Environmental Engineering Reference
In-Depth Information
periodic status summaries as well as the downlink of science measurement
results and requests for help. Because the nature of beacon mode is to inform
the ground of all onboard “experience” the spacecraft deems to be interesting
to the ground, beacon mode operation can involve the interaction of the com-
munications agent with nearly all the other onboard agents, including SI data
processing, SI data storage (potentially part of communications), data moni-
toring and trending, smart fault detection, diagnosis, isolation, correction, etc.
6.4.10 Resource Management
Spacecraft operations concepts usually are driven by constraints imposed by
limitations in onboard resources, both of the expendable varieties (for exam-
ple, fuel or cryogen) and renewable varieties (such as electrical power, com-
puting power, data storage, and telemetry bandwidth). When these resources
are in demand by more than one distinct spacecraft subsystem or component,
a mechanism must be provided (either ground-based or flight-based) to deal
with the inevitable conflicts that will result. Other potential sources of con-
flict (which may also be thought of somewhat abstractly as resources) are
priorities on use of onboard functionality, such as attitude control or thruster
utilization/orbit adjustment. A Remote Agent formalism provides a partic-
ularly convenient infrastructure for resolving issues arising from overlapping
needs.
In this application, one can envision a resources management agent (pos-
sibly subsumed under the executive agent) responsible for evaluating all re-
source requests in excess of a nominal set of limits associated with the set of
agent users of those resources. The management agent would evaluate those
requests relative to overall resource envelopes to determine whether the re-
quest can be honored, whether it must be rejected, or whether the need is
high enough in priority that other agents must surrender a portion or all of
their individual assets. The management agent would have to perform a simi-
lar function if an onboard anomaly unexpectedly reduced the availability of a
resource. Due to the broad characterization of what constitutes a resource, re-
source management potentially can involve the interaction of that agent with
all the other onboard agents. The management agent would also ensure that
no resource deadlock situations arise.
6.5 Advantages of Remote Agent Design
The Remote Agent design described in the previous sections presents the
opportunity for significant overall mission cost savings arising from its en-
abling of higher operational eciencies, reduced FSW development costs, and
reduced FSW testing costs. In the following subsections, each of these con-
tributing factors is discussed.
