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Surveillance Aircraft SRA-1

Description of the radar set, tactical-technical characteristics

Figure 1: Golfstream III fitted with the SRA-1

Figure 1: Golfstream III fitted with the SRA-1

frequency: X-band
pulse repetition time (PRT):
pulse repetition frequency (PRF):
pulsewidth (τ):
receiving time:
dead time:
peak power:
average power:
instrumented range: 200 km
range resolution:
hits per scan:
antenna rotation:

Surveillance Aircraft SRA-1

In 1984 Grumman introduced the SRA-1, a modified Gulfstream III intended to advertise the type’s adaptability to more warlike roles. The SRA-1 featured a mockup of a Motorola SLAMMR (“Side-Looking Airborne Modulated Multimode Radar”) system in a pod under the fuselage; three dummy stores pylons under each wing, for a total of six; and small dummy pods on the wingtips for an “electronic support measures (ESM, or emitter targeting)” or other EW system. The SRA-1 also featured a new, large cargo door, apparently not only to support getting large pieces of electronics gear in and out but to give the aircraft a secondary cargo-lifter role.

SLAMMR is a long-range surveillance radar intended for use in maritime patrol, border surveillance and mapping. The aircraft installation consists of seven main subassemblies: antennas, antenna switching unit, receiver/transmitter, display processor, display, control unit and signal processor. The antenna consists of two yaw stabilized, horizontally or vertically polarised, slotted waveguide arrays. These can be mounted back-to-back within a single pod, or individually mounted on either side of the aircraft in two 16ft canoe-shaped radomes to provide an unobstructed view. The US-American version on Boeing 737/200 is designated as AN/APS-135.

The remaining units are either pallet- or rack-mounted inside the aircraft for easy removal. The display processor provides radar timing and control functions and, based on inputs from the aircraft inertial navigation system, creates latitude and longitude references for display with the radar imagery. The receiver/transmitter contains the magnetron transmitter and the low noise receiver. The antenna switching unit directs the radiated power and received signal to either the left or right antenna.

The data can also be recorded for future use as well as transmitted to ground stations, in real time, via a radio link. The signal processor is a moving target indicator option that is available for the detection of moving targets at long-range for border surveillance. By the use of this processor, surveillance can be carried out at ranges up to 148 km. A high-quality fixed target map is also available for radar mapping and geological exploration.

SRA-1 was the start for a development of a wide program of reconnaissance aircrafts based on bizjets. General Dynamics has developed their own concepts for a Gulfstream V EW variant, designated the “EC-37 Special Missions Aircraft (SMA)” and clearly a descendant of the SRA-1.

Picture gallery of SLAMMR

Figure 2: Boeing 737/200 with two SLAMMR antennas mounted on both sides of the rear fuselage