Observations in the thermal IR and visible of a retired satellite in the graveyard orbit, and comparisons to active satellites in GEO

• We observed a retired GEO communications satellite, DirecTV-2, in the graveyard orbit.
• The satellite is no longer under active control, and is in a yaw spin.
• We made simultaneous visible and 3–13 μm observations of the satellite.
• The lightcurves look not at all like the lightcurves for active GEO satellites.
• The data collected should allow modeling of the satellite to predict the flux collected.

There exists a population of defunct satellites in the geo-stationary arc that potentially pose a hazard to current and future operational satellites. These drifting, non-station-kept objects have a variety of ages and sizes, and many are trapped in libration orbits around the Earth׳s two gravitational potential wells (the non-spherical nature of the Earth gives rise to two geo-potential wells or “stable points” that affect objects in geostationary and geosynchronous orbits), whereas others were boosted to higher altitudes into so-called “graveyard” orbits.We have observed several of the approximately 49 objects in libration orbits about the Western stable point (R. Choc, T. Flohrer, and B. Bastida, “Classification of Geosynchronous Objects,” Issue 13, ESA/ESOC, February 2011), as well as objects in graveyard orbits. We have carried out an observational campaign utilizing The Aerospace Corporation׳s 3–13 µm Broadband Array Spectrograph System (BASS), as well as with several optical sensors to collect data on a representative sample of these objects at a variety of solar phase angles. Here we report on recent BASS observations of a retired satellite in the “graveyard” orbit, and compare them with data we had collected over six years ago, while the satellite was still active. Data are also presented on similar satellites that are still active. We describe our methods, the data collected, our results, and our future plans.