In this section we talk about what is called contingency planning. The purpose of contingency planning is to preclude goblins in the first place, and to preserve the science data return when some goblins do sneak through our defenses. Just imagine how different things would be to homeowners of the Oakland hills if someone happened to be standing right where the fires of 1992 started with a bucket of water. Nevertheless, it is prudent to take some actions to plan against problems, and we are not so naive as to think that everything will be perfect all the time. During JPL's Voyager missions to the outer planets there have been all sorts of aches and pains, though none so serious as to cause a significant loss of science.
Goblins generally come in three varieties.
One area we need to do contingency planning involves problems as we near the opening of the launch period. To enable recovery from launch delays, the Cassini project has more than one trajectory to Saturn, each with a different launch date. Multiple missions typically protect us against launch slips that occur after the spacecraft assembly is complete, but can't be diagnosed and fixed quickly enough to meet the primary launch schedule. Typical problems are technical difficulties with the spacecraft or launch vehicle, recent launch vehicle failures, and inclement weather. The primary mission , which has the best trajectory, launches in October of 1997 and has a compatible launch period duration of more than a month.