For mission controllers, a solar conjunction means that a spacecraft, the Sun and the Earth are in alignment. Monday, engineers at the European Space Agency successfully brought Mars Express out of a lengthy and long-planned nap as it travelled out of a conjunction and away from potential Sun-caused communications interference.
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http://www.esa.int/spacecraftops/ESOC-Article-fullArticle_idBanner-1091611717294_par-40_1093589522422.html