17 th AIAA/USU Conference on Small Satellites @ Logan, Utah, USA. - 2003.8.13. Exploring Space on a Small Satellite, STSAT-2 : A Test Bed for New Technologies Jong-Tae LIM, Myeong-Ryong NAM, Kwangsun RYU, Kyung-Mo TAHK, Sung-Ho RHEE, and Kyung-Hee KIM Satellite Technology Research Center Korea Advanced Institute of Science and Technology
Will be Launched Next Month in Russia! KAISTSAT-4 Mission STSAT-2 / 1
SaTReC Missions KITSAT-1 KITSAT-1 (1992) (1992) KITSAT-2 KITSAT-2 (1993) (1993) KITSAT-3 KITSAT-3 (1999) (1999) KAISTSAT-4 KAISTSAT-4 (2003) (2003) STSAT-2 STSAT-2 (2005) (2005) Technology acquisition Manpower training Technology verification Modification Enhancement Technology development Engineering test Advanced payloads Technology Optimization Stabilize Technology Space Science Research Compact Design Technology Experiments Solar Observation STSAT-2 / 2
Contents STSAT-2 Mission Overview Mission Objectives of STSAT-2 Science Mission Payloads LIST (Lyman-alpha Imaging Solar Telescope) SLR (Satellite Laser Ranging) Spacecraft Technology Experiments Detailed Item Will be Introduced Overall Spacecraft Design Concluding Remarks STSAT-2 / 3
STSAT-2 Mission Overview Small Satellite of ~100 kg Launched by the 1 st Korean Launch Vehicle (KSLV-1) Advanced Bus Technology Experiments State-of-the-Art Payloads Development and Operation Total Budget ~ $10M STSAT-2 / 4
Mission Objectives and Parameters Mission Objectives Continuous Observation of Solar Lyman-Alpha (121.6 nm) Image in the LEO Precise Measurement of Orbit Insertion Using Laser Ranging Technology Development of Several Advanced Bus Technologies Launch KSLV-1 : Plan to be Dec. 2005. Mission Orbit (Designated by KSLV-1) Elliptical Orbit : 300 km (perigee) 1,500 km (apogee) Inclination Angle : 80 Mission Life Time Less than 2 years STSAT-2 / 5
Space Segment Spacecraft Payloads Ground Segment STSAT-2 Ground Station Satellite Operation Image Data Reception SLR Ground Stations Launch Service Segment STSAT-2 : Science and Technology Satellite 2 LIST : Lyman-α Imaging Solar Telescope SLR : Satellite Laser Reflector System Architecture STSAT-2 / 6
Orbit and Its Effects Not a Sun Synchronous Orbit Irregular Ground Contact Time and Irregular Satellite to Ground Station Range Orbit Analysis 2.5 times/day with 5 minute contact time average based on the X-band Science Data Download Link Budget (2,100 km range with elevation more than 10 degree) Full Sunlight Duration (No Eclipse Time) ~ 23 days Thermal Problem Deployable Solar Panel and Heat Pipe Sweeps Lower Part of the Inner Radiation Belt Radiation Shield on Memory and Critical FET s Software or Hardware EDAC Implementation Air Drag Effect Mission Lifetime is Limited to 2 Years Electric Propulsion is Considered STSAT-2 / 7
LIST : Science Mission Payload To Understand the Evolution of Structures in the Chromo-sphere To Improve Models of Solar VUV (Vacuum Ultra Violet) Variability To Study the Physical Properties and Processes in the Solar Active Region with Lyman-α and Spectroscopic Data STSAT-2 / 8
SLR : Technology Mission Payload Satellite Laser Ranging Space Geodetic Technology Measure the distance between a ground station and a satellite most precisely in current method A very short laser pulse transmitted from a telescope retro-reflected by corner cube reflector array on a satellite The round trip time is measured and converted to the distance STSAT-2 / 9
Spacecraft Technology Experiments Frame-Type Satellite Structure Composite Material Solar Panel Dual-Head Star Tracker CCD Digital Sun Sensor Pulsed Plasma Thruster Compact On-Board Computer High X-band Transmitter Z 2 Z 1 Z α X 1 X 2 ( CMOS CCD ) Sensor 센서헤드 Head 11 센서헤드 Sensor 2Head 2 Y X STSAT-2 / 10
CCD Digital Sun Sensor Item FOV Accuracy Weight Power Size Specifications 128 128 <0.03 <1.0 Kg <1W 150 150 100 mm 3 STSAT-2 / 11
Dual Head Star Tracker FIFO AMP & ADC DRIVER CCD COOLER LENS ASSEMBLY CCD_PROC FPGA FIFO AMP & ADC DRIVER CCD COOLER LENS ASSEMBLY COOLER POWER PWM DSP FPGA EDAC SRAM DSP EPROM EEPROM UART Interface Use Similar Sensor Head of K4 Star Tracker Combination of CCD Processor Logic into One FPGA Increase Processing Power of DSP 10 arcsecond precision has proven through K-3 and K-4 mission But Limited to X, and Y axis Achieve ~5 arcsecond regardless of optical axis STSAT-2 / 12
Electric Propulsion Candidates Pulsed Plasma Thruster Hall Thruster Specific Impulse : 800s Specific Impulse : 1600s Impulse Bit : 20uNs Thrust : 100mN (typical) Charge Voltage : 2000V Propellant : Zenon Discharge Rate : 1 Hz Commercial Product? Prototype has Developed Propellant : Teflon STSAT-2 / 13
On Board Computer Item Specifications TCU, MMU, LIST, ACS MODEM CPU Program Memory PowerPC 603e SRAM 2 Mbytes (H/W EDAC) Code Storage Memory EPROM 1 Mbytes Updated Code Storage Memory EEPROM 1 Mbytes Comm. Buffer Memory Dual port SRAM 2 Kbytes UART UART USART USART Communication Control Logic RAM Disk SRAM 6 Mbytes (TBD, S/W EDAC) Code Storage Memory Updated Code Storage Memory Watchdog Timer Serial Port Mass Size Power EPROM 1 Mbytes EEPROM 1 Mbytes 1 UART:18, USART:2 900g 225 x 200 x 15 mm 3 4W @ 5V CPU PowerPC 603e Watchdo g Timer Program Memory SRAM 2 Mbytes OS : VxWorks EDAC Logic EDAC Memory SRAM 2 Mbytes RAM Disk SRAM 4 Mbytes Efficient Task Management Multitasking, Unlimited Number of Tasks Fast, Flexible Inter-Task Communications Package Type : CGA DAC SPR DAC STSAT-2 / 14
Spacecraft Specifications Item Mass Size Power Attitude Control TT&C PDTx Payload Data Storage Specification 100 kg < Φ1 m x 1 m 152 W@EOL, GaAs/Ge DOD < 25% with NiCd 7AHr (Li-Ion) 3-axis stabilization (0.5 /s Maneuver Capability) Pointing Accuracy of 0.15 (2 σ) Pointing Control Stability of 0.002 in 1 second S-Band Tx (9.6, 38.4 kbps @ 2,252MHz) S-Band Rx (1.2, 9.6 kbps @ 2075MHz) X-Band Tx (10 Mbps @ 8,127MHz) 2GbSDRAM STSAT-2 / 15
Electrical Architecture ACS CDS Payload GYR FOG GYR O O FDSS WIST DHST OBC LIST RW RWRWRW RWA WIST GPSR MTQR MTQR MTQR PPT FASS CASS FS NMAG S TCU MMU PDTx ANT Solar Array (-Z) Solar Array (Mount) SPR PSU BM PDU +5 +12-12 +20 +28 MOD DEMOD Tx Rx ANT Solar Array (+x) EPS Battery PD Serial Link Digital Status Power Line Bi-level Command Analog Telemetry CMS STSAT-2 / 16
Structure Design Concept Torquer Bar LIST Tx, Rx Wheel Array PDTx DHST Ebx 2 (AC) Ebx 3 (EP) Deployable Solar Panels S-Band ANT FDSS GPS ANT FOG Ebx 1(CD) PPT Battery Pack X-Band ANT LRA (Laser Reflector Array) CASS STSAT-2 / 17
Major Milestones SRR : 2003.1. Concluding Remarks SDR : 2003.5. Start of Prototype Development PDR : 2003.11. Start of Engineering Model Development CDR : 2004.7. System Design Fix Through EM Test PFM(2005.2) and FM(2005.7) Manufacturing and Environmental Test Launch : 2005. 12. 100 Kg Small Satellite will be Launched by KSLV-1 in the year of 2005 Will Provide Compact and Efficient Small Satellite Standard That Will Be Used In Successive Korean Small Satellite Missions Covering Space Science, Technology Experiment, and Exploring Missions STSAT-2 / 18