[astroseminar at Sapienza] today at 16:00: Rudenko Valentin N.

[Elia Battistelli]

Title: Gravitational Red Shift effect measurement with orbital probe
Speaker:  Rudenko Valentin N.
Institution: SAI MSU, Moscow
Date: Wednesday, 6 December 2017
Time: 4:00pm
Location: Aula Rasetti, Marconi Building, Dept. of Physics, Sapienza 
University

Abstract:
At present the Radioastron (RA) Earth's satellite having very elliptic 
orbit is used for probing of the gravitational red shift effect [1,2]. 
Objective of this test consists in the enhancing accuracy of measurement 
to prove the correspondence of the effect to the Einstein's theory at 
one order of value better then in was done in the GP-A experiment [3 ]. 
There are two H-masers in disposal, one at the board RA and other at the 
Land Tracking Station (LTS). One can compare its mutual time rate using 
communication radio links between RA and LTS. In contrast with the GP-A 
experiment for RA there is a possibility of measurement repetition and 
accumulation of data in the process of orbital circulation. It could be 
resulted in increasing of the integral accuracy. Receipt for a 
compensation of the coherent hindrances (Doppler, troposphere and 
ionosphere influence) developed during GP-A mission consists in 
simultaneously using the two modes communication of the LTS with RA: one 
way (H-maser) and two ways (Coherent) modes. However such opportunity 
was not foreseen for RA. Only a periodic switching between these modes 
is available.
    In this talk we investigate the achievable accuracy using a special 
algorithm of red shift extraction associated with technical specific of 
the RA satellite. Some experimental illustrations having been got during 
of RA functioning are presented as well as preliminary results of the 
red shift effect measurement.

References
1.	 A.V. Biriukov, V.L. Kauts, V.V. Kulagin, D.A. Litvinov, V.N. 
Rudenko,
Gravitational redshift test with the space radio telescope 
"RadioAstron", Astron. Rep. 58(11) (2014) 783-795,
http://dx.doi.org/10.1134/S1063772914110018
2.	2. D. A. Litvinov, V. N. Rudenko, A. V. Alakoz  et al Probing the
gravitational redshift with an Earth-orbiting satellite. Physics 
Letters A  v
381  (2017)
3.	3. R.F.C. Vessot, M.W. Levine, E.M. Mattison, et al.  Test of 
relativistic
gravitation with a space-borne hydrogen maser, Phys. Rev. Lett. 45 
(1980) 2081-2084, http://dx.doi.org/10.1103/PhysRevLett.45.2081

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