5 space technology “paving the way for future micro-satellite missions” 1 nasa’s space...
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5Space Technology
“Paving the Way for Future Micro-Satellite Missions”
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NASA’s Space Technology 5 Mission
NSF workshop on Small Satellite Missions for Space Weather and Atmospheric Research
J.A. SlavinNASA GSFCMay 15 -17, 2007
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ST5 Mission Overview• NASA New Millennium Program mission to flight-
validate new concepts and technologies
• Design and build 25 kg spacecraft:
- Design, develop, integrate, test and operate three full service spacecraft, through the use of breakthrough technologies and provide a roadmap (written report). Integrate and validate technologies.
• Research-quality spacecraft:
- Demonstrate the ability to achieve accurate, research-quality scientific measurements utilizing a constellation of 3 micro-satellites.
• Constellation Operations:
- Execute the design, development, test and operation of multiple spacecraft to act as a single constellation rather than as individual elements.
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ST-5 Spacecraft• Developed by GSFC in-house• Description
- 3 spin-stabilized (~20 rpm) micro-spacecraft- Mass 25 kg (each)- ~50 cm x 48 cm 8-sided spacecraft- Integral card cage structure (for C&DH, PSE)- Cold Gas Propulsion (10 m/s)- Intended to fly as “secondary” to GTO- Launched on Pegasus to 300 x 4500 km (105.6 deg)
• Key performance parameters- Spin axis knowledge – 0.2 deg; Control - 0.5 deg- 25 W Triple Junction Solar Array (29% Efficiency)- 5 V bus with new generation Lithium Ion Battery- X-band up/down 1 – 100 kbps- Onboard science event triggers and data storage- Magnetically Clean S/C (< 1 nT achieved)- Radiation Qualified to 100 krad
• Science & Operations demonstration- Research-grade miniature flux-gate magnetometer (UCLA)- “Lights-Out” totally autonomous operations for several weeks
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Micro-Thruster
CULPRiT
Transponder
Variable Emittance Coatings
Low Voltage Power System
ST5 New Millennium Program Technologies• Power System incorporating a Lithium-Ion Battery and
triple-junction solar cells: Provide s/c power- Battery effective Capacity = 7.5A-h
(to 6Vdc C/2 discharge)
- Solar array beginning of Life Electrical output per panel (30oC, 1 Sun Air-Mass Zero): load voltage = 10.2Vdc, current = 1.16 amps
• Microthruster: Used for attitude maintenance and Delta-V maneuvers to constellation formations
- Can be operated in pulse and continuous fire modes
- Specific impulse greater than 60 sec.
- Thrust greater than 2.1 N at 2000 psi, and greater than 0.1 N at 100 psi.
• X-Band Transponder: Provides coherent uplink and downlink
- Uplink rate 1 kbps; Downlink rate 1 kbps and 100 kbps.
- Average bit error rate (BER) of less than 1x10-5 for each downlink pass.
• Complimentary Metal Oxide Semiconductor, Ultra Low Power Logic (CULPRiT): Low-voltage CMOS technology
- Radiation and latch-up tolerant
- Used as Reed Solomon encoder
- Operating voltage of 0.5V
• Variable Emittance Thermal Coatings: Thermal control demonstration
- Range of emissivity variation 0.4 to 0.6
• Software Tools for Autonomous Ground Operations: Perform model-based constellation health and safety management and provide efficient constellation management with a high degree of automation.
Autonomous Operations
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ST5 Mission Profile• Launched March 22, 2006
- Pegasus out of Vandenberg
- Approximately 10 min after launch, ejected 3 min apart Frisbee-style
• Mission Duration: 90 days
- 7 day launch & early orbit period
- Mission completed June 20, 2006
• Orbit
- 105.6 deg inclination (full sun orbit)
- ~ 300 km perigee; ~ 4500 km apogee
- 136 minute period
• Communications: Deep Space Network, McMurdo Ground Station
• Constellation Configuration: "String of Pearls"
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Research-quality Science Demonstration
• ST5 validated the constellation concept by the measurement of important physical parameters that cannot be determined by single spacecraft
• Formation fly in pre-determined configuration over the Earth’s northern and southern auroral zones (position uncertainty < 1 km)
• Returned research-grade magnetometer measurements from a suitable platform
• Measured auroral current sheet motion and thickness, electric current density, and temporal stability using the ST-5 constellation data
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ST-5 Field-aligned Current Observations
“Slow” “Typical” “Rapid”
Rate of Field-Aligned Current Sheet Change (10 s – 10 min)
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ST5 Observations of Magnetization of Earth’s Crust – 2/2
First Micro-spacecraft Gradiometer MeasurementsGreen: SC094 Observations
Red: Comprehensive model (CM4) Model Prediction
Along-Track Gradient of the Crustal Magnetic Field
2006 Day 091Start UT: 0200
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ST5 Autonomous Operations
• Data Return Statistics
- Overall data return rate: 94.13% (94.44% ENG data, 91.93% MAG data)
• SC094: 91.74%
• SC155: 93.68%
• SC224: 94.13%
- Data return rate during AUTO OPS demonstration week: 81.31% (86.40% ENG, 76.22% MAG)
• SC094: 73.67%
• SC155: 84.34%
• SC224: 84.54%
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Summary RemarksSpace Technology 5 demonstrated the functionality of
micro-satellites for Space Weather applications.
Technical Highlights:
• Autonomous Operations Test (> 80% data recovery)
• Power Systems – 5 Volt bus
• CULPRIT Low Voltage Rad Hard Reed-Solomon Encoder
• Miniature X-Band Transponder (1 – 100 kbps)
• Propulsion (10 m/s)
• LEO Magnetic Fields Science Validation
Primary Disappointment:
• Could not obtain a secondary launch from any source within our 2 year launch window (except Ariane)
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Technology Transfer
• Space Technology 5 Technology Symposium was held on September 13, 2006 (CD Proceedings is ITAR Controlled – please contact Candace Carlisle [[email protected]] for more information; see also nmp.nasa.gov).
• Space Technology 5 open literature articles can be found in major Aerospace Journals and Meetings Proceedings.
• Preparations are underway for Special ST-5 Section of Geophysical Research Letters.