Measurement of Martian boundary layer winds by the displacement of jettisoned lander hardware

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http://hdl.handle.net/10138/313452

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Paton , M D , Harri , A-M & Savijärvi , H 2018 , ' Measurement of Martian boundary layer winds by the displacement of jettisoned lander hardware ' , Icarus , vol. 309 , pp. 345-362 . https://doi.org/10.1016/j.icarus.2018.03.020

Title: Measurement of Martian boundary layer winds by the displacement of jettisoned lander hardware
Author: Paton, M.D.; Harri, A.-M.; Savijärvi, H.
Contributor: University of Helsinki, Department of Physics
Date: 2018-07-15
Language: eng
Number of pages: 18
Belongs to series: Icarus
ISSN: 0019-1035
URI: http://hdl.handle.net/10138/313452
Abstract: Abstract Martian boundary layer wind speed and direction measurements, from a variety of locations, seasons and times, are provided. For each lander sent to Mars over the last four decades a unique record of the winds blowing during their descent is preserved at each landing site. By comparing images acquired from orbiting spacecraft of the impact points of jettisoned hardware, such as heat shields and parachutes, to a trajectory model the winds can be measured. We start our investigations with the Viking lander 1 mission and end with Schiaparelli. In-between we extract wind measurements based on observations of the Beagle 2, Spirit, Opportunity, Phoenix and Curiosity landing sites. With one exception the wind at each site during the lander’s descent were found to be  < 8 m s − 1 . High speed winds were required to explain the displacement of jettisoned hardware at the Phoenix landing site. We found a tail wind ( > 20 m s − 1 ), blowing from the north-west was required at a high altitude ( > 2 km) together with a gust close to the surface ( < 500 m altitude) originating from the north. All in all our investigations yielded a total of ten unique wind measurements in the PBL. One each from the Viking landers and one each from Beagle 2, Spirit, Opportunity and Schiaparelli. Two wind measurements, one above about 1 km altitude and one below, were possible from observations of the Curiosity and Phoenix landing site. Our findings are consistent with a turbulent PBL in the afternoon and calm PBL in the morning. When comparing our results to a GCM we found a good match in wind direction but not for wind speed. The information provided here makes available wind measurements previously unavailable to Mars atmosphere modellers and investigators.
Subject: Mars
wind
trajectory
lander
PBL
Wind
LANDING PERFORMANCE
Lander
ENTRY
RECONSTRUCTION
MODEL
DESCENT
MARS PATHFINDER LANDER
DUST
PHOENIX LANDER
MOTION
Trajectory
SIMULATIONS
114 Physical sciences
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