ESA GNC Conference Papers Repository

A debris-free space environment is becoming a necessity for current and future missions and activities planned in the coming years. The only means of sustaining the orbital environment at a safe level for strategic orbits (in particular Sun Synchronous Orbits, SSO) in the long term is by carrying out Active Debris Removal (ADR) at the rate of a few removals per year [1]. Infrared (IR) technology has been used for a long time in Earth Observations but its use for navigation and guidance has not been subject of research and technology development so far in Europe. The ATV-5 LIRIS experiment in 2014 carrying a Commercial-of-The-Shelf (COTS) infrared sensor was a first step in de-risking the use of IR technology for objects detection in space. In this context, Cranfield University, SODERN and ESA are collaborating on a research to investigate the potential of IR-based relative navigation for debris removal systems. This paper reports the findings and developments in this field till date and the contributions from the three partners in this research. The precise relative navigation of a chaser spacecraft towards a dead satellite is one of the most difficult tasks to accomplish within an ADR mission, due to the fact that target is uncooperative, tumbling, and in general in an unknown state [2]. The current Guidance Navigation & Control (GNC) systems technology can handle cooperative rendezvous, but for an ADR mission the number of unknowns is greater than an ordinary mission and further developments are needed [3]. The proposed paper shows the review of the state of the art literature in all areas relating to the problem with ADR scenarios, applications, and missions. Then the current ADR proposed missions and the role of Infrared-based navigation on them are explained. Since there are more uncertainties in the navigation function of an ADR mission, it is favourable to have continuous measurements which would require sensors working in all environmental conditions possible [4]. The paper explains that vision-based cameras, which are already suffering from poor illumination conditions even in cooperative rendezvous with 3-axis stabilised target holding fiducial markers, cannot match the IR cameras that can perform in all possible illumination conditions of ADR. An infrared camera can overcome the illumination problem by providing information without any discontinuity as it does not depend on external light source but the emitted radiation. Long wave infrared (LWIR) imaging techniques offer many potential benefits when applied to the remote sensing of space debris. Imaging space objects in the LWIR band has the inherent advantage of not being dependent upon constant Solar or Earth illumination which makes the observations and measurements possible even when observed objects are in eclipse. The paper explains that the appearance of objects under Sun direct illumination is expected to be smoother in infrared when compared to the reflection of visible light on reflecting surfaces like multi-layer insulation. Imaging space objects in the LWIR band may also allow for the imaging of objects looking at with the Sun in the field of view without saturation of the imaging system. So challenges in terms of illumination changes could be dealt with using an infrared-based rendezvous sensor providing navigation data from 'standard' features detectors/extractors algorithms for flexible relative navigation and guidance to targets. In our work, we defined a possible ADR scenario and evaluate for target illumination conditions which is more challenging than an ordinary cooperative rendezvous mission. Next, we addressed the infrared imaging facts considering ADR targets, space debris. Then the simulated measurements of respective system had been assessed for navigation filter running in this particular scenario to define required performance of each. The result of this analysis was then used to quantify the benefits of infrared systems over visual cameras for ADR relative navigation system, highlighting the phases that have been neglected for visual based approaches. Finally, it had been found out that infrared based relative navigation systems have several advantages over visual based systems for ADR and further developments of algorithms using infrared measurements would be beneficial.