A broad range of novel technologies will be essential to make Proba-3 a success. The mission’s formation flying system includes components in both satellites, with a Formation Flying Management system being in charge of scheduling and planning formation flying activities.
The mission includes also a RdV experiment to test sensors and algorithms for Rendezvous (cooperative and uncooperative) in elliptical orbit. This technology could be used for a future Mars Sample return mission and for de-orbiting satellites from low-Earth orbit.
The satellites will employ various methods to determine their relative positions. First of all, inter-satellite RF links will be established via an S-band system between the two spacecraft. Around perigee, GPS receivers will provide relative position of the satellites and the data will be propagated for the phase of the orbit where GPS signals are not available.
For fine measurements during closer separations of less than 250 metres, this relative GPS system will be supplemented by a coarse optical metrology and visual-based sensor, then by a fine optical metrology on the coronagraph spacecraft, with corner cubes placed on the face of the Occulter spacecraft for tracking of relative position and attitude by the coronagraph satellite.
Star trackers will be used for absolute attitude determination. The high precision requirements demand the co-location of all the star trackers and fine metrology sensors and instrument on an optical bench.
Precision cold gas thrusters – working at 10 millinewton scale – will be placed aboard the Occulter spacecraft to precisely maintain the relative positions of the two satellites.
The Coronagraph satellite will incorporate a one-newton scale monopropellant propulsion system for perigee passage manoeuvres and collision avoidance manoeuvres.
Proba stands for the ‘PRoject for OnBoard Autonomy’ and the decision has been taken to make an expanded use of autonomous on-board control procedures for this mission. The majority of formation flying experiments will take place on an automated and autonomous basis.
To serve widely-distributed project partners a new web-based data distribution system will be implemented. The aim is to make all operational information, including telemetry, available to all project partners on a reliable and secure basis within a very short timescale.
Proba-3’s Systems Preliminary Design Review has been successfully passed in November 2012. marking the end of Phase B. The key technologies are reaching TRL 5 and the demanding formation flying software has been prototyped and run closed loop with a simulator.