Space-time dynamics estimation from space mission tracking data

Abstract

Aims. Many physical parameters that can be estimated from space mission tracking data influence both the translational dynamics and proper time rates of observers. These different proper time rates cause a variability of the time transfer observable beyond that caused by their translational (and rotational) dynamics. With the near-future implementation of transponder laser ranging, these effects will become increasingly important, and will require a re-evaluation of the common data analysis practice of using a priori time ephemerides, which is the goal of this paper. Methods. We develop a framework for the simultaneous estimation of the initial translational state and the initial proper time of an observer, with the goal of facilitating robust tracking data analysis from next-generation space missions carrying highly accurate clocks and tracking equipment. Using our approach, the influence of physical parameters on both translational and time dynamics are considered at the same level in the analysis, and mutual correlations between the signatures of the two are automatically identified. We perform a covariance analysis using our proposed method with simulated laser data from Earth-based stations to both a Mars and Mercury lander. Results. Using four years of tracking data for the Mars lander simulations, we find a difference between our results using the simultaneous space-time dynamics estimation and the classical analysis technique (with an a priori time ephemeris) of around 0.1% in formal errors and correlation coefficients. For a Mercury lander this rises to around 1% for a one-month mission and 10% for a four-year mission. By means of Monte Carlo simulations, we find that using an a priori time ephemeris of representative accuracy will result in estimation errors that are orders of magnitude above the formal error when processing highly accurate laser time transfer data.

Astrovirology, Astrobiology, Artificial Intelligence: Extra-Solar System Investigations

“…Lasers have numerous uses, including communications, optical transponders, precision clocks, pathfinding, orbital dynamics, altimetry, laser propulsion in space, navigation, attitude control, construction, precision alignment, structural control in space, power generation and distribution, resource location including 3D-sensing, materials science, planetary, satellite, asteroid, cometary interior structure and geology, regolith and ice surface mapping, and of course, fulfilling measurement requirements due to Special and General Relativity. Further development will be essential for exo-solar system interplanetary exploration [115,116]. Such development is perfect for robotics, AI, and QCs.…”

High Performance Clocks and Gravity Field Determination

“…In this preliminary analysis, we have not analyzed the possibilities to decouple the signature of the spacecraft's velocity and gravitational potential from the frequency comparison measurements. Such an approach, as is discussed by Dirkx et al [2016] for planetary laser ranging data, could be used to quantify more robustly the influence of velocity uncertainties on potential measurements using clocks. Conversely, such an analysis would quantify the degree to which the relativistic Doppler shift can be used to dynamically determine the spacecraft's state when making use of clock comparisons.…”

Relativistic time transfer for a Mars lander: from proper time to Areocentric Coordinate Time

“…Experiments involving time/frequency transfer might also be used for testing theories of gravity (Samain 2002;Cacciapuoti & Salomon 2009;Wolf et al 2009;Christophe et al 2009;Schiller et al 2009;Christophe et al 2012;Deng & Xie 2013a,b, 2014Zhang et al 2014;Xie & Huang 2015;Hees et al 2014;Angélil et al 2014;Delva et al 2015;Deng 2016). There are other performed or proposed tests of GR and non-Newtonian gravity that use existing or proposed orbiters (Iorio 2006(Iorio , 2009(Iorio , 2010Turyshev et al 2010;Le Poncin-Lafitte 2011;Dirkx et al 2016;Oberst et al 2012).…”

“…Relativistic time transfers in various contexts, such as in the vicinity of Earth (Klioner 1992;Petit & Wolf 1994;Wolf & Petit 1995;Petit & Wolf 1997;Kouba 2002Kouba , 2004Petit & Wolf 2005;Nelson 2007Nelson , 2011; Xie 2016) and in the Solar System (Nelson 2007;Minazzoli & Chauvineau 2009;Nelson 2011;Deng 2012;Hees et al 2012;Pan & Xie 2013, 2014Deng 2015;Dirkx et al 2015Dirkx et al , 2016, have been intensively studied and discussed. In those contexts, one clock is onboard a satellite or an orbiter and the other one is on the ground.…”