Have you been impressed by the spectacular images and landmark discoveries produced with the Hubble Space Telescope over the last 17 years? Well, you ain't seen nothin' yet.That's the message driven home today at the American Astronomical Society meeting now under way in Austin, Texas. After the upcoming servicing mission by Space Shuttle astronauts, currently scheduled for August, Hubble will be "at its apex, unequalled in terms of capability," says Alan Stern, NASA's associate administrator for science.
The main reason for the superlatives is the planned installation of two powerful new scientific instruments: the Wide Field Camera 3 (WFC3) and the Cosmic Origins Spectrograph (COS). WFC3, which operates at visible, infrared, and ultraviolet wavelengths, offers higher resolution, greater sensitivity, and a more expansive field of view than the camera it's replacing. COS will dissect the ultraviolet light from faint stars and remote active galactic nuclei with unprecedented sensitivity. It'll go in the instrument bay now occupied by COSTAR, the device installed in 1993 to compensate for the telescope's misshapen primary mirror. (All the instruments installed since then include their own corrective optics, so COSTAR isn't needed anymore.)
According to NASA astronaut John M. Grunsfeld, the lead spacewalker on the mission and a veteran of two previous Hubble visits, the most challenging tasks on the flight will be repairs to two other scientific instruments.The Space Telescope Imaging Spectrograph (STIS) and Advanced Camera for Surveys (ACS) were knocked out of action by separate electrical problems. Grunsfeld and his crewmates will attempt to replace circuit boards in each instrument, which involves opening electronics boxes never designed to be serviced in orbit. The tough part will be removing hundreds of tiny screws without letting any of them float into the telescope's innards, where they could cause short circuits or other disasters.
Besides adding and fixing instruments, the astronauts plan to replace one of Hubble's guidance sensors and all its batteries and gyroscopes. They'll also add new insulation blankets and use the shuttle's rockets to raise the telescope's orbital altitude. This should enable Hubble to operate for another 5 to 10 years, long enough to overlap with the James Webb Space Telescope, a larger reflector scheduled for launch in 2013 and optimized for observations at infrared wavelengths. Without servicing, Hubble would probably stop working within the next two to three years due to gyroscope or battery failures.
Grunsfeld says that he and his crewmates have convinced themselves they can do all that's being asked of them. All that remains between now and their launch aboard the shuttle Atlantis is to practice...and practice...and practice.
David Leckrone (NASA/Goddard Space Flight Center), Hubble's senior project scientist, says that if the astronauts manage to complete all the planned repairs and upgrades, the telescope will have nearly 100 times the "discovery power" that it has now. In other words, it'll be able to acquire images and spectra with vastly greater efficiency, thanks to its improved sensitivity and resolution over wider fields. NASA's flagship orbiting observatory will be "better than it has ever been before," says Leckrone.
It almost wasn't going to happen. In 2004, then NASA administrator Sean O'Keefe put an end to Hubble servicing amid safety concerns following the tragic loss of the shuttle Columbia and her crew of seven. New administrator Michael Griffin reversed that decision after post-Columbia improvements to the shuttle program made flying to Hubble safer. It didn't hurt that a high-level panel of astronomers and other scientists had also concluded that Hubble would continue to produce world-class science.
Sometime around 2020, astronauts may visit Hubble one last time presumably aboard NASA's new Orion spacecraft but not to service it. Instead, they'll attach a retrorocket to the telescope's aft end. Or maybe that'll be done robotically. However it gets there, the rocket will be used to steer Hubble to a harmless reentry over the Pacific Ocean.