[meteorite-list] Space Shuttle Laser Test Could Help Guide Asteroid Missions

[Ron Baalke]

http://www.spaceflightnow.com/shuttle/sts134/110530storrm/

Space shuttle laser test could help guide asteroid missions
BY STEPHEN CLARK 
SPACEFLIGHT NOW
May 30, 2011

Astronauts piloted the shuttle Endeavour on a unique course back toward
the International Space Station Monday, testing a next-generation
laser-based navigation sensor in hopes of verifying it can help guide
future voyages to the space station, distant asteroids and Mars.
 
After undocking from the orbiting lab at 11:55 p.m. EDT Sunday, pilot
Greg Johnson flew Endeavour on a 360-degree flyaround of the station,
then sent the shuttle on a looping trajectory more than 5 miles above
and behind the station.

A series of thruster firings next propelled the ship back toward the
outpost, approaching from behind and below as a laser system fired
pulses 30 times per second to compute range and bearing data.

The shuttle halted its approach 950 feet below the station, then burned
its jets again to exit the lab's vicinity as Endeavour's crew began
preparations for their return to Earth early Wednesday.

"Over the past year and a half, it's been a pleasure to work with the
hardware and software developers for STORRM," radioed Drew Feustel, the
astronaut charged with monitoring the experiment.

Endeavour commander Mark Kelly and pilot Greg Johnson oversaw the jet
firings from the shuttle's flight deck.

"Everybody did a great job in getting the components ready for the
flight, and we look forward to continued developments of this hardware
and software and hope that it contributes to the development of future
vehicles," Feustel said after the STORRM demo was complete. "It's been
an honor and a privilege for the crew of Endeavour."

Endeavour faded from view in the space station's cameras around 5 a.m. EDT.

"The word I'd use to sum it up is pretty much flawless," said Gary
Horlacher, the lead flight director for Endeavour's mission.

The second approach, called a re-rendezvous in NASA parlance, capped
Endeavour's 12-day stay at the space station, which added a $2 billion
particle physics experiment named the Alpha Magnetic Spectrometer,
delivered a platform full of spare parts and helped maintain the lab's
finicky oxygen generation and carbon dioxide scrubbing systems.

Called STORRM, the experiment's objective was to try out a high-tech
laser navigation system that NASA could use on future voyages to the
space station and beyond. STORRM stands for Sensor Test for Orion
Relative Navigation Risk Mitigation.

NASA tapped Endeavour to take the sensor on a test run. The shuttle flew
back to the space station on a unique trajectory designed to mimic how
an Orion spacecraft would approach the complex.

"People don't understand there are several different ways to approach
the station and rendezvous," said John Karas, vice president and general
manager of human spaceflight at Lockheed Martin Corp., Orion's prime
contractor. "We're using the set of trajectories specifically designed
if we were at the moon or asteroids. We're going to be flying that exact
trajectory with those sensors. It's not just the sensors we're testing."
 
The Orion capsule, also known as the multi-purpose crew vehicle, could
use the laser sensor to guide itself to destinations across the solar
system, ranging from the space station 200 miles from Earth to asteroids
millions of miles away.

The Orion spacecraft was part of the Constellation moon program
terminated by the White House last year. But lawmakers passed a NASA
authorization act directing the agency to start development of an
interplanetary spacecraft and to base the design on Orion, in which NASA
has invested $5 billion since 2006.

NASA officially announced May 24 the new MPCV deep space capsule will be
based on the Orion design.

Heather Hinkel, STORRM's principal investigator, said the laser sensor
worked as expected throughout Endeavour's undocking and second approach.
A high-definition docking camera, a secondary sensor in the STORRM demo,
was sidelined by a faulty data recorder.

Both sensors worked perfectly during Endeavour's docking with the space
station May 18, and engineers captured the lion's share of the data they
needed from the docking camera, Hinkel said.

Officials said they will continue analyzing data from the STORRM
experiment, and workers expect to remove the sensors from the shuttle's
payload bay about a week after landing. After some initial testing at
the Kennedy Space Center, the laser and docking camera will be shipped
to a Lockheed Martin docking simulation facility in Denver.

Embedded in the bedrock of the Front Range of the Rocky Mountains, the
new facility will host ground demonstrations of STORRM with a full-scale
model of the space station docking system and against a backdrop
resembling the surface of a rocky asteroid.

Engineers will mount the laser emitter on a mobile platform that can
move in and out, side to side and up and down to simulate a spacecraft
docking or rendezvous with an asteroid.

On one end of the massive facility, a replica of the front of the space
station stands ready for testing. A mold of an asteroid surface sits on
the other side of the simulator.

"We're just showing the versatility of the technology we're developing,"
Karas said. "We're testing in the environment it's going to be in when
we go explore."

Although the space shuttle's STORRM test used strategically-positioned
mirrors, the system could track targets without reflectors. STORRM's
data from the Endeavour's docking showed it could generate a
three-dimensional representation of the space station even without the
help of markings and reflectors, Hinkel said.

"Our sensor is good enough to pick out details if the spacecraft is
spinning or if it doesn't have any feedback to it," Karas said in an
interview. "This sensor can actually track it and pick out reference
points. So that actually works well for asteroids with formation-flying.
This sensor is really one size fits all. It can do a whole bunch of
missions."

Scientists from the robotic OSIRIS-REx asteroid explorer selected by
NASA last week already contacted STORRM engineers about using a similar
laser sensor when it launches to an asteroid in 2016, Hinkel said.
OSIRIS-REx will study a nearby asteroid and return samples to Earth.
It's a potential stepping stone to manned expeditions.

During Monday's test, STORRM's laser fired 30 pulses per second at
reflectors positioned on the space station, precisely measuring the time
it took the signals to bounce back to the sensor to create a 3D map of
the complex.

The laser pulses are invisible to the human eye, making the vision
navigation sensor an ideal candidate for use on manned voyages.

"You could use this for imaging or hazard avoidance for performing
landings. There's very broad application for this technology," Hinkel
said. "This has very valid application for any space vehicle trying to
perform the function of rendezvous and docking either with another
vehicle or trying to land on a surface."
 
Hinkel said early looks at the data show the laser sensor acquired the
space station beyond its design goal of 5 kilometers during docking May
18 and in Monday morning's test. STORRM collected nearly 600 gigabytes
of data throughout the mission, according to Hinkel.

The laser instrument and docking camera were built by Ball Aerospace &
Technologies Corp. in Boulder, Colo.

STORRM's data was recorded by an on-board computer and didn't play an
active role in Endeavour's re-rendezvous. The shuttle used its own laser
rangefinder and radar systems throughout Monday's activities.

"We have a lot of good data analysis days coming ahead of us once we get
the boxes off the vehicle in Florida," Hinkel said. "And the team will
start working together to analyze that data."

Engineers hope the STORRM test proves the sensors are nearly ready to be
operational, but there's still work to be done developing software
algorithms to tie the laser and docking camera into Orion's guidance
computer. The ultimate objective is to use the system for automatic
dockings.

Russian Soyuz spacecraft and Progress cargo freighters use a rendezvous
radar for automated dockings at the space station, and Europe's
Automated Transfer Vehicle uses a vision-based laser system similar to
STORRM for its autopilot approach.

"All spaceflight hardware gets designed on the ground and tested to the
best we can, but you can't really simulate the entire space environment
here," Horlacher said before Endeavour's mission. "Until you get into
orbit, there's only so far we can take it."