NASA Now May Not Lose Four Months Of Pioneering Data From Space Telescope

The Hubble Space Telescope, after being sidelined by multiple glitches, is edging slowly back toward operational capability, and NASA experts believe they probably know one root cause of the crisis: a simple, momentary short circuit or open circuit.

Since the cause of the mess now appears to be known, and since systems now are coming up in normal fashion, NASA expects to resume Hubble science observations this week.

Wide Field Planetary Camera 2 came up over the weekend.

This information, explained to news media in a NASA conference call, is a huge relief to astronomy researchers who worried that the glitches might cause the loss of priceless data from the orbiting Hubble during a third of a year, which has performed pioneering work, peering back to somewhere near the beginning of the universe, and sending stunning pictures back to Earth.

It had been feared that problems on Hubble might not be repaired until an upcoming rescue and servicing mission by Space Shuttle Atlantis. That mission was to have lifted off earlier this month, until the glitches forced postponement of the STS-125 Mission to sometime in February.

Briefers said no firm date for the launch has been set. The go or no go determination will be made in the middle of next month.

The briefing was provided by John Morse, director of the Astrophysics Division in the Science Mission Directorate at NASA headquarters in Washington, and Art Whipple, manager of the Hubble Systems Management Office at Goddard Space Flight Center in Greenbelt, Md.

"We expect to resume science observations with the ACS (Advanced Camera for Survey) solar blind channel," Whipple said.

Aside from the short circuit or open circuit — "transient electrical event" — that triggered the problems, other woes included a master clock that was set so there was too little time between some events, which led to shutdowns. So the clock was reset.

That transient short also caused a reset of the command unit science data formatter and the NASA standard spacecraft computer in the science instrument command and data handling system.

It all began Sept. 27, when an anomaly hit a data formatter unit, and then an attempt to switch to a backup unit failed as other gremlins struck. (Please see Space & Missile Defense Report, Monday, Oct. 20, 2008.)

That in turn caused NASA to delay the Atlantis lift-off by four months, so that technicians at Goddard could ready a new formatter unit that the shuttle crew will install on Hubble, removing the problem-plagued existing unit.

Meanwhile, NASA experts responded to the crisis by attempting to shift from a Side A formatter to Side B, but two glitches occurred.

For example, there was a suspension of the ACS on Oct. 16. Then, that evening, there came a safing of science payload, taking instruments offline.

That caused NASA experts to begin sleuthing just what went wrong, what caused the problems, and how to fix them.

In the ACS shutdown, its operation was suspended because of a software test that runs in the ACS microprocessor. It tripped before a parallel data collection application had time to collect sufficient valid data. Experts managed to rule out another suspected cause, finding that there were no actual problems with the ACS power supply at the time of the suspension.

Timing of the two parallel processes always has been tight, and recent changes to the software to support the upcoming Atlantis mission repairs to Hubble, along with a resetting of the onboard master clock during the reconfiguration, made the timing too tight, leading to major problems.

To fix this, NASA is resetting timing in activation of the ACS software, Whipple explained.

They think they have divined just what went wrong, and are resuming recovery of the science payload, getting systems back to work.

While Goddard experts now are succeeding in shifting from the Side A formatter where the trouble first began to the Side B unit, which has had some problems of its own, the Atlantis crew will swap out an entire tray of systems, including both the old Side A and Side B, with replacement gear. When the Atlantis crew members reach Hubble and open panels to access the Side A and B units, whatever shape they’re in, spacewalking astronauts will still conduct the servicing mission and swap them out, even if Side B still is working. Side A and Side B were designed to be replaced as a single unit, on a tray full of gear measuring about 25 by 34 by 10 inches.

This should keep Hubble up and running until 2013, when it will be replaced by the next-generation James Webb Space Telescope.

Until that swap-out, however, Side B may continue operating, allowing Hubble to press forward with its electrifying work for a third of a year.

Side B is being pressed into service after 18 years of inactivity, which may have been one reason for the short circuit or open circuit. That’s not uncommon in systems that have been dormant for extended periods, Whipple explained.

Whipple warned that it won’t be surprising if similar circuit problems occur on Side B, leading to further outages of the Hubble.

But the circuit problems don’t appear to have caused any damage to systems on the telescope, he said. No fuses were blown in these incidents.

The space telescope also had problems with short circuits early last year.

This isn’t the worst that has occurred with Hubble. In a previous crisis, the eye in the sky went down for about six weeks.