2016.B.4.4. Alternatives for Autonomous Navigation of Small Solar System Explorers
Graciela González Peytaví (1)
Alena Probst (1)
Thomas P. Andert (1)
Bernd Eissfeller (1)
Roger Förstner (1)
- ISTA – Bundeswehr University Munich, Germany
Distributed mission structures consisting of cooperative modules entangle significant operational complexity. Some specially demanding aspects are communication networking, parallel mission planning and formation control. However, distributed structures also offer a wide range of advantages for scientific exploration and prospection. Cooperative remote sensing increases data spatial and temporal coverage. They enable the execution of multi-mode experiments requiring larger baselines than those available on a single spacecraft. Furthermore, mission safety can be increased through spatially distributed redundancy as well as mission risk can be minimized by separation of critical modules requiring diverse thermal, radiation and dynamical configurations. For all these reasons, the exploration of solar system bodies by means of cooperative networks is desirable. Cubesats provide an attractive solution with reduced launch mass increments. Still, in deep space, cubesats remain highly dependent on the propulsion, communication and navigation subsystems from larger master spacecraft. Upcoming deep space cubesat demonstrators will adopt such master-slave relations i.e. MarCO on NASA’s InSight Mars Explorer and COPINS on ESA’s AIM binary asteroid explorer.
Within this paper, we intend to review a comprehensive set of alternatives which could potentially increase the navigation autonomy of cubesats during interplanetary cruise and explorative proximity operations. Autonomous navigation could enable self-reliant course-corrections and independent execution of targeting/observation manoeuvres for cubesats. Furthermore, it could support scientific investigations of trajectory perturbing phenomena like gravity, radiation or drag, among others. Autonomous navigation could also reduce the use of ground-tracking for trajectory determination, freeing valuable platform resources for further mission tasks.
Among the alternatives for absolute positioning through the solar system, some have received strong attention within the last few years: optical tracking of bodies with known ephemerides against star backgrounds, optical solar interferometry and triangulation by pulsar radio or x-ray signals. In proximity to a target, optical tracking of surface landmarks is a de-facto standard for relative navigation. A combined optical-inertial navigation system can support close-proximity and highly-dynamic operations e.g., docking or landing. As of today, particular interest is being placed on the use of imaging LiDAR technology for target relative navigation. LiDAR units are active sensors which would permit operations in non-illuminated areas using ideally less computational resources. A LiDAR altimeter could be constructed to serve also as optical communication terminal, a development which could turn favourable for small platforms.
A review of autonomous navigation alternatives will be presented, including functional description, expected performance, technology readiness level and state of the art platform requirements
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