have a square meter and you go through a 5-kilometer layer where we can, at the moment, neglect density variations, you have 5000 cubic meters (about 150,000 ambient cubic feet); with 100 square centimeters, you would have only 1500 ambient cubic feet, and you are two to three orders of magnitude short of the sample that Lester says you have to have. My question is, if somebody tells you that he could get a 1000-ambient-cubic- foot sample, but he can't get 100, 000 ambient cubic feet, would you say, "Don't collect the sample?" Or would you have some ideas of what you might be able to do with this sample? Dr. Kalkstein: I can't at the moment, without pulling out a pencil, even relate the volume. I think in dealing with this problem it is more meaningful to talk about what fraction of the earth's surface is covered by the cross section of the column you are going to collect. Depending on someof these things, talking in terms of volume assumes that what you are looking for goes as the density. I hope that for some of the things of interest this won't be so. For this reason, I think that whether the sought particulate goes with the density or not, you know where you are if you talk about sweeping out an area, Floor: What do you want, 100 square centimeters or a square meter? Ithink 100 square centimeters is very reasonable to talk about without an awful lot of complicated technology. If you have to sweep out a square meter, this is much harder, and, if you have to sweep out 100 square meters, then I think we are going to have to start talking about windows and some of the things that we hear about. Dr. Kalkstein: People are already playing with samplers for different experiments, looking for micrometeorites and such, in which they do have on the order of a square meter. the nose of the rocket. I wouldn't say they have been successful. They unfold You easily can expose the square meter and just carry it up after you are high enough to avoid disturbing the rocket's flight. Dr. Lockhart: One thing more that I think should be considered here is what, specifically, you are looking for. Are you looking for a general something that is up there now, or are you going to look for something specific that may have very low concentration and there is nothing you can do about it? Floor: Let's say that, of all the things that Lester put on the slide, we can get three of them; then we could start studying these and new things that get put in. constituents already there. With this we might hope to get additions in terms of someof the What size sample do you need? Or, do you feel that there is a potential for in- creasing sensitivity one or two orders of magnitude and in so doing be able to use samples smaller than those that your present methods would allow? 90