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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