That is unless they have an apparently malfunctioning spacecraft on their hands. Paul Fieseler, one of the engineers behind the Galileo spacecraft , recently got that home-run feeling after Galileo had a little attitude problem. No one was more surprised than Fieseler. It just kind of came up after the spacecraft called back for help.
Variable stars are typically part of a binary system, in which two stars orbit one another.
From our vantage point, the light from the two stars appears as one. But when one passes in front of the other, it shadows it and the total amount of light reaching Earth decreases. Galileo , being a smart spacecraft, knows this. So it uses only steady stars for navigation and for maintaining its attitude as it zooms through space. At least that's the plan.