Space debris is a serious issue in the outer space and it seems that the situation will only get worse in the future. Thus, it is important to establish rules and technologies that deal with this issue. Technologies that could capture and then de-commission the satellites is becoming a popular topic. These tasks are not trivial and require a lot of engineering considering that the targets are un-coorperative . Also, these systems should be relatively cheap and should not contribute to additional space debris when their lifetime has reached its end. The guidance and navigation is probably one of the most important components when it comes to space debris removal systems. The authors of the paper designed a highly intelligent camera system, which involves autonomous control software technologies and commercial-off-the-shelf (COTS) components.

The main components of the system are COTS high resolution imager and field-programmable-gate-array (FPGA), which result in low cost, high resolution, and high computational power. The developed system can be used for visual guidance and navigation in space debris removal scenarios.


Figure 1. System architecture of the intelligent camera system for space debris Removal. source



The system plays two roles:

1) Autonomous target tracking, which involves calculations that output the position and orientation of the space debris of interest.
2) Real-time monitoring of the space-debris

ELSA-d satellite was used as a platform for testing the proposed design. The goal of this mission is to retrieve decommissioned satellites for the satellite operators. The goal of this mission is not directly targeting the space debris issue, but the concept for guidance and navigation remains the same. The mission was successfully launched in 2021.

Before the real life mission the navigation and guidance system was tested in a specially designed test-bed. The test bed consisted of a attitude/orbit simulator and real on-board computers that represent other satellite circuitry. The attitude/orbit simulator involved a display that contained the simulated location of the target satellite. Cameras captured images of the display ans the designed system was able to determine the position and the orientation of the satellite in the display. The output of the proposed navigation and guidance system was then transformed in attitude control information which was used to change the position of the target satellite in the display.

Both the chaser and target satellites were placed in the same orbit being 300 m apart. As the simulation progressed, the distance between the chaser and the target decreased as it is expected. At some points the image was contaminated with Earth light pollution, but the chaser satellite was still able to determine the position of the target based on calculations that depend on stored previous positions. The orbit determination function of the camera system was validated throughout various conditions in the simulation.

The authors were able to develop a guidance and navigation system that is meant for space debris removal. The system was not verified in real life, when the paper was published, but in 2021 the ELSA-d mission was launched and successfully performed its mission, which also validates the proposed design of the guidance and navigation system.


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