Formation flying and mission design for Proba-3

The Proba-3 mission is an ambitious European mission to test the design, implementation and operation of a two-spacecraft formation flying system with a high degree of autonomy with a launch foreseen in the 2015/2016 time-frame. It comprises two spacecraft, the coronagraph and the occulter, which are to be inserted into a highly elliptical orbit. It is intended to perform the formation flying demonstration around the apogee and use the perigee pass for telemetry, orbit determination, orbit correction, and formation configuration manoeuvres. The design of the target orbit is driven by the minimisation of disturbances to the spacecraft formation, and is constrained by the rather low ΔvΔv capability of the spacecraft of less than 100ms−1 as well as the characteristics of the selected launch vehicle. The secondary mission objective of Proba-3 is to operate the formation as a coronagraph with one spacecraft being the occulter and the other carrying the optics and detectors. The alignment of the formation with the Sun-direction has as a consequence that the geometry of the formation relative to the orbit is prescribed for the perigee pass. This geometry also determines the relative dynamics of the formation. The relationship between formation configuration and orbital parameters is typical for formation flying missions on elliptical orbits and requires a careful choice of the launch time such that the constraints on the angle between the Sun-direction and the orbital plane are fulfilled. Here we present the design of the operational orbit and transfer phase of Proba-3 together with an analysis of the separation, formation acquisition, and target formation maintenance. Also the benefit of available tracking data for contingency situations in the Proba-3 missions is discussed.

► The mission and formation flying design of the ESA Proba-3 mission to be launched around 2015 by an Indian launch vehicle is presented.
► The baseline target orbit is a geo-synchronous elliptical orbit at low inclination and optimised apogee longitude.
► The transfer ΔvΔv is below 100 m s−1.
► While not base-lined it is recommended to add ground-based radiometric measurements to the navigation baseline.
► The formation is acquired and maintained at a very low propulsive cost.