Appendix E 



International Ice Patrol's Side-Looking Airborne 



Radar Experiment (SLAREX) 1988 



Lt M. A. Alfultis, USCG 

 CDR S. R. Osmer, USCG 



Abstract 



During the period 7 through 16 

 June 1988, the international Ice 

 Patrol conducted an evaluation of 

 the AN/APS-131 Side-Looking 

 Airborne Radar (SLAR). This 

 SLAR, installed as part of the 

 multi-sensor surveillance AIREYE 

 system onboard the U. S. Coast 

 Guard HU-25B medium endur- 

 ance aircraft, was evaluated for its 

 ability to detect icebergs. The 

 data collection occurred in an 

 iceberg infested area off the coast 

 of Newfoundland, Canada. 



The fundamental goal of this 

 research was to provide guidance 

 on the ability of the AIREYE- 

 equipped HU-25B to perform the 

 iceberg detection mission of the 

 International Ice Patrol. Specifi- 

 cally, there were two objectives: 



1 . Determine the optimum 

 altitude for iceberg reconnais- 

 sance, and predict the probability 

 of detection as a function of sea 

 state, lateral range, and iceberg 

 size. 



2. Compare the iceberg 

 detection capability of the AN/ 

 APS-131 SLAR with the AN/APS- 

 135 SLAR currently used on the 

 International Ice Patrol's HC-130 

 long range reconnaissance 

 aircraft. 



Ground truth (i.e. iceberg dimen- 

 sions and positions, and environ- 

 mental conditions) were collected 

 by the U. S. Coast Guard ice- 

 breaker NORTHWiND (WAGB 



282). The HU-25 and HC-130 

 aircraft flew a box pattern around 

 the iceberg search area. Several 

 different altitudes were used. 



The Ice Branch of the Atmospheric 

 Environment Service of Canada 

 also had two of its SLAR-equipped 

 ice reconnaissance aircraft (an 

 Electra and a Dash-7) participate 

 in the experiment. 



Results indicate the AN/APS-131, 

 while not having the azimuth 

 resolution of the AN/APS-135, is 

 capable of performing the iceberg 

 reconnaissance mission. These 

 preliminary results indicate an 

 altitude of 4000 to 6000 feet is 

 best for the AN/APS-1 31 for this 

 mission. 



Current plans for the 1989 iceberg 

 season are for the HU-25B to 

 complement the HC-130H recon- 

 naissance aircraft. Due to its 

 limited endurance, the HU-25B 

 aircraft will not be able to replace 

 the longer-range HC-130. How- 

 ever, during certain times of the 

 year and in certain light ice years, 

 the HU-25B should be able to 

 conduct the International Ice 

 Patrol mission. 



Introduction 



After the sinking of the RMS 

 TITANIC on April 14-15, 1912, an 

 International Ice Patrol Service 

 was created to monitor the pres- 

 ence of icebergs near the Grand 

 Banks of Newfoundland, and to 

 warn mariners of these hazards. 

 The International Ice Patrol (IIP), a 



unit of the U. S. Coast Guard, has 

 provided this service since its 

 initiation in 1914. From 1914 to 

 1945, IIP used visual reconnais- 

 sance from ships to monitor the 

 icebergs. After World War II, and 

 up to 1983, IIP used aircraft visual 

 reconnaissance as its primary 

 method of iceberg detection. 

 Since 1983, IIP has utilized a 

 Motorola AN/APS-135 Side- 

 Looking Airborne Radar (SLAR) 

 onboard HC-130H Hercules long- 

 range aircraft as its primary 

 method of iceberg reconnais- 

 sance. 



In 1983, the U. S. Coast Guard 

 installed the Motorola AN/APS- 

 131 SLAR as part of the airborne 

 multi-sensor surveillance AIREYE 

 system on its HU-25B Falcon 

 medium- range aircraft. The AN/ 

 APS-131 SLAR is very similar to 

 the AN/APS-135 SLAR on the HC- 

 130, except that the antenna 

 length of the APS-1 31 is half that 

 of the APS-135. This results in 

 the APS-131 having a lower 

 azimuth resolution than the APS- 

 135. Although the iceberg detec- 

 tion ability of the APS-135 SLAR 

 has been previously evaluated, no 

 evaluation of the iceberg detection 

 ability of the APS-131 SLAR has 

 been made. 



The AIREYE system on the HU- 

 25B contains other sensors in 

 addition to the SLAR, and are all 

 connected by a computerized 

 multipurpose display system. The 

 AIREYE system has a dry film 

 processor, as does the HC-130H. 

 This film was the object of evalu- 

 ation. 



101 



