Mars Spacecraft Teams on Alert for Dust-Storm Season
- From: baalke@xxxxxxxxxxxxx
- Date: Wed, 15 Apr 2009 17:18:38 -0700 (PDT)
http://www.jpl.nasa.gov/news/news.cfm?release=2009-067
Mars Spacecraft Teams on Alert for Dust-Storm Season
Jet Propulsion Laboratory
April 15, 2009
PASADENA, Calif. -- Heading into a period of the Martian year prone to
major dust storms, the team operating NASA's twin Mars rovers is
taking
advantage of eye-in-the-sky weather reports.
On April 21, Mars will be at the closest point to the sun in the
planet's 23-month, elliptical orbit. One month later, the planet's
equinox will mark the start of summer in Mars' southern hemisphere.
This
atmospheric-warming combination makes the coming weeks the most likely
time of the Martian year for dust storms severe enough to minimize
activities of the rovers.
"Since the rovers are solar powered, the dust in the atmosphere is
extremely important to us," said Bill Nelson of NASA's Jet Propulsion
Laboratory, Pasadena, Calif., chief of the engineering team for Spirit
and Opportunity.
Unexplained computer reboots by Spirit in the past week are not
related
to dust's effects on the rover's power supply, but the dust-storm
season
remains a concern. Spirit received commands Tuesday to transmit more
engineering data in coming days to aid in diagnosis of the reboots.
After months of relatively clear air, increased haze in March reduced
Spirit's daily energy supply by about 20 percent and Opportunity's by
about 30 percent. Widespread haze resulted from a regional storm that
made skies far south of the rovers very dusty. Conditions at the
rovers'
sites remained much milder than the worst they have endured. In July
2007, nearly one Martian year ago, airborne dust blocked more than 99
percent of the direct sunlight at each rover's site.
The rovers point cameras toward the sun to check the clarity of the
atmosphere virtually every day. These measurements let the planning
team
estimate how much energy the rovers will have available on the
following
day. Observations of changes in the Martian atmosphere by NASA's Mars
Reconnaissance Orbiter, which reached Mars in 2006, and NASA's Mars
Odyssey, which reached Mars in 2001, are available to supplement the
rover's own skywatch.
The Mars Color Imager camera on Mars Reconnaissance Orbiter sees the
entire planet every day at resolution comparable to weather satellites
around Earth.
"We can identify where dust is rising into the atmosphere and where it
is moving from day to day," said Michael Malin of Malin Space Science
Systems, San Diego, principal investigator for Mars Color Imager. "Our
historical baseline of observing Martian weather, including data from
the Mars Global Surveyor mission from 1998 to 2007, helps us know what
to expect. Weather on Mars is more repetitive from year to year than
weather on Earth. Global dust events do not occur every Mars year, but
if they do occur, they are at this time of year."
Two other instruments -- the Thermal Emission Imaging System on Mars
Odyssey and the Mars Climate Sounder on Mars Reconnaissance Orbiter --
monitor changes in airborne dust or dust-related temperatures in Mars'
upper atmosphere. Orbiters also aid surface missions with radio
relays,
imaging to aid drive plans, and studies of possible future landing
sites.
When orbital observations indicate a dust-raising storm is approaching
a
rover, the rover team can take steps to conserve energy. For example,
the team can reduce the length of time the rover will be active or can
shorten or delete some communication events.
In recent weeks, frequent weather reports from Bruce Cantor of Malin's
Mars Color Imager team let the rover team know that the March increase
in haziness was not the front edge of a bad storm. "Bruce's weather
reports have let us be more aggressive about using the rovers," said
Mark Lemmon, a rover-team atmospheric scientist at Texas A&M
University,
College Station. "There have been fewer false alarms. Earlier in the
mission, we backed off a lot on operations whenever we saw a small
increase in dust. Now, we have enough information to know whether
there's really a significant dust storm headed our way."
At other times, the weather reports prompt quick precautionary
actions.
On Saturday, Nov. 8, 2008, the rover team received word from Cantor of
a
dust storm nearing Spirit. The team deleted a communication session
that
Sunday and sent a minimal-activity set of commands that Monday.
Without
those responses, Spirit would likely have depleted its batteries to a
dangerous level.
Winds that can lift dust into the air can also blow dust off the
rovers'
solar panels. The five-year-old rover missions, originally planned to
last for three months, would have ended long ago if beneficial winds
didn't occasionally remove some of the dust that accumulates on the
panels. A cleaning event in early April aided Opportunity's power
output, and Spirit got two minor cleanings in February, but the last
major cleaning for Spirit was nearly a full Martian year ago.
Nelson said, "We're all hoping we'll get another good cleaning."
JPL, a division of the California Institute of Technology, Pasadena,
manages the Mars Exploration Rovers, Mars Odyssey and Mars
Reconnaissance Orbiter for NASA's Science Mission Directorate,
Washington. More information about the rovers is at
http://www.nasa.gov/rovers . Dust reports from the Thermal Emission
Imaging System, operated by Arizona State University, Tempe, are at
http://themis.asu.edu/dustmaps/ . Weather reports from the Mars Color
Imager team are at http://www.msss.com/msss_images/latest_weather.html
..
Media contact: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster@xxxxxxxxxxxx
Dwayne Brown 202-358-1726
NASA Headquarters, Washington
dwayne.c.brown@xxxxxxxx
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