GNC concept definition for RendezVous Mission in Mars Elliptical Orbit
- Paper number
IAC-07-C1.6.03
- Author
Mr. Emanuele Di Sotto, DEIMOS Engenharia, Portugal
- Coauthor
Mr. Juan-Carlos Bastante, DEIMOS Engenharia, Portugal
- Coauthor
Mr. Rémi Drai, Pacific Northwest National Laboratory, The Netherlands
- Year
2007
- Abstract
In the frame of the Mars Sample Return mission a preliminary design has been performed in the context of ESA-Aurora programme in which a circular orbit around Mars is proposed for the orbiter vehicle. The orbiter and the Mars Ascent Vehicle (MAV) will carry out autonomous rendezvous operations in this orbit to transfer the collected sample from one vehicle to the other. The choice for the circular orbit has been derived from the existing European technology for autonomous rendezvous operations that have been studied and developed since the late eighties. However, it appears worth investigate also the elliptical orbit scenario for several advantages provided to the overall mission design. The elliptic orbit represents a very appealing solution due to the possibility of saving considerably propellant mass at least in two of the most critical manoeuvres to be faced with the Orbiter propulsion system: Target Orbit Acquisition (TOA) manoeuvre and the Mars Escape manoeuvre (ME). Moreover, elliptical orbit would allow saving ΔV also for the rendezvous manoeuvre foreseen during the approach phase. In this phase, the most demanding manoeuvre is the one dedicated to bring the two vehicles into coplanar obits, due to eventual difference in orbital inclinations and orbital nodes. An elliptical orbit would permit carrying out this manoeuvre with a substantial benefit for the required propellant mass. Both these aspects will be addressed and detailed in this paper where the baseline elliptical orbit is defined taking into account the performance of the current Mars Ascent Vehicle configuration (as designed for the circular scenario) into mars elliptical orbit. This represents the main system driver when defining the proper elliptical orbit, where injecting the Orbiter vehicle and carry out rendezvous operations with the MAV. In this work we propose ascent strategy for the current MAV configuration aiming at reaching the proper Mars elliptical orbit that minimize the orbiter propellant consumption and fulfill the operational constraints. The proposed strategy is driven by the choice of equipping the MAV with a re-startable upper stage. This allows introducing a coast arc in the exo-atmospheric steered flight that considerably increases the vehicle performance. The results show that elliptical orbits of 2000 km apocenter altitude is attainable through an intermediate ballistic arc. This turns in about 1000 kg propellant mass saved for the orbiter overall mass budget. Once characterized the elliptical orbit where is possible and convenient to inject both the vehicles, RV approach phase is fully characterized in terms of mission timeline and manoeuvres schedule. This phase aims at bringing the chaser vehicle into the same orbit attained by the MAV at the end of the ascent path from Mars. The main driver when designing this phase is represented by the MAV injection accuracy being the main cause for the lost of co-orbital conditions required to initialize the Terminal Rendezvous Phase (TRP). This phase will be exhaustively addressed within this work being its main requirement the need of autonomous RV operations. This is essentially due to the signal delay between Mars and the Earth (43 minutes two-ways) that will not allow performing a ground operated TRP. This requirement demands for an autonomous GNC concept based on a relative navigation system that relies on a Lidar and Camera sensor. Requirements and constraints (especially the ones deriving from the optical sensors) affect directly the design of TRP profiles. Different options have been considered when designing the TRP being important to define the approach direction and especially the need of distinguishing in elliptical orbit between V-BAR and Local Horizontal (LH). A baseline is also provided for the TRP and a complete phase timeline is reported accounting for the impulsive manoeuvre as well as the deterministic controller action required by the different phases.
The work presented in this paper was done under an ESA/ESTEC contract
- Abstract document
- Manuscript document
IAC-07-C1.6.03.pdf (🔒 authorized access only).
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