Radiophysical Relativistic Gravimeter

The author in 2005 developed an original radiophysical method for measuring the parameters of the gravitational field in the radio frequency range using the relativistic effect ”redshift”. A stationary radiophysical relativistic gravimeter (RRG) was designed, manufactured, tested, and certified, which allows you to measure the absolute value of gravitational acceleration with an accuracy of $3-5\mu \mathrm{g}\mathrm{a}\mathrm{l}$, as well as a change in gravitational potential at a height of less than 1 cm. The main element of the gravimeter is the hydrogen frequency standard VCH-1005 Russia). A modification of the differential radiophysical gravimeter was also developed, the measurement scheme of which allows to exclude the Doppler frequency shift, which occurs when measuring on mobile objects, including spacecraft.The ACES (Atomic Clock Ensemble in Space) is a project led by the European Space Agency, where a highly stable atomic clock was placed at the International Space Station (ISS) in 2019. Functioning in a microgravity environment made it possible to obtain stable and precise measurements of time for different areas of research, including general relativity, time and frequency metrology and others. Currently payload consists of two clocks: cesium clock for long-term stability and a hydrogen maser for short-term stability (or PHARAO and SHM), which generate the reference frequency instability and inaccuracy of $1*10^{-16}.$The characteristics of PHARAO and VCH-1005 are very close, which allows us to create a three-axis differential radiophysical gravimeter onboard the ISS, which allows us to measure the absolute value of the acceleration of gravity with an accuracy of 3-5 $\mu \mathrm{g}$ and ensure resolution on the Earth’s surface not worse than 5-10 km. It should also be noted that the cost of gravimeter equipment, except PHARAO, will not exceed 500 thousand euros. The characteristics of the differential radiophysical gravimeter are close to the parameters of the GOCE and GRACE missions, the cost of which creation exceeds 500 million euros.