Combining observations of GNSS and astronomical sources: Can you see both through a single lens?
Abstract
We begin with the question: "Is it possible to develop an instrument concept in which GNSS signals and astronomical source signals are sampled via the same signal chain, effectively ensuring that both measurements are made from the same antenna phase center, when processed in conjunction with measurements from a VLBI-like antenna?"
The advantage of this approach would be to potentially open the door to direct measurement of GNSS-VLBI baselines between electrical phase centers. Such inter-instrument ties at fundamental stations are critically important to the formation of the international terrestrial reference frame. However, the low gain of the standard GNSS antennas, and the limited frequency range over which they operate, would seem to make this an unlikely concept. We will describe our efforts to observe bright celestial sources through a combination of small 3-m dish antenna and a modified low-gain GNSS antenna and the High Rate Tracking receiver (HRTR) - a mixed antenna interferometer. We will describe the HRTR, an FPGA-based receiver developed to allow high-rate observations of GNSS signals. This allows us to perform many of the same observations as a dish antenna, by substituting integration time for the signal gain provided by the dish. We provide a detailed description of our interferometer and it's components, and describe our measurement configuration. We will describe our attempt at an observation of Cygnus-A on a short 140 meter baseline. This observation yielded a tentative detection. Finally, we will outline some of the difficulties with this type of measurement and directions for future research.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.G11A..08Y
- Keywords:
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- 1229 Reference systems;
- GEODESY AND GRAVITY;
- 1295 Integrations of techniques;
- GEODESY AND GRAVITY;
- 1299 General or miscellaneous;
- GEODESY AND GRAVITY