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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0 80 160 240 320

Detector position ( mm )

Imag

e di

amet

er (

arc-

sec

)

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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55

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90

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


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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


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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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100.0

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


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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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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


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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)



Baseline Conceptual Design


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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


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Data Volumes Similar to MostDemanding HEP Projects

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5000

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15000

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.


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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.


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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


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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.


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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).


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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


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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.


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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


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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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lsst technical review · – rapid transient alerting • lsst data management system capabilities...

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