Roberts Jr. L.C.,Jet Propulsion Laboratory |
Bradford L.W.,Pacific Defense Solutions, LLC
Optics Express | Year: 2011
An understanding of wind speed and direction as a function of height are critical to the proper modeling of atmospheric turbulence. We have used radiosonde data from launch sites near significant astronomical observatories and created mean profiles of wind speed and direction and have also computed Richardson number profiles. Using data from the last 30 years, we extend the 1977 Greenwood wind profile to include parameters that show seasonal variations and differences in location. The added information from our models is useful for the design of adaptive optics systems and other imaging systems. Our analysis of the Richardson number suggests that persistent turbulent layers may be inferred when low values are present in our long term averaged data. Knowledge of the presence of these layers may help with planning for adaptive optics and laser communications. © 2011 Optical Society of America. Source
Wetterer C.J.,Pacific Defense Solutions, LLC |
Linares R.,State University of New York at Buffalo |
Crassidis J.L.,State University of New York at Buffalo |
Kelecy T.M.,Boeing Company |
And 3 more authors.
Journal of Guidance, Control, and Dynamics | Year: 2014
High-fidelity orbit propagation requires detailed knowledge of the solar radiation pressure on a space object. The solar radiation pressure depends not only on the space object's shape and attitude, but also on the absorption and reflectance properties of each surface on the object. These properties are typically modeled in a simplistic fashion, but are here described by a surface bidirectional reflectance distribution function. Several analytic bidirectional reflectance distribution function models exist, and are typically complicated functions of illumination angle and material properties represented by parameters within the model. In general, the resulting calculation of the solar radiation pressure would require a time-consuming numerical integration. This might be impractical if multiple solar radiation pressure calculations are required for a variety of material properties in real time; for example, in a filter where the particular surface parameters are being estimated. This paper develops a method to make accurate and precise solar radiation pressure calculations quickly for some commonly used analytic bidirectional reflectance distribution functions. In addition, other radiation pressures exist, including Earth albedo/Earth infrared radiation pressure, and thermal radiation pressure from the space object itself, and are influenced by the specific bidirectional reflectance distribution function. A description of these various radiation pressures and a comparison of the magnitude of the resulting accelerations at various orbital heights and the degree to which they affect the space object's orbit are also presented. Significantly, this study suggests that, for space debris whose interactions with electro-magnetic radiation are described accurately with a bidirectional reflectance distribution function, then hitherto unmodeled torques would account for rotational characteristics affecting both tracking signatures and the ability to predict the orbital evolution of the objects. © 2013 by the American Institute of Aeronautics and Astronautics, Inc. Source
Hill K.,Pacific Defense Solutions, LLC |
Sabol C.,Air Force Research Lab |
Alfriend K.T.,Texas A&M University
Journal of the Astronautical Sciences | Year: 2012
When the Air Force Space Surveillance Network observes an object that does not correlate to an entry in the Space Object Catalog, it is called an Uncorrelated Track (UCT). Some of these UCTs arise from objects that are not in the Space Catalog. Before a new object can be added to the catalog, three or four UCTs must be associated so that a meaningful state can be estimated. Covariance matrices can be used to associate the UCTs in a more statistically valid and automated manner than the current labor-intensive process; however, the choice of parameters used to represent the orbit state have a large impact on the results. Covariance-based track association was performed in 10-day simulations of 1,000 space objects within a 20-km band of semimajor axis using many different orbit parameters and propagation methods and compared with a fixed position gate association method. It was found that Cartesian covariance with linearized propagation performed poorly, but when the covariance was propagated with the Unscented Transform the results were much better. Elliptical curvilinear coordinates also performed well, as did covariance in osculating equinoctial elements propagated with the Unscented Transform, but a covariance in mean equinoctial elements propagated with the Unscented Transform achieved the best results. Source
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 149.93K | Year: 2012
ABSTRACT: This research plans to use existing MSSS sensors to investigate methods to detect and track faint objects (greater than or equal to 14th visual magnitude) in any orbit around the Earth using ground-based electro-optics sensors, without prior knowledge of the object's orbit. The basic technique is to image part of the sky with a wide field-of-view detector. Processing algorithms will be developed to detect objects in earth orbit as they pass through the image. Slow moving objects will appear as a short streaks or points in successive image frames. Faster objects my pass completely through a single frame leaving only a streak. An initial estimate of the orbit will be made from these images. Methods to increase the accuracy of this initial estimate will be studied. Possible methods include: tasking an agile telescope or looking for the track in another, nearby staring sensor. BENEFIT: PDS is leveraging their experience on developing operational dim object detection algorithms for wide field-of-view (WFOV) optical system, such as Pan-STARRS and the Air Force's Space-based Space Surveillance (SBSS) system. PDS's proposed innovative processing algorithms for dim object detection will benefit USSTRATCOM's Space Surveillance mission by increasing the awareness of the space volume with the capability of providing initial orbit determination for follow-on tracking of previously uncorrelated objects.
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 149.97K | Year: 2012
ABSTRACT: Space situational awareness is often limited by the ability of sensors to produce resolved data on space objects. Large objects cannot be resolved with small low-cost telescopes; objects in geo-synchronous orbit are too remote to be resolved. The best hope of ending these limitations is to make it possible to determine important features of space objects from unresolved data, typically the temporal light curves that are produced by measuring only the integrated brightness of the space object as it passes overhead a sensor on the ground. Both supervised processing (i.e., pattern classification) and unsupervised processing (i.e., Kalman filter) of light curve data have shown success in extracting space object features. In this proposal we set forth a system that combines the merits of both supervised and unsupervised processing to more fully automate the exploitation of unresolved space object temporal light curve data. BENEFIT: The successful results of this project will offer Space Situational Awareness (SSA) data from low-cost deployable telescopes that can travel to the world-wide locations where USA military assets operate and can benefit from the immediate response of the simpler SSA systems offered by this technology. The Potential Commercial Applications of this project extend to the construction and delivery, maintenance and upgrade of such worldwide assets, including delivery of workstations and full SSA packages, as well as cross-over applications in areas such as autonomous navigation.