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Cassini-Huygens is widely thought to be the last of NASA's great Cadillac probes--multibillion-dollar ships stuffed with instruments and complex backup systems. In the planning stage for 19 years, the craft cost $1.4 billion to design and build and nearly $2 billion to fly. When NASA adopted its "faster, better, cheaper" philosophy in the 1990s, it drove the cost of its unmanned ships down to the range of a couple of hundred million dollars--mostly by relying on off-the-shelf parts and eliminating redundant systems.
But the frugality came at a price. Cheap ships can't carry as many instruments as luxury models, so it may take more than one mission to bring back the same science. What's more, the lower price means more frequent breakdowns, as the string of bad luck NASA had with its Mars probes in the 1990s painfully demonstrated. The upside of flying economy is that if one spacecraft is lost, it's a relatively small matter to cobble together another. That thrift-shop technology has succeeded in getting three rovers onto the surface of Mars and will be at work again this summer when NASA launches the MESSENGER probe for a 2008 rendezvous with Mercury, and in 2006 when the New Horizons spacecraft takes off for Pluto.
Not all NASA scientists are impressed by these plans. Many believe there would be plenty of money to fly top-shelf ships if the space agency would drop its preoccupation with manned space travel. The International Space Station has been a scientific black hole, swallowing nearly $100 billion and delivering little of real value. President Bush's manned moon-Mars initiative will cost at least $170 billion--and that's from an agency that has never met a cost estimate it couldn't overrun. Forget the fixation with getting bodies in orbit or boots in the soil, critics say, and you could fairly blanket other planets with Cassini-quality landers and orbiters and still have billions left over. NASA administrator Sean O'Keefe, not surprisingly, disagrees: "Robotic missions are precursor missions." The most thorough exploration, he says, "requires the unique cognitive skills that only human beings can bring to the equation."
If Cassini really does represent the end of an era, it's a glorious end. Space scientists can justly take pride in the ship they have built and launched. They ought to be humbled too by the enormousness of the frontier they are mapping. "We have always tended to underestimate the splendor that the solar system has to offer," says physicist Soderblum. Knowing that this may be the last time--at least in our lives--that we get such a good look at Saturn makes the wonder of what we're seeing all the sweeter. --Reported by Dan Cray/Pasadena with other bureaus