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UPDATE #72 - June 8, 1998

PART 1: Upcoming missions in our background sectio
PART 2: New student work
PART 3: Mars Global Surveyor mission status
PART 4: Subscribing & Unsubscribing: How to do it


We're in the process of adding new material about upcoming Mars missions to
our Mars Team Online Background section. Have you heard about the probe that
will penetrate the Martian surface to a depth of two meters at an impact
velocity of 200 meters per second, and still work afterwards? How about the
the lander to be launched next year that will include a microphone as part
of its payload? You can find all kinds of info about these Mars missions and
Mars in general at:


In the Mars Team Online Student Gallery, students exhibit their creative
side while learning about Mars. We've just posted new Mars drawings by Antoni
Parra's 11-year-old students. You can find them at:

Also, check out that link for new student work about the retrograde orbit of
Mars, available in both Spanish and English!


[Editor's note: This flight status report was prepared by the 
Office of the Flight Operations Manager, Mars Surveyor 
Operations Project, Jet Propulsion Laboratory.]

May 1, 1998

This week, the Mars Global Surveyor flight team closed out a 
successful month of dedicated science operations. For over sixty 
consecutive orbits starting in early April and ending on Tuesday, the 
spacecraft's scientific instruments collected data near the low point of 
its 11.6-hour orbit. Every day of that month, Surveyor transmitted nearly 
25 megabytes of data back to Earth. 

Much of the publicity generated by April's science collection 
activities focused on targeted observations of several selected sites on 
the Martian surface. Because explicit targeting is not part of the 
Surveyor spacecraft's inherent abilities, these operations involved a 
substantial collaborative effort between Dr. Michael Malin's camera team, 
Dr. David Smith's laser altimeter team that assisted with Mars map 
corrections, and project engineering elements such as mission planning, 
spacecraft systems, and navigation.

Major imaging highlights included three photographs of the Cydonia 
region in the northern hemisphere. This area is home to a one-mile (1.5-
km) wide object known popularly as the "face on Mars." One of the three 
Cydonia images shows the so-called face at 14.1-feet (4.3 meters) per 
pixel, a resolution about 10 times better than the best Viking Orbiter 
image from 1976. 

In addition to the Cydonia images, Surveyor's camera also obtained 
two photographs of the Viking 1 landing site in Chryse Planitia, and one 
image of the Mars Pathfinder landing site in the Ares Valles region. Some 
of the objects visible in the Pathfinder image include major landmarks 
photographed on July 4th, 1997, including the famous "twin peaks" and "big 
crater." However, the lander and rover are not discernible in part 
because at the imaging range of about 497 miles (800 km), their size in 
the photograph is less than one pixel.

Despite this fact, the resolution of the current image still 
exceeds the best photograph of Ares Valles taken during the Viking 
Orbiter mission over twenty years ago. During mapping operations next 
year, the camera may have an opportunity to image the Pathfinder landing 
site again at ranges as low as 235 miles (378 km). In those images, small 
objects such as the lander and parachute may be visible.

The Viking 2 lander site at Utopia Planitia was also targeted by 
the camera for observation. Unfortunately, clouds obscured the site 
during each one of the three attempts. Similar to the situation with the 
Pathfinder site, further attempts at imaging the Viking 2 site may occur 
next year during mapping operations.

Other experiments on the spacecraft have also been busy acquiring 
data. Besides the camera, the laser altimeter, magnetometer, thermal 
emission spectrometer, and radio science investigation teams have also 
collected data since the beginning of April. These measurements include 
northern hemisphere topography by the laser, local and global magnetic 
properties by the magnetometer, atmosphere and mineralogy studies by the 
spectrometer, and atmosphere and gravity field experiments by the radio 
science team.

Of particular interest,  Dr. David Smith's laser altimeter team has 
been gathering data about the Martian north polar ice caps. On every 
orbit, the laser measures the cap's topography in order to calculate its 
thickness. In June, the ice cap's thickness will reach a maximum during 
the height of the northern winter season. Thickness measurements from 
April compared to those that will be taken in June will contribute toward 
a greater understanding of the Martian cap formation.

Although extremely successful, the flight team temporarily 
suspended science operations on Tuesday in preparation for a month-long 
event called solar conjunction. Starting this weekend, communications 
with the spacecraft will degrade as Mars begins to pass behind the Sun's 
corona as viewed from the Earth. As a consequence, the radio signals sent 
to and from Surveyor will experience a noise effect from solar 
electromagnetic interference. During the middle of the month, the Sun 
will directly eclipse the red planet and physically block radio 
communications with the spacecraft.

Solar conjunction will end in late May as Mars moves out from 
behind the Sun. At that time, the flight team will re-establish 
commanding capability and resume science operations. Data collection will 
then continue until the restart of aerobraking on September 11th. The goal 
of this next phase of aerobraking will be to lower the current, highly 
elliptical, 11.6-hour orbit to a low, circular, two-hour mapping orbit by 
April 1999.


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