coverage of the interior portion of a standard 

 parallel leg type search (Figure 3). Moderate 

 orgreaterturbulence and moderate orgreater 

 precipitation reduces the SLAR's ability to 

 detect targets. Flights are planned to avoid 

 both of these factors. Flight cancellations due 

 to poor on-scene weather conditions were 

 greatly reduced with the introduction of SLAR. 



Also in 1983, Ice Patrol moved its base 

 of operations from St. Johns to Gander, New- 

 foundland. In 1988, Ice Patrol returned its 

 base of operations to St. Johns. Both of these 

 moves had little effect on Ice Patrol opera- 

 tions. Although St. Johns is a little closerto the 

 southern portion of the area of iceberg danger, 

 the small increase in flight transit time and 

 corresponding decrease in search area had a 

 minimal effect on Ice Patrol reconnaissance 

 efforts. 



The use of SLAR drastically altered the 

 Ice Patrol aircraft deployment schedule. In- 

 stead of having an aircraft deployed to Canada 

 on a continuous basis during the ice season, a 

 SLAR equipped aircraft was deployed for a 

 one week period every other week. With 

 SLAR, Ice Patrol was able to conduct a similar 

 number of flights and increase the coverage of 

 the operations area. Transit legs to and from 

 the search area could be searched with SLAR, 

 increasing area coverage per flight. During 

 the visual flight era, the transit legs were flown 

 at altitude, generally above the clouds and 

 very few iceberg sightings were recorded. 

 The change in aircraft deployment schedule 

 placed a larger reliance on Ice Patrol's iceberg 

 drift and deterioration prediction models. Re- 

 search efforts during the period 1986-1988 

 focused on evaluating the model performance. 

 The results indicted, with good environmental 

 input, the models performed within acceptable 

 errortolerances (Murphy and Anderson, 1 985, 

 and Hanson, 1987). 



Research was conducted in 1984 and 

 1985 to evaluate the APS-135 SLAR perfor- 

 mance. The results indicated the SLAR was a 

 very capable iceberg detection tool (Rositter, 

 et al., 1985 and Robe et al., 1985). 



In 1 989, the HU-25B Falcon jet equipped 

 with an APS-1 31 SLAR was first used as a Ice 

 Patrol aerial reconnaissance platform. The 



APS-1 31 SLAR also provides a near all- 

 weather target detection capability. There is 

 only one central antenna pod on the Falcon 

 with the antenna being half as long as the 

 antenna on the HC-130. The HU-25B is a 

 much smaller airframe and is more suscep- 

 tible to being rocked by air turbulence. On a 

 turtDulence free flight, the detection capability 

 of the APS-1 31 SLAR is similar to that of the 

 APS-135 SLAR (Alfultis and Osmer, 1988). 

 The Falcon's range of 700 nautical miles is 

 considerably less than the HC-1 30 and thus it 

 is not capable of reaching and then searching 

 the limits of iceberg danger during the peak of 

 the season. The HU-25B is generally only 

 used near the beginning and end of the sea- 

 son and is deployed in place of an HC-1 30 as 

 part of the same every other week schedule. 

 The HU-25B flies two three hour sorties per 

 day compared to one seven hour sortie for an 

 HC-1 30. The total area covered perday by the 

 HU-25 is considerably less than the HC-130. 

 Due to its limited range, the HU-25B has not 

 been used extensively. 



Along with SLAR's operational benefits 

 came an important problem, targetdiscrimina- 

 tion. When unable to see the surface, the 

 operator must decide whether the target de- 

 tected is an iceberg or not. Farmer (1972) 

 provides a general overview of why SLAR is a 

 good iceberg detection tool and a description 

 of the visual cues used to classify SLAR tar- 

 gets. On the basis of this study, Ice Patrol 

 decided to make identifications without seeing 

 icebergs using the available cues. The cues 

 on the film aid the experienced operator in 

 determining the identification of some targets. 

 When two looks at the same target from differ- 

 ent legs of the search pattern are available, 

 movement or lack of movement of the target is 

 a particularly useful tool in deciding if a target 

 was an iceberg or not. For targets without any 

 cues, the operator's ability to discriminate be- 

 tween an iceberg and a vessel correctly is only 

 just above chance (Thayer, 1985). 



During the first several years use of the 

 SLAR, the operators were learning how to use 

 the available cues to discriminate between 

 vessel and iceberg targets. This target dis- 

 crimination problem effects Ice Patrol's esti- 

 mate of the number of icebergs drifting south 

 of 48 North. During the first several years of 



55 



