Environmental Engineering Reference
In-Depth Information
the physical world. In addition to their primary sensors, many robots have
the ability to communicate with other agents to receive orders and report
problems and results.
Many agents have mobility. Mobility in robots is easy to understand since
many robots travel to achieve their objectives. Some software agents are mo-
bile and are able to move themselves (their code and data) from one computing
platform to another. Software agents may move to gain access to resources
they cannot access e ciently from their original computing platform.
Agents work in either the physical or the virtual world. When in the phys-
ical world, the sensors and actuators take up space, cost money, undergo wear
and tear, and consume resources while performing their mission. If the mis-
sion goal requires the physical world to be sensed and manipulated, then these
costs must be paid. Software agents live in a virtual world made up of one or
more computers connected by networking. In this world, moving information
fulfills the roles of sensing and acting and the only direct resource consumed
is computation.
1.4.1 Software Agents
Software agents are being used in many domains and encompass a wide range
of technologies. At least three broad categories of software agents are being
developed and applied:
Informational agents : Informational agents interact with their owner to de-
termine the types and quantities of information the owner desires. These
agents then utilize electronic sources to locate the appropriate informa-
tion, which the agent then organizes and formats for presentation to the
owner.
As an example, currently FSW provides subscription services so that
onboard applications can subscribe to spacecraft ephemeris information
and receive that information when it is calculated. An agent-based en-
hancement of this arrangement might entail a scenario like the following.
Suppose that predicted spacecraft ephemeris is generated onboard once
per second (which is typical of current spacecraft) and represents, second
by second, the best available estimation of the spacecraft position and ve-
locity. The informational agent ensures that the information is provided
once per second to applications that need it.
But occasionally the spacecraft needs to plan and schedule an orbit
stationkeeping maneuver, which would be planned so as to minimize dis-
ruption to high priority onboard activities, but could (depending on orbit
geometric constraints) disrupt scheduled routine onboard activities, in-
cluding science. To devise the plan and incorporate the maneuver into the
schedule, it needs the best predicted spacecraft ephemeris data available
for an interval covering a few days in the future from the current time.
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