The winds in the Martian nocturnal boundary layer at the time of the Pathfinder landing

• DOI: 10.5194/epsc2021-666
• Publication Date: 2021-07-22T07:54:38Z
• Authors: Mark Paton; Hannu Savijärvi; Ari-Matti Harri; Joonas Leino
• Keywords: Descent (aeronautics); Pathfinder

AbstractIn 1997 Pathfinder descended on its parachute through the nocturnal boundary layer of Mars. early in morning a few hours before possible formation low level jet [1]. We use an EDL trajectory model to simulate landing and jettisoned hardware together with HiRISE images site we are able constrain wind speeds directions during descent.BackgroundPathfinder deployment occured at altitude around 10 km. The heat shield was 15 s later. Shortly afterwards enveloped deflated airbags lowered down bridle. were then inflated hundred metres. High powered rockets, attached back shell, fired about 80 m reducing vertical velocity nearly zero 20 above surface. lander released dropped surface while rockets used remaining propellant shoot backshell upwards away from lander. proceeded bounce 1 km towards northeast coming rest after two minutes [2].MethodWe numerically integrate equations motion trajectories spacecraft shield. relative distance between is compared that using similar method [3]. first impact point airbags, which require help lander, not visible image so reconstruct likely based information [2]. To infer vary Hill climbing algorithm until predicted points match those reconstructed airbags. There levels winds 0 9.6 upper lower one. division line free parameter. In figure set altitude.ResultsFigure shows ground track starting dots tracks intervals have been fitted locations inferred location.    Figure : Ground shield.SummaryWe varied dividing 500 2000 m. also 400 1000 found can be fairly well constrained even if these parameters varied. Above 500-2000 west (240-310°) below southeast (120-150°).  obtain fits observations speed required 30 s-1 range.References[1] Savijärvi, H., Määttänen, A., Kauhanen, J. Harri, A.-M.: Mars pathfinder: New data new simulations, Quarterly Journal Royal Meteorological Society, 130, 669-683, 2004.[2] Golombek, M.P., Anderson, Robert, Barnes, Jeffrey, Bell, J.F., Bridges, Nathan, Britt, Daniel, Brückner, J., Cook, R.A., Crisp, David, J.A., Economou, Thanasis, Folkner, W., Greeley, R., Haberle, Hargraves, R.B., Harris, Haldemann, Herkenhoff, K., Hviid, S.F., Wilson, G.R.: Overview Mission: Launch Landing, Surface Operations, Data Sets, Science Results, Geophysical Research, 104, 8523-8554, 1999.[3] Paton, M. D., A.-M. H.: Measurement Martian by displacement hardware, Icarus, 309, 345-362, 2018.