ELECTRONIC SUPPORT MEASURE (ESM) PROGRAM

LEARNING OBJECTIVES: Describe the necessary data for the ESM program and interpret the output. Identify limitations and assumptions. Interpret the ESM range tables. The ESM program is used to calculate and display the maximum intercept ranges of U.S. and Russian surface emitters by user-specified ESM receivers. Input to the program consists of receiver and emitter characteristics from the data base file and a refractivity data set from the environmental data files (EDFs). The refractivity data set consists of a modified refractive index (M-unit) profile with respect to height, the height of the evaporation duct, and the surface wind speed.

Figure 7-3.-Example output of the LOSS display.

ESM range tables provide the capability to determine the probable effectiveness of various ESM receivers against a predefine set of both U.S. and Russian emitters. This allows the development of an ESM employment plan that maximizes the potential for detecting target emitters.

The restrictions as well as the principles taken for granted in using the ESM program areas follows:

. Make sure the environment selected from the refractivity data set is indicative of the location and time of interest. The ESM program is range- and time-independent.

. The maximum intercept range output is limited to 1000 km (541 nmi). The atmosphere is usually not horizontally homogeneous over these great distances.

. Emitters are limited to a preset list. If you wish to find the ESM intercept range of some other emitter, use the Platform Vulnerability (PV) program.

. Emitter frequencies are nominal frequencies. Intercept ranges of zero indicate that this nominal frequency does not fall within the prescribed receivers bandwidth.

. The ESM program does not account for absorption of EM energy. In general, the absorption of EM energy by things such as oxygen, water vapor, fog, rain, or snow adds little to the propagation loss. Refraction is considered the main factor in transmission.

. The ESM program is valid for frequencies between 100 Mhz and 20 GHz.

. Sea-reflected interference is considered.

. ESM accounts for ducting in evaporation ducts, surface-based ducts, and low-elevated ducts, provided the antenna is within the elevated duct. This program does not properly account for the over-the-horizon region for low-elevated ducts when the bottom of the duct is above the antenna. Errors are small and should be insignificant when the separation exceeds a few thousand feet.

. The effects of a surface-based evaporation duct. duct are considered to dominate any contributions from the

. The ESM program assumes the emitters are radiating at peak power. . The probability of detection associated with the output ranges depends upon the receiver sensitivities.

. If you are attempting to verify ESM intercept ranges achieved by your own receiver, remember that PV outputs maximum intercept ranges. If a platforms emitters arent turned on at that range, there will be nothing to intercept.

FUNCTIONAL DESCRIPTION ESM computes the maximum ESMR of an emitter. ESMR is computed only if the emitters frequency falls within one of the frequency bands of the receiver. Table 7-2 shows an example of ESM range tables.

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