Jovan Skuljan, Defence Technology Agency
Keywords: GEO satellites, observations, astrometry, photometry, proximity
Abstract:
A large number of observations of geostationary satellites in proximity operations were collected in February 2020 from New Zealand. The measurements were part of the “Phantom Echoes” experiment, a collaborative activity between Australia, Canada, New Zealand, the United Kingdom and the United States (five-eyes countries). As a suitable case study, the docking between the Mission Extension Vehicle 1 (MEV-1) and Intelsat 901 was selected. During the final part of the proximity operation, the two satellites were positioned over the Pacific Ocean and therefore visible from New Zealand.
The observations were made from the Defence Technology Agency’s (DTA) Space Situational Awareness (SSA) Observatory on Whangaparaoa Peninsula north of Auckland. All images were taken with a 11-inch (279 mm) Celestron Edge HD telescope, equipped with a FLI ML11002 CCD camera. The DTA observatory has recently been fully automated, allowing for continuous data collection throughout the night. Up to 1500 images were routinely collected on every clear night, using a sampling rate of about 3 frames per minute (180 per hour) for increased time resolution both in photometry and astrometry. The apparent magnitude limit for satellite detection was about 15, based on the exposure time of 5 seconds. In practice, the results were only acceptable when the objects were at around magnitude 14, or brighter.
The data reductions were performed in StarView, a dedicated software tool developed at DTA for SSA image analysis. A specially developed data analysis algorithm was used for the astrometric calibration of both stellar (sidereal) images and satellite (non-sidereal) images. A typical RMS error of the astrometric solution was 0.2 arc seconds, based on about 100-400 stars identified in the field of view. The European Space Agency’s GAIA catalogue (DR2), limited down to magnitude 16, was used for the calibration. The random measurement errors in relative astrometry between the two satellites was typically about 40-50 mas, corresponding to less than 10 m in space at the GEO range. A typical photometric calibration based on the GAIA G-band produced an RMS error of about 0.1 magnitudes. At the same time, the random errors in aperture photometry were only between about 0.015 and 0.025 over a wide range of apparent magnitudes.
Using the high-quality measurements obtained during the proximity operations of MEV-1 and Intelsat 901 it was possible to correlate certain characteristic features in the observed astrometric and photometric data with the actual maneuvers and other key events performed during the mission. It was demonstrated that readily available small-aperture optical equipment can successfully be used to monitor proximity operations in the GEO regime and collect important information for space situational awareness.
Date of Conference: September 15-18, 2020
Track: Non-Resolved Object Characterization