SLARGUS

A HISTORY
BY
REG THOMPSON

                In the early ‘70s, a series of projects at the Maritime Proving and Evaluation Unit were planned to gain experience with remote sensing systems. The most extensive system to be examined was an APS-94D Side Looking Radar (SLAR). The SLAR antenna was 24 feet long and due to the number of others sensors to be installed was decided to assign a second Argus to MP&EU, dedicated to the remote sensing projects.  10728 was chosen and in the fall of 1971 it was sent to the Aerospace Engineering and Test Establishment (AETE) at Cold Lake Alberta to have the antenna installation designed, installed and flight tested.

 It was decided to mount the antenna below the rear bomb bay. The hydraulic actuators for the right rear bomb bay door were disconnected from the hydraulic system and the door was locked closed. Two holes were cut in the door and supporting structure for the antenna protruded through the holes and was attached to the weapon mount hard points in the bomb bay. Racks were also installed in the bomb bay to carry the SLAR RF equipment.  In January 1972, 10728 deployed to Phoenix, Arizona, for the installation of the remaining SLAR equipment and acceptance testing.  While in Phoenix, 10728 was painted with a Road Runner character and nicknamed “SLARGUS” by Motorola. 

The APS-94D used film to record the SLAR imagery.  A “wet” process was used to develop the film as it ran through the recorder, allowing near real time presentation of the imagery. The APS-94D was originally designed for the OV-10 reconnaissance aircraft and the recorder station was designed to occupy the area in front of the right seat in the OV-10 cockpit. Two of these stations were installed on the port side of the mid rest area of the Argus, in the area normally occupied by a bunk. One station was used with the wet film process and the other was used to expose the film, but it was processed on the ground and produced higher quality images. 

The testing of the SLAR performance was carried out in conjunction with AETE. In particular, the Moving Target Indicator (MTI) mode would produce imagery, which indicated the radial velocity of targets based on doppler shift.  This involved having vehicles of various sizes; travelling up and down a runway at various speeds while SLARGUS flew by to determine the resolution and sensitivity of the MTI. 

Later in the program, extensive work was done on the SLAR by the Defence Research Establishment Ottawa to improve the performance of the SLAR through enhanced signal processing. As well, the people in the Department of the Environment used SLAR in their studies of ice in the arctic.  This resulted in many flights out of Thule, Greenland over the next several years.

 

We never determined the real cause (possibly the SLAR antenna being a little off the centre line), but 10728 had about +/- one degree of roll oscillation when flying on autopilot. The period was fairly long, but the back and forth rolling caused a venetian blind effect in the SLAR imagery. It was not practical to hand fly the aircraft to the required steadiness for more than one or two minutes, so it was standard practise for both pilots to lean over on the yoke to try to slow the oscillations down even more.

 

In April 1975, 10728 participated in Exercise AIDJEX, a study of ice dynamics. There was a station on the arctic ice north of Alaska and 10728 flew several missions out of Inuvik, NWT. The ice station had been built with material and personnel flown in by Hercules. 10728 carried out ice profiling flights and general SLAR imaging of the ice station.  One of the characteristics of the SLAR imagery is that it is able to see through snow cover and give an accurate image of the ice below.  When we examined the SLAR imagery of the ice station, I commented on how many major cracks there were. About two weeks later, the ice changed rather dynamically and the station broke into several pieces. The station had to be evacuated using Twin Otter aircraft as there wasn’t a piece of ice big enough for the Hercules.  

 

Another interesting exercise (Exercise Brisk) was conducted in October 1976. Both MP&EU aircraft carried out a rendezvous in the arctic north of Alert, with the RN submarine HMS Sovereign.  10728 was specially equipped with a laser profilometer and carried an infrared line scan camera in addition to the SLAR.  10728 carried out a profiling of the ice surface from the air, while the submarine travelled the same track and profiled the ice from below. Meanwhile, 10729 had been fitted with a new Magnetic Anomaly Detection (MAD) system and laid claim to the most northerly MAD detection of a submarine. Later in the exercise, 10728 over flew the North Pole to check out how the LTN-51 inertial navigation system and the Marconi OMEGA navigation system performed at the pole.  That trip ended with a precautionary engine shut down at about 84N and an uneventful 3-engine landing at Thule.

 

A side bar to the Exercise Brisk saga was the logistic needs of the Argus. Standard fuel for the Argus was 115/145 and it was getting vary scarce. Thule had enough on hand to support one Argus, so 10728 was based in Thule, but the fuel used had to be replaced by the Canadian Forces. 10729 was based in Söndre Strömfjord Greenland where 115/145 fuel was in good supply. During the next annual exercise to re-supply of the Canadian Forces station at Alert, a Hercules took 115/145 fuel from Söndre Strömfjord to Thule to satisfy the agreement with the USAF.

 

In August 1977, the SLARGUS era ended when the SLAR was removed from 10728 and the equipment was transferred to the Department of the Environment. It was later installed in a Nordair Lockheed Electra where it continued to be used for ice reconnaissance. 10728 continued with MP&EU until it was retired from service in January 1979

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This was the nickname given to MP&EU's Argus 728 which was fitted out with a Side-looking Radar. Dave Askett, an Argus enthusiast, had these photos sent to him and he has kindly pass them on for this site. The photos were taken at an airshow back in 1975. If you have any photos or information on this particular aircraft please let me know...... 

From a contributor

I remember seeing a SLAR-generated map taken of PEI in its entirety by MPEU in 728. The   'map' had a line down its centre which indicated the track of the aircraft. It also showed continuous transverse striping down the length of the Island. Reg Thompson (I think) explained to me that these stripes were because the aircraft was flown on autopilot. You may recall that the Argus flew with a constant oscillation in bank when on autopilot. It was a small, but gentle rocking from side to side through one or two degrees of bank. Manual flying cured the stripe problem on future SLAR maps.