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A. Hellerschmied, L. McCallum, J. McCallum, J. Böhm, J. Sun:
"Observing the APOD Satellite with the AuScope VLBI Network";
in: "IVS 2018 General Meeting Proceedings", issued by: Kyla L. Armstrong, Karen D. Baver, and Dirk Behrend; NASA/CP-2019-219039, 2019, 259 - 263.

The Chinese APOD-A nano satellite, launched in September 2015, is the first LEO satellite co-locating three space-geodetic techniques including VLBI. Being equipped with a dual-frequency GNSSreceiver, an SLR retro-reflector, and a VLBI beacon transmitting DOR tones in the S- and X-band, it can be considered as a first prototype of a geodetic co-location satellite in space. With the focus on VLBI observations we present a series of experiments carried out by the AuScope geodetic VLBI array in November 2016. These experiments represent first observations of a LEO satellite by VLBI radio telescopes with the goal of deriving baseline delays as common in thegeodetic VLBI. In this paper we give an overview on the applied process chain that covers all tasks and aspects from scheduling and observations, over correlation and fringe fitting, to the actual data analysis. To stay as close as possible to the operational analysis scheme for geodetic VLBI sessions, we widely adopted the use of standard software such as DiFX for correlation and the Haystack Observatory Post-Processing System (HOPS). In the subsequent analysis of the derived delays in the Vienna VLBI and Satellite Software (VieVS) we find residuals in the range of a few nanoseconds. VieVS provides options to estimate a variety of geodetic parameters based on such data, including orbit offsets. The discussed experiments represent the first end-to-end realizations of VLBI observations of a tie satellite on a LEO orbit and are a valuable resource for future, more sophisticated space tie satellite missions in the style of E-GRASP/Eratosthenes.

APOD, VLBI satellite tracking, AuScope

https://ivscc.gsfc.nasa.gov/publications/gm2018/54_hellerschmied_etal.pdf