We explore the problem of reconstructing a 3-d model of a convex object from unresolved time-series photometric measurements (i.e., lightcurves). The problem is broken into three steps. First, the lightcurves are used to recover the albedo-area density of the object as a function of the surface normal. The ill-posedness of this inversion is considered and a suitable regularization scheme proposed. Second, the albedo and area contributions are separated using either transits or additional measurements at different wavelengths. Finally, the Minkowski problem is solved to produce the 3-dimensional shape corresponding to the area density.
The number of objects orbiting the Earth has been increasing dramatically since the launch of Sputnik in the late 1950's. Thousands of orbiting objects, active satellites or debris, need to be tracked to ensure the accuracy of their orbital elements. To meet the growing needs for space surveillance and orbital debris tracking, the Air Force Maui Optical and Supercomputing Site (AMOS) on Maui, Hawaii is bringing back one of the original Baker-Nunn cameras as the Phoenix Telescope to contribute to these efforts. The Phoenix Telescope retains the wide-field attribute of the original system, while the addition of enhanced optics allows the use of a 4k × 4k pixels back-illuminated CCD array as the imaging camera to provide a field-of-view of 6.8 degrees square (9.6 degrees diagonal). An integrated software suite automates the majority of the operational functions, and allows the system to process in-frame multiple-object acquisitions. The wide-field capability of the Phoenix Telescope is not only an effective tool in the space surveillance effort, but it also has a very high potential value for efforts in searching for and tracking Near-Earth objects (NEO). The large sky coverage provided by the Phoenix Telescope also has the potential to be used in searching for supernova and other astronomical phenomena. An overview of the Phoenix system and results obtained since first-light are presented.
The purpose of this research is to improve the knowledge of the physical properties of orbital debris, specifically the material type. Combining the use of the fast-tracking United States Air Force Research Laboratory (AFRL) telescopes with a common astronomical technique, spectroscopy, and NASA resources was a natural step toward determining the material type of orbiting objects remotely. Currently operating at the AFRL Maui Optical Site (AMOS) is a 1.6-meter telescope designed to track fast moving objects like those found in lower Earth orbit (LEO). Using the spectral range of 0.4 - 0.9 microns (4000 - 9000 angstroms), researchers can separate materials into classification ranges. Within the above range, aluminum, paints, plastics, and other metals have different absorption features as well as slopes in their respective spectra. The spectrograph used on this telescope yields a three-angstrom resolution; large enough to see smaller features mentioned and thus determine the material type of the object. The results of the NASA AMOS Spectral Study (NASS) are presented herein.
The Spica and Kala spectrographs located at the rear blanchard of the 1.6 m telescope and the trunnion port of the AEOS 3.67 m telescope, respectively, have been utilized by several DoD and NASA agencies requiring relatively high resolution spectroscopic observations. The sensors are located at the Air Force Maui Optical Station (AMOS), Haleakala, Maui. Three R&D programs utilizing these instruments will be described. The AFRL propulsion directorate's demonstration called the electric propulsion space experiment (ESEX) utilized Spica to evaluate high powered arc-jet thruster firings from the ARGOS satellite. AFRL Det. 15 and Air Force Battlelab sponsored a project called SILC to explore the advantages of applying spectroscopic analysis to help reduce satellite cross- tagging and augment Satellite Object Identification (SOI). Thirdly, the NASA Johnson Space Center Space Debris Program obtained spectroscopic data on Low Earth Orbit (LEO) targets to help determine albedo and material composition of space debris.
The AMOS 1.2-m telescope is being used 18 nights per month to search for Near-Earth Asteroids (NEA). Since telescope time is a very valuable resource, our goal is to use the telescope as efficiently as possible. This includes striving to maximize the utility of each observation. Since the NEAT searches are within the ecliptic, the same part of the sky as geosynchronous satellites, these search fields contain satellite tracks as well as asteroids. We present the results of simulations of the number of satellites that should be found within the field of view based upon the field centers and times for several nights. We have also examined the NEAT images for geosynchronous objects and present these results. During the remaining nights each month, we use the NEAT camera to obtain observations of deep-space satellites. This data will also be presented. We also present the results of simulations for optimizing search strategies for deep-space objects using NEAT and other AMOS sensors.
The NASA/JPL Near Earth Asteroid Tracking (NEAT) Program was in operation using the Maui GEODSS as its observing platform for about three years starting in late 1995 and continuing into 1998. In October of 1998 the NASA/AFSPC Near Earth Object Working Group (NEOWG) recommended that the NASA/JPL NEAT program be moved to the AMOS 1.2 m/B37 telescope. This paper describes the technical efforts that were required to facilitate the move. The task requirements specified that the modified 1.2 m/B37 system be capable of producing a field of view (FOV) greater than or equal to 1.4 degrees X 1.4 degrees at the NEAT camera focal plane. Further, it was specified that no modifications be made to the 1.2 m/B37 mirror or the NASA/JPL camera. Thus, activity focused on the development of suitable focal reduction optics (FRO). A new headring and spider, based on the original design, were also built to receive the NEAT FRO and the NASA/JPL camera. Operation of the NEAT system, for asteroid search and discovery, will be autonomous and remotely directed from NASA/JPL. Finally, the potential for use of the NEAT system as regards the satellite metric mission will also be presented.
The Raven optical sensor is a commercial system being developed and tested by the Air Force Research Laboratory. It allows for a low cost method for obtaining high accuracy angular observations of space objects (manmade and celestial) with a standard deviation of approximately one arcsecond or less. Presented here is an overview of the past and present successes and future projects utilizing Raven. This system has evolved into a very viable and cost effective solution for obtaining low-cost observations for satellite and asteroid catalog and follow-up maintenance. Collaborative efforts between AFRL and several space agencies (JPL, NASA, Space Battlelab, Canadian Defense Ministry, etc) have successfully demonstrated and utilized the Raven system for their missions, including improved satellite orbit determination accuracy, NEO follow-ups, and remote autonomous collecting and reporting of metric data on deep space objects.
Not all realms of observation require an 8-meter telescope. Some, such as space surveillance of asteroids and man-made satellites, are too important to ignore, yet obviously inappropriate to consign to the new generation of large telescopes. The United States Air Force Research Laboratory (AFRL), with Boeing, Rocketdyne Technical Services (RTS), has developed a low-cost, rapidly deployable surveillance telescope concept called Raven which takes advantage of commercial off-the-shelf (COTS) telescopes, detectors and software. The development of the Raven concept was originally a response to a recognized need to support the timely follow- up of asteroid discoveries. Early astrometric tests using Raven telescope in the 12- to 16-inch diameter range proved to be comparable in accuracy to the much larger telescopes of the existing space surveillance network. Observations of man-made satellites have also produced quality results. A high level of productivity is achieved by automating all of the observing functions and much of the data reduction and analysis. Performance data in both the areas of asteroid and satellite metrics will be presented, and performance parameters discussed.
The Air Force Maui Optical Station (AMOS) has demonstrated follow-up astrometry and photometry for near-earth objects (NEOs), with results published in the Minor Planet Circulars. Although this information is important for the cataloging of all NEOs, it does not provide all of the data needed to assess the potential hazard posed by these objects, i.e. composition, size, shape, and dynamics. AMOS has increased its capability by adding a six position filter wheel (in conjunction with Phillip's Laboratory's Geophysics Directorate and the University of Arizona), for use on the Jet Propulsion Laboratory's CCD camera mounted on the AMOS 1.2 meter telescope. The paper provides the rationale for three-color photometry for determination of NEO characteristics, as well as preliminary results of the observations of several NEOs an main-belt asteroids. It also discusses the design of a photo-polarimeter, to be built in the near future, which will add more capability to AMOS, and determination of albedo and size of NEOs of particular interest to both the scientific and government communities.
Within the last decade, the declassification of adaptive optics techniques and systems developed for defense purposes opened new opportunities to the astronomical community. Since the military resolution requirements are not qualitatively different from the astronomical ones, astronomers may profit from the quite sizable investments already made. On the other hand, the astronomical observations are much more demanding than the military ones with respect to the required accuracy, stability and sensitivity. In 1994, after contacts made during an adaptive optics meeting in Munich, we started a joint project to observe the ejected matter from the luminous blue variable (LBV) P-Cygni with the AMOS compensated imaging system (CIS). In this paper we describe the problems encountered and the experience gained in more than two years of operations with CIS. The satisfactory results obtained so far prompted us to plan a more ambitious program. We aim to profit from the acquired know-how for preparing a proposal of astronomical observations designed in such a way of taking the utmost advantage of the capabilities of the new USAF AEOS adaptive optics system.
To better characterize the orbital debris environment, improvements must be made to the overall sensitivity of the orbital debris surveillance system. There are many ways to improve the sensitivity of the optical system: through hardware and software improvements, and through observing techniques. AMOS has been investigating algorithms for processing video data as a technique for improving the sensitivity of the optical sensors. This paper discusses preliminary results for two different approaches to the sensitivity issue, and the potential for implementing them in real time.
The Air Force Maui Optical Station (AMOS) conducted searches, measurements, and analyses of the orbital debris environment for the Air Force Space Command and the Phillips Laboratory since May 1991 in support of the Air Force Orbital Debris Measurements Program. The objective of this program was to detect orbiting low earth objects not currently in the United States Space Command Space Surveillance Center catalog. Once objects were detected, further objectives were to track, catalog, and maintain those objects locally, to determine statistics on detected objects, and perform relevant analyses. AMOS has developed a prototype surveillance system for the detection and tracking of orbital debris. In addition to this surveillance activity, AMOS has also automated the post-processing videotape streak detection process and is automating the analysis process. Both the optical tracking of orbital debris and the automatic streak detection process were thought to be virtually impossible only a few years ago. The AMOS program employed wide field of view optical telescopes using the Maui Groundbased Electro-Optical Deep Space Surveillance site and AMOS narrow field of view tracking telescopes, both located at the Maui Space Surveillance Site.
The Air Force Phillips Laboratory (PL) is tasked by Air Force Space Command to characterize the orbital debris environment. Part of this task is to search for and detect debris using the optical facilities at the PL Air Force Maui Optical Station (AMOS), which is located at the Maui Space Surveillance Site (MSSS). The goals of the program are discussed, with emphasis on the detection program. This includes telescopes and sensors available, how they are used, and handoffs from one sensor to another. Results of this correlation, as well as conclusions on the orbital debris environment, are presented.
The Relay Mirror Experiment (RME) has successfully demonstrated long-range, low-jitter tracking and pointing capabilities appropriate for ground-based laser (GBL) propagation. The RME program includes (1) a passively maneuverable, free-flying low-orbit spacecraft with a laser diode beacon and spoiled retroreflectors as acquisition aids; (2) a payload experiment package (PEP) consisting of sensors, optics, steerable mirrors, and control electronics. This subsystem accomplishes GBL tracking and pointing and the associated positioning of a space-based relay mirror sufficiently to relay an infrared beam between two ground sites. Design considerations for the control system included base motion disturbance and calibration; (3) two GBL sites each a tracking and pointing exercise in itself, using a combination of sensors and acquisition and tracking capabilities. One site includes a beam relay scoring capability.
The Relay Mirror Experiment is a space experiment in which an IR laser beam is propagated from one ground station, the Laser Source Site (LSS), to an orbiting relay mirror and back to another ground station, the Target Scoring System (TSS). A sparse array of 37 telescopes senses the position of the relayed beam at the second ground station for purposes of scoring the pointing capability of the relay mirror. Data from these telescopes is processed to determine the position of the beam as a function of time. These signals contain the effects of atmospheric turbulence on both the uplink and downlink of the IR beam. Spectral and correlation analysis is used on the telescope data to minimize the effects of atmospheric turbulence, as well as other environmental effects.