W hat w e leaned from the Tokyo Tech 5 0 kg- satellite TSUBAME

Transcription

1 W hat w e leaned from the Tokyo Tech 5 0 kg- satellite TSUBAME Yoichi Yatsu N. Kawai, S. Matunaga, M. Matsushita, S. Kawajiri, K. Tawara, K. Ohta, M. Koga, Tokyo I nstitute of Technology S. Kim ura Tokyo Universit y of Science on behalf of TSUBAME team

2 OUTLI NE Introduction Overview of TSUBAME Developm ent Flight Operation Discussion SSC17-WK-41 2

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4 Motivation of this talk We cam e here for challenging the student com petition in the Sm allsatconf We started developing TSUBAME in TSUBAME was launched in We had lost the satellite three m onths later. We have come back here for presenting HOW and WHY WE FAILED. SSC17-WK-41 4

5 Overview of TSUBAME Mission: Polarim etry of Gam m a- ray Bursts( GRB) ~ 1 GRB/ day som ewhere in universe, with short duration (1) Detection & Localization of GRB (~2 sec) (2) Quick Pointing (~10 sec covering half the sky) (3) On-axis polarimetry (~1000s) Engineering goal: Agile satellite bus w ith CMGs CMG has high-torque, BUT... Power consumption ~40 W Complicated algorithm => Made it Harder & Challenging SSC17-WK-41 5

6 Design Sum m ary Cute-1.7+ APD TSUBAME New Size 10 x 20 x 20 cm x 4 6 x 5 0 cm 3 Weight 5 kg kg Wattage 5 W 9 0 W ( Max) Com m. Speed 1.2 kbps (UHF) kbps ( S- band) MNV Speed - 6 deg/ s Orbit 600 km Sun-sync km Sun- sync This means we could not use the components demonstrated in our CUBESATs. SSC17-WK-41 6

7 Block diagram Purchased Assembled in the Lab We developed alm ost everyt hing. At that m om ent we cannot purchase these com ponents. SSC17-WK-41 7

8 Developm ent regim e Core team ~15 grad students Optical Camera Kimura-lab / Tokyo Univ. of Sci. 1 staff + 2~3 grad students Detector System Kawai-lab / Tokyo Tech. 2 staff + 2~3 grad students Satellite System Matunaga-lab / Tokyo Tech. 1 staff + 10 grad students Structure NIPPI Corporation CMGs Tamagawa seiki co., ltd Consulting Space link co., ltd Mem ber m aj ored in Mechanical Engineering or Physics. Most of students can work 3 years until their graduation. 2~ 3 students were assigned to each subsystem. SSC17-WK-41 8

9 History of developm ent DEADLINES: Proposal submission Budget period Launch Contract Shipping Deadline Shipping Deadline Shipping Deadline The given time period for the each phase was ~9 months. We tended to move on to the next phase without complete debugging. SSC17-WK-41 9

10 Flight operation The Critical phase looked alm ost perfect but with m inor troubles FM-RX(CMD) m 6 day degradat ion of LNA Burnout of DC/ CD in FM-RX S-RX turned off@y+ 36 day m ay be due to another burnout of the sam e DC/ DC converter Battery Protection shutdown the satellite CW-Tx m Y+ 83 day m ay be due to another burnout of the sam e DC/ DC converter Normal (only minor errors) CW only SSC17-WK

11 Failures we m et in orbit Fatal minor NOT used Fatal errors were concentrated in the RF-system H/ W: ANT design, FM-Rx degradation, FM- Rx/ Tx/ CW burned- out SSC17-WK

12 Properties of the failures We m et thousands of bugs during the developm ent. Most of them had been detected and fixed before the launch. The bugs survived under our debugging were: Added in the early phase We forget everything within 2~ 3 years. Rare events Suspicious DC/ DC convert er survived 1week~ Arise from m ultiple failures Malfunction of the com plicated redundant system SSC17-WK

13 Technological aspect Therm al-structure was perfect. RF SYSTEM Software Circuit Parts selection SYSTEM DESIGN Heat dissipation of the electronics We m ust do electronics m ore. The m alfunction in heat dissipation of the electronics We had not experienced the heat issues in the electronics in CUBESATs. And STR team did NOT concerned with the inside of the com ponents SSC17-WK

14 Managem ent I ssues Schedule w as alm ost collapsed BBM and EM phase were too short to develop 50 kg satellite from scratch. Review/Approve Human Resource Scheduling Malfunction of review ing system Our reviewing system could not catch the m inor signs of bugs. Configuration Risk Management Management May be due to lack of experim ents or knowledges. We need do electronics m ore. SSC17-WK

15 Sum m ary We developed a 50 kg challenging satellite but failed. Differences between 50kg-sat and Cubesat m ight cause this result s. To m ake 50 kg satellite, we m ust concern how to skill up the entire team m em bers (Electronics) how to optim ize the schedule how to handover the tasks and inform ation beyond the turnover of m em bers SSC17-WK

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17 Ground Control Station UHF: Tokyo Tech Ground Station & Am ateur radio operators S-band: I SAS/ JAXA Φ2m Parabolic Antenna Freq Modulation Speed Up 144MHz AFSK 1200bps S-band PSK Down 430MHz AFSK 9600bps x 2 430MHz S-band CW 1char/s BPSK 10~100kbps 17