Hubble trouble

Its great eye on the universe is giving up the ghost.

The Hubble Space Telescope’s main camera — the ACS (advanced camera for surveys) — has stopped working. It went into safe mode early Saturday morning, and engineers for the space telescope have little hope it can be fixed.

The ACS was installed in 2002 and increased the discovery capability of the telescope by a factor of 10. It consists of three electronic cameras, filters and dispersers that can detect light from the ultraviolet to the near-infrared end of the spectrum and had become the primary instrument of the telescope. The ACS was valuable to astronomers because it could take deep imaging surveys of clusters of galaxies, allowing scientists to study these environments. Hubble still has other cameras which look at different spectrums that are still operating.

NASA has scheduled a shuttle mission to fly to Hubble in September 2008, but that mission is so full already that Preston Burch, Hubble associate director at the Goddard Space Flight Center, says he doesn’t believe a spacewalk to fix the camera is possible.

“It’s not as easy or straightforward to fix ACS as it is to fix the STIS [space telescope imaging spectrograph] camera,” he says. “In order to access the box cover and restore capability we would need to turn off the cooling system, and disconnect connections to the control module. It’s a big job, the area is pretty limited; we are already challenged enough to do the other repairs and this spacewalk would be considerably more labor-intensive.”

I was at Kennedy and then at Johnson for the shuttle mission during which astronauts installed ACS. That mission was the highlight of my time on the HST project, so for me personally it’s more than a little sad to hear that the ACS is dying or dead. ACS has been an incredible instrument and has accomplished more than it was planned to do. Fixing it on orbit would be, as Mr. Burch says, next to impossible. The cameras are built for a sort of plug and play installation on Hubble, which has several complex support systems on board that all need tending to during astronaut visits. The cameras were never intended to be serviced themselves on orbit, though at least one, the near-infrared camera, was outfitted with a cooling system during the same mission that saw the ACS installation. That mission should go down as one of the most intricate space missions in history.

The good news is that NASA is on board with a last servicing mission and the Wide Field Camera 3, which astronauts will install during that mission, will pick up where ACS leaves off in many important ways. Like ACS, WFC3 will be a visible light camera so it will keep Hubble in the pretty picture business for a few more years. WFC3 will expand Hubble’s discovery capabilities beyond ACS, as will the Cosmic Origins Spectrograph which will also be installed during SM4 (though the latter won’t take great pictures).


Wide Field Camera 3