For the first time since the 1970s, a NASA
spacecraft will get clear pictures of Apollo relics on the Moon.
by Patrick L Barry and Dr Tony
Inside the lunar lander
Challenger, a radio loudspeaker crackled.
Houston: "We've got you
on television now. We have a good picture."
Gene Cernan, Apollo 17 commander:
"Glad to see old Rover's still working."
"Rover," the moon
buggy, sat outside with no one in the driver's seat, its side-mounted
TV camera fixed on Challenger. Back in Houston and around the world,
millions watched. The date was Dec. 19, 1972, and history was about
to be made.
Challenger split in two. The base of the ship, the part with the
landing pads, stayed put. The top, the lunar module with Cernan
and Jack Schmitt inside, blasted off in a spray of gold foil. It
rose, turned, and headed off to rendezvous with the orbiter America,
the craft that would take them home again.
17 moon buggy, circled, waits to film the departure of
its mothership, Challenger.
Those were the last men on the
Moon. After they were gone, the camera panned back and forth. There
was no one there, nothing, only the rover, the lander and some equipment
scattered around the dusty floor of the Taurus-Littrow valley. Eventually,
Rover's battery died and the TV transmissions stopped.
That was our last good look
at an Apollo landing site.
Many people find this
surprising, even disconcerting. Conspiracy theorists have long insisted
that NASA never went to the Moon. It was all a hoax, they say, a
way to win the Space Race by trickery. The fact that Apollo landing
sites have not been photographed in detail since the early 1970s
encourages their claims.
And why haven't we photographed
them? There are six landing sites scattered across the Moon. They
always face Earth, always in plain view. Surely the Hubble Space
Telescope could photograph the rovers and other things astronauts
left behind. Right?
Wrong. Not even Hubble can do
it. The Moon is 384,400 km away. At that distance, the smallest
things Hubble can distinguish are about 60 meters wide. The biggest
piece of left-behind Apollo equipment is only 9 meters across and
thus smaller than a single pixel in a Hubble image.
Better pictures are coming.
In 2008 NASA's Lunar Reconnaissance Orbiter will carry a powerful
modern camera into low orbit over the Moon's surface. Its primary
mission is not to photograph old Apollo landing sites, but it will
photograph them, many times, providing the first recognizable images
of Apollo relics since 1972.
The spacecraft's high-resolution
camera, called "LROC," short for Lunar Reconnaissance
Orbiter Camera, has a resolution of about half a meter. That means
that a half-meter square on the Moon's surface would fill a single
pixel in its digital images.
Apollo moon buggies are about
2 meters wide and 3 meters long. So in the LROC images, those abandoned
vehicles will fill about 4 by 6 pixels.
What does a half-meter resolution
picture look like? This image of an airport on Earth has the same
resolution as an LROC image. Moon buggy-sized objects (automobiles
and luggage carts) are clear:
Image courtesy MIT
Digital Orthophoto Project
of half-meter resolution overhead photography, the same
resolution that LROC images will be. This photo of an
airport shows airplanes of various sizes as well as many
car-sized service vehicles. Notice how shadows help the
objects to stand out from the background. The LROC high-res
images will also be grayscale, but will be less grainy
than the example above thanks to its digital imaging technology
I would say the rovers will
look angular and distinct," says Mark Robinson, research associate
professor at Northwestern University in Evanston, Illinois, and
Principal Investigator for LROC. "We might see some shading
differences on top from seats, depending on the sun angle. Even
the rovers' tracks might be detectable in some instances."
Even more recognizable
will be the discarded lander platforms. Their main bodies are 4
meters on a side, and so will fill an 8 by 8 pixel square in the
LROC images. The four legs jutting out from the platforms' four
corners span a diameter of 9 meters. So, from landing pad to landing
pad, the landers will occupy about 18 pixels in LROC images, more
than enough to trace their distinctive shapes. Shadows
help, too. Long black shadows cast across gray lunar terrain will
reveal the shape of what cast them: the rovers and landers. "During
the course of its year-long mission, LROC will image each landing
site several times with the sunlight at different angles each time,"
says Robinson. Comparing the different shadows produced would allow
for a more accurate analysis of the shape of the objects.
Enough nostalgia. LROC's
main mission is about the future. According to NASA's Vision for
Space Exploration, astronauts are returning to the Moon no later
than 2020. Lunar Reconnaissance Orbiter is a scout. It will sample
the Moon's radiation environment, search for patches of frozen water,
make laser maps of lunar terrain and, using LROC, photograph the
Moon's entire surface. By the time astronauts return, they'll know
the best places to land and much of what awaits them.
Two high-priority targets for
LROC are the Moon's poles.
Pat Rawlings' concept of a polar moonbase
"We're particularly interested
in the poles as a potential location for a moon base," Robinson
explains. "There are some cratered regions near the poles that
are in shadow year-round. These places might be cold enough to harbor
permanent deposits of water ice. And nearby are high regions that
are sunlit all year. With constant sunlight for warmth and solar
power, and a potential source of water nearby, these high regions
would make an ideal location for a base." Data from LROC will
help pinpoint the best ridge or plateau for setting up a lunar home.
Once a moonbase is established,
what's the danger of it being hit by a big meteorite? LROC will
help answer that question.
"We can compare LROC images
of the Apollo landing sites with Apollo-era photos," says Robinson.
The presence or absence of fresh craters will tell researchers something
about the frequency of meteor strikes.
LROC will also be hunting for
ancient hardened lava tubes. These are cave-like places, hinted
at in some Apollo images, where astronauts could take shelter in
case of an unexpected solar storm. A global map of these natural
storm shelters will help astronauts plan their explorations.
No one knows what else LROC
might find. The Moon has never been surveyed in such detail before.
Surely new things await; old abandoned spaceships are just the beginning.