OVERVIEW

There seem to be a host of malevolent factors that work in concert to inhibit the collection of accurate RCS information. They range from random internal thermal noise generated in the instrumentation system to residual external echoes from optically invisible obstacles on the test range. The cumulative result of this multiplicity of internal and external errors is an absolute limit on data accuracy that is seldom better than 0.5 dB (about 12 percent).

The potential error due to some mechanisms may be reduced to values significantly lower than this by means of careful instrumentation and facility design, and the implementation of sophisticated test procedures. Although those designs and schemes may reduce the total error to as little as 5 percent (0.2 dB), the reduction is usually achieved only at great cost. That cost is eventually paid in the coin of the realm, whether due to additional design, engineering and fabrication costs of equipment, additional data processing requirements, or additional time on the range to implement unusual test procedures.

Thus, the ultimate configuration of an RCS test facility, and the procedures developed to acquire the data, are the result of balancing accuracy against cost. Because accuracy never seems more important than the cost of achieving it, and because few applications of the data, if any, require accuracies better than 0.5 dB, the 0.5 dB figure has been tacitly accepted in the RCS measurement industry as eminently acceptable. The overall error depends on both relative and absolute errors, the latter of which...