effort and
lower the performance risks to have the
dome and telescope mount driven using
the same technology.
1100
Flat
2015
SY4-U
Comprehensive
Construction All-
Risk Insurance
The baseline approach to the LSST
construction is for each contractor
working on the site to provide its own
Construction All-Risk insurance to protect
against the financial impact of damage to
property on site. A single policy held by
LSST would reduce the financial risk and
would dramatically reduce the schedule
and complication of any claims. With the
distributed insurance approach, an
incident will likely cause significant
schedule delay as issues of responsibility
and costs are clarified. A single LSST
policy will allow the contractors to
remove the cost of this insurance from
contract prices and will greatly improve
the risk posture of the site program.
1000
Flat
2016
TS4-U
Summit Fuel
Storage
This option would increase the summit
fuel storage from 3 days to 7 days. The
baseline capacity was determined for an
average ability to get fuel trucks to the
summit in the event that long term
generator use is required for back-up
power. Recent examples of weather
related problems and an increase in grid
power problems indicate the Program risk
for the construction effort has increased
and would be significantly reduced with 7
50
Flat
2016

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8
to 8 days of fuel on hand.
DM3-U
Develop
Specialized
Codes for
Crowded Field
Processing
The planned LSST data processing codes,
though expected to yield acceptable
results in areas of moderately high
crowding, are not guaranteed to reach
the accuracy or completeness of purpose-
built crowded field photometry codes.
Specifically, they are not required to work
well in regions such as dense clusters or
the Galactic plane. Developing specialized
codes for crowded fields would enable
science cases dependent on processing of
dense stellar fields.
1000
Flat
2017
TS2-U
TMA Shipping
from Vendor
This option would transfer
shipping/summit delivery scope of the
Telescope Mount Assembly from LSST to
GHESA. Currently LSST has budgeted
$560k to insure and transport the
hardware. Scope transfer to GHESA
would mitigate potential
warranty/performance issues in between
factory test and summit integration.
280
Flat
2017
TS5-U
M1M3 Thermal
Control System
Testbed
This option would establish a work
package to build a M1M3 testbed with a
surrogate section of a mirror for thermal
control system testing. The current plan is
to deploy the thermal management
system on the operational mirror cell and
debug and commission the system on the
real mirror. A testbed would significantly
reduce the risk of development and allow
work to be completed early and
decoupled from the mirror system
development.
300
Flat
2017
TS3-U
Enhanced
Summit
Infrastructure
Additional office and staff support space
on the summit will reduce the logistical
complexity of the telescope and site
integration and project wide
commissioning phase. The baseline plan
is to utilize the very minimal
infrastructure in place to support current
Project efforts with the only new
infrastructure being the actual summit
support building and the base facility.
300
Flat
2018

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DM1-U
Store Multi-fit
Likelihood
Samples for All
Six Bands
Currently, the likelihoods are sampled
and stored only for g, r, I, and z bands,
while only the associated and derived
quantities (e.g., maximum likelihood
values or means) are stored for u and y.
This option would enable science cases
dependent on accurate knowledge of
extended object shapes in u and y bands.
125
Flat
2019
DM2-U
Store All Raw
Data on Dist
Rather than Tape
Enables real-time generation of forced
photometry for transient alerts, going
back to the beginning of the survey.
Makes it feasible to generate image
differencing templates on the fly, if
needed, rather than from the annual co-
adds.
1347
Flat
2019
DM4-U
Diverse Network
Path from
Summit to Base
In the event of a primary path failure (e.g.
Fiber cut on the primary route) camera
images would no longer flow to the Base,
which would cease alerts for the time of
the outage. Other operational functions
in Chile would also be affected, although
we should be able to maintain voice and
vital safety-related communications over
Microwave radio. Estimated 4-6 hours to
repair and restore scientific flows.
350
Flat
2019
SY1-U
Extend Early
Integration and
Test Activities
Extending the time available for
integrating and testing the subsystems
(telescope, commissioning and full size
camera, and data management software)
on the summit will result in a more robust
system, with lower risk to success
through improved knowledge of its
behavior and fixes of its potential
shortcomings.
4,500
Flat
2020
SY5-U
EPO Technology
Enhancement
The scope of the EPO capabilities is based
on technologies available circa 2014. It
may be that new technologies emerge
that significantly enhance the EPO impact
beginning with survey operations in 2022.
600
Flat
2020
SY3-U
Early Shutdown
to Address
Improvements
Developed out of
Commissioning
The risk of successful completion is
reduced and the system would end up
having higher performance and reliability
at the conclusion of commissioning than
would otherwise be expected.
3600
Flat
2022

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4 Scope Option Timeline
The options to reduce the baseline scope are plotted as a function of available value versus time. The
sand chart below includes the full list of options that currently value $40.2M. The legend refers to the
Scope ID number.
The scope opportunities can also be plotted as a function of cost versus time. None of the opportunity
items are plotted with tapering values, just flat value until the time when the opportunity no longer
exists or would be reasonable feasible.
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
2014
2015
2016
2017
2018
2019
2020
2021
2022
De
-
Scope Potential in $K
Fiscal Year
De-Scope Potential by Fiscal Year
TS9
TS7
TS6
TS5
TS4
TS2
TS1
DM6
DM5
DM4
DM3
DM2
SY4
SY3
SY2
0
5000
10000
15000
20000
2014
2015
2016
2017
2018
2019
2020
2021
2022
Scope Potential in $K
Fiscal Year
Potential Opportunities by Fiscal Year
TS5-U
TS4-U
TS3-U
TS2-U
TS1-U
DM4-U
DM3-U
DM2-U
DM1-U
SY5-U
SY4-U
SY3-U
SY1-U

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5 Scope Option Conclusion
Scope options have been identified that value more than 10% of the cost to complete. In April 2015 the
baseline plan has a cost to complete of $372M. Fifteen descopes are identified in the scope options
registry that total $40.2M or 11% of the completion cost.
LSST has also identified and estimated the cost for 13 scope enhancements that would improve the risk
profile of the project and extend the performance toward the Science Requirement stretch goals. These
13 items have an estimated cost of $14.5M.

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