docushare.lsst.org€¦ · web viewthe first year of activities under system integration and test...

Large Synoptic Survey Telescope (LSST)The 2-year LSST

Commissioning Plan:System Integration and Science

Verification

Chuck Claver & Christopher Stubbs

LSE-79

Last Release Date: August 15, 2011

LSST 2-Year Commissioning Plan LSE-79

8/15/2011

Change Record

Version Date Description Owner name

1.0 7/8/2011 Initial version Chuck Claver

1.1 8/2/2011Added activity sequences for DM pipeline testing and verification; added staffing tables by year-type at the commissioning activity centers.

Chuck Claver

1.2 8/15/2011 Updated schedule and resources to PMCS baseline Chuck Claver

i


8/15/2011

Table of ContentsChange Record.............................................................................................................................................. i

1 Purpose & Scope..................................................................................................................................1

1.1. Related Documents......................................................................................................................1

1.2. Acronyms and Abbreviations.......................................................................................................2

2. Commissioning Overview and Preconditions.......................................................................................3

2.1. Time Line Overview......................................................................................................................3

2.2. Commissioning Pre-Conditions....................................................................................................5

2.2.1. Telescope and Site...............................................................................................................5

2.2.2. Camera.................................................................................................................................6

2.2.3. Data Management...............................................................................................................7

2.2.4. Observatory Control System................................................................................................7

2.2.5. Auxiliary Telescope..............................................................................................................8

2.2.6. Ancillary Equipment.............................................................................................................8

2.2.7. Tools and Other Capabilities................................................................................................8

2.2.8. External Data Sets................................................................................................................9

3. System I &T activities and system performance tests........................................................................10

3.1. Camera-Telescope Integration...................................................................................................10

3.1.1. Fixtures and Handling:.......................................................................................................11

3.1.2. Final Camera Utilities Install:..............................................................................................11

3.1.3. Camera – Telescope Physical Integration:..........................................................................11

3.1.4. Pre-Observations Check Out:.............................................................................................12

3.1.5. Initial Camera-Telescope Alignment:.................................................................................12

3.1.6. Initial On-Sky Characterization:..........................................................................................13

3.2. Active Optics Commissioning.....................................................................................................13

3.2.1. Wavefront Sensor to Focal-Plane-Array Calibration:..........................................................13

3.2.2. Optical Reconstruction Verification:..................................................................................14

3.3. Data Management Integration..................................................................................................15

3.3.1. DM + Camera + Telescope Integration...............................................................................15

3.3.2. Database and Pipeline Data Access....................................................................................16

ii


8/15/2011

3.3.3. Base Center Infrastructure Integration and Testing...........................................................16

3.3.4. Calibration Data Products Pipeline.....................................................................................16

3.3.5. Instrumental Signature Removal........................................................................................17

3.3.6. Alert Production Pipeline...................................................................................................17

3.3.7. Data Release Production....................................................................................................17

3.3.8. Science User Interface........................................................................................................17

3.4. Additional System Performance Characterization (will need to fold this into the above discussion).............................................................................................................................................18

4. Science Verification Activities............................................................................................................19

4.1. Science (SRD) Verification Tests.................................................................................................21

4.1.1. Single image/visit performance.........................................................................................21

4.1.2. Scheduler Automation Tests..............................................................................................21

4.1.3. Full survey Performance (mini-surveys).............................................................................22

4.2. Parallel Data Management Activities.........................................................................................23

4.2.1. Archive Center and US DAC Integration and Testing.......................................................23

4.2.2. Calibration Data Products Verification...............................................................................24

4.2.3. Alert Production Verification:............................................................................................24

4.2.4. Data Release Production Verification:................................................................................24

4.3. Other data sets needed during commissioning..........................................................................24

5. Operations Readiness........................................................................................................................26

5.1. 30-day mini-survey....................................................................................................................26

5.2. Readiness review.......................................................................................................................26

5.3. Pre-Operations Engineering.......................................................................................................27

5.3.1. M1M3 Mirror Re-Coating...................................................................................................27

5.3.2. Camera Maintenance and Servicing...................................................................................27

5.3.3. Base Facility DM Infrastructure Updates............................................................................28

6. Managing and Staffing the Commissioning Effort..............................................................................29

6.1. Issue and Event Tracking............................................................................................................29

6.2. Work Cycle during Commissioning.............................................................................................29

6.3. Commissioning Staffing..............................................................................................................30

iii


8/15/2011

6.3.1. Commissioning Science Team............................................................................................30

6.4. Commissioning Oversight..........................................................................................................30

6.4.1. Data release policy.............................................................................................................30

Contingency Planning................................................................................................................................32

6.5. Commissioning with a partially populated science array...........................................................32

6.6. Other Contingencies..................................................................................................................32

2 Appendices........................................................................................................................................33

2.1 A.1 Survey Bootstrapping...........................................................................................................33

2.2 A.2 Example Mini-Surveys..........................................................................................................34

iv


8/15/2011

The 2-year LSST Commissioning Plan:System Integration and Science Verification

1 Purpose & Scope

1) Describe the necessary pre-conditions that each of the three subsystems, Camera, Telescope and Site, and Data Management, along with the Observatory Control system must satisfy prior to the start of the two year commissioning period;

2) Outline the remaining technical integration activities and tests that must be accomplished during the System Integration and Test period;

3) Outline the verification methods that will be used to show compliance with the survey performance detailed in the LSST SRD (document LPM-17) and the LSST System Requirements (LSE-29);

4) Describe the specific tests, measurements, and analysis that will be done to show compliance with the SRD;

5) Define the criteria, methods, and review process that establishes the readiness of the LSST for operations;

6) Define the overall management structure, lines of authority, oversight, and data distribution policies that will be in place for the 2-year commissioning period; and

7) Outline contingency plans in the event key preconditions are not met.

The principal outputs from the Commissioning Phase are:

1) Operational procedures and documentation for operation of the LSST observatory as a science facility, including end-to-end data management;

2) Reports documenting as-built performance of the hardware and software including: modifications, exceptions, recommendations for improvement; and

3) Test data showing compliance with the requirements in the SRD (LPM-17), LSR (LSE-29), and OSS (LSE-30).

This plan covers the full set of activities for commissioning the LSST Observatory facilities in Chile and the partial commissioning of the Archive Facility at NCSA. It does not cover final commissioning of the annual data release processing pipelines and data products production, as these are covered under operations.

1.1. Related Documents

1


8/15/2011

LSST Science Requirements Document (SRD) v5.1.3: LPM-17 LSST System Requirements (LSR) v1.5: LSE-29 LSST Observatory System Specifications (OSS) v1.2: LSE-30 LSST Telescope & Site Subsystem Requirement LSE-60 LSST Camera Subsystem Requirements LSE-59 LSST Data Management Subsystem Requirements LSE-61 Telescope & Site Integration Plan: LTS-104 Camera Integration Plan: LCA-40 Data Management Integration Plan: TBD

1.2. Acronyms and AbbreviationsBFP: Best fit planeCCS: Camera Control SystemDAC: Data Access CenterISR: Instrument signature removalFPA: Focal Plane ArrayLSR: LSST System RequirementsM1M3: Primary-Tertiary mirror monolithM2: Secondary mirrorSRD: Science Requirements DocumentRVC: Reciprocating vertical conveyorOCS: Observatory Control SystemOSS: Observatory System SpecificationsORR: Operations Readiness ReviewTCS: Telescope Control SystemWCS: World Coordinate System

2


8/15/2011

2. Commissioning Overview and Preconditions

2.1. Time Line Overview

The commissioning phase of the project is defined roughly by two phases; a period dominated by the technical activities of System Integration and Test followed by a period that is focused on Science Verification. It is important to understand that these two phases represent a continuum and that the plan presented here is meant to be flexible to take full advantage of opportunities as they occur.

The transition from the project Construction phase to the Commissioning follows “Engineering First Light”, where the telescope has demonstrated SRD like on-axis image quality with a test camera. “Engineering First Light” occurs approximately 4 years after the start of MREFC construction (see Figure 1). As a necessary precondition (see Section 2) for initiating the Commissioning phase each of the three subsystems, Data Management, Camera, and Telescope & Site, along with the Observatory Control System must each pass their acceptance test milestones.

The first year of activities under System Integration and Test are designed to complete the technical integration of the three subsystems, show compliance with system level requirements (detailed in the Observatory System Specifications LSE-30) and ICDs, and provided early data for DM software debugging. System level requirements that flow directly to subsystems without any further derivation will be tested for compliance at the subsystem level and below under the supervision on the project Systems Engineer. This document includes general approach and goals for these tests. It is expected that roughly 4-6 months into the System I&T phase the telescope and camera will be fully integrated and producing (at least periodically) science grade images over the full FOV, at which point “System First Light” will be declared.

The second year’s activities under Science Verification are designed to show compliance with the survey performance specifications detailed in the LSST Science Requirements Document. These activities are based sole on the measured “On-Sky” performance of the LSST system. The data from these activities will be released to the Science Collaborations for analysis and early scientific studies. The content of this document discusses the general philosophy and structure of the observational verification. The detailed description of the observational programs used for science verification will be covered in the Science Verification Matrix.

3


8/15/2011

Figure 1: Key milestones in the LSST project assuming a FY2014 funding start.

4


8/15/2011

2.2. Commissioning Pre-Conditions

Each of the LSST subsystems will have gone through substantial testing and are expected to be in an advanced state of readiness prior to the start of the Commissioning Phase covered by this plan. The acceptance criteria and expected state for each of the three subsystems and the OCS required to enter the Commissioning Phase are described in the sections that follow.

2.2.1. Telescope and Site

The telescope will be integrated on site at the Summit Facility. In this sense there is not a single moment of delivery for the telescope to the LSST Observatory. Approximately 6 months prior to the start of Commissioning the telescope integration plan (LTS-104) includes optical tests of the M1M3 assembly using an interferometer the M3 radius of curvature to verify the M1M3 pre-shipping support matrices. This test configuration will also be used to build the initial look-up tables for the M1M3 mirror support. After these tests M2 is installed along with an independent “commissioning camera” and surrogate mass to simulate the science camera on the rotator-hexapod assembly. A laser metrology system is used to establish initial alignment and look-up tables for M2 and the camera hexapod/rotator. There will be roughly 4-months of on-sky time with the telescope in this configuration allowing the on-axis optical aberrations to be analyzed and refine the alignment and mirror support look-up tables.

Figure 2: Level 2 milestones for the Telescope & Site construction phase showing the key telescope integration

5


8/15/2011

activities coming ready prior to the end of FY2017 – the start of Commissioning.

Given the tests summarized above, it is expected that the telescope is essentially fully functional at the start of the Commissioning Phase. Using its own “commissioning” camera the telescope will be delivering SRD like image quality over a limited field-of-view around the optical axis and can point and track to its open loop specifications (OSS-REQ-0303). Further, the dome mechanisms are assumed to be working including azimuth tracking, elevation tracking of the entrance opening, ventilation louvers, and HVAC system for daytime thermal conditioning. The calibration dome-screen will be installed with both the tunable narrow band and broadband light sources function to specification. The “Engineering First Light” milestone coincides with the start of Commissioning and will be declared when the telescope is producing SRD like image quality and having passed its acceptance criteria.

2.2.2. Camera

The LSST science Camera will be integrated and tested at the SLAC National Accelerator Laboratory per the Camera Integration and Test Plan (document LCA-40). During this phase of the Camera construction all of the camera subsystem requirements (document LSE-59) will be verified to the extent possible without integration onto the telescope. Demonstration compliance with its requirements signifies the Camera has met its shipping readiness milestone. The camera, its support hardware, and test apparatus will then be shipped to Chile from SLAC.

The Camera is scheduled to arrive in Chile via airfreight and brought to the Summit Facility by truck roughly 6 months prior to the start of Commissioning. During this time the camera will be reassembled (if need be) in the camera service space and the set of verification tests run at SLAC to show shipping readiness will be re-run to verify that no functional or performance damaged occurred during shipping.

Once the post shipping evaluation has been completed the camera will be connected to the Summit Facility network. With camera on the network the data path between the Camera and the DM processing pipelines at Base Facility will be established and verified with live pixel data from the science FPA. During this initial testing the command and control of all Camera functions with the OCS will also be verified. Successful completion of these tests will signify that the camera has met its acceptance criteria and is ready to enter the commissioning phase and start System Integration and Test.

6


8/15/2011

Figure 3: Level 2 milestones for the Camera construction phase, showing the camera being delivered to the summit and verified prior to the end of FY2017 – the start of Commissioning.

2.2.3. Data Management

The Base Facility computing and data archiving infrastructure is expected to be installed and working. The Data Management processing pipelines for Instrumental Signature Removal, Calibration Data Products, Transient Alert Processing, and nightly photometry and astrometry processing will be installed and functional. These pipelines will have been tested and verified 2 kinds of data; 1) simulated data generated for the Data Challenges used in the project development phase and 2) legacy data from previous surveys (e.g., CFHT Legacy Survey, SLOAN Digital Sky Survey, and other surveys currently in the early stages of operation).

The 100Gb/sec between the Summit and Base facilities will be installed and shown to be fully functioning. An early Science DAQ System (SDS) from the camera team will be delivered to Chile approximately ## months prior to the start of Commissioning. The SDS will be capable of creating and sending synthesized pixel data in the LSST format across the Summit-Base network. This will allow early testing of the multiple instances SDS server-client connections used to pass the pixel data to the processing pipelines at the base. The operational data path (data source at the camera location on the telescope) and the service data path (data source in the Summit Facility camera laboratory) will be tested and verified using SDS synthetic pixel data, simulated image data, and legacy survey data.

7


8/15/2011

Figure 4: Level 2 milestones for the Data Management construction phase showing the Base Center, Data Release, Mountain-Base Network, and US-Chile Network coming ready at the end of FY2017 – the start of Commissioning.

2.2.4. Observatory Control System

The OCS implementation schedule has the OCS developed in terms of annual releases with increasing levels of functionality at each stage. The purpose of this methodology is to make available portions of OCS to other subsystems developers that need to interface with this package. At start of commissioning the OCS software will have had its 4th annual release. It is expected that in this release the OCS software functionality fully implemented including the following:

Communications Middleware with messaging software; Engineering and Facility Database; Scheduler; Operator GUIs; Monitor software with status displays; Maintenance support software; and Application control software with sequencer to synchronize the subsystems.

2.2.5. Auxiliary TelescopeThe auxiliary telescope (1.2m Calypso) is expected to be installed and fully operational. This includes the telescope and its control system, the spectrometer, and the software to process the spectroscopic data from raw images to calibrated spectra. The analysis software to convert time and spatially dependent spectra to the required atmospheric transmission function needed for the photometric calibration of the LSST science data is also expected to be operational prior to the start of the Commissioning period. It is recognized that the atmospheric transmission function will be validated during the photometric analysis during Commissioning.

8


8/15/2011

2.2.6. Ancillary Equipment In addition to the main LSST observatory components described above a suite of ancillary equipment are also expected to operational at the start of the Commissioning Phase. These include the following items:

Science image visualization system; Meteorological monitoring equipment at the Summit Facility, including wind and temperature

stations in the dome interior; Visible and IR all-sky cloud cameras; MASS / DIMM atmospheric turbulence profiler; and Network monitoring equipment and software.

2.2.7. Tools and Other CapabilitiesIn addition to the operational deliverable systems that make up the LSST Observatory, additional display, analytic, and scripting tools will be needed to facilitate the Commissioning effort.

The observatory “quick-look” image display system is needed to start the Commissioning phase. The “quick look” display system includes stand-alone interactive image analysis functions (e.g., PyRAF, LSST Analysis stack, or similar) that will allow targeted analysis of images during commissioning independent of the DM pipelines. The analysis functions will also allow scripting so that more sophisticated analysis can be done on multiple images from the science FPA, including the following:

Determine the sensor-to-sensor and amplifier-to-amplifier crosstalk from a stack of images where a bright source(s) has been scanned over each amplifier segment;

Determine photon transfer functions (measured variance versus count level) to determine amplifier gain, linearity, and read out noise from wideband dome-screen flats;

Determine pixels dependent shutter timing variations from alternating short-long-short integration wideband dome-screen flats;

Using the full science camera as a wavefront sensor is critical in the early stages of the Commissioning phase. This is done by intentionally defocussing the camera by a known amount to obtain intra and extra focal images to map the optical aberrations over the full field-of-view. Software will be needed for analyzing the science array as a wavefront sensor along with specific Optical reconstruction software to using the science 189 sensors in the FPA to estimate the system misalignment and figure errors on M1M3 and M2. This wavefront estimation software will be derived from wavefront curvature algorithm used in operations. The optical reconstructor will be specifically calculated for the mean wavefront aberrations at the center of each of the 189 science sensors.

2.2.8. External Data Sets

The following data sets are expected to be available to assist in the verification of the LSST performance:

Gaia astrometric and photometric catalogs

9


8/15/2011

UCAC Astrometric Catalog Sky Mapper Database SLOAN Digital Sky Survey Database PanSTARRS Database DES Database Known moving objects. Others

10


8/15/2011

3. System I &T activities and system performance tests

The scope of the systems integration and test period includes:

Acceptance tests for each of the three major subsystem to demonstrate that the criteria to start the System I&T milestone as outlined above have been satisfied;

Tests for remaining subsystem requirements that need the presence of another subsystem to show compliance;

Verification of command and control of the three LSST subsystems with the Observatory Control System;

Show that the Observatory System Specifications (OSS, LSE-30) have been met at the end of System I&T, along with the following:

o Test camera + telescope integrated functions;

o DM + camera + telescope interaction and meta-data;

o Testing DM algorithms at the base with “real” data; and

o Calibration operations & pipelines tested.

Initiate Data Quality Analysis on “real” camera data.

3.1. Camera-Telescope Integration

The key camera-telescope activities during the system integration and test period have been identified, time estimates made, and a schedule developed (Figure 5). These are presented in summary form below. Further detail for each of the bulleted item will be developed as this Commissioning Plan evolves from the time of this writing through the project construction phase.

11


8/15/2011

Figure 5: The sequencing of key activities for Camera-Telescope integration. Note the inclusion of a 6 week period near the end of the first year of commissioning to service both the Telescope and Camera.

3.1.1. Fixtures and Handling:

Activity Scope: All fixtures needed for handling the camera at the Summit facility are checked and verified for proper fit.Priority: High.Primary Tasks:

Safety measures for handling the camera are checked and verified. Handling procedure documentation is updated to reflect any changes that are made.

"Dry runs" of all handling procedures needed to install the camera on the telescope are executed without the camera. Any procedure modification are incorporated in to the LSST Observatory documentation

Any changes to fixtures needed to adapt to any refinement of the installation procedures are made.

3.1.2. Final Camera Utilities Install:

Activity Scope: All remaining utilities that are needed to run the camera on the telescope are installed.Priority: High.Primary Tasks:

SLAC supplied refrigeration system that is delivered with camera is installed during this period; and

Final checkout and verification of utilities on the telescope is done.

3.1.3. Camera – Telescope Physical Integration:

12


8/15/2011

Activity Scope: The camera is mated with the top end integrating structure of the telescope, moved from the Summit Facility camera lab to the dome floor, and installed on the telescope.Priority: High.Primary Tasks:

The telescope integrating structure (including the camera support hexapod and rotator) is removed from the top end assembly, mated with the handling cart, and transported to the camera staging area in the Summit Facility;

The camera is mated to the top end integrating structure;

The dome crane is fitted with the camera lifting fixture;

The camera + hexapod + rotator + integrating structure are physically moved from the camera staging are to the dome floor using the 80T reciprocating vertical conveyor (RVC).

Camera insertion guide rods are installed on the telescope top end assembly;

The camera + hexapod + rotator + integrating structure are physically installed and secured into the telescope top end assembly;

All camera utility connections are made to the telescope top end assembly;

Basic camera functionality is verified through the Camera Control System; and

Connectivity between the Camera Control System and Observatory Control system is established and verified.

Note: No on-sky data from the camera + telescope is expected during these activities.

3.1.4. Pre-Observations Check Out:

Activity Scope: The basic functionality of camera and telescope pair will be verified and initial instrumental characterization established.Priority: High.Primary Tasks:

Verify all camera functions can be controlled through the OCS, from both locally at the Summit Facility and remotely at the Base Facility.

Establish and verify connectivity between the camera on the telescope and the Data Management System

Verify camera telemetry is being recorded by the OCS's Engineering and Facility Database

Exercise the process and procedures needed to swap out one of the internal filters with the filter currently in storage.

Verify filter position repeatability.

Using the telescope mounted laser tracker to perform flexure and alignment measurements over the full range of elevations and rotator angles.

Characterize the on telescope performance of the Camera Focal Plane Array, including:

13


8/15/2011

o Photon transfer curves to determine amplifier linearity, noise, and gains;

o Shutter timing uniformity, repeatability, and pixel dependent corrections;

o Narrow band dome flats from the dome screen sampling each filter at 5-10nm intervals;

o Wide band (white) dome flats from the dome screen through each filter;

o Zero exposure bias images for mapping low level additive pixel structure;

o Dark images, include long darks for verifying dark current specs;

o Shutter leakage characterization by comparing long darks with and without the wideband dome screen illuminating the entrance pupil

Verify nominal telescope mount performance with camera installed

3.1.5. Initial Camera-Telescope Alignment:

Using the telescope mounted laser tracker determine the camera alignment dependencies over the full range of elevation, azimuth, and rotator angles. Build initial camera alignment look-up tables using these measurements.

Verify look-up tables maintain camera alignment within the measurement tolerance of the laser tracker.

3.1.6. Initial On-Sky Characterization:

Initial on sky characterization of the camera and telescope with the following objectives:

Establish and verify feedback to the TCS from the corner raft guide sensors; verify the camera-telescope guider interface

Map the position of best focus using “focus-sequences” over the full focal-plane-array as a function of elevation, azimuth and rotator angle, adjust hexapod control to best fit focal surface, update hexapod control look-up tables as needed;

Map the PSF size and shape over the full focal-plane-array;

Map the optical aberrations over the full focal-plane-array using the camera FPA as a wavefront sensor;

Process all images through the DMS instrumental signature removal pipeline;

Calibration data products for the instrument signature removal are updated including:

o Bias & dark master images

o Narrow band flat images from the dome screen in each filter

o Wide band flat images from the dome screen

o Shutter timing corrections

o Illumination corrections

Characterize stray and scattered light versus lunar angle and azimuth to verify the FRED point source transmittance function; and

14


8/15/2011

Obtain early data for DM pipeline debugging

This represents the first time that real from the sky data will be flowing from the Summit Facility to the Base Facility.

3.2. Active Optics Commissioning

Once the basic camera-telescope integration is completed.

3.2.1. Wavefront Sensor to Focal-Plane-Array Calibration:

Activity Scope: The 4 dedicated wavefront sensors used for alignment and figure control will be calibrated to the as built focal-plane-array and telescope active optics control system.Priority: High – Emphasis will be on obtaining wavefront calibration data. Other data will also be obtained to evaluate ISR and other data processing pipelines.Primary Tasks:

Using the full science camera FPA, alternating intra, extra, and in focus image sets will be used to calibration the focus position of the wavefront sensors with respect to the FPA. The mean of the focus Zernike coefficient (Z4) is determined for each of the 189 science sensors from the intra and extra focal image pairs. A best fit plane to the 189 mean Z4 coefficients is estimated. The offsets between the in focus Z4 coefficients from the 4 corner wavefront sensors and the FPA best fit plane are computed. The hexapod is adjusted iteratively until the mean value of the FPA best fit plane is zero. The Z4 offsets for each of the corner wavefront sensors are recorded as a function of elevation, azimuth, and rotator angle.

Using the data described above, the wavefront errors from the both 4 wavefront sensors and the 189 science sensors will be evaluated using separate optical reconstructors to evaluate consistencies in determined alignment and surface error corrections.

The Instrument Signature Removal pipeline will process all on sky images.

The transient alert pipeline will further process the in focus images.

Calibration data products for the instrument signature removal are updated including:

o Bias & dark master images

o Narrow band flat images from the dome screen in each filter

o Wide band flat images from the dome screen

o Shutter timing corrections

o Illumination corrections

3.2.2. Optical Reconstruction Verification:

Activity Scope: The conversion from wavefront error to misalignments and mirror surface errors will be verified for each degree of freedom in the active optics system.

15


8/15/2011

Priority: HighPrimary Tasks:

Each of the 10 degrees of freedom (camera =5, secondary mirror=5) used for alignment will be perturbed by known amounts increasing in amplitude. For each perturbation on sky wavefromt measurements will be made using both the 4 dedicated wavefront sensors and the camera itself. The wavefront errors from the 4 sensors will be converted to misalignments to determine the efficiency of recovering the known error and the linear response range.

Each of the controlled bending modes used for surface figure control on the primary-tertiary and secondary mirrors will be perturbed by a known mount (based on force patterns). For each perturbation on sky wavefront measurements will be made using both the 4 dedicated wavefront sensors and the camera itself. The wavefront errors from the 4 corner sensors and the 189 science sensors will be independently converted to surface errors to determine the validity of the force functions, the efficiency of recovering the known error, and the linear response range.

The Instrument Signature Removal pipeline will process all data from the camera.

In focus data will be processed by the transient alert pipelines and will be coordinated with the Data Management integration activities.

3.3. Data Management IntegrationIn parallel with the Camera-Telescope integration activities the Data Management pipelines will be tested using live camera data. The sequencing of DM pipeline testing in the first year of commissioning is shown in Figure 5, with details in the sections that follow.

Figure 6: Key Data Management pipeline integration activities and milestones.

3.3.1. DM + Camera + Telescope Integration

Activity Scope: Test the interface connections between DMS and the telescope, camera, and Engineering & Facility Database. Initiate testing for Science Data Quality Assessment and computational performance.

16


8/15/2011

Priority: NormalPrimary Tasks:

All interfaces (as defined by the ICDs) will also be tested in their operational configuration, including:

o Camera SDS - DM interfaces (science data transfer, raw and cross-talk corrected)

o Telescope - DM interfaces (power/cooling supply/reliability, mountain - base network transfers at 3 Gb/s rates)

o OCS - DM interfaces (command, status, data quality, daily transfer of Engineering and Facility database from Summit to Base)

Science Data Quality Assessment will be done via examining SDQA pipeline output from images taken from the Camera mounted on the Telescope.

Test computational performance by repeatedly operating the Base Center/Alert Production for an entire night, from acquisition of science data from the SDS, up to and including the creation of alerts and delivery to a local VOEvent broker (but not the further distribution of alerts).

3.3.2. Database and Pipeline Data Access

Activity Scope: Testing database and pipeline data access performance.Priority: NormalPrimary Tasks:

Test database and pipeline data access performance by repeatedly operating the Base Center/Alert Production for an entire night, from acquisition of science data from the SDS, up to and including the creation of alerts and delivery to a local VOEvent broker (but not the further distribution of alerts).

Serve pipeline input data from the database (e.g. known solar system objects) at full operational rates.

Ingest pipeline output data into the database at full operational rates.

3.3.3. Base Center Infrastructure Integration and Testing

Activity Scope: This activity includes support by the NCSA members of the DM team for integration of the DMS with the Telescope and Camera. The NCSA team has primary responsibility in this testing for acquiring, configuring, testing, and shipping infrastructure for the Base Center, and for hosting development and integration testing of new pipelines as they are enhanced during System Integration Test. The NOAO team has primary responsibility in this testing for infrastructure at the Base Center. Priority: NormalPrimary Tasks:

Test pipelines (see Section 2.4 below) by repeatedly operating the Base Center/Alert Production for an entire night, from acquisition of science data from the SDS, up to and including the creation of alerts and delivery to a local VOEvent broker (but not the

17


8/15/2011

further distribution of alerts).

Periodically update pipelines with new software releases of these pipelines during this testing phase as improvements are made based on performance analysis.

Updates to the Base Center infrastructure will be prepared and installed during this time frame.

Simulated network outage tests coupled with image retrieval from summit data buffer in the Camera Science Data Acquisition system will be tested

3.3.4. Calibration Data Products Pipeline

Activity Scope: Test the Calibration Products Production and the generation of Calibration Data Products for Alert Production.Priority: NormalPrimary Tasks:

Process wideband and wavelength dependent dome-screen flats to produce reference flat field images for each filter.

Process high-density rastered fields to produce illumination correction images for each filter.

Process image stack and camera meta data to produce pixel dependent shutter timing correction map.

Process image stacks to produce reference zero exposure bias image and reference 15 sec. dark current image.

Process spectroscopic data from calibration telescope to produce wavelength and temporally dependent atmospheric transmission function.

Process image stack to determine chip-to-chip and amplifier-to-amplifier pixel crosstalk correction matrix.

3.3.5. Instrumental Signature Removal

3.3.6. Alert Production Pipeline

Activity Scope: Test the deployment and administration of the Alert Production pipeline and install updates as enhancements are made during System Integration Test period.Priority: NormalPrimary Tasks:

Test Alert Production pipelines by repeatedly operating the Base Center/Alert Production for an entire night, from acquisition of science data from the SDS, up to and including the creation of alerts and delivery to a local VOEvent broker (but not the further distribution of alerts).

Periodically install new software releases of these pipelines as improvements are made during this testing phase.

18


8/15/2011

3.3.7. Data Release Production

Activity Scope: This activity includes support by the Princeton members of the DM team for integration of the DMS with the Telescope and Camera. The Princeton team has primary responsibility in this testing for the supporting the Data Release Production, which while not under full acceptance test until Science Verification, the DRP will be tested in a preliminary fashion using commissioning data.Priority: NormalPrimary Tasks:

The Data Release Production will be tested by periodically processing accumulated commissioning data up to that point. This processing will be paced by the production of commissioning data. Whenever the Observatory produces data meeting the single image quality requirements, a monthly processing of that data is planned (on servers hosted at NCSA). Princeton will support enhancements and maintenance of the DRP software.

3.3.8. Science User Interface

Activity Scope: Testing the Science User Interfaces and Analytical Tools.Priority: Normal

Primary Tasks:

Test SUI and Analytical Tools by repeatedly operating the Base Center/Alert Production for an entire night, from acquisition of science data from the SDS, up to and including the creation of alerts and delivery to a local VOEvent broker (but not the further distribution of alerts).

Pipeline output data will be accessed using the SUI and Analytical tools to exercise all functions in this WBS on commissioning data.

3.4. Additional System Performance Characterization (will need to fold this into the above discussion)

Wind speed / direction vs DIQ (characterize mount/camera vibration and procedure for dome vent control)

Stray and Scattered light vs lunar angle (verifications of FRED PST)

Characterize Ghosts vs field vs filter

Determine X-talk correction matrix

Characterize elevation and azimuth dependence of the system

Characterize temperature dependence of the system

19


8/15/2011

4. Science Verification Activities

The science verification period is structured around demonstrating that the survey functional and performance specifications given in the Science Requirements Document and LSST System Requirements are being met. For planning purposes we have structured the Science Verification period into a 4-phase frame work (Figure 5); 1) a 4-month period where the emphasis is in verifying compliance with single visit performance requirements; 2) verifying the functional performance of the LSST scheduler and autonomous operation; 3) verification of the full survey performance requirements for image stacks and area coverage; and 4) final science verification and acceptance tests for operation readiness. The Science Verification framework includes time for engineering related activities throughout, but is more heavily proportioned at the beginning transitioning to something near early operational levels by the end.

Figure 7: The framework for the 1-year Science Verification period being used for planning purposes has 4 phases: 1) Single image verification; 2) Autonomous scheduling and operations testing; 3) Full survey performance verification; and 4) Final science verification and operations readiness.

20


8/15/2011

Figure 8: The science verification matrix shows what methods are to be used to verify each of the SRD performance requirements.

21


8/15/2011

4.1. Science (SRD) Verification Tests

4.1.1. Single image/visit performance

Activity Scope: The first 4-months of the Science Verification is divided equally into 4 1-month activities divided approximately 50/50 between on-sky observing and engineering with an emphasis on verifying SRD image quality specifications. At the end of this period compliance with the SRD single image specifications shall be demonstrated per the methods indicated by the Science Verification Matrix (Figure 6).Priority: High

Primary Tasks:

Measure delivered image quality (DIQ) performance (FWHM & ellipticity) over the full FOV on successive exposures and visits. Correlate measured DIQ in time, Alt, Az, and rotator angle with MASS/DIMM measurements of the atmosphere wavefront measurements of the field dependent optical aberrations. After the effects of the atmosphere is removed test system image quality against SRD specifications as identified in the verification matrix.

Evaluate active optics look-up tables for systematic wavefront based correction versus altitude, azimuth and rotator angle. Updated active optics look-up tables as necessary to minimize systematic corrections.

Apply photometric color corrections using the atmospheric transmission function determined from the auxiliary telescope and test against SRD photometry requirements as identified in the verification matrix.

Using a known reference catalog (e.g. GAIA)

Test the data release production pipelines using all accumulated data at the end of each 1-month period.

4.1.2. Scheduler Automation Tests

Activity Scope: This is a concentrated effort to commission the LSST scheduler in all its modes of operation. This activity is divided into 4 2-week periods that are meant to ramp up autonomous operations where at the end the LSST can safely demonstrate consistent autonomous operations over a 1 week period. Additional single image performance verification will occur during this period to show full compliance with all single image SRD specifications.Priority: HighPrimary Tasks:

Initial trial scheduler commissioning. At completion the LSST system is demonstrated to run autonomously over a minimum 1-2 hour period, with various fail-safe modes demonstrated. In parallel with the observing effort there is an engineering effort to respond to scheduler issues uncovered during this period.

A demonstration of clean autonomous operation lasting a minimum of 4 hours. Along

22


8/15/2011

with further commissioning of various fail safe modes.

A demonstration clean of autonomous operation lasting a minimum of 8 hours (1 full night). Along with further commissioning of various fail safe modes.

A demonstration of clean autonomous operation lasting a minimum of 8 hours each night for a 1-week period. Along with further commissioning of various fail safe modes. During this time special mini surveys will be conducted. Upon the conclusion of this effort there is a readiness review for scheduler driven autonomous operation needed for the remainder of the commissioning period.

4.1.3. Full survey Performance (mini-surveys)

4.1.3.1. Stacked Image Performance

Activity Scope: Demonstrate compliance with the stacked image specifications over a limited number of fields with full 10 year survey equivalent visits (825 total visits as defined in SRD spec Nv1). Each trial is in itself a mini-survey where its data will be processed as if it were from the regular survey and made available to the LSST Commissioning team and science collaborations for analysis.Priority: HighPrimary Tasks:

A concentrated observing campaign to demonstrate image depth compliance (as defined in SRD Table 22) with the full survey equivalent image stack on a limited set of LSST fields (approximately 5-10).

A concentrated observing campaign to demonstrate final PSF shape residuals (as defined in SRD Table 25) with full 10 year survey equivalent stack on a limited number of fields (approximately 5-10). Note this campaign will require better than average seeing conditions to show compliance.

4.1.3.2. 10-year Area and Temporal Coverage

Activity Scope: Demonstrate compliance with meeting the area and temporal coverage specifications.Priority: HighPrimary Tasks:

Demonstrate that the rate of area coverage is sufficient that the SRD area specification Asky can be met over the 10 year survey lifetime. These tasks will result in a large area mini survey with a limited number of visits for each field and limited depth. Data from this effort will be processed as regular survey data and released to the science collaborations for analysis.

Demonstrate compliance with the full survey SRD temporal sampling specifications detailed by RVA1, RVA2, RVA3. This effort will result in a mini survey over a modest area (~2000 sq. deg) with fractional portion showing compliance with SRD temporal specifications.

23


8/15/2011

4.2. Parallel Data Management Activities

In parallel with the science verification tests outlined above the LSST Data Management system will under go additional verification tests. These tests will cause periodic updates to the software algorithms and the data processing pipelines. Included in these activities are updates to the Data Management System infrastructure at the Base and Archive Facilities as well as the Chilean and US DACs. The sequencing of key science verification activities in Data Management is shown in Figure 9.

Figure 9: The key Science Verification activities and milestones for the Data Management pipelines.

4.2.1. Archive Center and US DAC Integration and Testing

Activity Scope: Test the Archive Center infrastructure by executing of all Data Productions and transfer of Data Releases to the Data Access Centers.Priority: High

Primary Tasks: Raw image data will be transferred at 40 Gb/s from the Base Center to the Archive Center

whenever data is collected. Data Release Production will periodically process the accumulated commissioning data up to

that point. This processing will be paced by the rate of production of commissioning data. Whenever the Observatory produces data meeting the single image quality requirements, a monthly processing of that data is planned (on servers hosted at NCSA).

New software releases of these pipelines will occur periodically during this testing phase. These software releases are developed, integrated, and tested using infrastructure located at and supported by NCSA.

24


8/15/2011

A disaster recovery test will be performed wherein a complete set of all commissioning data will be recovered from offline storage and Catalogs from the DAC will be restored to the Archive Center.

4.2.2. Calibration Data Products Verification

Activity Scope: Verify accuracy and correctness of the Calibration Products Production and the generation of Calibration Data Products for Production processing using commissioning data.Priority: NormalPrimary Tasks:

Calibration Data Products will be created on servers hosted at NCSA, by UW-developed CPP software, and delivered to the Base Center via 3 Gb/s network to the Base Center for use in processing commissioning data by the Alert Production. UW will support enhancements and maintenance of the CPP software.

4.2.3. Alert Production Verification:

Activity Scope: Process all image data obtained during the science verification period through the Alert Production Pipeline.Priority: NormalPrimary Tasks:

The Alert Production will be tested by repeatedly operating the Base Center/Alert Production during all observing block in the Science Verification period, from acquistion of science data from the SDS, up to and including the creation of alerts and delivery to a local VOEvent broker and delivery to a local VOEvent broker and the further distribution of alerts to "test" subscribers.

4.2.4. Data Release Production Verification:

Activity Scope: At the end of each observing block process all image data obtained to date through the Data Release Production pipeline.Priority: Normal

Primary Tasks:

Test the Data Release Production by processing accumulated commissioning data up to that point. This processing will be paced by the production of commissioning data. Whenever the Observatory produces data meeting the single image quality requirements, a monthly processing of that data is planned (on servers hosted at NCSA).

4.3. Other data sets needed during commissioning

This section contains a list of additional data set needed during the commissioning period that may not otherwise be identified but are deemed useful. These include:

0) Raster single field across each detector, for determination of illumination corrections, initial color term determination, and verification of astrometric solutions.

25


8/15/2011

1) Dense rastering with 70-90% overlap of an area 3-5 times the field of view to determine illumination correction from the self-calibration algorithm (Tim Axelrod concept).

2) Repeated observations of fields across various airmasses, in multiple bands, to determine photometric repeatability.

3) Repeated observations of celestial pole field, at different rotations, to understand fixed-airmass atmospheric systematics.

4) Observations of celestial pole field though different amounts and kinds of clouds, to verify how well we suppress transparency variations.

5) Other engineering time for pointing model, wavefront correction tweaking, etc.

26


8/15/2011

5. Operations Readiness

This section is meant to define the conditions, terms, and criteria that are used to determine that the LSST is ready for operations.

5.1. 30-day mini-survey

The final survey verification phase will consist of a 30-day continuous mini survey to demonstrate readiness for full LSST science operations. This survey will be under full autonomous scheduler driven operation. 30 days of survey operations is sufficient to cover the operational cycle over a full lunation, including the u-band filter swap over dark time. Assuming the typical usable weather fraction, the 30-day mini survey will yield approximately 20000 visits sufficient multi epoch coverage of the sky in 2-3 filters or a single epoch with all 6 filters (see A.2 example mini-survey #1).The data from this effort will be treated as if it were part of normal survey operations and will be an early release data product for the community. This data will also be used to start boot strapping the planned 10-year survey.

Figure 10: An example of the sky coverage and visit density achievable of a 30-day period. Three “deep drilling” fields are visible as well as areas with higher temporal sampling (dark blue).

5.2. Readiness review

An Operations Readiness Review (ORR) will be held jointly by the Project and the federal funding agencies as a means to formally close the construction project and initiate full survey operations. At the ORR the project will present the following:

Documented analysis showing compliance with the performance specifications called out in Section 3 of the SRD;

27


8/15/2011

Successful completion of the 30-day mini-survey showing that the LSST Observatory can sustain operational status over the critical cycle of one full lunation.

Analysis of the 30-day mini-survey that shows extrapolated performance that meets the 10-year survey specifications;

The ability of the LSST Observatory to monitor and asses the progress of the survey towards its 10-year specifications;

Operational procedures developed during the Commissioning period have been documented and are shown to comply with the LSST Safety Plan;

A prioritized “punch” list of outstanding technical issue that will need to be addressed during the early stages of operations.

5.3. Pre-Operations Engineering

In parallel with the analysis of the 30-day mini survey data the LSST Observatory will enter a 45-day “shutdown” period where on-sky observation will halt. At this point in time 2 years will have elapsed since initial subsystem assembly and system integration, which places the LSST Observatory on schedule for its 2-year major maintenance and servicing.

5.3.1. M1M3 Mirror Re-Coating

Activity Scope: Remove, strip, clean, and re-coat the M1M3 mirror surfaces. Reinstall M1M3 mirror back into telescope.Priority: Normal / HighPrimary Tasks:

Remove Top-End Integrating Structure with Camera and transfer to Summit Facility camera lab.

Install camera dummy mass to allow the telescope to point to zenith for removal of the M1M3 mirror cell. Remove M1M3 mirror assembly and transfer to Summit Facility re-coating plant.

Strip old coating, clean and re-coat mirror surfaces.

Re-install M1M3 in telescope and prepare to receive the top-end integrating structure with the camera.

5.3.2. Camera Maintenance and Servicing

Activity Scope: Clean, service, maintenance, and scheduled shutter replacement.Priority: Normal / HighPrimary Tasks:

Replace camera shutter with “fresh” operational unit;

Inspect, service – repair filter mechanisms;

Clean internal camera optics;

Inspect, service, and repair utility trunk electroncs

28


8/15/2011

5.3.3. Base Facility DM Infrastructure Updates

Activity Scope: Implement needed Base Facility computing infrastructure and software.Priority: NormalPrimary Tasks:

Scheduled update / upgraded to Base Facility compute hardware.

Update data processing pipelines running at the Base Facility

29


8/15/2011

6. Managing and Staffing the Commissioning Effort

Throughout the construction phase of the project the three technical teams will have been operating nearly independently of each other, except where critical interfaces requires close interaction between teams. During the commissioning phase the three technical teams will be merged into single team. All commissioning and remaining technical activities shall be coordinated through the LSST project systems engineering office. The Project Systems Engineer and System Scientist will be responsible for the primary deliverables from the Commissioning Phase. The Project Systems Engineer and System Scientist will be responsible for prioritizing the commissioning activities to ensure these deliverables are met. The Project Manager will hold overall authority over all commissioning activities, schedule, and budget.

6.1. Issue and Event Tracking

During commissioning the Project will implement an electronic issue and event tracking (i.e. Trac, see http://trac.edgewall.org/) system to assist in coordinating and prioritizing the detailed day-to-day activities. This system will be referred to the Commissioning Tracking Database. This will be the primary means for documenting the commissioning activities, their results, and prioritizing work to address open issues.

Initially, the issue Commissioning Tracking Database will be populated with the suite of tests derived from the activities and tasks described above in Sections 2 & 3. In addition, the current technical issues carrying over from the subsystem assemblies will be migrated to the Commissioning Tracking Database.

6.2. Work Cycle during Commissioning

During the Commissioning phase it is important that a balance is maintained between obtaining on-sky astronomical data needed for science verification and allowing extended periods for technical work. Built into the scoping of each on-sky commissioning activity is roughly a 50/50 duty cycle between obtaining astronomical data and technical work.There two scheduled breaks dedicated solely to engineering and technical work during the commission phase to allow uninterrupted time to address critical issues. These are scheduled at the end of System Integration & Test and at the end of Science Verification.

The first scheduled engineering block is 30 days long and follows the Camera-Telescope integration. This time is meant primarily as an inspection period for the camera and telescope mechanisms. The camera will be removed from the telescope and taken to the Summit Facility labs for inspection, internal optics cleaning, servicing of worn components, and replacement of the shutter mechanism. These activities will become part of the routine maintenance of the LSST Observatory. The high priority repair/rework items from the Commissioning Track Database that needed extended time will also be addressed during this period.

The second period comes at the end of the science verification phase following the final 30-day mini-survey. This is a 45-day time block where primary goal is preparing the LSST Observatory for

30

http://trac.edgewall.org/


8/15/2011

routine survey operations. During this engineering time the camera will be removed from the telescope for its annual routine servicing, cleaning, and repair. The M1M3 mirror system will also be removed and recoated.

6.3. Commissioning Staffing

The 3 technical teams from the Telescope & Site, Camera, and Data Management subsystems will be merged into single team during the commissioning period. The Telescope and Site and Data Management teams will be supported by the NSF MREFC construction funding, where the Camera team will be supported from DOE operations funding. This single technical team shall take direction and priorities for day-to-day activities from the Project Systems Engineering office. The make up of this team and its distribution by activity center and skill type over the 2-year commissioning is given in Table 1 below. The resources for each of the two years are nearly level, but the distribution of scientists and software engineers working on the Data Management Pipelines shifts from a focus at the Base Facility in the first year to the Data Archive Facility in the second year.

6.3.1. Commissioning Science TeamIn addition to the technical team, the Project will add a dedicated team of scientist and post-docs, whose purpose will be to evaluate the science quality of the commissioning data and provided feedback to the technical team. The science quality assessment will be based primarily on the demonstrating the SRD performance requirements and extending this analysis “user level” science programs.

The science team consists of the System Scientist and a senior Commissioning Scientists, who will take the lead in assessing the science data quality and be the primary contact point with the Project Scientist and Systems Engineer to coordinate observing planning and scheduling. Supporting the Commissioning Scientists are 3 junior scientist and 2 post-docs.

6.4. Commissioning Oversight

As with many projects the LSST will face enormous pressure from its user community to make its data available to the public as quickly as possible. Indeed, by necessity the LSST Project will need to rely on scientists (not funded by the Project) from the 11 science collaborations for assistance in analyzing the data produced during the commissioning period to provide the project with needed feedback on its quality. There will also be a need to avoid the appearance that the Project is “skimming the cream” of early science by making sure the data that are released are only of the highest quality.

The LSST Project believes that the best solution to these inevitable tensions will be to convene at the start of the Commissioning Period an external Commissioning Oversight Panel of scientists from its user community. This panel will be advisory to the Project Director and advise the director on the whether and when the commissioning date should be released. This same panel would also advise the agencies on the Project’s readiness for operations.

6.4.1. Data release policy

TBD (Requires LSST Board approval)

31


8/15/2011

32


8/15/2011

Table 1: FTE resources by year-category at each of the activity centers during Commissioning.

33


8/15/2011

Contingency Planning

6.5. Commissioning with a partially populated science array

In order to initiate the Commissioning phase the Camera shall be delivered with, as a minimum, the focal plane array populated with all four corner rafts and five, out of 21, science rafts. The 4 corner rafts contain the wavefront and guide sensors and are needed to complete the commissioning of the active optics control system. The 5 science rafts shall be placed such that the center (on-axis) position is filled along with four positions adjacent to each of the corner rafts. This arrangement provides sampling of the field-of-view around the optical axis so that variations in the telescope bore-sight can be evaluated as well as sampling the extreme field points that have the most leverage in the optical sensitivity and reconstruction matrices.

6.6. Other ContingenciesTBD

34


8/15/2011

2 Appendices

2.1 A.1 Survey Bootstrapping

One of the purposes of the 30-day mini survey described above is to begin the survey bootstrapping necessary to enable full functionality of the survey data analysis. “Bootstrap” here means that the full functioning of the system requires data that can only be gathered once the system itself is fully functioning. Full functionality, therefore, must be achieved iteratively with each bootstrap item improving in quality. Here we have identified the needed bootstrap items that will be obtained in part from data obtained from the operation readiness mini survey, these include:

Co-added Images: Prior to creation of detection co-adds only single frame measurements can be supported. Over time co-added images will be produced for deep detection used for “forced photometry”.

Subtraction (image differencing) Templates: Image differencing is strongly dependent on the quality of the differencing template. Selection of quality templates will require many high quality images and will be initiated from the mini-survey data.

Astrometric Standards: These are needed for generating high quality WCS. We can possible start with previous surveys (e.g. GAIA), but will need to quickly add data from the LSST survey to achieve desired density of high quality references per CCD.

Photometric Standards: Early quality standards are need for the nightly alert production. We will need to boot strap from existing standards to LSST data to provide the reference source density desired per CCD.

Standards for “Global” Calibration: These will need to be carefully cleaned of low-level variability as the calibration accuracy improves and the time baseline lengthens.

Moving Object Catalogs: We will either start with an empty catalog or one populated from a precursor survey. Initial catalog will be relatively “poor” and will lead to “leak through” of moving objects as transients or variables.

Variable Identification: This will be built up over time and is needed by the moving object processing and vice versa.

Generalized of variability: We will need an object history for alert classification. Object astrometric models: These will start off poor and will need time to become reliable for

producing proper motions and parallaxes. It may be possible of using precursor surveys (e.g GAIA, SKYMAPPER, Pan STARRS) to seed the models.

Object Catalogs: These can only be built up as images accumulate. It will start out empty, but will begin to be populated from the final min-survey prior to the start of operations.

35


8/15/2011

2.2 A.2 Example Mini-Surveys

Mini-survey #1: If entire survey region is 18,000 sq degrees, and the 10 year survey achieves of order 150 visits total in each of r,i,z,y, and 60 in u and g, a total of 4x150+2x60=720 to 800 visits to each part of the sky, total. If we allocate the best and most photometric 10% of workable nights in the second commissioning year to a mini-survey, that’s 1% of the total survey so we would get about 7 visits to each region on the sky, to spread across the passbands. If this is split between r and i, so that we get a color for each object, we would be at 3 visits per field per band. This would allow the following:

i. Full “uber-cal” validation in two bands.

ii. Scaling tests for N dependence.

iii. Gives first epoch across entire sky at close to survey depth, for eventual proper motion comparisons.

iv. Provides CMD in i, r-i for entire sky.

v. Initial designation of variable objects, feeds veto list for subsequent classification of frame subtraction variables.

Alternatively, we could spend the 7 visits doing a single-epoch 6 band map of the entire survey region, to single-visit depth in each band. Need to learn how to properly do cosmic ray rejection from just two images, though.

Mini-survey #2: An alternative mini-survey in 10% of the time in science year would be full depth over a partial area, presumably starting at dec=90 and coming North. Based on above computation, 0.1 survey-years gives us a coverage of 18000*7=126K square degree*visits. If we go to survey depth with 800 visits across all bands, that would be area of ~160 square degrees. So only 16 pointings! Cutting back to 400 visits total doubles the area to 320 square degrees, or 32 pointings. This is would be all RA’s from dec of -90 to dec of -80.

36