Amale Kanj, Joseph Achkar and Daniele Rovera LNE-SYRTE, Observatoire de Paris/LNE/CNRS/UPMC, Paris amale.kanj@obspm.r
Introduction and motivation Principle o TWSTFT carrier phase technique TWSTFT equation system Experimental validation o the system set up Understanding the satellite LO requency distortion Characterization o the TWCP link (stability) Conclusion and outlooks 2
Frequency stability GPS P3 GPS CP TWSTFT Best results: 8x0 6 @ day in 2009 with 2.5 Mchips/s Same perormance can be reached today at Mchips/s. TWSTFT GPS CP Results obtained with 2.5 Mchips/s, OP NPL link (Bauch et al., Metrologia 43 (2006) 09 20). 3
Introduction and motivation Principle o TWSTFT carrier phase technique TWSTFT equation system Experimental validation o the system set up Understanding the satellite LO requency distortion Characterization o the TWCP link (stability) Conclusion and outlooks 4
U/C D/C U/C2 D/C2 TX RX RX2 F/PC TX RX RX2 F/PC2 CLK TIC CLK2 TIC2 clk=sys clk2=sys+ Δ Station Station 2 5
tx k tx slo tx k tx slo k2 tx k tx slo tx k tx tx F2 U/C D/C U/C2 D/C2 TX RX RX2 F/PC TX RX RX2 F/PC2 CLK TIC CLK2 TIC2 clk=sys clk2=sys+ Δ Station Station 2 6
tx k tx slo tx k tx slo k tx k tx slo tx k tx tx U/C D/C F F 2 k k tx slo TX RX RX2 F/PC CLK clk=sys TIC Station 7
The Doppler coeicients are calculated using the ollowing equation : k n t t vn (t): projection o the satellite velocity in the direction o station n at the instant t. c : speed o light v n c 8
Introduction and motivation Principle o TWSTFT carrier phase technique TWSTFT equation system Experimental validation o the system set up Understanding the satellite LO requency distortion Characterization o the TWCP link (stability) Conclusion and outlooks 9
0 2 2 2 22 2 2 2 2 2 2 k k F k k k F k k k F k k F sys sys slo tx sys sys slo sys sys tx slo sys sys tx slo tx
The unknowns o the system are : Δ: requency shit between clocks in comparison k : Doppler coeicient according to station k 2 : Doppler coeicient according to station 2 slo : on board satellite LO requency
Linearization o the equations o the TWSTFT carrier phase system by applying Taylor development and neglecting the terms rom the second order sys F F 22 2 F 2 F 2 tx ( F tx 2 F slo 22 ) 2 tx F, F 22, F 2, F 2 are measured. slo, k and k 2 must be known by other means. 2
Introduction and motivation Principle o TWSTFT carrier phase technique TWSTFT equation system Experimental validation o the system set up Understanding the satellite LO requency distortion Characterization o the TWCP link (stability) Conclusion and outlooks 3
Equipment used : 2 TWSTFT stations 2 SATRE modems Maser clock Satellite simulator Experimental data recorded every second: Mchip/s code delay Carrier requency Satellite: Telstar N in the Ku band 50 min o measurements during odd hours over one month 3 days o continuous s measurements 4
F F22 F2F2 0 3,00E-02 2,00E-02 (F F 22 -F 2 F 2 )/ tx 2,00E-02 0,00E+000 -,00E-02-2,00E-02-3,00E-02 55736,5 55737,0 55737,5 55738,0 55738,5 55739,0 55739,5 No drit nor oset observed MJD 5
6
329999950 [ F ( k ) ( k ) slo tx ] 329999900 50 Hz F slo (Hz) 3299999050 3299999000 3299998950 3299998900 3299998850 3299998800 55736.5 55737.0 55737.5 55738.0 55738.5 55739.0 55739.5 MJD 7
Introduction and motivation Principle o TWSTFT carrier phase technique TWSTFT equation system Experimental validation o the system set up Understanding the satellite LO requency distortion Characterization o the TWCP link (stability) Conclusion and outlooks 8
50 Hz Frequency (Hz) 699700 6997050 6997000 69970950 69970900 69970850 69970800 69970750 69970700 69970650 69970600 F F 2-00 F 2-200 F 22-300 55736.5 55737.0 55737.5 55738.0 55738.5 55739.0 55739.5 MJD 9
6997350 50 Hz 6997300 Frequency (Hz) 6997250 6997200 699750 699700 55645 55646 55647 55648 55649 55650 MJD 2
Introduction and motivation Principle o TWSTFT carrier phase technique TWSTFT equation system Experimental validation o the system set up Understanding the satellite LO requency distortion Characterization o the TWCP link (stability) Conclusion and outlooks 22
3.0x0-2 2.0x0-2.0x0-2 0.0 -.0x0-2 -2.0x0-2 -3.0x0-2 0 00 200 300 400 500 600 700 800 Measurement time (s) 23
Allan deviation, y () OPMT-OPM4 by GPS CP 0 - OP0-OP02 by TWSTFT phase with MChip/s OP0-OP02 by TWSTFT phase with MChip/s best result SATSIM-OP0 TWSTFT phase with MChip/s SATSIM-OP0 TWSTFT phase with MChip/s best result OPMT-OPM4 by GPS CP 0 - OP0-OP02 by TWSTFT phase with MChip/s 0-2 OP0-OP02 by TWSTFT phase with MChip/s best result SATSIM-OP0 TWSTFT phase with MChip/s SATSIM-OP0 TWSTFT phase with MChip/s best result H890-H889 typical 0-2 Allan deviation, y () 0-3 0-4 0-5 0-3 0-4 0-5 H890-H889 typical mixer LO Ku band dual oset gregory antenna simulator horn IF RF simulator ilter TX path SSPA LNA -- Ku band -- up/down converters -- IF band -- station horn RX path station 0-6 0 00 000 0000 00000 000000 0-6 clock signal modem Averaging time, (s) 0 00 000 0000 00000 000000 Averaging time, (s) 24
Satellite Atmospheric propagation Up and down converters 25
Satellite Atmospheric propagation 26
Satellite Atmospheric propagation Up and down converters 27
Introduction and motivation Principle o TWSTFT carrier phase technique TWSTFT equation system Experimental validation o the system set up Understanding the satellite LO requency distortion Characterization o the TWCP link (stability) Conclusion and outlooks 28
We have presented the irst results o application o TWSTFT carrier phase method in colocation at LNE SYRTE and we have reported the ollowing perormances: x0 2 at s. 3x0 4 at 00 s. X Stability degradation at 300 s seems coming rom the used equipments. The use o phase data instead o requency data to overcome the need or doing continuous measurements as in the present case. Study o atmospheric eects impact on TWSTFT carrier phase. 29
This work is partially unded by CNES Thank you Acknowledgement Authors would like to thank : B. Fonville, D. Matsakis (USNO); W. Schaeer (Timetech); The CCTF WG on TWSTFT. Pierre Uhrich, 202 30