Gravitational redshift test with the space radio telescope “RadioAstron”

RadioAstron as a target and as an instrument: Enhancing the Space VLBI mission’s scientific output

“…This sets a limit for the accuracy of experimental determination of γ at the level of 1.8 × 10 −5 over ∼1000 h if no noise-compensation scheme is used. In case such a scheme is utilised, the accuracy can be improved by an order of magnitude (Biriukov et al 2014), which is comparable to or even better than the result obtained using Cassini spacecraft tracking during solar conjunction (Bertotti et al 2003).…”

“…Precise measurement of this quantity will make it possible to achieve a better constraint on the value of the post-Newtonian parameter γ, which is equal to unity in general relativity, but which deviates from it slightly in alternative models. Accurate Doppler measurements of the RadioAstron's downlink signal might play an important role in such an experiment (for details, see Biriukov et al 2014). To demonstrate the achievable precision, we performed the following test.…”

Laboratory modeling of the giant gravitational shift of gamma-radiation frequency

“…В микроволновом диапазоне гравитационное смещение было показано при сравнении частоты водородного мазера, находящегося на спутнике на околоземной орбите, с частотой такого же мазера на Земле (эксперимент Gravity Probe A [4]). В других измерениях ГКС применялась радиоинтерферометрия со сверхдлинной базой, использующая спутники с высокоэллиптической орбитой [5,6].…”

RadioAstron gravitational redshift experiment: Status update

“…1c). In this mode the 7.2 GHz uplink tone, the 8.4 GHz downlink tone and the 15 GHz data downlink carrier are phaselocked to the ground H-maser signal, while the modulation frequency of the data downlink is phase-locked to the on-board H-maser [7]. We do not give a detailed account of this approach here because it will not likely be used in the observations due to technical reasons.…”