Observations of a Geosynchronous Satellite with Optical Interferometry

摘要

We report a tentative interferometric detection of an earth-orbiting artificial satellite using optical interferometry. We targeted four geosynchronous communications satellites with the Navy Prototype Optical Interferometer (NPOI) near Flagstaff, AZ, and obtained interferometric fringes on one of them, DIRECTV-9S. We used an east-west 15.9-meter baseline of the NPOI and took data in 16 spectral channels covering the 500-850 nm wavelength range. Observations took place during the "glint season" of 28 February to 3 March 2008, when the geometry of the solar panel arrays and the Sun's position creates glints as bright as 2nd magnitude of a few minutes' duration each night. We detected fringes on the satellite at approximately the 2 r level on 1 March at magnitude 4.5. Subsequent analysis shows that the fringe amplitudes are consistent with a size scale of 2 meters (50 nanoradians at geosynchronous orbit) in an east-west direction. This detection shows that interferometric detection of satellites at visual wavelengths is possible, and suggests that a multi-baseline interferometer array tailored to the angular size and brightness of geosynchronous satellites could lead to images of these satellites.