Studies of Phobos polar illumination and thermal conditions
Final Report Abstract
In this project, we made new positional measurements of Phobos and Deimos using astrometric observations to improve orbit models of the two Martian satellites. We updated the reference frame and rotation model for Phobos. The equilibrium shape of Phobos in its special gravitational and tidal regime was thoroughly studied, enabling important conclusions for place of origin and probable evolution of the satellite. We have studied various effects contributing to the illumination conditions and temperatures (including surface and subsurface) of Phobos. The irregular shape causes relevant scattering, adding to the direct solar incoming flux. The proximity to Mars has a strong effect on the overall illumination conditions and thermal budget due to reflected solar radiation and thermal emissions by the planet. On the Mars-facing hemisphere minimum daily temperatures for consecutive nights may vary by as much as 20𝐾. During polar winter Mars radiation is the dominant contribution to the thermal budget. As a main result, our studies of illumination conditions reveal intricate patterns of areas under illumination or in darkness on the odd-shaped satellite. Maps were produced showing daylight hours for areas on Phobos. Very long daylight hours (up to 142 Earth days) and times in complete shadow (up to 460 Earth days) are demonstrated for the summer seasons in polar areas. The analysis of thermal conditions reveals that Mars radiation makes a significant contribution to the thermal conditions. Illumination and thermal conditions are important constraints for landing site selection and operation of the upcoming MMX Phobos sample return mission.
Publications
-
2018. Determination of Phobos’ rotational parameters by an inertial frame bundle block adjustment. Journal of Geodesy 92, 963–973
Burmeister, S., Willner, K., Schmidt, V., Oberst, J.
-
2018. Mutual event observations of solar system objects by SRC on Mars Express. Analysis and release of observations. Astronomy and Astrophysics 614, A15
Ziese, R., Willner, K.
-
2018. Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2015. Celestial Mechanics and Dynamical Astronomy 130, 22
Archinal, B.~A., …, Oberst, J., …
-
2019. Erratum: Correction to: Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2015. Celestial Mechanics and Dynamical Astronomy 131, 61
Archinal, B.~A., …, Oberst, J., …, Stark, A., …
-
2020. Equipotential Figure of Phobos Suggests Its Late Accretion Near 3.3 Mars Radii. Geophysical Research Letters 47, e85958
Hu, X., Oberst, J., Willner, K.
-
2020. Phobos Environment Requirement Document for the MMX Rover Mission. ROV-MIS-RD-5- CNES_DLR, Issue 01, 21/05/2020. CNES DLR MMX rover project internal document
Biele, J., Tardivel, Simon (ed.), Biele, J., Buse, F., Hoerdt, A., Lichtenheldt, R., Michel, P., Ogawa, K., Schroeder, S., Tardivel, S., Willner, K., Wolff, F., Ziese, R.
