ASTROMETRY OFCASSINIWITH THE VLBA TO IMPROVE THE SATURN EPHEMERIS

Abstract

Planetary ephemerides have been developed and improved over centuries. They are a fundamental tool for understanding solar system dynamics, and essential for planetary and small body mass determinations, occultation predictions, high-precision tests of general relativity, pulsar timing, and interplanetary spacecraft navigation. This paper presents recent results from a continuing program of high-precision astrometric very-long-baseline interferometry (VLBI) observations of the Cassini spacecraft orbiting Saturn, using the Very Long Baseline Array (VLBA). We have previously shown that VLBA measurements can be combined with spacecraft orbit determinations from Doppler and range tracking and VLBI links to the inertial extragalactic reference frame

Does Newton’s gravitational constant vary sinusoidally with time? Orbital motions say no

“…7 of Pitjeva (2013) it can be noticed that the differences between the Kronian Celestial computer used has a 64-bit operating system. coordinates calculated with the EPM2011 and DE424 ephemerides over a time interval as little as 10 years (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014) are smaller than the residuals in Hees et al (2014); Jones et al (2015) obtained with the DE430 ephemerides.…”

“…Both numerical integrations, with and without ∆G(t), share the same initial conditions for the known bodies of the Solar system retrieved from Tables 1 to 2. From the resulting time series of the Earth and Saturn, we numerically compute the time series of ρ, α, δ of Saturn, with and without ∆G(t); then, for all of the three Kronian Celestial coordinates, we compute differential time series ∆α(t), ∆δ(t), ∆ρ(t) which show up the impact of ∆G(t) over the 2004-2014 interval of time covered by the most recent Cassini data analyses (Hees et al 2014;Jones et al 2015); also Gaussian white noise is added to properly simulate the impact of the measurement errors. The results are displayed in Fig.…”

“…5 of Hees et al (2014) and Fig. 2 of Jones et al (2015), which were produced without explicitly modelling the perturbing action of ∆G(t).…”

“…Here, we will use recently released Cassini data analyses spanning ten years (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014) of the orbit of Saturn in terms of its geocentric range ρ, right ascension α, declination δ (Hees et al 2014;Jones et al 2015) to independently test the G(t) scenario of eq. (1)-eq.…”

Geodetic VLBI with an artificial radio source on the Moon: a simulation study

“…VLBI has also been used to observe spacecrafts (e.g., Lebreton et al 2005;Duev et al 2012). Moreover, there are efforts to use the technique for the determination of planetary orbits (Jones et al 2015) and relating those to the International Celestial Reference Frame (ICRF; Fey et al 2015). Usually, differential VLBI ( VLBI) is used in order to cancel common error sources and achieve highly precise angular coordinates.…”