Paul W. Kervin

The Near-Earth Asteroid Tracking (NEAT) Program: An Automated System for Telescope Control, Wide-Field Imaging, and Object Detection

The Near-Earth Asteroid Tracking (NEAT) system operates autonomously at the Maui Space Surveillance Site on the summit of the extinct Haleakala Volcano Crater, Hawaii. The program began in 1995 December and continues with an observing run every month. Its astrometric observations result in discoveries of near-Earth objects (NEOs), both asteroids (NEAs) and comets, and other unusual minor planets. Each six-night run NEAT covers about 10% of the accessible sky, detects thousands of asteroids, and detects two to five NEAs. NEAT has also contributed more than 1500 preliminary designations of minor planets and 26,000 detections of main-belt asteroids. This paper presents a description of the NEAT system and discusses its capabilities, including sky coverage, limiting magnitude, and detection efficiency. NEAT is an effective discoverer of NEAs larger than 1 km and is a major contributor to NASAs goal of identifying all NEAs of this size. An expansion of NEAT into a network of three similar systems would be capable of discovering 90% of the 1 km and larger NEAs within the next 10–40 yr, while serving the additional role of satellite detection and tracking for the US Air Force. Daily updates of NEAT results during operational periods can be found at JPLs Web site (http://huey.jpl.nasa.gov/~spravdo/neat.html). The images and information about the detected objects, including times of observation, positions, and magnitudes are made available via NASAs SkyMorph program.

Demonstration of new technology MEMS and liquid crystal adaptive optics on bright astronomical objects and satellites

We present here results using two novel adaptive optic elements, an electro-static membrane mirror, and a dual frequency nematic liquid crystal. These devices have the advantage of low cost, low power consumption, and compact size. Possible applications of the devices are astronomical adaptive optics, laser beam control, laser cavity mode control, and real time holography. Field experiments were performed on the Air Force Research Laboratory, Directed Energy Directorates 3.67 meter AMOS telescope on Maui, Hawaii.

Photometric signature inversion

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.

Time-Resolved I-Band Photometry of Calibration Spheres and NaK Droplets

Wehave developed a program to obtain photometry of Earth-orbiting satellites using the U.S. Air Force advanced electrooptical system 3.6m telescope’s Visible Imager instrument, which acquires time-series charge-coupled device images at typical rates of 0.1 to 2.1 Hz. Observations of 12 spherical satellites provide measurements of I-band albedos (i.e., reflectances) and evaluation of surface nonuniformities. Best-fit specular diffuse albedo models enable brightness predictions and a means to grade the quality of the spheres as photometric calibration reference objects. CalSphere-4A appears to be the highest quality calibrator of the 12, with the best-fitmodel reproducing 90% of the measurements to within 0:03 stellar magnitudes. This four-decade-old sphere reflects in a predominantly diffuse fashion and has a total albedo of 67% that is somewhat lower than expected for fresh white paint, effects likely due to space weathering. The aluminum Lincoln Calibration Sphere-1 shows predominantly specular reflection (albedos 59%) but with 0:3 magnitude deviations between data and model that recur every 30–90 s, likely due to one or more surface irregularities. Three other predominantly specular aluminum spheres display less frequent but larger amplitude deviations. Observations indicate that sodium/potassium droplets leaked from Soviet radar ocean reconnaissance satellite reactors are highly reflective specular spheres that can also serve as optical calibrators.

Spectroscopic observations of space objects and phenomena using Spica and Kala at AMOS

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 directorates 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.

Raven automated small telescope systems

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.

A Geosynchronous Orbit Search Strategy

Since more than 10 years there is evidence that small-size space debris is accumulating in the geosynchronous orbit (GEO), probably as the result of breakups. Two break-ups have been reported in GEO. The 1978 break-up of an EKRAN 2 satellite, SSN 10365, was identified in 1992, and in 1992 a Titan 3C Transtage, SSN 3432, break-up produced at least twenty observable pieces. Subsequently several nations performed optical surveys of the GEO region in the form of independent observation campaigns. Such surveys suffer from the fact that the field of view of optical telescopes is small compared with the total area covered by the GEO ring. As a consequence only a small volume of the orbital element-magnitude-space is covered by each individual survey. Results from these surveys are thus affected by observational biases and therefore difficult to compare. This paper describes the development of a common search strategy to overcome these limitations. The strategy optimizes the sampling for objects in orbits similar to the orbits of the known GEO population but does not exclude the detection of objects with other orbital planes. A properly designed common search strategy clearly eases the comparison of results from different groups and the extrapolation from the sparse (biased) samples to the entire GEO environment.

Phoenix Telescope at AMOS: return of the Baker-Nunn camera

The number of objects orbiting the Earth has been increasing dramatically since the launch of Sputnik in the late 1950s. 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.

Deep space satellite observations using the near-Earth asteroid tracking (NEAT) camera at AMOS

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.

Determining the material type of man-made orbiting objects using low-resolution reflectance spectroscopy

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.