Planetary and lunar ephemeris EPM2021 and its significance for Solar system research

Abstract

We present an updated public version of EPM (Ephemerides of Planets and the Moon). Since the last public version, EPM2017, many improvements were made in both the observational database and the mathematical model. Latest lunar laser ranging observations have been added, as well as radio ranges of Juno spacecraft and more recent ranges of Odyssey and Mars Reconnaissance Orbiter. EPM2021 uses a new improved way to calculate radio signal delays in solar plasma and has a major update in the method of determination of asteroid masses. Also, a delay-capable multistep numerical integrator was implemented for EPM in order to properly account for tide delay in the equations of the motion of the Moon. The improved processing accuracy has allowed to refine existing estimates of the mass of the Sun and its change rate, parameters of the Earth–Moon system, masses of the Main asteroid belt and the Kuiper belt; and also to raise important questions about existing numerical models of solar wind.

VLBI with SKA: Possible Arrays and Astrometric Science

“…where G is the gravitational constant, M e and R e are the solar mass and radius, respectively, a and e are the semimajor axis and the eccentricity of the orbit of Mercury, respectively, c is the speed of light, and J 2 , the solar quadrupole moment, is ∼10 −7 (see chapter 8 in Ni 2017). The second term is smaller than the first term by a factor of ∼6 × 10 −4 , and the precision of J 2 can currently reach ∼10 −2 (e.g., Pitjeva et al 2022). Therefore, assuming a precision for γ of 10 −6 , it is expected that SKA-VLBI will allow astronomers to test the PPN parameter β at a precision of ∼10 −6 .…”