Jeffrey J. Bloch, Applied Research Associates; Lynda Liptak, Applied Research Associates, AFRL/RVES; David Briscoe, Applied Research Associates; Suzzanne Falvey, Applied Research Associates; Tasha Adams, Applied Research Associates (ARA)
Keywords: Orbit Determination, Passive Optical Observations, Astrodynamics, Novel Focal Plane Technology
Abstract:
In the increasingly contested, congested and competitive space environment, accurate and timely Space Domain Awareness (SDA) is the key for this domain to remain safe and usable. Determining the orbital parameters of new or maneuvered space objects as soon as possible is one of the key ingredients to having space domain decision-making operate within appropriately actionable timelines. Applied Research Associates, Inc. (ARA) has developed the Advanced Uni-sensor Rapid Orbit Reconstruction Algorithm and Sensing (AURORAS) technique; a revolutionary combination of an algorithm and optical sensing approach that enables an unknown orbit to be estimated much faster and more accurately than current methods. The approach is applicable from Low-Earth Orbit (LEO) to cis-lunar orbits. For many important scenarios, this capability will provide critical time savings to support faster decision making. The AURORAS approach replaces the conventional three separate angles only observations separated in time with an angle, an angular velocity, and an angular acceleration measurement at a single time to determine an initial orbit.
The task of determining the unknown orbit of an object circling the Earth or Sun with separate and distinct passive optical angle measurements has had a long and strenuous scientific and technical history, as outlined in reference texts such as Fundamentals of Astrodynamics and Applications by Vallado. For accurate initial orbit determinations from passive optical sensor observations, a general rule of thumb is that the angles data (at least three sightings) must span about an eighth of an orbit to achieve a reasonably accurate initial orbit determination. For objects near geostationary or geosynchronous orbits, this requires observations over at least three hours to determine a new object’s orbit accurately. As the space domain has become more and more congested and dynamic, three hours may be too long a time to determine an object’s orbit given the frequency that orbital systems can now maneuver with ever evolving propulsive technology. In addition, the congestion of space objects (for example from a satellite or rocket body breakup, or even a large deployment of CubeSats) can make the association of observations to the correct object difficult if the observation gaps are significant compared to the relative motion of the collection of objects. Space traffic management, debris avoidance and space domain awareness sensor tasking all now require reduced latency times between observation and orbit catalog updates.
Unconventional orbits further challenge our Space Domain Awareness (SDA) as there is exponentially increased complexity conducting orbital determination in these new orbit regimes. With so many possibilities of where a satellite may travel, SDA just became more uncertain. A faster initial orbital determination capability will decrease that uncertainty. Determining preliminary orbital information with fewer collections or in a shorter period would significantly assist the Indications and Warning (I&W) capability for characterizing evolving space events. The AURORAS algorithm and optical sensing approach enables a more accurate initial orbit to be estimated in seconds to minutes instead, which may provide critical time savings in responding to an incident in the space domain.
In this paper we describe how the current revolutionary transformation in passive optical focal plane technology (ironically driven by other areas of the economy such as sensing for self-driving cars) will enable rapid initial orbit determination in seconds instead of hours. The key idea behind AURORAS is that these advancements will allow angle, angular velocity, and angular acceleration all to be measured independently with high precision over a short time span. We describe the algorithms and analysis (with heritage back to Laplace) that can take these six independent angular position and motion parameters and estimate an initial orbit. We also provide examples of the range of new technologies that are making this approach possible and provide some real-world examples of their performance. These technologies include 1) High Time Resolution Photon Counting Imaging Sensors, 2) Event Based (Neuromorphic) Cameras, and 3) High Frame Rate Scientific CMOS Focal Planes. We present the strengths and weaknesses of each of these technologies using example systems that collected data on space objects in a variety of orbits.
We also describe a fourth novel sensor design concept that maps angular motion into periodic photometric intensity variation measurements. These measurements can then be combined with signal processing techniques to recover angular rates and accelerations. We describe the laboratory benchtop experiments that we have carried out to demonstrate this approach.
In the paper we discuss the pros and cons of all these emerging technical approaches to obtain optical angular derivative measurements. We outline the spatial and timing resolution required to achieve this alternative initial orbit determination approach and describe the needed calibration requirements for the sensors. We believe that optical sensor technology advancements on multiple fronts coupled with a re-evaluation of traditional algorithms have brought the passive optical space surveillance community to a tipping point for a disruptive innovation regarding initial orbit determination. This transformation will be as revolutionary as when optical tracking systems first changed from film to electronic focal planes.
Date of Conference: September 27-20, 2022
Track: Astrodynamics