Angles and Range: Initial Orbital Determination with the Air Force Space Surveillance Telescope (AFSST)
Abstract : The institution of a robust, comprehensive program of Space Situational Awareness (SSA) necessarily includes observations by ground-based optical and infrared (OIR) telescopes. The Air Force Space Surveillance Telescope (AFSST) has been proposed as a system of telescopes designed to address the ground-based component of comprehensive SSA. A hallmark of our definition of AFSST is that it be composed of inexpensive, replicable telescopes programmed to accomplish multiple surveillance programs, but designed to achieve the difficult design-driving task of accomplishing an uncued search for small objects in Low Earth Orbit (LEO). We discuss the configuration of AFSST and describe one technique by which AFSST simultaneously acquires angle and range data for accurate real-time determination of LEO orbital elements, even upon first detection of the object.
Multiple observing modes for wide-field optical surveillance of GEO space
Very wide field of view optical sensors with silicon detectors are being used in multiple survey modes by J. T. McGraw and Associates to provide persistent, affordable surveillance of GEO space to faint limiting magnitudes. Examples include: • classical staring mode with typical integration times of seconds provided by multiple co-directed sensors to provide a deep mosaic of tens of square degrees per exposure to faint limiting magnitude • step-and-stare observations of several second integration time from which a continuous, overlapped, mosaicked image of GEO space can be provided • time-delay and integrate (TDI) imagery obtained by driving the telescope in declination and stepping the telescope in the E-W direction, which produces repeated, overlapping (if desired), synoptic images of GEO space With current 350 mm diameter optics, detection limits for concentrated observations (e.g. “neighborhood watch”) detection limits of magnitude 18 are achieved, and for uncued survey the detection limits are fainter than magnitude 16. Each of these techniques can employ multiple telescopes to obtain search rates in excess of 1000 square degrees per hour, allowing complete uncued CONUS GEO surveillance to +/15 degrees latitude every two nighttime hours. With appropriate placement, sensors could provide complete coverage of GEO to these limiting magnitudes at the same survey rate. At each step of the development of this unique capability we discuss the fundamental underlying physical principals of optics, detectors, search modes and siting that enable this survey, a valuable adjunct to RF, radar, GEODSS and other optical surveys of GEO space.
Curved Focal-Plane Arrays Using Back-Illuminated High-Purity Photodetectors
NASA Tech Briefs, October 2003 dimmed (or missing) beacon, making it possible to continue to compensate for vibrations and other motions when the system is partially or totally blind to the beacon. The time during which compensation can be maintained is limited by the accumulation of integration error since the last observation of the beacon at adequate intensity. Typical atmospheric fades last about 1 ms. It has been estimated that compensation could be maintained for times ranging from tens of milliseconds to tens of seconds, depending on the amount of pointing error that can be tolerated. This work was done by Gerardo Ortiz and Shinhak Lee of Caltech for NASA’s Jet Propulsion Laboratory. Further information is contained in a TSP (see page 1). NPO-40061 Beacon CCD