This application is a notional battle management system for coastal defense from cruise missiles and bombers. It was implemented collaboratively by the General Dynamics Corporation and Jensen’s Archons Project at Carnegie Mellon University’s Computer Science Department [Maynard 88]. It is included here to further illustrate the dynamic adaptivity possible with time/utility functions, which would be very difficult to achieve with priorities or even deadlines.

Here it suffices to consider a subset of this system’s mission – to destroy incoming hostile cruise missiles (for brevity we will disregard the hostile bombers), by using guided interceptor missiles (for brevity we will ignore the defensive surface-to-air missiles).

There may be more cruise missiles and decoys than can be intercepted, due to the number of cruise missiles, insufficient interceptors, and insufficient computational resources for battle management. Cruise missiles maneuver during flight, but do not try to evade the interceptors. Interceptors are guided by airborne defenders using airborne (AWACS, etc.), spaceborne, and ground based, sensor platform data.

The cruise missile defense (CMD) application quality of service metric here is the weapon spherical error probable (WSEP).  Spherical error probable (SEP) is the radius in meters of a sphere centered on a point, within which the true value of an estimated point will lie with a probability of 0.5. The WSEP is an SEP radius around the cruise missile chosen such that if the interceptor gets within that distance, the interceptor’s terminal guidance sensor system can take over and cause the interceptor to either impact the cruise missile or detonate close enough to the cruise missile to destroy it.

This experimental coastal air defense application consists of a number of activities, as depicted in Figure 1.

Figure 1. Coastal Air Defense System Activities

Some activities resemble corresponding activities in the AWACS
surveillance tracker. The plot correlation and track database
maintenance threads have critical times corresponding to the
radar frame arrival rate. In both cases, it is better if the
processing is completed before the next frame of sensor data
arrives. It is acceptable for the processing to slip as much as
one additional time frame under extreme overload situations.
The plot correlation activity has a much greater utility to the
system under overload conditions. The TUF’s for those two
threads are shown in Figures 2 and 3.

Figure 2. Plot Correlation TUF

Figure 3. Track Database Maintenance TUF

But the timeliness requirements for the interceptor missile control threads are more complex because they vary over the course of an interception engagement. After an interceptor is launched, the guidance control threads must issue timely aperiodic course updates to ensure a successful intercept. The required timeliness of these updates, and the importance of completing the course corrections at the desired time, change as the distance decreases between the interceptor and the cruise missile, and between the cruise missile and the coastline.

Figure 4 shows three snapshots of an interceptor missile control thread as its shape is adapted, progressing from the right-most (launch phase) to the left-most (intercept) phase; the number of these adaptations is variable.

Figure 4. Three snapshots of an interceptor missile
control thread as its shape is adapted

To accomplish this adaptation, three TUF shape parameters of each interceptor’s control thread are changed during the engagement, as seen in Figure 5.

Figure 5. Three TUF Shape Parameters Change During the Engagement

This richly expressive adaptation is extremely difficult to achieve by manipulating priorities or deadlines.

References

Maynard et al. 88 D. P. Maynard, S. E. Shipman, and R. K. Clark. et al., “An example real-time command, control, and battle management application for alpha,” Technical Report Archons Project TR-88121, CMU Computer Science Department, December 1988.

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