NASA Wednesday announced more details in its plan for its Asteroid
Redirect Mission (ARM), which in the mid-2020s will test a number of new
capabilities needed for future human expeditions to deep space,
including to Mars. NASA also announced it has increased the detection of
near-Earth asteroids by 65 percent since launching its asteroid
initiative three years ago.
For ARM, a robotic spacecraft will capture a boulder from the surface
of a near-Earth asteroid and move it into a stable orbit around the
moon for exploration by astronauts, all in support of advancing the
nation’s journey to Mars.
"The Asteroid Redirect Mission will provide an initial demonstration
of several spaceflight capabilities we will need to send astronauts
deeper into space, and eventually, to Mars," said NASA Associate
Administrator Robert Lightfoot. "The option to retrieve a boulder from
an asteroid will have a direct impact on planning for future human
missions to deep space and begin a new era of spaceflight."
The agency plans to announce the specific asteroid selected for the
mission no earlier than 2019, approximately a year before launching the
robotic spacecraft. Before an asteroid is considered a valid candidate
for the mission, scientists must first determine its characteristics, in
addition to size, such as rotation, shape and precise orbit. NASA has
identified three valid candidates for the mission so far: Itokawa, Bennu
and 2008 EV5. The agency expects to identify one or two additional
candidates each year leading up to the mission.
Following its rendezvous with the target asteroid, the uncrewed ARM
spacecraft will deploy robotic arms to capture a boulder from its
surface. It then will begin a multi-year journey to redirect the boulder
into orbit around the moon.
Throughout its mission, the ARM robotic spacecraft will test a number
of capabilities needed for future human missions, including advanced
Solar Electric Propulsion (SEP), a valuable capability that converts
sunlight to electrical power through solar arrays and then uses the
resulting power to propel charged atoms to move a spacecraft. This
method of propulsion can move massive cargo very efficiently. While
slower than conventional chemical rocket propulsion, SEP-powered
spacecraft require significantly less propellant and fewer launches to
support human exploration missions, which could reduce costs.
Future SEP-powered spacecraft could pre-position cargo or vehicles
for future human missions into deep space, either awaiting crews at Mars
or staged around the moon as a waypoint for expeditions to the Red
Planet.
ARM's SEP-powered robotic spacecraft will test new trajectory and
navigation techniques in deep space, working with the moon's gravity to
place the asteroid in a stable lunar orbit called a distant retrograde
orbit. This is a suitable staging point for astronauts to rendezvous
with a deep space habitat that will carry them to Mars.
Before the piece of the asteroid is moved to lunar orbit, NASA will
use the opportunity to test planetary defense techniques to help
mitigate potential asteroid impact threats in the future. The
experience and knowledge acquired through this operation will help NASA
develop options to move an asteroid off an Earth-impacting course, if
and when that becomes necessary.
In 2005, NASA's Deep Impact comet science mission tested technology
that could assist in changing the course of a near-Earth object using a
direct hit with a spacecraft. The ARM robotic spacecraft opens a new and
second option for planetary defense using a technique called a gravity
tractor. All mass exerts and experiences gravity and, in space, the
gravitational attraction even between masses of modest size can
significantly affect their motion. This means that by rendezvousing with
the asteroid and holding a halo orbit in the appropriate direction, the
ARM robotic spacecraft can slowly pull the asteroid without touching
it. The effectiveness of this maneuver is increased, moreover, if mass
is moved from the asteroid to the spacecraft by the capture of a
boulder.
It will take approximately six years for the ARM robotic spacecraft
to move the asteroid mass into lunar orbit. In the mid-2020s, NASA's
Orion spacecraft will launch on the agency’s Space Launch System rocket,
carrying astronauts on a mission to rendezvous with and explore the
asteroid mass. The current concept for the crewed mission component of
ARM is a two-astronaut, 24-25 day mission.
This crewed mission will further test many capabilities needed to
advance human spaceflight for deep space missions to Mars and elsewhere,
including new sensor technologies and a docking system that will
connect Orion to the robotic spacecraft carrying the asteroid mass.
Astronauts will conduct spacewalks outside Orion to study and collect
samples of the asteroid boulder wearing new spacesuits designed for deep
space missions.
Collecting these samples will help astronauts and mission managers
determine how best to secure and safely return samples from future Mars
missions. And, because asteroids are made of remnants from the formation
of the solar system, the returned samples could provide valuable data
for scientific research or commercial entities interested in asteroid
mining as a future resources.
In 2012, the president's NASA budget included, and Congress
authorized, $20.4 million for an expanded NASA Near-Earth Object (NEO)
Observations Program, increasing the resources for this critical program
from the $4 million per year it had received since the 1990s. The
program was again expanded in fiscal year 2014, with a budget of $40.5
million. NASA is asking Congress for $50 million for this important work
in the 2016 budget.
"Asteroids are a hot topic," said Jim Green, director of NASA
Planetary Science. "Not just because they could pose a threat to Earth,
but also for their scientific value and NASA's planned mission to one as
a stepping stone to Mars."
NASA has identified more than 12,000 NEOs to date, including 96
percent of near-Earth asteroids larger than 0.6 miles (1 kilometer) in
size. NASA has not detected any objects of this size that pose an impact
hazard to Earth in the next 100 years. Smaller asteroids do pass near
Earth, however, and some could pose an impact threat. In 2011, 893
near-Earth asteroids were found. In 2014, that number was increased to
1,472.
In addition to NASA's ongoing work detecting and cataloging
asteroids, the agency has engaged the public in the hunt for these space
rocks through the agency's Asteroid Grand Challenge activities,
including prize competitions. During the recent South by Southwest
Festival in Austin, Texas, the agency announced the release of a
software application based on an algorithm created by a NASA challenge
that has the potential to increase the number of new asteroid
discoveries by amateur astronomers.
