Aerial radiometric and magnetic survey: Baker National Topographic Map, Idaho and Oregon

Geo-Life, a joint venture between High Life Helicopters, Inc., Puyallup, Washington, and Geodata International, Inc., Dallas, Texas conducted an airborne gamma ray and total magnetic field survey during the period September 8--18, 1977, which covered a region of the states of Oregon and Idaho identified as the Baker National Topographic Map, NL, 11-11. The specific area was surveyed from an aircraft using large-volume radiation detectors with associated airborne electronic equipment. Each map line was flown in an east-west direction with an average length of 104 miles and each tie line was flown in a north--south direction with an average length of 69 miles. Map lines and tie lines surveyed were spaced at intervals of 3 miles and 12 miles respectively. The data for the total area were gathered during September, 1977. The area was surveyed from north to south. Map Line 1 was not surveyed because of the fallout of 140Ba/140La during heavy rains following September 18, 1977, as a result of a Chinese nuclear test. 140Ba has a half-life of 12.8 days. Approximately four half-lives are necessary to allow the 140Ba to decay to 5% of its initial concentration. The Baker NTMS report is separated into two volumes, Volume 1 giving the description of the program and results, and Volume 2 presenting the flight line profile data and statistical analysis results