Spacecraft Design And Mission Operations

SNAP Spacecraft & Mission Ops 29 March, 2000

SPACECRAFT DESIGN and MISSION OPERATIONS

Michael Lampton (for H. Heetderks) Page 1 of 10

SNAP Spacecraft & Mission Ops 29 March, 2000

SNAP ORBIT • "Prometheus" Orbit Baselined Following Preliminary Trade Study • Uses Lunar Assist to Achieve a 14 day (19 X 57 Re) Orbit, or 7 day (8 X 40 Re) Orbit with a Delta III 8930 or Delta IV-M Launch Vehicle • Good Overall Optimization of Mission Trade-offs • Low Earth Albedo Provides Multiple Advantages: • Facilitates Passive Cooling of Detectors • Minimizes Stray Light in Telescope • Minimum Thermal Change on Structure Reduces Demand on ACS • Excellent Coverage from Berkeley Groundstation • Outside Radiation Belts

• Orbit Reachable with Available Launch Vehicle

Michael Lampton (for H. Heetderks) Page 2 of 10

SNAP Spacecraft & Mission Ops 29 March, 2000 •

High northern hemisphere orbit has excellent telemetry: ~ 50 Mbit/s for 19/57 orbit, > 50 Mbit/s for 8/40 orbit

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8 Gbit (compressed) image every 200s: 40 Mbit/s

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Data content: 1/3 optical images, 1/3 spectroscopy, 1/3 IR photometry 8Re X 40Re, inc=70 deg, AOP=270 deg (8 day orbit)

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Michael Lampton (for H. Heetderks) Page 3 of 10

SNAP Spacecraft & Mission Ops 29 March, 2000

SPACECRAFT DESCRIPTION • Detailed Design and Specification of S/C will be Done by Industry Teaming Partner • We have Developed a Strawman Spacecraft to Support Costing, and Payload Layout • Power from 4 sq m GaAs cells mounted directly to Sun Shade (No Deployable Arrays Required) • Propulsion System Uses Monopropellant Hydrazine • Telecom System uses 25W TWTA and 50 cm dish to Achieve 50 Mbit/sec downlink • Standard Rad-Hard Processor System will be used for C&DH

Michael Lampton (for H. Heetderks) Page 4 of 10

SNAP Spacecraft & Mission Ops 29 March, 2000

4 meter Composite Fairing Heat Shield Assy Solar Panels Sun Shield

Optical Bench Main Baffle Tube Instrument Deck Bus Assy Truss CCD Radiator Propulsion Deck 1666-4 PAF

Delta IV Launch vehicle Michael Lampton (for H. Heetderks) Page 5 of 10

SNAP Spacecraft & Mission Ops 29 March, 2000

ACS System • Two Ball CT 602 Star Trackers Used for Coarse Tracking • Fast Read-out CCD in Science Telescope Provides 25 Hz Update Rate for Fine Attitude Sensor • This System will provide overall Pointing Accuracy/Stability of .03 Arc-Sec (1 Sigma) for Observatory • Reaction Wheel Package Consists of 4 Each of L3 Micro-balanced RWA-15 Units • Gyro Package Comprised of Redundant L3 RGA-20 Units with low drift

Michael Lampton (for H. Heetderks) Page 6 of 10

SNAP Spacecraft & Mission Ops 29 March, 2000

Space Frame Solar Panels Sun Shield MLI Blanket Baffles

Star Tracker TTL Star Guider Gyro Assy

BusAssy Truss Composite shear CCD Radiator Reaction wheel 3 x 50cm dia. Hi-gain GMAs 2 x Lo-Gain Antennas Transponder Battery Mass Memory Unit (MMU) Spacecraft Control Unit (SCU) Power Control Unit (PCU)

Propulsion Deck 12 x .5 lbf engines 1 x 5.0 lbf engine 3 x 47 cm dia. tanks Controls Michael Lampton (for H. Heetderks) Page 7 of 10

SNAP Spacecraft & Mission Ops 29 March, 2000

OBSERVATORY INTEGRATION and TESTING • Detailed I&T Plan will be Developed During Study Phase • Test Philosophy Includes: • Build Test Functions into Hardware • Perform System Level Tests as Early as Possible • e.g. Do Subsystem Interface Tests at Bread Board Level • Test End-to-End Whenever Possible • Ability to Support Tests is an Important Factor in Choice of Teaming Partners • Strawman Plans Include: • Optics Testing Done by Optics Subcontractor • Spacecraft Contractor will Deliver a Fully Tested Spacecraft • Mechanical and Electrical Integration will be Done in an Appropriate Facility • Observatory Vibration and T/V Done in an Appropriate Facility • Final End-to-End Optical Test will be Done in an Appropriate Facility

Michael Lampton (for H. Heetderks) Page 8 of 10

SNAP Spacecraft & Mission Ops 29 March, 2000

MISSION OPERATIONS • Mission Operations Center (MOC) at Space Sciences Using Berkeley Ground Station • Fully Automated System Tracks Multiple Spacecraft • Science Operations Center (SOC) at Lawrence Berkeley Laboratory Built Around the National Energy Research Super Computer (NERSC) • Multiple Terabytes Data Storage • High Speed Links to CPU Farms & Supercomputers • Intensive Processing Done on Supercomputer with Final Analysis on PC's • Operations are Based on a Four Day Period • Autonomous Operation of the Spacecraft • Coincident SOC Review of Data with Build of Next Target List • Upload Instrument Configuration for Next Period

Michael Lampton (for H. Heetderks) Page 9 of 10

SNAP Spacecraft & Mission Ops 29 March, 2000

Mission Planning, TLM and CMD

Science Data Processing and Archiving at NERSC

On-line Data and Archives

SatTrack

World Wide Web

Real-time Orbit Displays Schedules Track Files

BGS

Data Reduction

Orbit Events State Vectors

Quick Look Data Analysis and Archiving

On-line Access

Station Interface Email / Log Files Ephemeris Files

Ephemeris Files

Media Production Supernova Data Catalog

Email / Log Files

SERS

MPS

System Monitor

Command Loads

Science Planning

TLM / CMD Log Files

Observing Schedules

ITOS

WFF

Telemetry Processing Command Generation Real-time Displays for Engineering Data

AGO

Station Interface TLM / CMD

MOC at SSL

Co-Investigators Internet / Media

Local Archive

Observing Summary Real-time Displays for Science Data

National Archive

SOC at LBNL

Scientific Community

SNAP Ground Data System File: snap_gds.fig

Data Flow Layout

M.Bester, 19Nov99

Michael Lampton (for H. Heetderks) Page 10 of 10