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
• 8 Gbit (compressed) image every 200s: 40 Mbit/s
• 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)
24
20
15
Hours Visible
10
5
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Day
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
BusAssy
Truss
Composite shear
Star Tracker CCD Radiator
TTL Star Guider Reaction wheel
Gyro Assy 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 On-line Data and Archives
and Archiving at NERSC
SatTrack World Wide Web
Real-time Orbit Displays Data Reduction
BGS Schedules Orbit Events
Track Files State Vectors Quick Look Data Analysis
and Archiving
Station Interface On-line Access
Email /
Log Files
Media Production
Ephemeris Files Ephemeris Files
Supernova Data Catalog
Co-Investigators
SERS MPS
Email / Log Files System Monitor Command Loads Internet /
Media
TLM / CMD Science Planning
Log Files
Observing Schedules
Local Archive
ITOS
Telemetry Processing
Command Generation Observing Summary
Real-time Displays Real-time Displays
National Archive
for Engineering Data for Science Data
WFF AGO
Station Interface
TLM / CMD
MOC at SSL 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