Interferometric imaging of geo-synchronous satellites with ground-based telescopes

Abstract

Inteferometric imaging with arrays of telescopes is now a routine technique in optical/infrared astronomy, delivering images with nano-radian resolution. Sensitive next generation arrays, such as the Magdalena Ridge Observatory Interferometer, thus offer a potentially important capability for space situational awareness, allowing satellites in geo-synchronous Earth orbit (GEO) to be inspected after launch. A critical factor for such observations is a lack of short spacings between the telescopes comprising the interferometric array. Large GEO satellites are frequently 20-30 m in size, hence ideally the shortest spacings used for the observations should be between 1.2-1.8 m for observations at 1 µm wavelength. These cannot easily be realised with existing separated-element arrays. In this paper we explore the approach of combining observations from a separated-element interferometer with interferometric data obtained by optical masking of a "single-dish" telescope. We present simulations that demonstrate that substantial improvements in image fidelity can be achieved in this way. Two shapes of generic satellite shape are investigated, intended to be representative of the majority of bright GEO targets, and the efficacy of the method is assessed for these different target shapes and differing brightness levels.

Laser-Guide-Star Satellite for Ground-Based Adaptive Optics Imaging of Geosynchronous Satellites

“…As the GEO belt becomes increasingly populated and contested, the need for imaging of critical commercial and military systems within the belt has continued to grow [25]. In the following sections, we present the motivation for imaging the GEO belt from Earth using AO and an SGS rather than imaging using satellite-based telescopes and cameras.…”

“…4 using synthetic-aperture interferometric imaging [25]. The panels show a truth satellite image at 1.65 μm of magnitude 8 (left), a reconstructed interferometric image (middle) using capabilities of the Magdalena Ridge Observatory Interferometer, and adding data from an 8-m-class telescope nonredundantly masked to increase image fidelity (right).…”

“…Fig. 4 Interferometric-imaging-simulation results from a bright GEO satellite as the imaging target; the left panel is the truth image, the center is reconstructed using only MROI capabilities, and the right panel shows the addition of nonredundantly masked interferometry [25]. 3) There are a limited number of stars bright enough to serve as NGSs.…”

“…1. Commercial and government agencies rely heavily on the continued performance of active systems within the GEO belt, and it would be useful to have the ability to image active systems for health status, confirm deployments, and to watch for proximity dangers (either orbital debris or small, active threats) [25].…”

Field of view for near-field aperture synthesis imaging

“…The above analysis shows that standard selfcalibration imaging algorithms should work well for geosynchronous satellite imaging applications at visible and near-infrared wavelengths. In this case, factors other than the imaging algorithm, such as providing sufficient dense sampling of the u − v plane [7], are likely to be the key challenges to successful imaging of the largest objects.…”