Beginning with the February 1969 mission, this gap was partiaily clo. jo by sampling at 16-3 km instead of 18.3 km at all Latitudes scleward : about 35° in beth hemispheres. The coverage in Figure 3b extends almost continucusly at the continuity between 10°s to 16°9S. Each mission is accomplished by con ducting return flights northward and southward from each of the four Air Force Bases Of operation: Eielson AFB 64°40'N Mendoza AFB 32°49'S Kirtland AFB Albrook AFB 147°06 ‘Ww 35°03 'N OB°57'N 106°36 ‘Ww 79934 ° Ww 68°47 'W AIR FILTER SAMPLES Air £iltes sampies are collected along the flight tract tude increments of approximately 3 altitudes using the U-l foil c Oo) indicated altitudes from 75°N to 51°S latitude except for a Slight di * h = * 3 Ra0L to 4° at each of the prescrived system. This system permits tial insertion of up to 12 IPC No. 1478 filter papers the sequen- (diamever 1o-3/8 into the sampling duct near the bomb bay on the right sidé of the a:ir- craft. The volume of aix sampled by each filter is calculated by the methods developed under Project Stardust and updated by Krazyewski and are reported as standard cubic meters atmosphere (SCM) under the ICAO standard (760 mm Hg and 15°C). TI - 10 (7). 4