WASHINGTON,
Feb. 7 (Xinhua) -- NASA's engineers are examining why two instruments aboard
Mars Reconnaissance Orbiter spacecraft are intermittently not performing
entirely as planned, according to a report announced on Wednesday.
NASA's Jet Propulsion Laboratory, which manages this
Mars spacecraft, said that all other spacecraft instruments are operating well
and continue to return science data at record levels.
In late November 2006 the spacecraft team operating
the High Resolution Imaging Science Experiment camera on Mars Reconnaissance
Orbiter 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 launch, has worsened. Images from the spacecraft camera last month
revealed the first signs of this problem in five other detectors.
While the current impact on image quality is small,
there is concern as to whether the problem will continue to worsen.
The second instrument concern is related to an
instrument designed to routinely scan from the surface across the atmosphere
above Mars' horizon. The Mars Climate Sounder maps the temperature, ice clouds
and dust distributions in the atmosphere on each of nearly 13 orbits every day.
In late December, the sounder appeared to skip steps occasionally, so that its
field of view was slightly out of position. Following uplink of new scan tables
to the instrument, the position errors stopped and the instrument operated
nominally.
In mid-January, the position errors reappeared.
Although still intermittent, the errors became more frequent, so the instrument
has been temporarily stowed while the science team investigates the problem.
In this month, the spacecraft is set to surpass the
record for the most science data returned by any Mars spacecraft. Since
beginning its primary science phase in November 2006, the orbiter has returned
enough data to fill nearly 1,000 CD-ROMs. This ties the record for Mars data
sent back between 1997 and 2006 by NASA's Mars Global Surveyor mission.
The rate of data return is expected 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. By the conclusion of its
first science phase in 2008, the mission is expected to have returned more than
30 terabits of science data, enough to fill more than 5,000 CD-ROMs.
Observations will be used to evaluate potential landing sites for future
missions and to increase our understanding of Mars and how planets change over
time.
