Space Technology 5 Paving the Way for Future

Space Technology 5 “Paving the Way for Future Micro-Satellite Missions” NASA’s Space Technology 5 Mission NSF workshop on Small Satellite Missions for Space Weather and Atmospheric Research J. A. Slavin NASA GSFC May 15 -17, 2007 1

Pathfinder for Magnetospheric Constellation 2

ST 5 Mission Overview • NASA New Millennium Program mission to flightvalidate 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, researchquality 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. 3

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 n. T achieved) - Radiation Qualified to 100 krad • Science & Operations demonstration - Research-grade miniature flux-gate magnetometer (UCLA) - “Lights-Out” totally autonomous operations for several weeks 4

ST 5 New Millennium Program Technologies • CULPRi. T Micro-Thruster • Transponder Power System incorporating a Lithium-Ion Battery and triple-junction solar cells: Provide s/c power - Battery effective Capacity = 7. 5 A-h (to 6 Vdc C/2 discharge) - Solar array beginning of Life Electrical output per panel (30 o. C, 1 Sun Air-Mass Zero): load voltage = 10. 2 Vdc, current = 1. 16 amps Microthruster: Used for attitude maintenance and Delta-V maneuvers to constellation formations - • Low Voltage Power System Autonomous Operations • Uplink rate 1 kbps; Downlink rate 1 kbps and 100 kbps. Average bit error rate (BER) of less than 1 x 10 -5 for each downlink pass. Radiation and latch-up tolerant Used as Reed Solomon encoder Operating voltage of 0. 5 V Variable Emittance Thermal Coatings: Thermal control demonstration - Variable Emittance Coatings Thrust greater than 2. 1 N at 2000 psi, and greater than 0. 1 N at 100 psi. Complimentary Metal Oxide Semiconductor, Ultra Low Power Logic (CULPRi. T): Low-voltage CMOS technology - • Specific impulse greater than 60 sec. X-Band Transponder: Provides coherent uplink and downlink - • Can be operated in pulse and continuous fire modes 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. 5

ST 5 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, Mc. Murdo Ground Station • Constellation Configuration: "String of Pearls" 6

Research-quality Science Demonstration • ST 5 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 7

ST-5 Field-aligned Current Observations “Slow” “Typical” “Rapid” Rate of Field-Aligned Current Sheet Change (10 s – 10 min) 8

ST 5 Observations of Magnetization of Earth’s Crust – 2/2 Along-Track Gradient of the Crustal Magnetic Field 2006 Day 091 Start UT: 0200 First Micro-spacecraft Gradiometer Measurements Green: SC 094 Observations Red: Comprehensive model (CM 4) Model Prediction 9

ST 5 Autonomous Operations • Data Return Statistics - Overall data return rate: 94. 13% (94. 44% ENG data, 91. 93% MAG data) • SC 094: 91. 74% • SC 155: 93. 68% • SC 224: 94. 13% - Data return rate during AUTO OPS demonstration week: 81. 31% (86. 40% ENG, 76. 22% MAG) • SC 094: 73. 67% • SC 155: 84. 34% • SC 224: 84. 54% 10

Summary Remarks Space 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) 11

Technology Transfer • Space Technology 5 Technology Symposium was held on September 13, 2006 (CD Proceedings is ITAR Controlled – please contact Candace Carlisle [candace. carlisle@nasa. gov] 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. 12

Thank You! 13