Delta-DOR in CE-3, MEX solar conjunction

Transcription

1 First International Workshop on VLBI observations of near-field targets Delta-DOR in CE-3, MEX solar conjunction Ma Maoli, Zheng Weimin, Huang Yidan, Chang Shengqi 1

2 Outline 1. CVN in Chang E-3 mission 2. CE-3 X-band Delta-DOR 上海天文台 3. MEX Interplanetary scintillation observation 2

3 1. CVN CVN, providing VLBI delay, delay rate, orbit, and angle data to Beijing Center. CE-1, CE-2, CE-3, CE5T1.

4 CVN upgrade in CE3 上海天文台 Ur,26m BJ,5m SH,65m KM,4m 1. New VLBI data center 2. Shanghai Tianma 65m radio telescope 3. New X-band receiver & digital terminal 4

5 2. CE-3 X-band Delta-DOR 上海天文台 Five-minute scan sequence: Quasar-CE3-Quasar-CE3 Angular distance between CE-3 and Quasar < 1 Remove media & system errors Peter Kroger: ΔDOR spacecraft tracking 5

6 F1pc F2pc F1L2 F2L2 F1L1 F1R1 F2L1 F2R1 F1R2 F2R2 7.7MHz 38.5MHz 7.7MHz 38.5MHz Two series of DOR signals, F1 and F2, located at both sides of the detector One is coherent( 1 ~ 1 ), the other is non-coherent( 1 ~ 1 ).

7 FX correlator in CVN Signal from station A Signal from station B St ( ), E Model for A Fringe stop Fringe stop Model for B FFT FFT 2d 1d Corr of A&B Amp and phase Fringe Fit E T 2( t2) T () t 1 2VLBImodel Bandwidth synthesis Quasar model 1VLBI E t E Delta - DOR

8 s3c9a UR-TM 上海天文台 FX correlator on DOR Cross spectrum(db) 4 F1PC F1R F1L F1R Frequency(MHz) Phase(rad) Samplerate 4MHz Bandwidth 2MHz FFT point 124 CNR loss due to Spectral resolution: 4 1log 18dB 1 124

9 Residual statistics 上海天文台 VLBI group delay residuals(x-band Delta-DOR): ~ 1ns in trans-lunar orbit ~.5ns in lunar orbit VLBI Delay Data Fit(unit: ns) Trans-lunar Orbit Lunar Orbit /2 12/3 12/4 12/5 12/6 12/7 12/8 12/9 12/1 12/11 12/12 12/13 real-time

10 A different correlator from FX correlator Sc Sc ρ () t Au ρ () t Bu ρ () t ρ () t Ad Bd ρ () t ρ () t Ad Bd C A B r A () t A B r A () t E E coherent ( t ) ( t ) ( t ) ( t ) ( t ) t t c c Bd Bu Ad Au ' DOR 2 2 non-coherent ( t ) ( t ) ( t ) t t c c Bd Ad ' DOR 1 1 Rogstad, Stephen P., et al.29;luciano Iess, Ricard AbellòPuyuelo, Alessandro Ardito, et al. The European ΔDOR Correlator.

11 Correlator 上海天文台 Input: transmit frequency Model: f ( t) Ad ( t) rsc ( t1 ) ra ( t) Ad let ( t) Au ( t) rc ( t2) rsc ( t1 ) geoa c st ( t) Re a expi 2Mf t Transmit signal Au ( t) sa ( t) Re aa expi 2 Mf t geoa ( t) sb( t) Re ab expi 2 Mf t geob( t) s ( t) expi 2 Mf t ( t) A,m geoa,m * a A s A(t) expi[2 M f( geoa,m (t) geoa (t)) ] 2 Delay, geo Received signal Range model A ( t ) s is a slow varying signal with low frequency.

12 Data process 上海天文台 CE-3, s3c7a, s3c8a, s3c9a, 1*1km lunar orbit Samplerate:4MHz Bandwidth:2MHz Quantification:2bit 1 3C273B :43: :11: BjKmUrTm :13: :42: BjKmUrTm 3 SAT-CE :46: :53: BjTm :56: :1: BjKmUrTm :21: :26: BjKmUrTm 39 SAT-CE :27: :35: BjKmUrTm :36: :41: BjKmUrTm 41 SAT-CE :42: :5: BjKmUrTm :51: :56: BjKmUrTm 43 SAT-CE :57: :5: BjKmUrTm :6: :11: BjKmUrTm 45 SAT-CE :12: :2: BjKmUrTm :21: :26: BjKmUrTm 47 SAT-CE :27: :35: BjKmUrTm :36: :41: BjKmUrTm :21: :26: BjKmUrTm 71 SAT-CE :27: :35: BjKmUrTm :36: :41: BjKmUrTm 73 SAT-CE :42: :46: BjKmUrTm 74 SAT-CE :46: :55: KmUr :56: :1: BjKmUrTm 76 SAT-CE :2: :12: KmUr

13 Received signal by VLBI station Power spectrum(db) s3c9a BJ 1 F1L2 F2L2 F1pc F1R1 F2pc F2R1 F1R2 F2R Frequency/Hz x 1 9 CNR of s3c9a BJ(dBHz) L2 pc R1 R2 F1, coherent F2,non-coherent CNR:1*log(power of signal/noise)

14 Coherent 上海天文台 In the coherent situation, the transmitted frequency station is exactly known. f from uplink Initial model Signal from station A and B,D PLL Judgement Delta-DOR Bandwidth synthesis Differential phase of two stations F and phase from single station Quasar

15 Take s3c9a as example 上海天文台 Frequency(mHz) Phase(rad) (a) (c) 2 (b) -2 2 (d) Time(hour) After integral filter After PLL BJ KM UR TM Frequency(mHz) Phase(rad)

16 TM F1pc after PLL Power spectrum(db) TM main carrier 6:17:-6:17:4 1 Amptitude Frequency(Hz) Time(s)

17 Phase compared with FX correlator Phase(rad) 1-1 (a) s3c9a TM-UR residuals(rad) (b) FX.38rad Local.12rad Time(hour)

18 Phase compared with FX correlator Baseline s3c7a s3c8a s3c9a New FX New FX New FX BJ-KM BJ-UR BJ-TM KM-UR KM-TM UR-TM Phase precision from new method is better than the FX correlator.

19 Non-coherent: Estimate f at first transmit frequency(hz) x s3c9a transmit frequency of F2pc difference between continuous two points frequency(hz) time(hour) Frequency difference between adjacent points is in the range of -1~1Hz

20 Difference transmit frequency between two stations.5 s3c9a different transmit frequency between two station BJ-KM mean=-28mhz std=74mhz.5 BJ-UR mean=-36mhz std=74mhz Frequency(Hz) BJ-TM.2 mean=-36mhz std=5mhz KM-TM.5 mean=-8.5mhz std=73mhz KM-UR.5 mean=-7.2mhz std=93mhz mean=-.79mhz std=84mhz Time(hour) Frequency std is about 1mHz

21 Orbit determination results 上海天文台 Orbit determination between two correlator, F1 code Delta-DOR+range(RMS) Delta-VLBI+range(RMS) Difference with (m) 61(ns) 51(m) distance(m) velocity(mm/s) s3c7a s3c8a s3c9a Orbit determination between two correlator, F2 code Delta-DOR+range(RMS) 73 51(m) s3c7a s3c8a s3c9a Difference with distance(m) velocity(mm/s)

22 Error analysis Wu Wei-ren, Wang Guangli, et al. 213

23 Conclusion 1. The delay residuals after orbit determination are.5ns and.7ns respectively. The CNR of F2 is 1dB weaker than F1. 2. The phase from the result is better than FX correlator, while no improvement in orbit determination, system errors from CVN should be estimated. 3. The method reported here is more suitable for weak signal process compared with FX correlator.

24 3.MEX Interplanetary scintillation observation MEX is flying around Mars. Sheshan 25m radio telescope have observed MEX from ~ The observations are conducted by JIVE. Solar elongation/degree (a) MJD x 1 4 heliocentric distance/solar radius MJD x 1 4 Solar elongation and minimum heliocentric distance vary from ~215.9 Orbit of MEX is got from ESA/ESOC. G. Molera Calves, et al. 214.

25 4 Phase variation(rad) Time(s) Phase Frequency 11R 21.2rad 16mHz 16R.1rad 3mHz

26 Phase spectral power density(rad 2 /Hz) scintillation band noise band B>B L I II III -2 1 L a S bl f -1 1 Frequency(Hz) Phase spectral power density at R=11R and 16 R 1 IV 1 1 Scintillation slope Slope of phase spectral power density Close to Komlogorov index 8/3 Komlogorov Turbulence, 3mHz~.3Hz, 13km~13km

27 Theory to explain phase scintillation x Inhomogeneous random medium Refraction Input signal Output signal x= x=l Refraction index n(x,t), Taylor frozen-in hypothesis. Structure function C W n S ( x ) c n ( f ).33c x L exp a1r 2 n k 2 2 S WS ( f ) df f f a1r 2f 1 p ( p 1) / 2 1 ( p / 2) Woo R, Yang F C. et al.1976

28 refraction structure constant -11 p=3.3 model log 1 (c n ) Ingress Engress c n R c R d c d = -1.98±.27 In Woo s paper(1976), d is close to 2.1

29 Conclusions with IPS 1.We use a single VLBI station to observe MEX. Doppler is used for IPS research. The method can be used in future Chinese Mars solar conjunction. 2.Solar wind and IPS theory are proposed in the 8s in last century. The research work reported here just confirmed earlier theory. Where is the break through point in solar wind and IPS research?

30 Thanks for attention!