Customer experiences -NASA JPL uses Working Model for Asteroid Mission with Japanese Space Institute-
NASA Jet Propulsion Laboratory (JPL) is using motion simulation software from
Working Model, Inc., to develop, test, and integrate a robotic rover as part of
the first asteroid mission ever with Japan?s Institute of Space and
Astronautical Science (ISAS).
The asteroid?s low gravity field poses specific challenges for this
mission. JPL is using motion simulation software to experiment with the
rover?s movements during the initial design phase of this sophisticated
Known as MUSES-C, the mission will be launched on a Japanese M-5 spacecraft in
January 2002 from Kagoshima Space Center, Japan. It is scheduled for a touchdown
on the asteroid Nereus in September 2003, and a return to Earth in 2006. The
goal of the mission is to collect samples from the asteroid?s surface and
bring them back to Earth for in-depth study.
Nereus, a small, near-Earth asteroid roughly one mile in diameter, was
discovered in 1982. At its closest point to the Sun, its orbit takes it just
inside the Earth?s orbit. Scientists want to study Nereus because its
composition, rotations, and length of days and nights remain a mystery.
"With a successful mission, we will have the first direct insight into
the composition of the materials that helped form the rocky inner planets more
than four billion years ago," says Dr. Jurgen Rahe, director of Solar
System Exploration at NASA headquarters in Washington, DC. NASA and ISAS will
cooperate on several aspects of the mission, including mission support and
NASA JPL will design and build the rover for an independent study of the
asteroid surface. JPL, a division of the California Institute of Technology and
a NASA field center, is the lead U.S. center for robotic exploration of the
JPL creates spacecraft, including robotic arms and rovers, that have visited
all known planets except Pluto. In addition to its work for NASA, JPL conducts
tasks for a variety of other federal agencies.
The rover will be the smallest ever flown in space. Its physical dimensions
are 6 inches by 6 inches by 4 inches, with a mass of less than 500 grams (2.2
pounds). The four-wheeled rover will carry two scientific instruments: a visible
spectrum imaging camera and a near-infrared point spectrometer. The camera will
record the asteroid?s physical form through photographs while the spectrometer
will study its surface properties.
The rover will "ride" as an attachment to the ISAS spacecraft
during flight and then will "hop off" just prior to the asteroid
sampling event on Nereus. Solar energy will power the rover?s movements while
the ISAS spacecraft will assist with communications for beaming rover data to
The mission will complete another NASA JPL engineering exercise. "We
hope the mission will send back valuable data from Nereus that will be science
useful for both engineers and scientists on Earth," comments Dr. Eric T.
Baumgartner, Ph.D., of JPL?s Science and Technology Development Section in the
Mechanical Engineering Division. He is involved in efforts related to the design
and development of the rover.
Space missions present considerable challenges because of the many unfamiliar or
unknown factors involved. In this case, the asteroid?s extremely low gravity
field will greatly affect the rover?s mission. "While Mars has one third
of the Earth?s gravity, and the moon one eighth, Nereus has 0.00002, which
makes rover movements highly unpredictable," Dr. Baumgartner remarks.
This significant factor has particular ramifications for the rover, whose
sole purpose is to explore the asteroid?s surface. Without a reasonable amount
of gravity, the rover?s wheels would not have sufficient traction, and could
possibly fly right off the asteroid.
Rover Dynamics with Working Model
Dr. Baumgartner has been using Working Model® 2D and Working
Model® 3D, software from Working Model, Inc., to visualize the
mechanical performance of the rover on the asteroid?s surface. Working Model
is a motion simulation software program that enables mechanical engineers to
perform design studies without building physical prototypes.
Dr. Baumgartner first used Working Model 2D version 4.0 to analyze the
rover?s dynamics. As a result, he clearly saw that the asteroid?s miniscule
level of gravity sufficiently provided traction for the wheels of the rover.
"Working Model 2D simply helped us to get the rover?s wheels
turning," he notes.
According to Dr. Baumgartner, using Working Model 2D helped determine what
the rover can do. This naturally led to investigating ways to command the
For this next stage, Dr. Baumgartner will be using Working Model 3D version
2.0 for developing navigation strategies for the rover. "It?s not only
important that we experiment in a 2D environment, but also in a 3D environment
to better understand the full range of the rover?s movements," he says.
Directing the rover?s movements ? both in simulation and on Nereus ?
will ensure that the rover can conduct a thorough study of the asteroid surface.
"We expect Working Model 3D to help us handle the unpredictable dynamics by
allowing accurate testing of the rover?s movements within a simulation
environment," he notes.
While take-off is a few years away, Dr. Baumgartner appreciates the fact that
Working Model helps him quickly visualize the mobility of the rover. Meanwhile,
Working Model 2D and 3D will continue to serve as tools in making the best
asteroid-capable rover to date. "With a successful mission, JPL will prove
that placing a rover on an asteroid is not only possible, but also
scientifically worthwhile," concludes Dr. Baumgartner.