IN SPACE, it seems, you get what you pay for. If you have $3 billion, you get Cassini, a sophisticated interplanetary craft that after a journey of 3.5 billion kilometres has now reached Saturn, the most distant planet ever to be orbited by a man-made probe.
Cassini is working astonishingly well. On 1 July, the spacecraft timed the firing of its main engine so precisely that it hit the required orbit spot-on, without any need for a planned trajectory adjustment.
The spacecraft, a joint mission put together by NASA, the European Space Agency (ESA) and the Italian space agency, has already spent seven years in space. It has faced extreme heat and cold, and it has twice crossed the plane of Saturn鈥檚 rings, where it was bombarded by hundreds of thousands of high-velocity microscopic particles. Nothing has gone wrong. Every subsystem of every instrument package is working perfectly.
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Mission scientists, understandably pleased, keep using words like 鈥渇lawless鈥� and 鈥渆xcellent鈥�, and Cassini is already sending back pictures and data that are changing ideas about Saturn鈥檚 rings and moons (see 鈥淔irst images of Saturn鈥檚 rings bring surprises鈥�).
If you spend less money, you get a lesser craft. Cassini was the last of the big missions to be approved before NASA adopted its 鈥渇aster, cheaper, better鈥� philosophy of the 1990s, which proved to be such a disaster. Sending out lots of cheap probes sounded like a good idea, but something always seemed to go wrong.
ESA too has flirted with the cut-price approach. Its Mars lander, Beagle 2, seemed a snip at about $73 million until it failed to respond to callers shortly after its supposed landing on the Red Planet on Christmas day. It may have encountered bad weather that made the atmosphere unexpectedly thin, causing the parachute or airbags to fail. Or they may have opened too late. Or the jettisoned back cover of the probe may have interfered with its parachute. We will never know.
In the past week, Cassini engineers have been saying how vitally important it was to always be able to ask for one more test. One more test might have saved Beagle 鈥� and many of the cut-price NASA craft too. The problem, of course, is that you cannot know in advance which test will be the one that uncovers the fatal flaw. That means doing lots of tests, which costs lots of money. But Cassini鈥檚 engineers seem to have spent their billions wisely, and the craft promises to be the most absorbing exploration of alien worlds since Voyager.