NASA's Mars Reconnaissance Orbiter is suffering science-reducing glitches, although the spacecraft is nearing a milestone in churning out record-setting levels of data.

The spacecraft carries six instruments for probing Mars' atmosphere [video], surface and subsurface to characterize the red planet and how it changed over time.

Two instruments onboard the Mars Reconnaissance Orbiter (MRO)--the super-powerful High Resolution Imaging Science Experiment (HiRISE) and the Mars Climate Sounder--are not in prime-time, science taking status. The problems were flagged February 7 by officials at the Jet Propulsion Laboratory (JPL) in Pasadena, California, manager of MRO's mission.

While engineers wrestle with MRO's anomalies, JPL noted that the orbiting probe this month is set to eclipse the record for the "most science data" returned by any Mars spacecraft.

The rate of data return is projected to increase over the coming months as the relative motions of Earth and Mars in their orbits around the Sun shrink the distance between the planets. That Mars-Earth positioning means MRO should relay more than 30 terabits of science data--equal to more than 5,000 information-packed CD-ROMs.

MRO observations are an essential element of on-going studies of potential exploration sites for future missions to that time-weathered world--such as the Phoenix Mars lander to launch this coming August.

Sounder stowed

MRO's Mars Climate Sounder (MCS) is built to map the temperature, ice clouds and dust distributions in the Mars' atmosphere on each of the spacecraft's nearly 13 orbits around the planet per day.

But in late December, the sounder appeared to skip steps sporadically--a problem that put the equipment's field of view slightly out of position. Following uplink of new scan tables to the instrument, the position errors stopped and the instrument operated nominally.

Last month, however, the position errors reappeared, becoming more frequent.

Due to the problem, the MCS has been temporarily stowed while the science team investigates the root cause of the trouble.

Detector noise

HiRISE is one of three cameras that are part of MRO's science payload--the largest-diameter telescopic camera ever sent to another planet.

The HiRISE instrument holds an array of 14 electronic detectors, each covered by a filter in one of three wavelength bands: 400 to 600 nanometers (blue-green), 550 to 850 nanometers (red), or 800 to 1000 nanometers (near infrared). Ten red detectors are positioned in a line totaling 20,028 pixels across to cover the whole width of the field of view.

In late November 2006, the HiRISE team noticed a significant increase in noise, such as bad pixels, in one of its 14 camera detector pairs. Another detector that developed the same problem soon after MRO's launch in August 2005 has worsened. Images from the spacecraft camera last month showed the first signs of this problem in five other detectors.

Minor dropouts

While the current impact on image quality is small, explained a JPL statement, there is concern as to whether the problem will continue to worsen. The camera stays on duty and is returning outstanding images of the martian landscape.

"For now we are using a slightly extended warm-up period before each image," explained Alfred McEwen, Director of the Planetary Image Research Lab at the University of Arizona in Tucson, Arizona. He is MRO's HiRISE principal investigator.

That warming, McEwen told SPACE.com, is sufficient to reduce the HiRISE problem to minor dropouts--easily interpolated--in RED 9, and no problems at all in other charge couple devices within the instrument except an infrared receiver channel (IR10 channel 1), where instrument specialists first saw this problem after MRO's blastoff from Florida in August 2005.

"When we have evaluated whether or not the extended warm-up has potential long-term detrimental effects, then we can decide to extend this warm-up period in the future if the problem continues to worsen," McEwen said.

Operational work-around

"HiRISE has been performing beautifully," said Richard Zurek, MRO's project scientist at JPL. "That's why any possible degradation in its performance concerns us," he told SPACE.com.

Zurek advised that the principal concern is not the present performance of HiRISE, but whether or not the noise will intensify, impacting the image quality of channels for which the noise is now hardly noticeable, if present at all.

"Fortunately, the two detectors--out of 14--for which the noise is often significant are on the edges of the panchromatic (black and white) and color fields of view, so that they leave no obvious gaps when they are too noisy," Zurek said.

The issue with HiRISE does appear, Zurek added, to have an "operational work-around". By operating the instrument a few degrees warmer, still in its nominal operating range, appears to significantly reduce, and often eliminate, the noise, he said.

HiRISE output

"A goal of the present troubleshooting effort is to confirm that this mode does not have some unforeseen side effects," Zurek noted. "We are of course trying to understand the cause of the noise to help define other mitigation procedures and to help us know if we need to conserve the number of images we can ultimately take."

While HiRISE is acting up, Zurek observed that the instrument's three months of science gathering to date has yielded roughly 1,000 images--more than 1.5 terabits (1,500 gigabits) of image data.

As part of that output, for example, HiRISE has redirected the landing site for the Phoenix Mars mission to a safer, boulder-free area, Zurek said, "and it has shown us Mars at a level of detail as good or better than you could see from a low-flying plane."

"Our expectation is that HiRISE will continue to do this for a long time once we understand the noise problem better and craft our operations procedures accordingly," Zurek concluded.

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