[meteorite-list] Mars Exploration Rover Status Report: Spirit Sees Dustier Sky

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 27 Jul 2007 13:47:01 -0700 (PDT)
Message-ID: <200707272047.NAA27753_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/features.cfm?feature=1426

Mars Exploration Rover Status Report: Spirit Sees Dustier Sky
Jet Propulsion Laboratory
July 26, 2007

As of Thursday, July 26, NASA rovers Spirit and Opportunity are both
enduring levels of reduced power supply. The rovers can survive at these
levels, but NASA continues to sharply restrict their activities.

Spirit is under the dustiest sky ever seen at that location. Sunlight at
Spirit's location is more obscured than current conditions for
Opportunity, though not as severe as what Opportunity faced a week ago.

Mission controllers Thursday received the first status report from
Opportunity in three days. This delay had been planned between
transmissions to minimize the rover's energy use. Energy output from
Opportunity's solar panels has climbed above 200 watt hours per day
(enough to run a 100 watt bulb for two hours), compared with daily
levels as low as 128 watt hours last week. Light must reach the solar
panels for them to provide electricity.

Opportunity has resumed measurements of how obscured the sun is. These
had been suspended for several days to save power. The new measurement
included in Thursday's downlink indicates slight clearing. However, some
dust has freshly settled onto the solar panels, lessening the increase
in power output.

"We are still waiting out the storms, and we don't know how long they
will last or how bad they will get," said John Callas, rover project
manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Each rover has eight radioisotope heater units that supplement electric
heaters for keeping batteries and electronics within their operating
temperature ranges. The radioisotope heater units use the decay heat
from plutonium-238. Each of them provides about one watt of heat. They
aid the rovers' survival on very low-power days and through cold nights,
though the electric heaters are also necessary.

Controllers are keeping Opportunity on an extremely low-power-use plan
under which the rover transmits information to Earth only once every
three days. A heater switch that has been stuck in the on position since
landing day makes Opportunity more vulnerable to low power than Spirit.
Spirit has suspended most activities, but is still communicating daily.

------------------------------------------------------------------------

Media contact: Guy Webster/JPL
818-354-6278
Received on Fri 27 Jul 2007 04:47:01 PM PDT