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Viking 1 landed 30 years ago today, on 20 July 1976.
It was the first U.S. landing on Mars and a very
exciting time for Mars exploration. Since that time,
four additional spacecraft have successfully landed
on Mars and conducted their science investigations.
Today, new missions to the martian surface are in the
works, with landings expected in 2008 (Phoenix)
and 2010 (Mars Science Laboratory).
The Viking 1 lander is difficult to see in Mars Global
Surveyor (MGS) Mars Orbiter Camera (MOC) images. The
western Chryse Planitia landing site is often
obscured by dust hazes and occasional storms,
especially during northern winter, which would otherwise be
the best time to look for the lander from orbit
because the sun casts longer shadows in winter.
When the atmosphere is clearest, in portions of
the spring and summer, the sun is higher in the
sky as seen from MGS’s orbit. The spacecraft always passes
over the landing site region around 2 p.m. in
the afternoon. The suite
of pictures shown here describes the best MOC view of
the landing site. These were
previously released
in May 2005, but the MOC team felt that 20 July 2006
is an appropriate time to review this story.
The first figure (left) visually tells how the lander was found.
The initial observations of the location of Viking
1, as originally determined by members of the Viking science team
based on sightlines to various crater rims seen in the lander images
(black lines), did not show the detailed
features we knew from the lander pictures (middle) to be in the area. Using geodetic
measurements, the late Merton Davies of the RAND Corporation, a MGS MOC
Co-Investigator, suggested that we should image areas to the east
and north of where Viking 1 was thought to be. Timothy J. Parker of the
Jet Propulsion Laboratory (Pasadena, California),
using sightlines to crater rims seen in the lander images (white lines),
deduced a location very close to that suggested by Davies. The MOC image of
that location, acquired in 2003, showed additional near-field features (rocks
associated with a nearby crater) that closely matched the Viking 1 images (center and
right frame, where B denotes "Volkswagen Rock"). The inset
(upper right) is an enlargement that shows the location of the Viking 1 lander.
The MOC image of the Viking 1 lander site (right) was acquired during
a test of the MGS Pitch and Roll Observation (PROTO) technique
conducted on 11 May 2003. (Following initial tests, the “c”
part of “cPROTO” was begun by adding compensation for the motion
of the planet to the technique). The PROTO or cPROTO approach
allows MOC to obtain images with better than its nominal
1.5 meters (5 ft) per pixel resolution. The image shown here (right)
was map projected at 50 centimeters (~20 inches) per pixel.
The full 11 May 2003 image can be viewed in the
MOC Gallery, it is image
R05-00966.
In addition to celebrating the 30th anniversary of the first U.S. robotic Mars
landing, we note that 20 July is also the 37th anniversary of the first human
landing on the Moon, on 20 July 1969. There are two dates that are most sacred
in the space business (three, if you count the 4 October 1957 launch of Sputnik 1).
The other date is 12 April, which celebrates the 1961 launch of the first human
in space, and the 1981 launch of the first space shuttle orbiter.
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