Gravitational redshift test of EEP with RadioAstron from near Earth to the distance of the Moon

N. V. Nunes*, N. Bartel, A. Belonenko, G. D. Manucharyan, V. N. Rudenko, L. I. Gurvits, G. Cimò, G. Molera Calvés, M. V. Zakhvatkin, More Authors

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

The Einstein Equivalence Principle (EEP) is a cornerstone of general relativity and predicts the existence of gravitational redshift. We report on new results of measuring this shift with RadioAstron (RA), a space very long baseline interferometry (VLBI) spacecraft launched into an evolving high eccentricity orbit around Earth with geocentric distances reaching 353 000 km. The spacecraft and ground tracking stations at Pushchino, Russia, and Green Bank, USA, were each equipped with a hydrogen maser frequency standard allowing a possible violation of the predicted gravitational redshift, in the form of a violation parameter ɛ, to be measured. By alternating between RA’s frequency referencing modes during dedicated sessions between 2015 and 2017, the recorded downlink frequencies can essentially be corrected for the non-relativistic Doppler shift. We report on an analysis using the Doppler-tracking frequency measurements made during these sessions and find ϵ = ( 2.1 ± 3.3 ) × 10 − 4 . We also discuss prospects for measuring ɛ with a significantly smaller uncertainty using instead the time-domain recordings of the spacecraft signals and envision how 10−7 might be possible for a future space VLBI mission.

Original languageEnglish
Article number175005
Number of pages21
JournalClassical and Quantum Gravity
Volume40
Issue number17
DOIs
Publication statusPublished - 2023

Keywords

  • general relativity
  • gravitational redshift
  • RadioAstron
  • test of Einstein Equivalence Principle

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