Large-scale space object tracking using APL2
Authors: Rudd Jack G. , Marsh Richard A. , Munger Marcus L. 
Published: January 2007

The number of space objects in earth orbit has increased steadily from the launch of the first space object (Sputnik) to the current level of approximately 10,000. The North American Defense Cheyenne Mountain Operations Center (CMOC), operated by the United States and Canada, provides continuous tracking of this growing constellation of space objects, including active and inactive satellites and space debris. This mission is accomplished for the most part using radar stations and ground-based optical tracking stations, with centralized orbit determination and satellite catalog maintenance performed at CMOC. The United States plans to augment this capability with satellite-based optical tracking. In this paper we discuss aspects of an extensive APL2 prototyping capability that we have developed to evaluate concepts for satellite-based tracking of space objects.Over the last 25 years, we have developed a library of APL prototyping and simulation capabilities to handle various aspects of space-based infrared sensor surveillance of missile launches (Ref. 1 and 2). In recent years we have expanded these capabilities to address the space object surveillance mission as well as Global Positioning System applications (Ref. 3). In this paper we discuss development of algorithms and simulations for the space object surveillance mission of a generic constellation of low-altitude surveillance satellites.In general, surveillance satellites can be equipped with several different kinds of infrared and visible wavelength sensors to accommodate a variety of surveillance missions. A given satellite platform may contain one or more acquisition sensors having a wide field of view for global coverage, in order for the satellite system to detect the occurrence of a space launch or a missile launch anywhere in the world. The same platform may also contain narrow field of view sensors that operate in different parts of the spectral band, in order to enhance detection of objects at various altitudes within the atmosphere or outside the atmosphere, and to enhance the system's ability to identify targets of different types.Finally, a given satellite platform may contain visible wavelength sensors with very small fields of view but very high resolution that are designed to track targets with greater precision. The "track sensors" that are used to detect and track objects in space are of this general type.The mission of tracking space objects includes maintaining orbital ephemerides for active satellites, inactive satellites, spent boosters and space debris primarily in earth orbit. This paper describes how our group (Lockheed Martin Mission Systems in Boulder, Colorado) has simulated the relevant aspects of this mission in considerable detail using APL2. We also discuss our simulation approach compared with other approaches, such as using COTS products. We also describe some of the data sources we used, with particular emphasis on capabilities available through the Internet. We also show examples of APL2 functions that we crafted for this work.This approach has effectively capitalized on the rich algorithm library we have developed over the years that enables us to evaluate new concepts and designs in a rapid and confident manner.