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James M Anderson
Type of contribution: oral

Software Development for D-VLBI Scheduling and Analysis of Spacecraft Observations

James M. Anderson, Deutsches GeoForschungsZentrum GFZ Li Liu, Deutsches GeoForschungsZentrum GFZ Robert Heinkelmann, Deutsches GeoForschungsZentrum GFZ Harald Schuh, Technische Universit{"a}t Berlin and Deutsches GeoForschungsZentrum GFZ Kyriakos Balidakis, Deutsches GeoForschungsZentrum GFZ Susanne Glaser, Technische Universit{"a}t Berlin Maria Karbon, Deutsches GeoForschungsZentrum GFZ Cuixian Lu, Deutsches GeoForschungsZentrum GFZ Julian Andres Mora-Diaz, Deutsches GeoForschungsZentrum GFZ Tobias Nilsson, Deutsches GeoForschungsZentrum GFZ Virginia Raposo-Pulido, Deutsches GeoForschungsZentrum GFZ Benedikt Soja, Deutsches GeoForschungsZentrum GFZ

We aim to demonstrate the potential of differential-VLBI (D-VLBI, known as phase referencing in the astronomical community) for the establishment of frame ties to spacecraft and Solar System dynamical reference frames with the international terrestrial reference frame (ITRF) and the international celestial reference frame (ICRF). By largely canceling common instrumental, atmospheric, and delay model error sources, D-VLBI observations enable precise relative astrometric measurements of space probe positions and velocities. As part of projects at the GFZ to assess the current capabilities of D-VLBI for making frame ties between dynamical systems and the ICRF, we are developing software to aid in the scheduling and analysis of D-VLBI observations of spacecraft. In contrast to astronomical phase referencing observations where the target and calibrator sources have fixed positions common to all telescopes, observations of nearby spacecraft, including GNSS, low Earth orbit (LEO), Lunar, and Lagrangian point (such as Gaia) spacecraft, must deal with rapid angular motion of the spacecraft and geocentric parallax effects. Thus, different telescopes often require different calibrator targets, the target to calibrator separation changes with time and telescope, and multiple calibrator targets are required as the target moves across the sky. We present an overview of the challenges faced by D-VLBI for nearby space missions and the status of our software developments to aid in calibrator source selection, the design of the scheduling sequence for D-VLBI observations of nearby spacecraft, and the calibration of the resulting observations for multiple calibrator and target geometries.