![](\"https:\/\/spaceweekly.com\/wp-content\/uploads\/2020\/01\/Huygens_wind_tunnel_test_card_full.png\")
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This movie was produced\u00a0in the wind tunnel at the PRISME Laboratory at the University of Orl\u00e9ans,\u00a0France, where subsonic testing was performed from 2017 to 2019 to\u00a0determine how\u00a0ESA\u2019s\u00a0Huygens\u00a0probe\u00a0spun during its descent to Titan.<\/p>\n
As part of the\u00a0international Cassini mission, Huygens made history on 14 January 2005 when it became\u00a0the first probe to successfully land on another world\u00a0in the outer Solar\u00a0System. However, during its descent, the probe\u00a0began spinning the \u2018wrong\u2019 way \u2013 and new results confirm why.<\/p>\n
The movie shows how air\u00a0flows over a 1:3 scale replica Huygens, as visualised using white smoke.\u00a0Various booms and appendages can be seen around the probe, the most\u00a0prominent\u00a0of which \u2013 one of the Huygens Atmospheric Structure Instrument (HASI)\u00a0booms \u2013 can be seen towards the top of the probe mock-up.<\/p>\n
Huygens was released\u00a0from Cassini spinning anti-clockwise but, approximately 10 minutes after\u00a0entering Titan\u2019s atmosphere, the probe\u2019s spin unexpectedly reversed\u00a0to\u00a0become\u00a0clockwise. It kept spinning this way for the rest of the descent; luckily, the\u00a0magnitude of this reversed spin was similar to that expected by the\u00a0researchers, meaning that the\u00a0unexpected flip affected the timing of the\u00a0planned observations, but did not dramatically affect their quality.<\/p>\n
Recent tests now\u00a0confirm the cause of this flip in spin direction. While the probe was equipped\u00a0with vanes to regulate its spin, other appendages on the spacecraft produced a\u00a0torque in the opposite direction. This was only exacerbated by the way in which\u00a0these vanes redirected the gas flow around the body of the probe, so that an\u00a0overall \u2018negative\u2019, or\u00a0clockwise, spin effect was created. There are also\u00a0indications that the HASI booms might have not been fully or symmetrically\u00a0deployed during descent; this effect is under\u00a0further\u00a0investigation.<\/p>\n
This\u00a0study was carried out under an ESA contract with LPC2E\/CNRS-University\u00a0of Orl\u00e9ans.<\/p>\n