Experiment of 348 Mbps downlink from 50-kg class satellite

Transcription

1 10th IAA Symposium on Small Satellites for Earth Observation April 20-24, 2015 Berlin, Germany IAA-B Experiment of 348 Mbps downlink from 50-kg class satellite Tomoya Fukami, The University of Tokyo fukami.tomoya at ac.jaxa.jp Hiromi Watanabe, Hirobumi Saito, Atsushi Tomiki Takahide Mizuno, Naohiko Iwakiri, Osamu Shigeta Hitoshi Nunomura, Kaname Kojima and Takahiro Shinke

2 Background Recent small satellite is equipped with a high-resolution camera. Skybox Imaging, Inc. GSD < 1m Planet Labs, Inc. GSD ~ 5m These 2 satellites require high-speed downlink system to transmit the observed data.

3 Background We can get the link budgets of these satellite on the Web. 3

4 Downlink system of existing satellite SkySat-1 Flock 1 Operator Skybox Imaging Planet Labs Launch date 21 November January 2014 Mass ~100 kg ~5 kg Spatial resolution ~1 m 3-5 m Downlink system Number of channels 3 1 Frequency 8 GHz 8 GHz Transmitter Power 1.0 W 3 ch. 3.2 W Modulation 8-PSK QPSK, 8-PSK Maximum data rate 101 Mbps 3 ch. 120 Mbps 4 How to increase the data rate?

5 For faster downlink communication Increasing the channels Many transmission modules is required. Using the higher frequency bands (e.g. Ku-band or Ka-band) Influence of rain attenuation becomes more serious. Using optical communications Ground station will be expensive. Using higher order modulation schemes (e.g. 16APSK) Amplitude-phase modulation requires high linearity of RF amplifier. Therefore, power efficiency of RF power amplifier degrades. 5

6 The purpose of our research High-Speed Downlink System using Amplitude-Phase Modulation for Small Satellite 348 Mbps Goal 50 kg-class 600 km orbit Power consumption < 25 W Small ground antenna < 4m Data rate > 300 Mbps Low total system cost 6

7 16QAM Downlink with Nonlinear Amplifier Why the amplitude-phase modulation is difficult? 7 Ref. SSC13-I-8

8 16QAM Downlink with Nonlinear Amplifier Why the amplitude-phase modulation is difficult? 8 Ref. SSC13-I-8

9 Output [dbm] Phase Shift [degree] 16QAM Downlink with Nonlinear Amplifier Why the amplitude-phase modulation is difficult? The nonlinearity of RF power amplifier increases bit error rate. Input [dbm] AM-AM Input [dbm] AM-PM IQ constellation 9

10 X Band Power Amplifiers We developed a new GaN-HEMT amplifier. Amplifier GaAs AB GaN AB GaN F Maximum Power 38dBm 37dBm 36dBm Maximum Gain 10dB 11dB 12dB Maximum PAE 37% 46% 60% PAE at 3dB OBO 23% 36% 38% Maximum Phase Shift Newly Developed 2W GaN HEMT AB Class 3cm 10

11 Output [dbm] Phase Shift [degree] Output [dbm] Phase Shift [degree] Output [dbm] Phase Shift [degree] AM/AM AM/PM IQ Constellation GaAs (AB) Input [dbm] Input [dbm] GaN (AB) Effect of AM-AM will be corrected by error correction code. Input [dbm] Input [dbm] GaN (F) 11 Input [dbm] Input [dbm]

12 Onboard Transmitter Baseband block RF block Flight model Specifications of onboard transmitter Frequency band 8160 ± 60 MHz RF output power 2 W Symbol rate 100 Msps Modulation schemes QPSK, 16QAM, 8PSK, 16APSK, 32APSK, 64APSK, 64QAM Data rate (user) 72 to 540 Mbps Error correction SCCC based on CCSDS code B-1 Data input interface LVDS DC power 28 V, 22 W Volume cm Weight 1330 g Operating -20 to +50 C temperature Radiation test 20 krad 12

13 Error Correction and Modulations CCSDS B-1 Blue book was published in QPSK to 64APSK DVB-S2 supports up to 32APSK. Turbo code Serial Concatenated Convolutional Code (SCCC) 13

14 Frame Error Rate Simulation Results of Frame Error Rate Es/N0 [db] Ref. ESA 14 The data rate can be changed based on link condition.

15 Simulation Results of Bit Error Rate 15 Simulation results of bit error rate.

16 Onboard small Antenna Body-Fixed Medium Gain Antenna Satellite 14 dbi, 68g, 7x7cm Active element Passive element 3.8m Ground Station Feed point For high bit rate mode, Satellite points ground station. 16

17 Onboard small Antenna Body-Fixed Iso-flux Antenna 5 dbi,150g For Earth-Pointing Satellite, Antenna pattern compensates range variation. 17

18 3.8m Ground Antenna for S / X Band S band : Telemetry & Command X band : Mission Data Down Link 36 dbi (S), 47.5 dbi (X) Ring-Focus Cassegrain 18

19 Ground Receiver There are some commercial ground receivers which support high data rate and SCCC error correction. Since these receivers were developed for large satellites, they are too expensive. 19 Zodiac ViaSat

20 Ground Receiver In general, real time demodulation is not necessarily required for mission data downlink. ->Software receiver 20

21 Link calculation This system can transmit up to 32.5 GBytes per pass from 600 km orbit with a 3.8 m ground antenna. (BER<10 6, 1 db margin) 21

22 Launch Japanese Hodoyoshi #4 satellite equipped with our downlink system was launched at June Hodoyoshi #3 Hodoyoshi #4 37 small satellites were launched 22 Dnepr Launch Vehicle Yasny, Russia

23 Hodoyoshi #4 6 m GSD camera X-band transmitter Ion Propulsion 23 Hodoyoshi #4 Launch 20 June 2014 Mass 64 kg Volume cm

24 Experiment of 348 Mbps downlink Results Elevation = 84.5 degrees Distance = 622 km C/N0 = 96 dbhz Es/N0 = 16 db Raw(400 Mbps) BER Decoded(348 Mbps) BER <

25 Recent result We began the challenge to 64APSK, for over the 500 Mbps. 26

26 Recent result of 64APSK Received signal Elevation = 83.3 degrees Distance = 658 km C/N0 = 100 dbhz Es/N0 = 20 db Ground receiver for 64APSK is now developing. Current version of demodulation software requires the tuning of parameter by human. 27 Raw(600 Mbps) BER Decoded(504 Mbps) BER <

27 Conclusion We developed the high speed transmitter for 50-kg class satellite and demonstrated the downlink of 348 Mbps on orbit. We began the challenge to 64APSK modulation, for over the 500 Mbps. By combining the two transmitters and high gain antenna (HGA, 25.5 dbi, 1.2 kg), the downlink of over the 1 Gbps from 50-kg class satellite can be achieved. High Gain Antenna for 50-kg class satellite 28 (PROCYON Spacecraft) Photo by Mynavi

28 The End Thank you for your attention! Manufacturer of Transmitter Manufacturer of Power Amplifier Manufacturer of Onboard Antenna Manufacturer of Ground Receiver 29