In preparation for the ESA Huygens Probe mission to descend through Titan's atmosphere on 14 January 2005 following a 7 years cruise phase while attached to NASA/JPL Cassini Orbiter, important Probe power system verification steps had to be passed before deciding on the final mission sequence scenario: 1-The Huygens Probe, equipped with 5 primary Batteries, had to demonstrate its capability to perform adequate Battery depassivation as nominally foreseen but also under load failure conditions with less power to depassivate the electrodes. 2-A more accurate estimate of the on-board electrical energy available to support the mission had to be made in order to decide upon an anticipated switch-on of the Probe systems before its entry into Titan's atmosphere. Such verification activities were carried out using the Huygens Probe Engineering Model (EM) available at the European Space Operation Centre (ESOC) in Darmstadt, and using Flight Spare Batteries manufactured at the same time as the Flight Models and stored at the ESTEC Battery Test Center under ambient temperature conditions. Following Battery depassivation tests and Battery discharge tests, the development of a numerical simulator allowed refining the Probe energy budgets accounting for different failure modes.
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