Proximity Experiments using the VBS Close Range Camera
Satellites flying in specific formation during proximity operations are relying on an accurately determined position. So far PRISMA has been relying on GPS for navigation. On 21st of April and from 2nd to 4th of May several proximity operations experiments below 30m relative distance have been performed with the VBS close range (CR) camera running as a passenger experiment in open loop.
One major aspect of the PRISMA mission is the safe approach of one satellite to the other. By this the road towards docking is completed one step further and de-orbiting of satellites at their end of life, refueling or repair gets more feasible.
The goal of this experiment is an approach to our target satellite Tango. Onboard Mango the Vision Based Sensor (VBS) system is mounted. The close range camera being part of the VBS was tested throughout the experiment campaign to asses its navigation performance. The goal is to use the close range camera as stand alone sensor during proximity operations to get independent from the GPS.
The formation flying proximity operations performed at the beginning of May are shown in Fig. 1. At the begin of the experiment a safe formation flying configuration was established in form of the presented ellipse. Starting with the approach the ellipse was reduced and Mango approaches towards Tango during one orbit from -30 m down to -20 m (Green arrow #1). After performing station keeping for one orbit at that position the retreat is triggered going back to the -30 m point. The same experiment was repeated on the other side of Tango (Blue arrow #2).
Fig. 1 Proximity flight sequence for VBS CR Experiments in open loop
Due to the statisfying results achieved during the first two experiments on Wednesday finally, an approach maneuver down to 10 m was conducted (Red arrow #3).