Environmental Engineering Reference
In-Depth Information
example is Dawn, a mission to aid in determining the origins of our universe,
which includes the use of an altimeter to map the surface of Ceres and Vesta,
two of the oldest celestial bodies in our solar system.
More and more, these unmanned missions are being developed as au-
tonomous systems, out of necessity. For example, almost entirely autonomous
decision-making will be necessary because the time lag for radio communi-
cations between a craft and human controllers on earth will be so large that
circumstances at the craft will no longer be relevant when commands arrive
back from the earth. For instance, for a rover on Mars during the months of
mission operations when the earth and Mars are on opposite sides of the sun
in their respective orbits, there would be a round-trip delay of upwards of
40 min (earth) in obtaining responses and guidance from mission control.
Historically, NASA missions have been designed around a single spacecraft
carrying one instrument, or possibly a small number of related instruments.
The spacecraft would send its raw data back to earth to a dedicated ground
control system which had a dedicated staff that controlled the spacecraft and
would trouble-shoot any problems. Many of the new missions are either very
complex, or have long communications delays, or require very fast responses
to mission circumstances. Manual control by humans becomes problematic or
impractical for such missions. Consequently, the onboard software to operate
the missions is increasingly complex, placing increasing demands on software
development technologies.
In anticipation of these missions, NASA has been doing research and devel-
opment into new software technologies for mission operations. Two of these
technologies enable autonomous and autonomic operations. Technology for
autonomy allows missions to operate on their own with little or no directions
from humans based on internal goals. Autonomicity builds on autonomy tech-
nology by giving the mission what is called
self-awareness
. These technologies
will enable missions to go to new planets or distant space environments with-
out constant real-time direction from human controllers.
Recent robotic missions to Mars have required constant inputs and com-
mands from mission control to move the rovers only inches at a time, as a
way to ensure that human controllers would not be too late in learning about
changed conditions or circumstances or too late in returning appropriate di-
rections to the rovers. With 20 min required for one-way communications be-
tween the earth and Mars, it takes a minimum of 40 min for mission control
to receive the most recent video or sensor inputs from a robot and send the
next commands back. Great care is required when moving a robot on Mars
or other distant location, because if it flipped over or got stuck, the mission
could be ended or become severely limited. There often elapsed several hours
between the receipt of new images from Mars and the transmission of move-
ment commands back to the robot. The result of the delays was a great, but
unavoidable, limitation on exploration by the robots.
If these missions could instead operate autonomously, much more explo-
ration could be accomplished, since the rovers, reacting independently and
