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From: Stig_Agermose@online.pol.dk (Stig Agermose)
To: updates@globalserve.net
Date: Fri, 27 Mar 1998 03:07:22 +0100
Subject: Mars Global Surveyor To Image "Face" Over The Next Few Months
Mars Global Surveyor will attempt to take images of the "Face on
Mars" and other features of public interest over the next few
months, according to this March 26 NASA press release. URL:
http://nssdc.gsfc.nasa.gov:80/planetary/text/mgs_pr_19980326.txt
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March 26, 1998
Douglas Isbell
Headquarters, Washington, DC
(Phone: 202/358-1547)
Diane Ainsworth
Jet Propulsion Laboratory, Pasadena, CA
(Phone: 818/354-5011)
RELEASE: 98-50
MARS GLOBAL SURVEYOR TO ATTEMPT IMAGING OF FEATURES OF PUBLIC INTEREST
NASA's Mars Global Surveyor spacecraft is about to begin a
summer-long set of scientific observations of the red planet from
an interim elliptical orbit, including several attempts to take
images of features of public interest ranging from the Mars
Pathfinder and Viking mission landing sites to the Cydonia
region.
The spacecraft will turn on its payload of science instruments on
March 27, about 12 hours after it suspends "aerobraking," a
technique that lowers the spacecraft's orbit by using atmospheric
drag each time it passes close to the planet on each looping
orbit.  Aerobraking will resume in September and continue until
March 1999, when the spacecraft will be in a final, circular
orbit for its prime mapping mission.
It will not be possible to predict on which orbit the spacecraft
will pass closest to specific features on Mars until Global
Surveyor has established a stable orbit and flight controllers
are able to project its ground track. This process should be
completed in the next few days. The exact time of observations
and the schedule for the subsequent availability of photographs
on the World Wide Web are expected to be announced early next
week.
"Global Surveyor will have three opportunities in the next month
to see each of the sites, including the Cydonia region, location
of the so-called 'Face on Mars,' " said Glenn E. Cunningham, Mars
Global Surveyor project manager at NASA's Jet Propulsion
Laboratory, Pasadena, CA. "The sites will be visible about once
every eight days, and we'll have a 30- to- 50-percent chance of
capturing images of the sites each time."
Several factors limit the chances of obtaining images of specific
features with the high-resolution mode of the camera on any one
pass. These factors are related primarily to uncertainties both
in the spacecraft's pointing and the knowledge of the
spacecraft's ground track from its navigation data. In addition,
current maps of Mars are derived from Viking data taken more than
20 years ago. Data obtained by Global Surveyor's laser altimeter
and camera during the last few months have indicated that our
knowledge of specific locations on the surface is uncertain by
0.6 to 1.2 miles (1 to 2 kilometers). As a result, the locations
of the landing sites and specific features in the Cydonia region
are not precisely known.
In addition, the Mars Pathfinder and Viking landers are very
small targets to image, even at the closest distance possible,
because they are the smallest objects that the camera can see.
The Cydonia features, on the other hand, are hundreds to
thousands of times larger and the camera should be able to
capture some of the features in that area.
Global Surveyor's observations of the Viking and Pathfinder
landing sites will provide scientists with important information
from which to tie together surface observations and orbital
measurements of the planet.  Data from landing sites provide
"ground truth" for observations of the planet made from space.
As for the "Face on Mars" feature, "most scientists believe that
everything we've seen on Mars is of natural origin," said Dr.
Carl Pilcher, acting science director for Solar System
Exploration in NASA's Office of Space Science, Washington, DC.
"However, we also believe it is appropriate to seek to resolve
speculation about features in the Cydonia region by obtaining
images when it is possible to do so."
Information about Viking observations of the Cydonia region and a
listing of those images are available on the World Wide Web at:
http://www.hq.nasa.gov/office/pao/facts/HTML/FS-016-HQ.html
New images of the landing sites and Cydonia region taken by Mars
Global Surveyor will be available on JPL's Mars news site at:
http://www.jpl.nasa.gov/marsnews
and on the Global Surveyor home page at
http://mars.jpl.nasa.gov
These sites will also carry detailed schedules of the imaging
attempts once they have been determined. Images will also be
available on NASA's Planetary Photojournal web site at:
http://photojournal.jpl.nasa.gov
So far in the aerobraking process, Global Surveyor's orbit has
been reduced from an initial 45-hour duration to less than 12
hours. During the aerobraking hiatus, the spacecraft will be
orbiting Mars about once every 11.6 hours, passing about 106
miles (170 kilometers) above the surface at closest approach and
about 11,100 miles (17,864 kilometers) at its farthest distance
from the planet. The pause in aerobraking allows the spacecraft
to achieve a final orbit with lighting conditions that are
optimal for science observations.
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 * SLMR 2.1a * Waddaya mean xhe can't fly?
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