Halfway - Formation flight in space

Peter Buist. (Photo: Sam Rentmeester/FMAX)

Name: Peter Buist (36)
Nationality: Dutch
PhD supervisor: Professor Peter Teunissen (Aerospace Engineering)
Subject: Relative positioning and attitude determination for formation flying
Thesis defence: One year to go

“Last year we let the faculty airplane fly circles above the buildings of TU Delft. I tested our method for the relative positioning between the plane and a reference station at the Nederlands Meet Instituut (NMI) on the Thijsseweg. I could determine precisely where the plane was with the new relative positioning method I’m currently developing.

The current trend is to launch several smaller satellites, acting as a large spacecraft in a so-called formation in space, instead of one big and heavy satellite. It’s very important to know where all the different elements of the mission are. When one wants to determine the relative position of a formation, a dynamic approach is often used. This kind of approach has a reduced performance when the orbit is actively controlled. Moreover, it’s not possible to use this approach to determine the relative position in other applications, such as for example planes flying in formation.

I’m working on a new kinematic approach for relative positioning and the determination of orientation, based solely on observations from Global Navigation Satellite Systems (GNSS) like GPS and Galileo. With the help of these observations, I determine where vehicles, like airplanes or satellites, are located relative to each other. My approach could be used independent of the mission or vehicle, which is an important advantage over the dynamic approach. It could also determine the relative position between airplanes when, for instance, a plane must be fuelled in air or when a plane wants to land on an aircraft carrier. My approach can determine the relative positions up to the centimetre-millimetre level.

We have done several experiments with a ship on the Schie. We put three GPS receivers onboard and another three at the reference station. Using observations from the receivers, we were able to determine the relative position of the ship to the reference station at the NMI. As we used three receivers, we also determined the orientation of the ship. I’ve also tested my method at the European Space Agency (ESA) office in Noordwijk. We simulated a space mission with multiple satellites.

The most spectacular testing of this method is done in Japan. A microgravity research vehicle is dropped from a balloon at an altitude of 40-kilometres. The vehicle is in a freefall and my system determines the relative position and the orientation, which is tricky because of the vehicle’s unpredictable movements.
Within a year I think I’ll be able to demonstrate that this kind of approach works well for different types of applications. But more research will have to be done after I receive my PhD, and therefore I would like to continue to work on it.”