Jovan Skuljan, Defence Technology Agency
Keywords: Geostationary satellites, photometry, data reduction techniques
Abstract:
The Defence Technology Agency (DTA) operates a small space situational awareness (SSA) observatory at the tip of Whangaparaoa Peninsula, north of Auckland, New Zealand. The observatory is equipped with two 11-inch instruments: an f/10 SchmidtCassegrain telescope and an f/2.2 Rowe-Ackermann Schmidt astrograph, on a Paramount MEII robotic telescope mount. The imaging equipment includes two FLI ML11002 cooled CCD cameras, as well as two smaller QSI 640 ws detectors. In addition, a specialised quadruple polarimetric camera (QuadCam) was recently built for polarimetric observations. The observatory is currently being modified to support fully automated and/or remotely operated operation for more efficient data collection.
Over the past several months the equipment was mainly used on geostationary satellites. A number of objects over the Western Pacific Region were observed in order to test the equipment and data reduction procedures, as well as to estimate the overall precision of astrometric and photometric measurements. It was found that high-quality data could be obtained for satellites as low as 5-10 degrees above the horizon, so that the total coverage of the equatorial belt extends to about 140 degrees. This includes all objects with eastern longitudes above 105 degrees and western longitudes above 115 degrees.
The latest GAIA catalogue from the European Space Agency (ESA) was used for the calibration of satellite images. The photometric calibration using the GAIA G-band magnitudes gives a typical uncertainty of about 0.1 magnitudes, based on 100-200 stars. The magnitude limit of our system is estimated to be about 15-16, depending on the exposure duration (20-60 seconds). The random error (standard deviation) in photometry is usually less than 0.01. The start and finish of every exposure is timed to a high accuracy of better than 1 millisecond, using a specialised GPS unit.
The measurements collected so far demonstrate that our equipment is capable of monitoring relatively faint objects (15-16 magnitude) in the geostationary belt. The high quality photometric data can be used to study any anomalies in the behaviour of the satellite, such as, for example, change in orientation and uncontrolled spin.
Date of Conference: September 11-14, 2018
Track: Poster