tracks must be flown as closely as possible to the planned tracks. A 

 5-mile displacement of the actual track from planned track may result 

 in considerable loss of coverage. While Doppler navigation has proven 

 useful for Ice Patrol, there are many inherent errors in this system, 

 especially during a normal flight featured by many diversions from 

 track. Doppler must depend on accurate loran fixes. Loran A cover- 

 age is fairly poor over the Ice Patrol area of responsibility. Estimated 

 positions are frequently over 5 miles in error, whereas a tolerance of 

 ±2 miles is considered normally necessary to obtain satisfactory cover- 

 age of the area and sufficiently accurate positions of ice sightings. 

 Wlien the problems of aerial ice observing are realized, it is no wonder 

 that we are subject to suifer the same feelings of frustration and futility 

 as suffered by the Patrol officials in the old days of operation on the 

 Ice Patrol Vessel. 



During light seasons, when ice is restricted to the northern Grand 

 Banks, or when only a couple of bergs manage to threaten ships near 

 the Tail of the Banks, the guarding of the ice limits and ice observa- 

 tion can be accomplished by aircraft alone. During heavy years, when 

 many icebergs survive to the Tail, aircraft cannot properly do the job 

 alone and the Ice Patrol Vessel must be used. It is easy to understand 

 that when icebergs menace the major tracks, a ship equipped with 

 radar, loran, fathometer, and other electronic gear essential to navi- 

 gation and ice observing, is potentially a. more positive and effective 

 instrument in guarding the most dangerous iceberg, and also in lim- 

 ited ice observing. True, on a day of excellent visibility the aircraft 

 will accomplish more by determining the entire limits and observing 

 ice well within the limits. A vessel simply cannot hope to search but 

 a small portion of the area necessary to determine the ice limits. 

 However, within a day or two after determination of the ice limits by 

 aerial observation, the ice conditions and consequently the ice limits 

 may have drastically changed. Another effective ice observation flight 

 may not be possible for days. Thus aircraft become practically useless 

 during this time and until a successful flight can be made, whereas 

 the Ice Patrol Vessel becomes the "ace in the hole" by being capable 

 of searching out at least the most dangerous areas and locating, observ- 

 ing, and continuously guarding the most dangerous iceberg and warn- 

 ing ships accordingly. When many icebergs threaten the major 

 tracks, the aircraft and the Ice Patrol Vessel are both required and 

 complement each other in carrying out the mission of the International 

 Ice Patrol. 



The use of satellites for ice observing has been considered. Ideally 

 a stationary satellite could hover over the Grand Banks constantly 

 observing the ice conditions, guarding the ice limits and relaying the 

 information to Ice Patrol Headquarters or directly to ships. How- 

 ever, a stationary satellite must be in an orbit too great a distance from 



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