Speakers
Description
Recent decades have seen the return of first measurements of the radiation environment from Mars’s orbit and surface. However, due to platform specific limitations, measurements from current orbital radiation monitors and spectrometers lack spatial resolution while the measurements from conventional rovers result in a lack of surface coverage. Moreover, interesting variations in the cosmic and ionizing radiation spectra, as observed by the RAD instrument, call for extensive measurements of exposure, spectral and angular distributions in the vicinity of diverse topographical features, at various altitudes and temporal scales.
Such measurements could be provided through the utilization of a swarm of rovers, which transform into a network of distributed measurement stations over time. We present the Tumbleweed Rover, an unconventional, wind-driven robotic platform that could provide these capabilities at low cost, through the implementation of a novel mission architecture. The Tumbleweed Mission Concept includes a suite of miniaturized instruments aimed at providing high return for Mars science and exploration goals, including holistic characterisation of the surface radiation environment, a vital factor in astrobiology investigations as well as a critical prerequisite for human exploration of the red planet. In addition to dosimetry and spectrometry of galactic cosmic rays (GCRs) and solar energetic particles (SEPs), measurements of secondary thermal and epithermal neutron flux would enable prospection for water-ice (inferred from WEH) over large surface regions. These measurements could be supplemented by electrical permittivity sensing of the upper layer of the martian soil through the use of patch electrodes mounted on the exterior of the rover. Miniaturized COTS instruments such as TimePix-based radiation spectrometers, floating gate dosimeters (FGDOS), triaxial fluxgate magnetometers and an environmental sensing suite will be distributed amongst the swarm for these purposes.
Technical challenges to these measurements can be categorized into platform related and instrument related factors. The latter consists of issues such as low detector sensitive volumes / areas for passive neutron spectrometry and energetic particle detection. The former includes mechanical disturbances and lack of static stability resulting from the tumbling nature of the platform, as well as SWaP constraints which call for onboard processing and compression of the acquired data from instruments in the Tumbleweed swarm.
In order to investigate and mitigate these issues, we have developed a terrestrial testbed - which is being employed for field tests in Mars analogous areas as well as planetary environment simulation facilities. Further experimental work will involve characterisation of the rover’s dynamics as well as collection of preliminary measurements from COTS instruments, including dosimeters and neutron detectors. The results from these experimental tests will inform the refinement of a physics based simulation tool, developed in-house for studying a plethora of mission profiles and navigation strategies for the swarm. This will be supplemented by radiation environment modelling via SPENVIS and Geant4 simulations of Tumbleweed rover(s) on the Martian surface.
