Shawn Seunghwan Choi, SpaceMap; Jun Young Byun, Hanyang University; Maxime Pognon, SAFRAN ELECTRONICS & DEFENSE; Juhwan Kim, Hanyang University; Hyeonggu Kim, KT SAT; Jaedong Seong, KARI; Baptiste Guillot, Safran; Thierry Balanche, Safran; Kevin Choi, KT SAT; Misoon Mah, M&K Research and Development Inc; Jae Wook Song, Hanyang University; Peter Joonghyun Ryu, SpaceMap; Douglas Deok-Soo Kim, SpaceMap
Keywords: Conjunction Assessment, Collision Avoidance, Space Traffic Management
Abstract:
Geospace has been and will be rapidly more crowded. This will increase the collision risk both between satellites and between satellites and debris The current space catalogues with O(10^4) resident space objects (RSOs) will soon contain O(10^6) objects because of evolving sensor technology, new space situational awareness (SSA) companies both ground-based and space-based, etc. The SINTRA project by IARPA is a good indicator [1]. On the other hand, space business environment requires faster, if not real-time, solutions to conjunction assessments (CA) and collision avoidance (COLA). This is because there will be exponentially more frequent collision-avoiding maneuvers, more human-on-board missions and space tours, many spaceplanes for intercontinental transportation of freights and passengers that will supplement airplanes if not replace them, etc. In addition, applications in the New Space Age tend to include computationally more demanding optimization problems involving many satellites that are not only about two objects, like conjunctions, but also many objects.These factors overwhelm the capabilities of existing algorithms which have been successful in existing computer programs. Due to this reason, among many, emails and phones are the only available methods of communication between involved parties, not only when the 18 SDS sent out a red-alarm to Starlink and OneWeb in 2021 [2] but also today.
Here, we present (i) an algorithm for real-time CA and COLA, (ii) a concurrent avoidance negotiation (CAN) platform based on web and graphics, and (iii) accuracy comparison between the Space-Track TLE data and passive ranging SSA data.
First, the proposed algorithm based on Voronoi diagrams responses to CA queries in real-time and COLA queries in near real-time on a moderate computational platform. Being application-independent, Voronoi diagrams can be used for efficiently solving not only CA/COLA queries, but also optimization problems. Its idea was introduced in AMOS2017 [3] and is publicly available as AstroLibrary [4].
Second, the near real-time solution capability for the COLA queries has naturally led us to a CAN-platform using web links, like GoogleMaps’ link. SpaceMap’s Astro-1 produces and sends conjunction data message (CDM) of conjunction-of-interest to involved parties with a link to its definition. Then, clicking the link downloads the Astro-1 platform with the conjunction data to a local device, either laptop or mobile phone, within a few seconds. The involved parties can real-time communicate through texts, voices, and videos. All participants share a synchronized visualization of conjunction. This feature is called “concurrent” “avoidance” “negotiation” because different avoidance maneuver alternatives can be created and evaluated concurrently in near real-time, with the consideration of tertiary conjunctions caused by new RSOs beyond the primary and secondary ones. We saw in 2021 [2], there is currently no hard rule to decide who is more responsible if a possibly catastrophic event occurs – Both should negotiate for a reasonable resolution. We believe that the first step to materialize this idea is to utilize an internet-based communication tool proposed by Astro-1, instead of emails and phones. This feature will be indispensable for conflict resolution in global space traffic management or coordination, e.g. TraCSS being developed by the Office of Space Commerce, Department of Commerce. The 2021-like events will be more frequent as constellations like Kuiper and Guowang are prepared for launches: “Concurrent negotiation” will have to be required!
Third, in addition to computational efficiency, the accuracy of CA is equally important to minimize false alarms for maneuvering. It is well-known that Starlink makes more collision avoidance maneuvers as its constellation grows. In fact, it was shown that the maneuver frequency follows a weakly exponential relationship to satellite count [5]. This observation suggests two issues. (A) Minimizing false alarms is important for keeping satellites longer. (B) The consequence of a maneuver on other maneuvers in the timeline seems to be random. This implies that maneuver generation might be a stochastic process that possesses the memoryless property. These observations suggest the following three issues that need to be carefully studied: (a) Increasing the accuracy of SSA data; (b) Increasing the efficiency of CA computation; (c) Reducing the latency of catalogue-update.
Here, we present a comparative analysis for solving (a) using data from four sources: (i) Space-Track TLE data, (ii) the passive radio-frequency data from SAFRAN, (iii) the ranging data of three primary GEO satellites of KTSAT [6], and (iv) the CDM from CSpOC. The primaries are KOREASAT 6 (NORAD ID: 37265), KOREASAT 7 (42691), and KOREASAT 5A (42984). Note that we have already solved (b) by using Voronoi diagrams and (c) is beyond the scope of this study.
We computed the conjunctions of the three primaries using the TLE, SAFRAN, and KTSAT data; TLE is used for all secondaries. Let ΔTLE and ΔSAFRAN be the differences between the CDM data and the computed conjunctions using TLE and SAFRAN, respectively. Let ΔKTSAT be the corresponding quantity calculated using the primaries’ ephemerides provided by KTSAT. Let Δ* be the ranging data of the primaries measured by KTSAT at the conjunction moment, i.e., we actually measured the primaries’ locations around the moments of TCAs of conjunctions. We concluded ΔKTSAT < ΔSAFRAN < ΔTLE through a rigorous statistical analysis.
References
[1] ISRO, Space Debris Identification and Tracking (SINTRA), https://www.iarpa.gov/research-programs/sintra
[2] SpaceNews, SpaceX emphasizes coordination with other satellite operators, https://spacenews.com/spacex-emphasizes-coordination-with-other-satellite-operators/
[3] Cha, Jehyun, et al. “DVD-COOP: Innovative conjunction prediction using Voronoi-filter based on the dynamic Voronoi diagram of 3D spheres.” Advanced Maui Optical and Space Surveillance (AMOS) Technologies Conference. 2017.
[4] Choi, Shawn SH, et al. “AstroLibrary: A library for real-time conjunction assessment and optimal collision avoidance.” Journal of Space Safety Engineering (2024).
[5] Lewis, Hugh G., and Vyara Yazadzhiyan. “Evaluation of low earth orbit post-mission disposal measures.” Journal of Space Safety Engineering (2024).
[6] KT SAT, https://www.ktsat.com/kr/mainPage.do
Date of Conference: September 17-20, 2024
Track: Conjunction/RPO