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- The loss of the Mars Climate Orbiter has not reduced
the science potential of the Mars Polar Lander in any way, officials at
the Jet Propulsion Laboratory said Thursday.
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- According to Richard Cook, project manager of the Mars
Surveyor Operations Project, although the lander lost its primary communications
relay station, backup systems will be able to fully meet all the mission's
requirements
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- The Surveyor project includes the Mars Polar Lander,
the Mars Global Surveyor now orbiting Mars and future Mars missions.
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- Since the Mars Global Surveyor is already equipped to
serve as a relay station, it should be able to stand in for the lost orbiter
to transmit data to Earth from the lander, which is due to reach Mars on
Dec. 3.
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- Even before the loss of the climate orbiter, the global
surveyor was set to relay information from the Deep Space 2 probes -- two
grapefruit-size devices which will drop to the surface independently of
the polar lander and punch through the planet's surface sending back data
for a few days.
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- That completed, the surveyor would be available for the
polar lander
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- "We think the Mars Global Surveyor can work in two
modes. Part of the day as a relay station, and part of the day for its
science mission," he said. A caveat: JPL will need enough antenna
time to support both communications with the lander, as well as continue
the global surveyor's own science mission.
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- There are other complications as well. The global surveyor
can only serve as a relay for data from the orbiter to mission scientists.
Also, mission operators will not know if the surveyor relay link will work
until the lander arrives.
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- If it does, there will be additional steps. All communications
relays would be transferred via surveyor's Mars Orbiter Camera (MCO), said
Richard Zurek, project scientist for the Mars Surveyor '98 mission. This
means decompression and data transfer must be sent to the MCO team, which
in turn decodes it before sending it to JPL.
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- Assuming all goes perfectly, the global surveyor could
begin relaying data from the lander by the fourth day after landing. Mission
controllers are busy rewriting the command sequences for the first few
days after the landing to accommodate this plan.
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- According to Cook, even if the global surveyor is not
used, the Lander's direct-to-Earth capability can send back all the data
necessary to make the mission a success.
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- This is not without a drawback: pushing data to Earth
takes 15 times the power it would take to reach a satellite a few hundred
miles overhead. This creates a sort of energy crisis, thus less power is
available to apply to science experiments.
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- Cook disagreed with some mission scientists who have
expressed concern that their experiments would not yield a full return
of data.
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- "Sheer numbers of data don't necessarily translate
into 'science,' " he said. "If you take a hundred pictures of
the same thing, that doesn't add anything."
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- "This is forcing us to be smarter. If you're smart,
you can do the science that you want to achieve."
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- For example, when taking a panoramic image of the surface,
camera operators might reduce the overlap between adjacent pictures, he
suggested.
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- Operators are now reorganizing the sequences of operations
and communications to make the spacecraft's surface mission "more
streamlined" and to compress data more efficiently, he said. The reorganization
effort is bringing to light many of the polar lander's hidden talents,
he added.
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- "The spacecraft is much more capable than we give
it credit for," said Cook. While each of the spacecraft's components
is designed to meet minimum requirements, most exceed those standards.
He also said he expects the craft to be operable on the surface for longer
than the planned 90 days.
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- If all goes well with the re-planned mission, the only
acknowledged weakness will be that by using the direct-to-Earth link, the
lander will be more susceptible to changes in the weather.
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- The solar powered craft will be landing at high latitudes
near the martian south pole, so the sun will be low in the horizon and
will not offer a great deal of energy, Zurek explained.
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- "If the atmosphere is dustier, or if there are more
fogs, or if they persist longer than we're expecting," said Zurek,
that limits the power that we can generate, the power that we can use to
either run the communications system or to do the science observations.
So we're a little more vulnerable to the vagaries of the weather."
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- One thing is certain: the loss of the climate orbiter
means that the Dec. 3 landing will not coincide with the release of spectacular
high-resolution images of the landing site as happened after Mars Pathfinder
dropped to Mars July 4, 1997.
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- Whether or not the global surveyor is eventually used
as a relay, the first few days the polar lander will have to rely on its
direct-to-Earth link, so images and data will have to be highly compressed.
Full images will not be returned for several days, at best, Zurek said.
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