Fred Hertwig, Air Force Institute of Technology (AFIT); John Colombi, AFIT; Richard Cobb, AFIT; David Meyer, AFIT
Keywords: Space Surveillance, Space Situational Awareness, Ground-Based Telescopes, GEO
Abstract:
Persistent Space Situational Awareness (SSA) is one of the top priorities of the DoD. In task-based surveillance, a list of unique taskings are sent to each surveillance site from the Combined Space Operations Center (CSpOC). The site then performs those taskings by taking images or observations of individual objects in space. The observations are then returned to the CSpOC. Images are only taken from the task list received by the site. The tasked-based process of tracking satellites leaves portions of the GEO belt un-viewed either for long periods of time or never viewed at all. Nightly surveying or searching of the GEO belt could increase the probability of detection of enemy movements and orbiting space debris. In search-based space surveillance, the site would image the entire viewable sky each night and not be limited to the predetermined task list.The goal of this research was to compare the current task-based space surveillance performance to a search-based method of space surveillance in the GEO belt region. The performance of a ground telescope network was modeled and simulated using AGIs Systems Tool Kit (STK) and Python. The model compared search-based and task-based space surveillance by simulating 813 Resident Space Objects (RSOs) from spacetrack.org on the summer solstice, fall equinox and winter solstice. Six different search patterns with ten different starting positions were investigated. The search-based method modeled six different search patterns that searched inclinations of 16.97, 12.73, 8.48, 4.24, 2.12, and 0.71 degrees. The largest inclination search area was chosen to include the debris that naturally oscillates between 0 and 15 degrees every 50 years. The ten starting positions were used to determine if starting searches in the eastern or western portion of the sky would affect performance. Four performance metrics for comparing the search-based and task-based methods were minimum detectable size, detection rate, coverage area, and latency. Results show that the minimum detectable size average for task-based was 47.6 cm in diameter while search-based methods ranged from 38.3 cm – 45.4 cm in diameter. Detection rate for task-based was 100 percent while the search-based ranged from 91.7 percent – 96.8 percent. Coverage area for task-based was 46 percent of the GEO belt and the search-based method ranged from 3.5 percent – 84.4 percent. Average latency for task-based was 78 minutes and search-based methods ranged from 62 – 469 minutes. It was found that task-based surveillance was the better method for current operational conditions by using a weighted decision criteria. However, as the number of RSOs increase there is a point at which the search method has better performance. Switching to a 100 percent search method may not be the full answer to providing the best ground-based space surveillance. The ultimate goal of SSA is to know where everything is at all times. No search method was able to detect 100 percent of the possible objects each night. It is very possible that a combination of task-based and search-based surveillance could be used to get the best performance.
Date of Conference: September 17-20, 2019
Track: Astrodynamics