The space shuttle Atlantis made a safe landing yesterday morning, capping the end to a truly historic mission. Over the past two weeks the shuttle crew rendezvoused with the Hubble Space Telescope, performed five space walks, fixed two failing instruments (the Advanced Camera for Surveys and the Space Telescope Imaging Spectrograph), installed two new instruments (the Cosmic Origins Spectrograph and the Wide Field Camera 3), did a host of other repairs and refurbishment, and then released a completely transformed telescope.
We have a tendency to forget just how remarkable this is. It is a highly non-trivial endeavor to send seven people into space (and get them back down safely). It is nothing short of miraculous to have them spend over 30 hours space “walking”, performing a major overhaul of an aging instrument (12 meters by 4 meters, weighing over 13 tons [it's "weightless" in space, of course; though it might have some inertia if you tried to move it]). You’ve got bulky gloves on, you can’t hear anything, you’re floating around with no balance, and you really, really don’t want anything to go wrong. Even something as trivial as a sticky bolt can derail months of preparation and millions of dollars of investment. There is a very slim margin for error.
The Atlantis mission is one of the finest examples of what excites people about manned space flight. It was an incredible success, from start to finish. And we can hope for a decade of mind-blowing science to prove it. It helps that Hubble is perhaps the most remarkable scientific instrument ever built. (Okay, the LHC is pretty cool too, but it doesn’t produce pretty pictures. And it isn’t working yet.) Without a doubt, the fact that Hubble was “serviceable” has played a large role in its success. With its initially flawed optics, Hubble would have been a catastrophic failure. It took a servicing mission to fix it, and provide us with an unparalleled scientific instrument. And now it is as if we have launched a brand new, state-of-the-art Hubble. These appear to be strong arguments in favor of manned maintenance of space telescopes.
But this mission is historic for another reason. It is likely to be the last time in our lives that human beings go to space to “fix” an orbiting scientific instrument. [Granted, prediction is very difficult, especially about the future.] It is incredibly expensive to send human beings up to fiddle on stuff in space. Furthermore, Hubble was placed in low-Earth orbit (600 kilometers up) to facilitate these sorts of repairs, which is a sub-optimal location for a telescope. The successor to Hubble, the James Webb Space Telescope (JWST), will be placed 1.5 million kilometers away at Lagrange point 2 (WMAP is already there, and Planck and Herschel are on their way). It will be a very long time before humans venture out that far from Earth. JWST is not being designed to be repaired or upgraded; it’s a one-shot deal. The additional costs of sending humans into space far outweigh the benefits. If you want to know whether there’s water on Mars, you send a rover. You do not spend many orders of magnitude more to send a human to dig with a shovel. Although the space shuttle is undeniably cool, and this latest Atlantis mission was astounding, manned space flight is not the economical way to do science.
With the successful landing of Atlantis we celebrate a transformed Hubble telescope. And we mark the end of the current era of human beings tinkering with telescopes in space.