[meteorite-list] Lunar Lost & Found: The Search for Old Spacecraft

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Mar 27 15:53:34 2006
Message-ID: <200603271849.k2RInc520093_at_zagami.jpl.nasa.gov>

http://space.com/scienceastronomy/060327_mystery_monday.html

Lunar Lost & Found: The Search for Old Spacecraft
By Leonard David
space.com
27 March 2006

One look at Earth's Moon is all it takes. It
has been mussed up by scads of incoming celestial objects that produced
lots of craters.

But our Moon has also been on the receiving end of artificial impacts
over the last few decades. Moon probes and leftover rocket stages have
contributed to the crater population - albeit too small to see from our
planet. Robotic lunar landers from the United States and the former
Soviet Union dot the Moon too.

Add in hardware castaways from human adventurers who made their way to
the Moon from 1969 through 1972 as part of NASA's Apollo program,
and you've got a lot of junk on the Moon.

Pinpointing old spacecraft and artificial impact craters is not only a
curatorial courtesy, but also can generate important science.

That's the report from Philip Stooke, an associate professor within the
department of geography at the University of Western Ontario in London,
Ontario, Canada. Stooke described his lunar detective story in a paper
released at the 37th Lunar and Planetary Science Conference (LPSC), held
March 13-17 in Houston.

Precise locales

Starting in the 1960s, the "space race" between the Soviet Union and the
United States was on full-speed. And the Moon was a place to demonstrate
one-upmanship.

NASA's Ranger, Surveyor and Lunar Orbiter spacecraft set the stage for
the piloted Apollo landers. For the Soviet Union, it was the robotic
Luna-series that plowed into the desolate landscape, as well as
soft-landed, roved around, and even shot samples back to Earth across
cis-lunar space.

NASA's Lunar Reconnaissance Orbiter (LRO), to be sent moonward in 2008,
will be able to spot some of this Space Age flotsam. LRO's camera system
has enough resolving power for the task.

But there is uncertainty in targeting LRO's imaging hardware to scout
out the precise locales of all that gear that has plopped down on the
aged Moon.

Tighter coordinates

"I've devoted almost all my time in the last five years to my Atlas of
Lunar Exploration, which is in the final stages now," Stooke told
SPACE.com. Part of his research is focused on tracking down the
whereabouts of decades-old mooncraft and identifying craters caused by
human-made objects. One might think the locations would be well-charted.

But spacecraft were "lost" because they were never found initially,
Stooke said. There are those craft that came to rest on the lunar
surface, with their positions known to within about 6 or 12 miles (10 or
20 kilometers), figured out by tracking a spacecraft's signals during
descent.

However, if future astronauts want to do a pinpoint landing near a piece
of equipment, or wheel over to examine an old lander, they'll need much
tighter coordinates.

In some instances, the imagery taken by landed spacecraft from the
surface is a big help.

"That is also important for establishing the geological context of
surface observations. So whenever something lands...people try to locate
it precisely," Stooke pointed out. "The well established method for
doing this is by comparing horizon relief features - hills or crater
rims - on panoramas with the same features on orbital images. If you can
match them you can locate the lander precisely."

Surveying for Surveyor

This method was basically invented, Stooke explained, by Ewen Whitaker
of the Lunar and Planetary Laboratory at the University of Arizona in
Tucson. He used it with Surveyor 1 and subsequent Surveyor craft that
set down on the Moon between 1966 and 1968.

"But it does depend on being able to match features," Stooke added. "In
very flat areas there may be nothing to match." Surveyor 5 is such a case.

"If you have only low resolution orbital images you may not be able to
make a match either - that applies partly to Surveyor 5 as well, but
especially to all the Soviet landers," Stooke said. "No Soviet
spacecraft has ever been located precisely in this way because they
didn't land in areas of good orbital photography."

Even with photos taken from the Moon's surface, questions can remain.
For example, is the Soviet Luna 9 landing area on the Moon back in 1966
in mare or highland terrain? "The argument has continued since it landed,"
Stooke said.

Part of the interest is purely historical.

"It would be nice to know where Luna 9 is, the first successful lander,"
Stooke said. "We may want to set up a register of historic sites, not to
be disturbed by future missions or hardware impacts. To do that we need
accurate locations."

Search for Lunokhod

One nifty exercise that's now being considered is attempting to bounce a
laser beam off a lost-on-the-Moon Soviet rover: Lunokhod 1.
That eight-wheel robotic lunar buggy is outfitted with laser
"retroreflectors" and rolled about within the Moon's Sea of Rains for
nearly a year after landing in November 1970.

Lunokhod 1 may still have value as a laser ranging target. That's if it
can be located precisely.

The Soviet machinery is sitting silent at the most northerly of all
landings on the Moon to date, "and would be a vital part of
understanding the Moon's exact rotation for geophysical purposes,"
Stooke said.

However, the robot's position is uncertain by at least 3 miles (5
kilometers), and stabs at getting laser returns all failed since early
in the Lunokhod 1's mission.

"We don't know if it is still clean or oriented suitably...if not
there's no hope. But if it is, we still need a good position," Stooke said.

Tantalizing target

"The recovery of Lunokhod 1 is on my wish list," said Jim Williams of
the Jet Propulsion Laboratory (JPL) in Pasadena, California. He and
fellow investigators are part of a Lunar Laser Ranging (LLR) data
analysis group at JPL.

Williams told SPACE.com that there are four laser retroreflector arrays
on the Moon that get ranged: the Apollo 11, 14, and 15 sites plus the
other Russian moonbuggy, Lunokhod 2. "As a result of the ranging, we know
those positions to better than one-meter accuracy" or roughly three feet, he said.

The arrays of 14 prisms on Lunokhods 1 and 2 were built by the
French. The Lunokhod 2 retroreflector has been ranged, so the design
works, Williams noted. The Lunokhod would rove during daylight, but was
parked at night so that the array was oriented properly for
Earth-to-Moon laser ranging.

Lunokhod 1 is a tantalizing target, Williams said.

"A few laser observations were reported early in the mobile Lunokhod 1's
journey and later after it stopped moving, but those observations have
never been publicly distributed or processed with a data analysis
program of modern accuracy," Williams explained. "It is unclear whether
the effectiveness of the Lunokhod 1 array has been compromised or
whether position uncertainty and weak signal conspired to prevent its
acquisition by standard ranging stations...but a modern search is in order."

Apache Point Observatory

The sole U.S. LLR station in the early 1970s tried to range Lunokhod 1,
Williams said, but did not find it.

"The task is more difficult than it sounds," Williams said. "The return
signal should be very weak and only a limited spread of distance and
angle could be searched...for a sequence of shots. The position may have
been too poor or the Lunokhod 1 retroreflector may be obscured somehow."

There is a new LLR station now undergoing checkout at Apache Point
Observatory in New Mexico.

"Once the new station is operational and returning data, then a Lunokhod
1 search will be practical," Williams said. This new equipment at the
facility will be a good instrument for the search, he added, but will
still require a major effort.

Location uncertainties

Meanwhile, Stooke is on the lunar lookout trail.

Early Apollo Moon landing craft and the moonwalkers themselves scuffed
up areas of the lunar surface. These disturbances are visible in orbital
imagery taken by later Apollo missions.

A number of discarded Apollo rocket stages and lunar module ascent
stages were tracked to narrow the search area. So those which fell in
areas subsequently imaged were identified fairly easily, Stooke reported
in his LPSC paper.

Ranger 6's impact area may now have been found
in Clementine images taken by that U.S. Defense Department Moon-orbiting
spacecraft in 1994, Stooke stated. On the other hand, many impact
craters made by orbiters at the end of their missions - or by failed
landers - will be difficult to find because of location uncertainties.

NASA Lunar Orbiter impact sites, for example, are uncertain by hundreds
of kilometers and would be very difficult to distinguish from natural
fresh impacts.

On the other hand, craters formed by camera-carrying Ranger probes were
found easily because images taken during their plunge toward the lunar
terrain allowed impact sites to be predicted. Two of the three
successful kamikaze-like Ranger missions imaged their impact points for
comparison with later images.

Hiten, a Japanese lunar orbiter, should be located easily using
Earth-based tracking data and observation of the impact, Stooke said.

Protection of sites

In his lunar work, Stooke noted that several challenges remain.

Can the site of Russia's Luna 2 impact be located? If it is, will visual
observers be vindicated after years of doubt? Can Luna 9 or Surveyor 5
be located at last? Can the craters caused by the hits of spent rocket
stages from the Apollo 15, 16 and 17 missions be found?

"The scientific value of this work includes placing lander data in
better context, refining seismic results from Apollo [rocket stage]
impacts, or planning future visits to old sites for study of old
hardware, as Apollo 12 did for Surveyor 3,
Stooke says. "If in the future it is decided to confer special
designations or protection these sites, finding them is essential."
Received on Mon 27 Mar 2006 01:49:38 PM PST