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Probing the Gravitational Redshift Effect with the RadioAstron satellite

Probing the Gravitational Redshift Effect with the RadioAstron satellite. Astro Space Center of the Lebedev Physical Institute (Russia) Lavochkin Scientific and Production Association (Russia) Sternberg Astronomical Institute (Russia) Keldysh Institute for Applied Mathematics (Russia)

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Probing the Gravitational Redshift Effect with the RadioAstron satellite

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  1. Probing the Gravitational Redshift Effect with the RadioAstron satellite Astro Space Center of the Lebedev Physical Institute (Russia) Lavochkin Scientific and Production Association (Russia) Sternberg Astronomical Institute (Russia) Keldysh Institute for Applied Mathematics (Russia) York University (Canada) Joint Institute for VLBI in Europe (the Netherlands) University of California in Santa-Barbara (USA) Hartebeesthoek Radio Observatory (South Africa) V. Rudenko (SAI MSU), N. Bartel (York U.), L. Gurvits (JIVE), K. Belousov (ASC), M. Bietenholz (HartRAO), A. Biriukov (ASC), W. Cannon (York U.), G. Cimo’ (JIVE), A. Fionov (SAI MSU), A. Gusev (SAI MSU), C. Gwinn (UCSB), D. Duev (JIVE), M. Johnson (UCSB), V. Kauts (ASC), G. Kopelyansky (ASC), A. Kovalenko (PRAO), V. Kulagin (SAI MSU), D. Litvinov (SAI MSU), G. Molera (JIVE), S. Pogrebenko (JIVE), N. Porayko (SAI MSU), S. Sazankov (ASC), A. Skripkin (Comcon), V. Soglasnov (ASC), K. Sokolovsky (ASC) Rencontre de Moriond, 21–28 March 2015

  2. Einstein obtained the gravitational redshift formula in 1906 considering the equivalence of homogeneous gravity field and inertia (accelerated reference system) a test of the grav. redshift effect is a test of the EP : measurement of the free fall acceleration of a photon RS astro test with Sirius B (W. Adams, 1925): light from massive stars arrives with decreased frequency

  3. EP – fundamental basis of GR • GR postulates equivalence of gravity and inertia • UFF – for test bodies ( ~ 10-12 – 10-13 ) • UGR – for photons ( ~ 10-4 ) • LLI – for physical laws ( ~ 10-4 ) • PPN parameters

  4. GP-A , 1976 Df/f=Dt/t~gh/c2~10-9 h~104km vmin~ 6 cm/s (Df/f)H10-13 ±0,01%

  5. (P/Q) – 2 (R/S)• •[1+(N/M)2 ] -1/2 0 • Online compensation • Doppler shift • - atmospheric shift

  6. Gravitational red shift experiment with SRT “Radioastron” increase sensitivity due to the measurement repetition 10^{-4}  10^{-5}

  7. RadioAstron orbit Moon  highly evolving orbit Period: 8 – 10 day GRS modulation: 0.4∙10-10 – 5.8∙10-10 9.4∙10-11 – 6.4∙10-10 1,000 – 80,000 km 6.8∙10-10 280,000 – 350,000km Orbit determination accuracy Position: 100 m radio, 10 cm SLR Velocity: 1 mm/s

  8. Green Bank tracking station (USA) Radio links: 8.4 GHz down (tone) 15 GHz down (data) 7.2 GHz up (tone) S-band T&C Pushchino tracking station (Russia)

  9. Effelsberg (Germany) Yebes (Spain) Svetloe (Russia) GBT (USA)

  10. VCH-1010 Hydrogen maser frequency standard of the space radio telescope “RadioAstron”

  11. Allan deviation: stochastic andsystematic log y() log 

  12. VCH-1010 (RadioAstron) vs. VLG-10 (GP-A) Allan deviation s(t) Averaging time t, s

  13. Frequency method: clock motion , orbit meteo data + model

  14. 1st-order Doppler effect 8.4 GHz link Frequency, Hz Distance, 103 km Date (January 2014) geocentric distance 1st-order Doppler

  15. Gravitational redshift and 2nd-order Doppler effect 8.4 GHz link Frequency, Hz Distance, 103 km Date (January 2014) geocentric distance 2nd-order Doppler gravitational redshift

  16. GRAVITATIONAL REDSHIFT EXPERIMENT WITH THE SRT “RADIOASTRON” • Contributions to the total frequency shift of the 8.4 GHz signal. • Puschino TS, Oct 2012

  17. GRAVITATIONAL REDSHIFT EXPERIMENT WITH THE SRT “RADIOASTRON” • Residual frequency of the 8.4 GHz signal. Puschino TS, Oct 2012 • geocentric distance • residual frequency • Distance, 103 km • Frequency, Hz • Date (October) Agreement between theory and experiment:3%

  18. Gravity Probe A (1976)

  19. RadioAstron radio links operating modes 1-way “H-Maser” mode 2-way “Coherent” mode

  20. RadioAstron radio links operating modes Mixed “Semi-Coherent” mode Biriukov et al. 2014, Astron. Rep. 58, N.11, p. 783 software processing

  21. SRT RADIOASTRON ON-BOARD HARDWARE SYNCHRONIZATION: “SEMI-COHERENT” MODE Spectrum of the 15 GHz signal, transmitted data is noise-like • Normalized spectral power density, dB • Frequency, Hz

  22. “Semi-Coherent” + “Test-2”  incompatibility with astronomy

  23. SRT RadioAstron on-board hardware synchronization: “Semi-coherent” mode Spectrum of the 15 GHz signal “Test-2” mode

  24. 2015/02/15 Onsala, 8.4 GHz, 2-way Recorded signal spectrum Normalized power (log scale) Frequency, Hz

  25. 2015/02/15 Onsala, 8.4 GHz, 2-way Signal phase Phase, rad Session time, s

  26. 2015/02/15 Onsala, 8.4 GHz, 2-way Stopped-phase signal spectrum Normalized power (log scale) f  0.001 Hz Frequency, Hz

  27. SRT RADIOASTRON ON-BOARD HARDWARE SYNCHRONIZATION: “SEMI-COHERENT” MODE Select components of the 15 GHz signal spectrum 31 Aug 2014, Puschino TS, 08:20:00 UTC, mode: “Test-2” 18 MHz

  28. Number of observing telescopes near perigee in 2016 Geocentric distance, 103 km

  29. Number of observing telescopes near perigee in 2016 Geocentric distance, 103 km ~10 experiments at <10,000 km distance and

  30. Experiment accuracy *) Work in progress

  31. Gravitational redshift tests

  32. Thanks for attention

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