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Following the loss of Mars Polar Lander in December 1999, the
MOC team began a 2-month intensive effort to acquire 1.5 meters
per pixel (~ 5 feet per pixel) images of the landing ellipse, in
hopes of spotting the lander and, perhaps, to provide additional
insight as to its fate. Those search efforts were described in
two previous Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC)
releases:
Mars Polar Lander: The Search Continues — 24 January 2000
Mars Polar Lander: The Search Begins — 21 December 1999.
In addition, a later year 2000 release included the full MOC image
mosaic of the site obtained during the search:
South Polar Terrain in “3-D” — 16 October 2000.
Based upon the configuration of Mars Exploration
Rover—Spirit and
Opportunity—lander
hardware observed from orbit by MOC in early 2004,
we revisited the December 1999/January 2000 images of the Mars Polar Lander
site. Earlier this year, we identified a location in images
acquired in January 2000 that included features reminiscent of
those that might be expected to exist at the location where the
Mars Polar Lander reached the surface.
Specifically, we identified a bright feature that resembled a
parachute, and a dark area with a small, light-toned central spot
that could be the location of the lander amid a dust-deflated
area cleared by the lander’s descent engines. This finding, along
with a definitive image of the Viking 2 lander, was
detailed in:
MGS Finds Viking Lander 2 and Mars Polar Lander (Maybe) — 5 May 2005.
At the time of this identification in early 2005, the Mars Polar Lander
landing ellipse was covered by seasonal carbon dioxide frost. As the
frost began to sublime away and spring gave way to summer, we attempted
to acquire an image of the candidate Mars Polar Lander site at
a spatial resolution that is higher than we were able to achieve
during the initial search in December 1999/January 2000. To obtain
an image with an effective spatial resolution better than 1 meter
per pixel, we used the
cPROTO (compensated Pitch and ROll Targeted Observation)
technique described and illustrated last year in:
cPROTO Views of Spirit’s Rover Tracks and Athabasca Vallis Flood Features — 27 September 2004.
Hitting a specific target with the cPROTO technique is challenging,
and often it takes 3–4 attempts before we hit. For the candidate Mars
Polar Lander location, we made 6 attempts. The first was in April 2005,
when the surface was still covered with frost—that image was saturated
white because of the frost. The next attempts were made after the frost
had sublimed away—these were made in July, August, and September 2005.
We finally hit the candidate lander location on 27 September 2005.
The figure above compares the features extracted from the earlier,
January 2000, image with the same location seen in the new,
September 2005, image. The two pictures were taken under nearly
identical illumination and atmospheric conditions, almost
exactly 3 Mars years apart.
The feature identified as a candidate for
Mars Polar Lander’s parachute is found
be the illuminated slope of a small hill. The hill is part of a
group of similar hills in the area. The dark feature that was
identified as possible rocket blast zone
has faded (which would be expected owing to dust deposited by dust storms),
but, more importantly, the spot interpreted to be the lander has disappeared.
In reality, this spot is a pixel whose value differed from its neighbors
in the first image owing to a bigger than average contribution of noise.
Close inspection of the January 2000 image (bottom left) shows many
small bright and dark blurry spots that do not show up in the
September 2005 image (bottom right).
There are even smaller, blurry spots in the second image, they
are also noise. The
fact that these pixels do not coincide is excellent evidence that
they are not real features on the surface of Mars.
We conclude that our interpretation of these features
was in error. This is NOT the location of the Mars Polar
Lander. Because the landing uncertainty ellipse is so much
larger than our images, and we do not have another candidate to
which to target additional cPROTOs, we cannot continue to hunt
for the lander. Finding it now falls to the High Resolution
Imaging Science Experiment
(HiRISE)
presently en route to Mars
on-board the Mars Reconnaissance Orbiter (MRO) spacecraft.
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