Environmental Engineering Reference
In-Depth Information
to impact backbone processing. Bandwidth limitation is also used to control
agent communications with spacecraft hardware through the backbone.
A list of potential Remote Agent functions is provided below, with more
detailed descriptions in the following subsections:
1.
Fine attitude determination
2.
Orbit determination (and other reference data)
3.
Attitude sensor/actuator and SI calibration
4.
Attitude control
5.
Orbit maneuvering
6.
Data monitoring and trending
7.
“Smart” fault detection, diagnosis, isolation, and correction
8.
Look-ahead modeling
9.
Target planning and scheduling
10.
SI commanding and configuration
11.
SI data storage and communications
12.
SI data processing
6.2.1 Fine Attitude Determination
For safemode or inertial-hold purposes, gyros and sun sensors supply adequate
information to guarantee acquisition and maintenance of a power-positive
spacecraft orientation, or to ensure that the spacecraft will not drift far from
its current attitude. So an autonomous onboard capability to determine a
fine-pointing attitude (i.e., pointing knowledge good to a few arcseconds) is
not critical to H&S. It is, however, essential for mission performance for any
precision pointer, be it earth- or sun-pointer.
Given that “Lost-in-Space” startrackers are now available that directly
output attitude quaternions, this function, for some missions, has already been
realized in an independent hardware unit. For other missions with higher ac-
curacy pointing requirements, FSW (which could be developed with an agent
structure) would still be required for interpreting and combining data from the
startracker with those from a fine error sensor or SI. The simplest implemen-
tation of this capability would involve creating a fine-attitude-determination
agent that continuously generated attitude solutions, independent of the need
of any other agent for their use. These solutions could then be stored in a
data “archive” pending a request by other agents. Calibration data and sen-
sor measurements needed by the attitude-determination agent could be stored
in similar archives until requested by the agent. Old data (either input to or
output from the agent) could be maintained onboard until downlinked, or if
not needed on the ground, simply overwritten periodically.
Orbit Determination (and Other Reference Data)
Typically, accurate spacecraft position information is not required to support
safemode processing or emergency communications, so orbit determination is
