1. VSOP-2 Ground Link Station - Tracking Station Requirements - National Astronomical Observatory of Japan Y. Kono

2. Link system H Maser Data Storage VLBI Data Downlink Frequency 37-38 GHz Bit Rate 1 Gbps Modulation QPSK TX-Power 20 W Phase Transfer Uplink Frequency 40 GHz Non Modulation TX-Power 10 W Phase Transfer Downlink Carrier wave of data downlink 2way Phase Comparison Ground Tracking Station Commanding Station TT&C Freq: 2GHz

3. VSOP-2 Link Function Data Transmission  Current design of observation system  Current design of downlink system Reference Phase transfer TT&C

4. Observation System IF-SWITCH (6 to 2 ) MOD × × × × ～ × × Synthesizer LO (36/34GHz) ～ LO (14.5GHz) ADC Observation Frequency Q-band: 41 - 45 GHz K-band: 21.5- 23.5 GHz X-band: 8.0 - 8.8 GHz VLBI DATA Rate: 512/256Msps Bit: 1/2bit Channel:2 ch Ka-TX Q-band (L) LNA Q-band (R) LNA K-band (L) LNA K-band (R) LNA X-band (L) LNA X-band (R) LNA 1024Mbps DF Intermediate Frequency 6.6- 8.8 GHz Base Band Frequency 1.3 GHz

5. ADC modes A/D bit VSOP2 A/D bit GRT BW (MHz) Quantization efficiency factor (K) Sensitivity of continuous spectrum obs (=K*√BW/128 ) No quantization 12811 2 ビット 1280.88 1 ビット 2560.630.90 1 ビット 2 ビット 2560.751.06 2Gbps for Ground radio telescope capability? - GRT (2Gbps), - Correlator (mixture correlation of 1bit and 2bit )

6. Observation System (MOD) VLBI DATA  1024 Mbps  Telemetry data merged Modulator  Single Carrier QPSK Modulation  SiGe device  Carrier 3.4GHz & Up Conversion to 37.5 GHz

7. TX Amplifier Output Power 20W TWTA  Boeing, Thales, Tesat, NT-Space,,,, NT-space TWTA for a satellite 42-44GHz Output power 30W efficiency:42% 1994 New TWTA for VSOP-2 will be developed

8. Ka Antenna Diameter 80cm Efficiency 65 %  WaveGuide  Rotary Joint

9. Link Design Bit Error Rate 0.01 Ground Link Station 10m (44%)

10. month Rain Loss 8dB Rain loss (2 mm/hour, Height 2km)  23 dB ( Halca condition, 5 mm/hour, Height 2km)

11. Reference Phase transfer H Maser Phase Transfer Uplink Frequency 40 GHz Non Modulation TX-Power 10 W Phase Transfer Downlink Frequency 37.5 GHz Carrier wave of data downlink 2way Phase Comparison Ground Link Station Diameter >10m T RX <60K

12. Reference Phase transfer Sufficient link margin available

13. Summary VSOP-2 Observation System summarized Link is severe in rain condition

14. VSOP-2 X-band

15. VSOP-2 K-band

16. VSOP-2 Q-band

17. Phase characteristics of instruments H up (f) H down (f) Transponder To the Earth

18. VSOP-2 data transmission Why do we need 37-38 GHz? Allocation of more than 1 GHz bandwidth VLBI requires wide band width for the observing sensitivity. Candidate 25.5 – 27 GHz, 37 – 38 GHz 25.5 – 27 GHz is not good because: - Closest uplink allocations are 15.3 (Secondary) or 40 GHz. - A large frequency offset between uplink and downlink leads to a problem in the compensation of the 2 way timing link in VLBI. - We cannot use same scale waveguide circuit for both up and down link signal. - It is close to the 22 GHz observing band.

19. Compensation error of 2 way link due to Ionosphere