Environmental Engineering Reference
In-Depth Information
Summarizing, implementing the following additional onboard functions as
Remote Agents would be consistent with the lights-out control center philos-
ophy for LEO earth pointers:
1.
Fine attitude determination (needed for orienting an imaging subsystem)
2.
Orbit determination (as discussed)
3.
Attitude sensor/actuator and SI calibration (as discussed)
4.
Attitude control (needed for orienting an imaging subsystem; fine
pointing)
5.
Orbit maneuvering (plan and execute orbit stationkeeping, as discussed)
6.
Data monitoring and trending (as discussed)
7.
“Smart” fault detection, diagnosis, isolation, and correction (as discussed)
8.
Look-ahead modeling (needed in conjunction with orbit-trending)
9.
Target planning and scheduling (scheduling as discussed)
10.
SI commanding and configuration (templates associated with targets)
11.
SI data storage and communications (in cooperation with ground agent)
12.
SI data processing (as discussed)
6.6.2 GEO Celestial Pointers
A GEO celestial pointer's operational constraints are much more straightfor-
ward than those for a comparable LEO mission, so much so that it is possible
to operate the spacecraft in a “joystick mode,” as demonstrated by the In-
ternational Ultraviolet Explorer (IUE), where blocks of time were assigned to
astronomers who could command the spacecraft directly when making their
observations. This is not to say that automation is not critically important for
enabling full utilization of spacecraft capabilities and performance accuracy
at optimal eciency, but that automation can be implemented on the ground
in support of a human operator rather than migrated onboard to provide au-
tonomous function. Since full contact with the ground station is nominally
possible at all times and time delays in transferring spacecraft supplied data
to the ground station are small, and because FSW development and testing
costs are likely to remain significantly higher than those of ground software of
corresponding size and complexity, this mission type is probably not a good
candidate for an onboard Remote Agent implementation on a cost-benefit ba-
sis. However, Remote Agents may find many useful applications within the
ground system's lights-out control center.
6.6.3 GEO Earth Pointers
As with the GEO celestial pointer described in the previous section, opera-
tional constraints are much more straightforward than those for a comparable
LEO mission. And as before, full contact with the ground station is nomi-
nally possible at all times and time delays in transferring spacecraft supplied
data to the ground station are small. Since FSW development and testing
