lsst technical review · – rapid transient alerting • lsst data management system capabilities...
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LSST Technical Review
Kirk GilmoreSLAC
24 Jan 06
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Traceability matrix
SLAC EPACJanuary 24-25, 2006
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Optical Design
0.6”
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LSST Optical Design V3
• Modified Paul-Baker 3-Mirror Telescope– F/1.23 with <0.20 arcsec FWHM images in u,g,r,i,z,Y– 3.5 ° FOV and Etendue = 319 m2deg2
– All Optics Manufacturing Within State of the Art
Polychromatic diffraction energy collection
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Detector position ( mm )
Imag
e di
amet
er (
arc-
sec
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U 80% G 80% R 80% I 80% Z 80% Y 80%
U 50% G 50% R 50% I 50% Z 50% Y 50%
M2M3
M1
8.36m Aperture
Camera
LSST optical layout
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Unique Monolithic Mirror Ordered
8.4 Meters
Primary Surface
Tertiary Surface
• Structured Spin- Cast Borosilicate Mirror– Contract In Place Using Private Funding– University of Arizona Steward Mirror Lab– Experience with Completed LBT Mirrors– M1 and M3 Surfaces in Single Blank
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Primary and Tertiary Monolith Mirror
• Primary Tertiary Monolith Section View
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Coating Development Effort to Combine Benefits of Al and Ag at 8 Meter Scale
Collaboration with Gemini to Produce an Al & Ag Coating Using System Already Demonstrated at 8m.
Protected Ag Coating Successfully Demonstrated at Gemini on 8m Primary Mirror
Initial Test of a Al/Ag Coating shows Promise in Blue and in Overall Response
S1 to S4 Samples reflectivity in the blue(made between Dec 2005 and Jan 2006) - Aluminum on the bottom
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300 320 340 360 380 400 420 440 460 480
Wavelength (nm)
Ref
lect
ivity
(%)
S1: 865 A of Aluminium_(HV: all nigth)S2: 1082A of Silver (HV: all nigth)S3: 100A of Ag - 865A of Al _(HV: all nigth)S4: 200A of Ag - 865A of Al_(HV: all nigth)U Filter
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Telescope Mount
Concept Design and Structural Analysis
Completed.
Industrial Contract to Evaluate:
Drives and Controls System
Top End Configuration
Performance Predictions
Risk Analysis
Cost and Schedule
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Telescope Mount - Updated Configuration
Telescope and Camera Interface Group
SystemsEngineer Mailer : TelCamICD
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WFS and Alignment – Focal Plane Concept with Embedded Utility Sensors
Shack-Hartman Sensors (magenta) at 4 locations
Each:•4cm x 4cm footprint•13.07 x 13.07 arcminutes•170.87 square arcminutes
Curvature Sensors (red) at 16 (4×4) locations
Each:•1cm x 1cm footprint•3.268 x 3.268 arcmin.•10.68 square arcmin.
Guider Sensors (yellow) at 8 locations
3.5 deg FOV
Illumination Limit
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WFS and Alignment
• Precision Metrology System Part of Baseline Design and Development Approach– Permanent Fiducials on all Optical
Elements– Rapid Initial Integration – Quick Re-
Assembly in Operations• Objective is to Enhance System
to Active Alignment– In Parallel with WFS During
Operation– Off – Load Rigid Body Alignment or
Limit Capture Range
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Software and Controls
OCSScheduler
TCS OTS
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crane beams & structure clear of rotational sphere of telescope(i.e. non co-rotating)
Wind & stray light screen
Roughly hemispherical (5/8), 32m D. dome w/ stacking up-and-over shutterand operable ventilation openings
Support Building & exterior platform lift
Baseline is removal of TEA using crane & cart(PMA on cart only)
Baseline Dome Concept Developed and Alternates Being Considered
TMA recessed into floor to improve stiffness.Also increases overhead clearance.
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LSST’s Three Finalist Sites - Each are Developed Observatories
San Pedro MartirLas CampanasCerro Pachon
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LSST Final Site Selection Scheduled for April 14 2005
• Final site selection done before MREFC• Site Selection Committee (12 members)
– Previous Site Selection Committee (7 independent experts. Chair is Marc Sarazin from ESO)
– 5 new members (3 from LSST + 2 new independent experts)• Final approval by the LSST Board
Preliminary Timeline
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EnclosureMirror coating facility
Camera shop
Lifting device
Engineering control room
Mechanical Equipment
Summit Support FacilityMain Control Room
Data Processing (early)
Machine/electronic shops
On-site management offices
Break room, etc.
Generator & Mech. Equip.
ExistingSupportFacilitiesSan Pedro Mártir,
Cerro Pachón, orLas Campanas
Ensenada or La Serena
LSST Summit and Support Facility General Layout
Base Support FacilityData processing (full)
Administration
Engineering Offices
More extensive shops
Conference facilityDorm
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Telescope Enclosure and Summit Support Concepts Developed
Cerro PachónEl Peñón site – topography advocates for a multi-level development
Space, conditions & infrastructure at all sites dependent on site host Proposals
Las CampanasSite of existing 1m Swope Telescope, others may be available
San Pedro MártirSite space ample if not shared with new Mexican Telescope
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The LSST Camera
SLAC EPACJanuary 24-25, 2006
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L1/L2 Camera Body Front-End
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LSST baseline camera optics
1.62 m
L1
L3
filter0.64 m flat detector
1.09 m
0.3 m
Space for shutter
L2
SLAC EPACJanuary 24-25, 2006
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LSST Ideal Filter
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Wavelength (nm
u g r i z Y
LSST Filter Set
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Final Bandpass Curves
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300.0 400.0 500.0 600.0 700.0 800.0 900.0 1000.0 1100.0
Wavelength (nm)
u
g r I z
Y
Optics
atm
Detector
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Shutter Position
Time-stamp Variation
Tim
e
Exposure Time
Shutter Design
Two-sheet design allows arbitrarily short exposure times
Shutter sheets must roll up
Shutter Operational RequirementsRequirement Value
Maximum time-stamp variation 1.0 secondMinimum exposure time 1.0 secondMaximum allowed exposure time variation 0.10%Operational life 107 cycles
Shutter Assembly
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Shutter Placement
L1
L3
Shutter
Filter
L2
Detector array
1.6m
Requirements– Shutter fits between the filter and L3– Aperture diameter: .76m
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Filter exchange mechanism
4-bar linkage allows filter to move past shutter and fit inside the outer camera Dewar
SLAC EPACJanuary 24-25, 2006
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Integrating Structure Material Comparison MatrixProperty Unit Alum. Invar 36 SiC
Total mass with rafts (25 kg) kg 100 246 112P-V gravity sag over aperture
0-90 elevation angle µm 1.350 1.400 0.25030-90 elevation angle µm 0.675 0.700 0.12545-90 elevation angle µm 0.395 0.410 0.07360-90 elevation angle µm 0.181 0.188 0.033
Mode shape and frequencyMode 1, torsion/twist Hz 205 184 463Mode 2, X translation Hz 241 217 546Mode 3, Y translation Hz 339 321 775Mode 4, Z translation Hz 366 346 846
Elastic modulus / density SI 25.56 17.67 130.16Thermal conductivity / CTE SI 10.00 8.08 75.00
0.25 µm p-v distortion under 1gout-of-plane gravity load (SiC)
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From LSST Science Requirements to Sensor Requirements
� High QE to 1000nm thick silicon (> 75 µm)
� PSF << 0.7 Ó (0.2Ó) high internal field in the sensor high resistivity substrate (> 5 kohm cm)
high applied voltages ( 30 - 50 V) small pixel size (0.2 Ó = 10 µm)
� Fast f/1.2 focal ratio sensor flatness < 5µm package with piston, tip, tilt adj . to ~1µm
� Wide FOV ~ 3200 cm 2 focal plane > 200-CCD mosaic (~16 cm 2 each) industrialized production process required
� High throughput > 90% fill factor 4-side buttable package, sub-mm gaps
� Fast readout (1 - 2 s) segmented sensors (~6400 TOTAL output ports) 150 I/O connections per sensor
� Low read noise < ~ 5 rms electrons
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SLAC EPACJanuary 24-25, 2006
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FPA Flatness Allocations
Sensor Module
5µm p-v flatness over entire sensor surface
Raft Assembly
6.5µm p-v flatness over entire surfaces of sensors
Focal Plane Assembly
10µm p-v flatness over entire surfaces of sensors
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Integrating structure
Raft structure
AlNUP
SLAC EPACJanuary 24-25, 2006
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Some Techniques Explored ForIn-Situ Cold Metrology
• A laser and 2D diffraction grating projects unique pattern of ellipses onto FPA. Ellipses centroided by CCD to ~1/3 µm. Spot motion and/or pattern distortion, determine flatness and/or other changes.
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32-port CCD32-port CCD32-port CCD
In-dewar electronics partitioning
Front End Boards (6 per raft):• 48-channel video signal chain through CDS processing• clock and bias drive• ASIC-based
BEE motherboard and backplane:• differential receiver• signal chain ADC• frame buffer• data transport to optical fiber• clock pattern generation• clock and bias DACs
LEFT
RIG
HT
180K
240K
Flex cables (~ 20,000 signals)
Cold sink
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sensorsraft base
front-end electronics
(48 chan./card)
cold sink #1
integrating structure
cold sink #2
back-end electronics
(flex cablesnot shown)
(flex cablesnot shown)
(flex cablesnot shown)
Baseline Conceptual Design
SLAC EPACJanuary 24-25, 2006
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How the LSST ScienceRequirements Drive the DMS
• Science Requirements– Very deep, wide field survey– Controlled systematics– Rapid transient alerting
• LSST Data Management system capabilities and performance– Highly distributed, scalable, and reliable– Acquires the scientific data, transports it from mountain to base to
archive center– Reduces the data, assesses its quality, and publishes the data for
broad access• Design and implementation features
– Advanced scientific algorithms– Layered architecture providing for extensibility and technology
evolution– High-performance computing, storage, and networking
technologies– Rigorous formal development process
SLAC EPACJanuary 24-25, 2006
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Data Volumes Similar to MostDemanding HEP Projects
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5000
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20000
GB
Raw Catalog
Estimated Nightly Data Volume
LSST Pan-STARRS 4 SDSS
LSST Estimated Nightly Data VolumesThe nightly data volumes generated by LSST will be an order of magnitude larger than those estimated for Pan-STARRS 4 and 2 orders of magnitude larger than SDSS. The data archive will grow at a rate of roughly 7 PB/yr. This requires scalability and reliability in LSST data management systems.
SLAC EPACJanuary 24-25, 2006
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Technological Evolution
Images courtesy of International Business Machines Corporation. Unauthorized use not permitted.
Technological EvolutionIf the useful life of the LSST Data Products is at least two decades, the raw data will be re-processed at least 20 times and the computers and software this is done by will be changed at least 4 times!
LSST will be updating software and data very frequently. This must be a largely automated process and highly documented as it occurs. We cannot afford to rewrite the entire software at one time or port to entirely new hardware en masse, so evolutionary change must be supported.
SLAC EPACJanuary 24-25, 2006
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DMS Layered Architecture
Infrastructure Layer
Middleware Layer
Application Layer
Application Layer• Contains Nightly Data Pipelines and Products and the
Science Data Archive• Provides all pipeline algorithms and components,
image and astronomical object data structures, end user tools for Data Products access, and “Algorithm”Fault-tolerance
Infrastructure Layer• Contains computing, storage, and networking
hardware and system software at each facility as well as the long-haul networks that interconnect the facilities
• Provides the parallel processing execution environment for pipelines, the distributed storage network for data products, and system-level fault-tolerance/autonomics
Middleware Layer• Contains distributed processing
services, data access services, user interface services, and system admin and operations services
• Provides isolation of the Application Layer from the Infrastructure Layer, pipeline component plug-in architecture, standard services for security, load-leveling, provenance, and software fault-tolerance
SLAC EPACJanuary 24-25, 2006
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Application LayerData
AcquisitionInfrastructure
Image Processing
Pipeline
Detection Pipeline
Association Pipeline
ImageArchive
SourceCatalog
ObjectCatalog
AlertArchive
Deep Detect Pipeline
DeepObject
Catalog
VO Compliant Interface Middleware
Classification Pipeline
Moving Object Pipeline
CalibrationPipeline
End UserTools
AlertProcessing
Eng/Fac DataArchive Common Pipeline
ComponentsNightly Pipelines and Data ProductsNightly Pipelines are executed and Data Products are produced within 60 seconds of the second exposure of each visit.
Science Data ArchiveThese pipelines are executed on a slower cadence andthe corresponding data products are those that require extensive computation and many observations for theirproduction.
SLAC EPACJanuary 24-25, 2006
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Middleware Layer Distributed Processing Services
Distributed Processing Services
Pipeline Management & Control
Pipeline Manager
Event System
Event DistributorEvent Publishing API
Pipeline Construction System
ConfiguratorPipeline
Distributed Processing ServicesThe Pipeline Manager is a process that handles overall control of executing pipelines. The Event System is for publishing & distributing asynchronous messages between processes and to system logs. The Pipeline Configurator is a service that creates an instance of a pipeline from a template. A Pipeline is an instance of a Pipeline class that carries out a logical set of data processing (e.g. Processing Nightly Observations).
SLAC EPACJanuary 24-25, 2006
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Middleware Layer Data Access Services
Data Access Services
Data Access Framework
Data StagerData ReplicatorDatabase API
Archive Services
Ingest Service
Data Access ServicesThe Data Stager copies/organizes data & software in preparation for and clean up from a pipeline execution.The Data Replicator is an inter-site data mirroring system. The Database API is an interface for inserting/extracting data to/from the database. The Ingest Service is a service that formally incorporates data into the archive, including replicating data to long-term storage and inserting associated metadata in the database
SLAC EPACJanuary 24-25, 2006
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Middleware Layer Other Services
System Admin/Ops Toolkit
User Interface Toolkit
Other ServicesOther ServicesThe Middleware Layer contains other services that support system administration and operations across the grid of DMS facilities as well as providing static and ocntinuous display user interfaces for visualization of DMS data and status.
SLAC EPACJanuary 24-25, 2006
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DMS Infrastructure LayerLong-Haul CommunicationsMountain/Base to Archive and Archive to Data Centers Networks are 2 - 10 Gbps protected clear channel fiber optics with protocols optimized for bulk data transfer
Base FacilityIn Chile, Mexico, or the United States. Nightly Data Pipelines and Products are hosted here on 25 TFLOPS class supercomputers to provide primary data reduction and transient alert generation in under 60 seconds.
Mountain SiteIn Chile or Mexico. Data acquisition from the Camera Subsystem and the Observatory Control System, with read-out in 2 seconds and data transfer to the Base at 10 Gbps
Archive/Data Access CentersIn the United States. Nightly Data Pipelines and Data Products and the Science Data Archive are hosted here. Supercomputers capable of60 TFLOPS provide analytical processing, re-processing, and community data access via Virtual Observatory interfaces to a 7 PB/yr archive.
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Preliminary Cost Analysis
SLAC EPACJanuary 24-25, 2006
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SLAC:Overall camera project management; camera mechanicaldesign; camera I&T
BNL:Sensor and FEE development;integration of sensors withFEE and BEE; support for focal plane assembly and test;sensor/raft metrology
LLNL:Mechanical and optical engineering; assembly and testof optical elements and filters
Harvard:Electronics development of BEE.
Ohio State:Development of guide sensor system
Key Institutional Roles
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