down 40-foot lengths of polyethylene duct to avoid re-entrainment. posed zeolite is dropped into canisters located under each frame, At the end of the sampling period the exMonitorized valves close to prevent contamination, Recovery of gases collected on the special test flight was performed using a procedure developed at this laboratory. This will not be discussed in detail, but it involved heating the zeolite and subsequent recovery of desorbed gases in a system of cold traps. The results of this test are given in tabular form below. MOLECULAR SIEVE GAS SAMPLER Experimental Flight March 15, 1961 Goodfellow AFB, Texas Unit #1 Unit_#2 Altitude 72,000 feet 72,000 feet Total Volume at STP* 678 ft? 657 f° H,O Recovered 1,22 grams 2.97 grams co, Recovered 6.20 liters (STP) 6.30 liters (STP) H,O Mixing Ratio 0.049 gm/kg 0.120 gm/kg CO, 0.032 percent 0.0338 percent 2 Concentration “Volumes obtained using calibrated PR-2 Flow Meters. For both units the amount of CO, recovered was in reasonable agreement with the theoretical value which assumes a constant mixing ratio of 0.030 percent. The slightly higher values actually obtained are attributed to uncertainties as to the exact operating altitude and small errors in flow measurement. With respect to water vapor, the mixing ratio obtained from Unit No. 1 is in reasonable agreement with values obtained by other workersin the U. S. The mixing ratio from Unit No. 2, however, was almost three times as great and this is attributed to an unfortunate last-minute change in that sampler's configuration involving the mounting of a large cardboard sun-shield over the sampler intake. source of contaminating water vapor at altitude. This subsequently served as a Additional tests of the zeolite gas samplers are planned for the near future. Future Capabilities In examining our present capability we find that there are a number of areas where improvements can be made. First, with respect to radioactive particulates the point is now being approached beyond which further advances in accuracy must include improvements in sample analysis. Second, the sampling capability should be extended to altitudes appreciably above 100, 000 feet; and finally, at these higher altitudes there will be a need for improved light weight collection systems which can efficiently sample the larger volumes required, Under a present contract with the Atomic Energy Commission we are working to improve our position with respect to the latter two areas, 155