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Mars Global Surveyor To Attempt Imaging of 'Face' On Mars, Viking & Pathfinder Landing Sites


MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Contact: Diane Ainsworth

FOR IMMEDIATE RELEASE March 26, 1998

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 1 to 2 kilometers (0.6 to 1.2
miles). 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.

Mars Global Surveyor is part of a sustained program of Mars exploration,
managed by JPL for NASA's Office of Space Science, Washington, DC. Lockheed
Martin Astronautics, Denver, CO, which built and operates the spacecraft, is
JPL's industrial partner in the mission. Malin Space Science Systems, Inc.,
San Diego, CA, built and operates the spacecraft camera. JPL is a division
of the California Institute of Technology, Pasadena, CA.

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