Although the "family" model has its benefits, it
also has some drawbacks.
While the "family" model increases the quality of
the surface coverage
and facilitates the astronauts' control over the
LMRs, it also limits the quantity of surface that
can be
covered. However, given that the duration of the
mission will be 402
days, such limitations are not too significant.
Far more serious disadvantages arise from the
dependency of the small LMRs on the medium LMR, and
the medium LMR on the base computer system and the
astronauts. If an individual small LMR were to
fail, then
the "family" could continue functioning. If a
medium sized
LMR were to fail, however, then the "family" as a
whole
would be incapable of operating. If something were to
happen to the base computer, or to the astronauts,
then
the entire mission could potentially fail.
Certain measures must be taken to account for these
possibilities. The solution to this problem comes
out of
the design of a capable decision making system for
each
of the LMRs.
Small-sized LMRs
The small LMRs are the most dependent autonomous
devices in
the mission. The following situations are possible
problems that could
arise, and they must be considered and addressed by
the decision
making system.
|
Communication with the medium LMR breaks down:
The small LMR must test for communication with other
small LMRs.
There is no communication with the other small LMRs:
The small LMR may be out of range. It must travel
towards the last known position of the nearest
medium or
small LMR and try again.
There is still no communication with other LMRs:
The small LMR probably has a damaged antenna. It must
return to the base. The small LMR will have sufficient
navigational skills to generate a follow a return
path.
|
The small LMRs will be capable of detecting
internal errors.
| A leg is broken:
The LMR will be continue operating, and
informs the humans through the medium LMR and stays
with the "family." It will continue scanning for
data, avoiding particularly
difficult terrain.
A sensor is malfunctioning:
The LMR informs the humans through the medium LMR
and stays
with the "family." It continues to perform as much
scientfic data retrieval
as possible until the "family" returns to the base for
routine repairs.
The solar panel is malfunctioning:
The LMR uses battery power to contact the
astronauts and the medium
LMR. Then it attempts to clean the solar panel.
The solar panel is still malfunctioning:
The LMR uses its remaining battery power to signal
the astronauts and
the medium LMR. The current position of the damaged
LMR will be logged and
the astronauts will decide on a course of action. They
could potentially drive to the small LMR and
retrieve it.
Other LMRs could be used to return video images of the
damaged small LMR in order to survey the extent of
damage.
The batteries are malfunctioning:
The LMR informs the humans through the medium LMR,
and continues
operating through the day and with restricted
"family" activities
during the night.
The vision systems are malfunctioning:
The LMR informs the astronauts through the medium
LMR, and stops
activities. It stays in the same position. If one
camera is
still functioning, the LMR continues working as
normal. The astronauts
could command the small LMR or the entire family to
return to base.
|
Medium-Sized LMRs
Beyond the many physical problems that could take
place
on the medium LMR, several communications issues
form the bulk of the emergency decision making
system of the medium LMR.
|
There is no communication from an individual small
LMR: The small LMR may be damaged, or it may be out of
range.
The medium LMR waits for a period of time as the
small LMR attempts to
reestablish contact.
There is still no communication from an individual
small
LMR:
The small LMR may be damaged. Under the astronauts'
authorization, the medium LMR sends another small
LMR to the last logged
location of the missing LMR and returns video imagery
to the base.
There is no communication with any small LMRs:
The communications system on the medium LMR may be
malfunctioning. If the long-range satellite link
works, the medium LMR uses it to
inform the astronauts and wait for commands. The
"family"
will eventually return to the base.
There is no satellite link:
The satellite may be malfunctioning. The medium LMR
must attempt to connect to
another satellite.
There is still no satellite link:
The long range communications system on the medium
LMR may be malfunctioning. The medium LMR returns
to the base with the
small LMRs.
There is no communication from the base:
The medium LMR waits for a designated time period,
and if there is still no communication from the base it attempts to connect
to Earth and follows the Earth based commands.
There is no communication from Earth:
There may be a problem with the satellite. The
medium LMR returns to the base
while periodically attempting to connect to the
base and
Earth.
|
With a built in decision making system designed to cover as many possible in-Mission problesm as possible, the medium and small LMRs should be
capable of handling the dependency problems associated
with the closely-knit communications network between
each other and the base.
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Copyright © 2000 Massachusetts Institute of Technology