A workhorse deep space camera on the Hubble Space Telescope has shut down for the third time in less than a year, and NASA scientists say that only a fraction of its capability will be restored.
The $86 million Advanced Camera for Surveys was near the end of its expected lifespan, officials said. Many of its functions will be assumed by new equipment scheduled to be installed during a space shuttle servicing mission in 2008.
The ACS went dark and the entire orbiting observatory entered a protective "safe mode" Saturday about 7:30 a.m., when a backup power supply system failed.
Scientists expect most of Hubble's scientific instruments to return to duty later this week, while engineers study the problem, said Preston Burch, Hubble program manager at the NASA Goddard Space Flight Center in Greenbelt.
The ACS shut down last year in June and again in September. But this time two of the instrument's three "channels," which function as separate cameras within the instrument, are likely to remain dark permanently, Burch said.
The Hubble still has an infrared camera capable of probing deep into space, guidance sensors that detect and track movements of distant stars and the renowned Wide Field Planetary Camera 2, which is responsible for nearly all of the famous images created by the orbiting telescope.
Engineers hope to restore one of the three ACS channels by the end of March so that it can help NASA's New Horizons spacecraft gather information about Jupiter and its atmosphere, Burch said.
But two-thirds of the requests from astronomers seeking time to use Hubble - awarded by a committee on a competitive basis - involved access to ACS because of its ability to peer deep into space. The single ACS channel that might be restored generally performs less than 10 percent of that work, Burch said.
"It is a significant loss in capability, but there's still no shortage of science to be done with Hubble," Burch said.
The lost channels included the high-resolution channel, which could examine interstellar dust created by the formation of planets, and the wide-field channel, credited a few years ago with recording the most distant observations of the early universe ever made, Burch said.
Hubble's existing wide-field camera will be able to perform some of the same deep space probing conducted by ACS, but it will take longer to gather the data, Burch said.
NASA has set up a panel to study the cause of the outage. The power failure was not a threat to Hubble's remaining instruments and will not affect plans for a Hubble servicing mission in September 2008, NASA officials say.
"We believe it's isolated to a very specific place within the telescope and will not affect any other instruments on the telescope," said Edward Ruitberg, Hubble Space Telescope deputy program manager.
Shuttle astronauts are scheduled to install two new scientific instruments - the Cosmic Origins Spectrograph and the Wide Field Camera 3 - in 2008. They also will repair Hubble's Space Telescope Imaging Spectrograph, idled since 2004 by an electrical failure.
The new Wide Field Camera is designed to perform many of the same functions as ACS, helping astronomers to peer further back in time to an era when the universe was a few hundred million years old, experts say.
The spectrograph will reveal secrets about the evolution and formation of galaxies, and probe the atmospheres on distant planets and the nature of the vast, dark voids of empty space between galaxies.
ACS failed just a month short of the five-year life span anticipated when it was installed on a servicing mission in March 2002, Burch said.
"We knew it's lifetime was going to be limited," he said.