March 25, 2015
NASA Announces Next Steps on Journey to Mars: Progress on Asteroid Initiative
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
