This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: There is a problem in low Earth orbit, and it's growing. According to the European Space Agency, there are about 19,440 satellites on orbit, 3,540 of which are nonfunctioning and/or not emitting a signal to warn other spacecraft of their location.
The need to service these sleepwalking satellites in space will only increase as more are launched. "There are also over 8,000 metric tons (8,800 tons) of debris, none of which is cooperative, in the sense that they cannot thrust or send a signal," said Minduli Wijayatunga, a new aerospace engineering faculty member in The Grainger College of Engineering, University of Illinois Urbana-Champaign. Although most of Wijayatunga's work can be applied to both debris and spacecraft, a recent study targets a spacecraft that needs repair but has lost the ability to communicate.
The servicer must approach it with no help from the target, which is like an unconscious patient. Wijayatunga said the repairs need to be done autonomously because of the time delay in communications between a repair spacecraft and Earth and the limited windows of time when communication is even possible. The study is published in the journal Acta Astronautica.
"These spacecraft must be able to track the trajectories of uncooperative objects autonomously but also make go/no-go decisions without waiting for the ground to decide," she said. "Suppose your thruster fails or you encounter high-order orbital perturbations that push you away from your nominal trajectory. In those instances, how do you make those decisions?" In response to this question, Wijayatunga created a framework for close-range rendezvous trajectory design and guidance and demonstrated it in a lab.
It's called CORTEX, which stands for Convex Optimization for Rendezvous Trajectory Execution. "CORTEX takes into account eclipses, timing the rendezvous when there is an optimal window of sunlight to see the target, complete your close-proximity operations and depart," she said. "For my Ph.D., I did a project on trajectory design and guidance using convex optimization for the transfer phases.
Eclipses matter there too; they can limit how much you can thrust. But they don't compromise safety to the same extent, so you don't need to replan or hold position because of them. "I wanted to bring that same idea into developing CORTEX and expand it, taking into consideration sunlight windows so we don't have to operate in darkness.
Extract — continue reading at the source.
