ESA GNC Conference Papers Repository
Adaptation of Pre-Existing Navigation Library BOLERO for Interplanetary Missions
The introduction of new low-cost tiny satellites has encouraged autonomous navigation research and development, benefiting other mission types such as deep-space navigation. Making the spacecraft more autonomous has two major advantages: While the communication delay between Earth and the spacecraft can be quite large, autonomous navigation has proven to be more reliable, allowing the spacecrafts safety to be increased, particularly in deep-space highly perturbed environment. Another advantage is the reduced involvement of ground tracking, which results in a reduction in total mission costs. BOLERO is a space navigation library developed by CNES, since 2000, for on-board orbit determination in the Earths vicinity. For that purpose, it includes a very complete dynamical model adapted for any types of Earth orbits from LEO to GEO. The navigation function is composed of an Extended Kalman Filter, and the library contains all the usual GNSS measurement functions such as pseudo-range and carrier phase, single or dual frequency, for single or multi-constellations. It can also process range and Doppler measurements from Ground stations. On top of that, BOLERO can perform multi satellites navigation, assuming the exchange of measurements through inter-satellites link. Bolero contributes to the notion of improving spacecraft autonomy by providing an onboard orbit determination library that may be paired with an onboard navigator and orbit controller. It has already been deployed on Thales Alenia Space Topstar receivers family (with multiple flying experience since 2000 (HETE2, DEMETER, Proba 2...), and is currently integrated on Syrlinks receivers (N-SPHERE). The library is completed with the generic navigator DIONE, based on BOLERO. DIONE provides the input and output interfaces and enables the control of the navigation function. It is currently used on ground for validation purpose, for performance analysis, but an on board qualified version is under development. The adaptation of BOLERO and of the DIONE navigator, for interplanetary missions, are presented in this paper. The evolution consists of implementing the missing interplanetary dynamical environment, as well as new reference frames and time scales. New measurement types, such as Lidar, optical navigation, and Doppler measurements, are also added. The study raised many concerns about measurement management, including the use of DSN measurements on board, clock management, and the generation of optical measurements. The navigation function also offers new possible interfaces to the user, such as the information about the solar system bodies (position and velocities, direction, ), or reference frame data, for to be used for mission or spacecraft guidance purpose. The paper presents the chosen models and validation process and results.