Posted: August 26, 2019 | Modified: April 13, 2021

The Advanced Low Altitude Radar Model, or ALARM, is a generic digital computer simulation designed to evaluate the performance of a ground-based radar system attempting to detect low-altitude aircraft. The purpose of ALARM is to provide a radar analyst with a software simulation tool to evaluate the detection performance of a ground-based radar system against the target of interest in a realistic environment. The model can simulate pulsed/Moving Target Indicator (MTI), and Pulse Doppler (PD)-type radar systems and has a limited capability to model Continuous Wave (CW) radar. Radar detection calculations are based on the Signal-to-Noise (S/N) radar range equations commonly used in radar analysis. ALARM has four simulation modes:  Flight Path Analysis (FPA) mode, Horizontal Detection Contour (HDC) mode, Vertical Coverage Envelope (VCE) mode, and Vertical Detection Contour (VDC) mode.

The primary application of ALARM is the evaluation of target detection range as a function of the environment. The model now includes the environmental effects of atmosphere, terrain masking, clutter, multipath, and electromagnetic propagation through the use of Joint Aircraft Survivability Program Common Modeling Component Set (JASP CMCS). Land clutter reflectivity probability distributions published by the Massachusetts Institute of Technology (MIT) Lincoln Laboratory and sea clutter reflectivity probability distribution from the Center for Naval Analysis (CNA) are also used in ALARM. Pattern propagation effects such as radar antenna pattern, spherical earth and knife edge diffraction, and multipath are included by use of the MIT Lincoln Labs Spherical Earth/Knife Edge (SEKE) Diffraction source code. Terrain masking is determined based on National Geospatial Intelligence Agency (NGA) Digital Terrain Elevation Data (DTED), which is put into the model for a specific radar site area. Additionally, ALARM supports limited modeling of onboard noise (self-screening) jammers, onboard deception (coherent) jammers, and standoff noise jammers.

ALARM Model Output Image
ALARM Sample Detection Plot
MTI Vertical Coverage Envelope
MTI, Vertical Coverage Envelope
MTI Vertical Detection Contour with Terrain
MTI, Vertical Detection Contour with Terrain

The input consists of user-supplied, engineering-level data, such as transmitter power, pulse width, pulse repetition frequency, antenna patterns, radar cross section (RCS) tables, and data needed to simulate pulsed/MTI, and PD processing. FPA mode requires aircraft flight data parameters to be specified for each data point. These parameters include altitude, heading, speed, bank, and pitch. Alternatively, the FPA mode can read a BlueMax output file for the flight path data. HDC mode requires a single aircraft speed and altitude. VDC mode only requires a single aircraft speed.

Classified dataset for threat systems are available.


The output consists of an output file and a data diary file. The output file is an ASCII text file that includes a summary of the simulation inputs. For FPA mode, the output file also contains the target flight path information summary, which gives detailed information for the target, jammers, target masking, and radar detection at each target location. The data diary file contains the simulation results. Each simulation mode has its own data diary format. The data diary can be in ASCII or binary. The supporting post-processing programs use the data diaries for generating plots.

Model Specifications
Version 5.4
Archived Versions Available 3.2, 4.4.1, 5.0, 5.1, 5.2
Host Systems SUN, PC
Program Language FORTRAN 90
Software Change Request Database
Page Distribution

Distribution Statement A: Approved for public release; distribution is unlimited.

Model Distribution

ALARM V5.4 is UNCLASSIFIED//FOUO and the ALARM Dataset CD is classified SECRET/NF.

DISTRIBUTION STATEMENT D. Distribution authorized to the Department of Defense and U.S. DoD contractors only, CRITICAL TECHNOLOGY, July 2006. Other requests for this document shall be referred to AFRL/IFSD, Wright-Patterson Air Force Base, Ohio 45433-7334.

WARNING− This media contains technical data whose export is restricted by the Arms Export Control Act (Title 22, U.S.C., Sec 2751, et seq.) or the Export Administration Act of 1979 (Title 50, U.S.C., App. 2401 et seq), as amended. Violations of these export laws are subject to severe criminal penalties. Disseminate in accordance with provisions of DoD Directive 5230.25.

PN- ALARM-CD-U-001 and ALARMDS-C-001

Requests from non-U.S. Agencies must be forwarded to their country’s U.S. embassy.

Note that technical questions/support for ALARM will not be able to be addressed due to support from the model manager being discontinued.

Model Request Instructions

To request this model you must be logged in. Please login or create an account.

Want to learn more about this topic?