Joshua Davis, Defence Science and Technology Laboratory; T. Jennings-Bramly, Defence Science Technology Laboratory; J Symons, Defence Science Technology Laboratory ; F Waltho, Defence Science Technology Laboratory
Keywords: SSA/SDA, astrodynamics, electric propulsion, RPO, Modelling and Simulation, NSGA-II
Abstract:
The expanding list of space-faring nations and the associated advancements in spacecraft control and propulsion technologies have created a more complex and diverse operational domain. Moreover, the rapid proliferation of space debris highlight the importance of improved SDA, in both traditional and novel sensing paradigms. Some examples of the key challenges are:
The realisation of mega-constellations, which are predicted to introduce approximately 20,000 new satellites by the end of this decade;
Increased numbers of low thrust EP orbital raising missions, mostly to efficiently insert satellites into an operators selected orbit, these pose an increased challenge due to the SDA resource required to track and maintain custody, especially if moving in cluster formation;
An assortment of new & novel space concepts in orbit: servicing missions, debris removal missions, catalogue maintenance, and rendezvous and proximity operations;
Debris clouds are increasingly likely to occur due increased collision probabilities from the increased population size and nations using ASAT technology.
Space-based sensing for Space Domain Awareness is growing in interest to help face these challenges and facilitate assured and timely action in a more diversified operational landscape. Space-based sensing is likely to increase in prevalence in the coming years, yet challenges still exist from a sensor management perspective. To address this we use modelling, simulation and optimization to quantify the possible SDA opportunities (or threats) and in in doing so propose methods to potentially improve space-based sensing capability. At scale, we model and simulate Resident Space Object (RSO) population scenarios and compute Time of Closest Approach (TCA) statistics to investigate the feasibility of space-based SDA opportunities and their dependency on a sensors orbital placement and manoeuvring dynamics. The TCA and the associated distance between pairs of orbiting objects is an important calculation in SDA. It forms the first step in estimating the objects likelihood of a collision. However, it is also useful in flagging the time opportunities when the objects are within a given relative distance, D*, such that space-based observations can be made. Alternatively, to indicate the times when an object is under threat of a close range detection, or from a payload of an unfriendly satellite.
In this paper, we begin by analyzing the close approaches experienced in a low-thrust electric propulsion (EP) transfer to GEO, obtained by fitting a Q-Law model to the TLE history of the MEV-2 mission. We then move on to apply an NSGA-II multi-objective optimization routine to construct constellations of space-based sensors that maximise the total number of SDA opportunities and a given RSO target population of interests coverage. Constellation solutions are then used to develop realisable multi-orbit missions that can in theory achieve similar coverage results over the manoeuvring space-based sensors lifetime. Here we use three standard orbit transfer models: single revolution Lambert RPO, Hohmann and Bielliptic. Optimal sequencing of these selected orbital transfers is achieved by posing as a Travelling Salesman Problem to solve for the minimum total DV needed to visit all orbits once.
Date of Conference: September 27-20, 2022
Track: Space-Based Assets