After 12 years, 3.7 billion miles, and four trips around the sun, the Starburst space probe is going to visit its second come, Tempel 1, the second visit by a spacecraft to this ancient speck of space debris.
Unmanned spacecraft have historically been throwaway machines, mostly because it would be pointless to build them any other way. Once you’ve flung a ship into space, its entire job is to send back pictures and data for as long as its fuel and power hold out. When it’s finished with that work, there’s simply no use for the metal hulk that remains. The problem is, those hulks cost a lot of coin. … For that reason, NASA has long found itself under pressure to squeeze as much use as possible from its Cadillac machines, and it’s been during recent explorations of comets that the agency has achieved that goal most ingeniously.