Erin Griggs, Trusted Space, Inc.; Sydney Bonbrest, Trusted Space, Inc.; Matt Schierholtz, Trusted Space, Inc.; Mark Bolden, Trusted Space, Inc.; Islam Hussein, Trusted Space, Inc.; Tom Kubancik, Trusted Space, Inc.; Blair Thompson, Department of Astronautics, United States Air Force Academy
Keywords: Geostationary Orbit, Patrol Orbit, Space Domain Awareness, Space Situational Awareness, Orbit Determination
Abstract:
Assets in geosynchronous equatorial orbits (GEO) are of high importance and utility, as they provide communications, broadcast, Earth-observation, and navigation services to military, academic, and civilian users. Their particular altitude of 35,786 km above the Earth’s equator results in an orbital period equal to that of the rotation rate of the Earth, enabling the satellite’s (nearly) fixed position in the sky with respect to a ground observer. Operators of GEO satellites must have knowledge of the satellite’s surrounding environment, as it is continually becoming more contested. In his testimony to the Senate Armed Services Committee’s strategic forces subcommittee in March 2023, the U.S. Space Force chief of operations, General Saltzman, described China’s latest capability to control and move satellites. He warned that China is “likely pursuing anti-satellite systems able to destroy satellites in geosynchronous orbit” [1]. Coverage of and around these high-valued GEO assets is imperative to deter nefarious actions.
Satellites in patrol orbits adjacent to the GEO belt could provide monitoring, observation, and support that is complementary to services traditionally provided by the ground. Patrol orbits were introduced by [2] as a family of orbits in the neighborhood of a GEO, created by introducing eccentricity to a typical geosynchronous orbit. A follow-on study, [3], described different strategies and concepts of operations to use patrol orbits for space domain awareness (SDA). This paper will focus on three novel areas of research: (1) the formulation and simplified mathematical description of a new asynchronous corkscrew patrol orbit type, (2) the investigation and optimization of an architecture of satellites in patrol orbits for surveillance of a specific region of the GEO belt, and (3) the enhanced orbit determination (OD) and cataloging of GEO assets through a combination of simulated ground- and space-based electro-optical (EO) observations. This paper aims to build upon the previous patrol orbit work to present an updated and simplified algorithmic formulation of an asynchronous type of patrol orbit. We use this efficient mathematical process to develop a conceptual use case for a constellation of satellites in patrol orbits around a longitudinal region and/or specific set of GEO assets. This constellation of patrol satellites provides deterrence through surveillance, providing SDA of the region surrounding the GEO satellites as a “neighborhood watch” function. With the proposed patrol satellite constellation, we demonstrate OD of the GEO assets through EO and ranging observations.
This paper introduces a new type of patrol orbit that we describe as the “corkscrew”. We provide a description of the algorithm formulation of this patrol orbit type, which includes a notable improvement to the complexity of the mathematical derivation and process. The flight profile of the corkscrew orbit is explored, including longitudinal and zonal coverage, retro- and pro-grade configurations, and a description of motion over time through the orbit lifecycle. We compare this patrol orbit to previous patrol orbit types described in [2] and [3], in terms of surveillance capability and orbit maintainability. We also investigate the delta-V requirements to move between corkscrew orbits and previously-investigated patrol orbits.
We then explore the utility of satellites in patrol orbits for the surveillance and tracking of objects in a particular region of the GEO belt. This investigation will focus on patrolling a region around the pair of Anik satellites, co-located in the GEO belt at ~107.3°W longitude. These Canadian telecommunications satellites, Anik F1 and Anik F1R, are challenging to distinguish separately by ground-based EO means [4], because of a separation of .03° in longitudinal position, or approximately 22 km [5]. We develop an architecture of patrol satellites equipped with an EO payload to observe a specified region about the Anik satellites. Using optical sensor pointing strategies described in [3], we conduct trades of patrol satellite constellation characteristics, including categories of patrol orbits, configuration, flight profile dynamics, and total number of satellites participating in the surveillance activities. We aim to optimize longitudinal/zonal coverage, revisit times, and custody of the Anik satellites.
Finally, we investigate the OD of the Anik satellites via a combination of EO and ranging observations from ground stations and the proposed constellation of patrol satellites. Through modeling and simulation, we generate optical observations to be received by ground-based EO observers and the optical/ranging payloads onboard the patrol satellites and characterize their uncertainties. These observations are processed by a two-body OD filter to estimate the position and velocity of the Anik satellites. We compare the accuracy and uncertainty of a ground-based solution versus one where we combine ground-based and patrol satellite observations, with the goal to show improvement to the OD accuracy and uncertainty estimates using a spatially diverse set of observers in combination with the ground sites. We also aim to demonstrate the robustness of the multi-observer patrol satellite constellation to cross-tagging by the closely-spaced Anik satellites, and to ground station outages.
References:
[1] S. Erwin, “Space Force: We expect to see ‘interfering, blinding’ of satellites during conflict,” 15 March 2023. [Online]. Available: https://spacenews.com/space-force-we-expect-to-see-interfering-blinding-of-satellites-during-conflict/.
[2] B. Thompson, T. Kelecy, T. Kubancik, T. Flora, M. Chylla and D. Rose, “Geosynchronous patrol orbit for space situational awareness,” in Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS), Maui, HI, 2017.
[3] M. Schierholtz, T. Kubancik, K. Charles, I. Hussein, E. Griggs, B. Thompson and E. Silva, “Geosynchronous Patrol Orbits for Optimized GEO Space Domain Awareness,” in Advanced Maui Optical and Space Surveillance Conference (AMOS), Maui, HI, 2023.
[4] K. Simon, “Passive RF in Support of Closely Spaced Objects Scenarios,” in Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) , Maui, HI, 2020.
[5] K. A. Sebastian, “UCS Satellite Database,” 1 May 2023. [Online]. Available: https://www.ucsusa.org/resources/satellite-database#.W7WcwpMza9Y.
Date of Conference: September 17-20, 2024
Track: Astrodynamics