larly in connection with the over-the-horizon radar in early warning missile detection work. Then perhaps I could tell for a few minutes about the VELA high-altitude spacecraft for doing research and development on the background within which one would have to observe nuclear explosions in space and perhaps because of the interest. your committee expressed just within the last hour or so about the Lasers, I can also talk a bit about ARPA's involvement in this. Would that be satisfactory? Mr. MAHON. Yes. Dr. SPROULL. This is the over-the-horizon missile detection system. that ARPA did some early research work in and is continuing to do research in. Within the last year there have been some notable successes. The system is as follows. (Discussion off the record.) Mr. FLOOD. What is the ceiling of the ionosphere in statute miles? Dr. SPROULL. There are several layers. The layer we talk about is about 150 kilometers, about 100 miles high. (Discussion off the record.) Mr. FLOOD. No two signatures could conceivably ever be alike? (Discussion off the record.) Mr. FLOOD. Including cloud layers and bad weather? Dr. SPROULL. Cloud layers and bad weather do not interfere at all with this system. (Discussion off the record.) The over-the-horizon radar in missile detection systems is one of the most interesting developments in DEFENDER. I would rather not go into a number of the other things in DEFENDER because I am afraid it would take you far beyond your time. I wonder if I could go now to the research and development we are doing in connection with the detection of nuclear explosions in space or in the upper atmosphere. Mr. FLOOD. Just this one question. How many really important things are there in DEFENDER? 12, 26? Right now, that is, that we have not utilized already. Dr. SPROULL. I am sorry-I do not know quite where my threshold would be as to what constitutes an important thing. This [pointing] is starting to be utilized right away. The most of the DEFENDERfor example the heart of it is our Project PRESS on reentry measurements. They will not really be utilized in the ordinary sense of the word Of course, most of DEFENDER's effort goes directly into that. The penetration aids part of DEFENDER is another part being used immediately in the sense that the output of its information is going into Air Force and Navy penetration aids development. Mr. FLOOD. Most successful idea, no question about it, the whole concept. Dr. SPROULL. We think that one of the things that makes the DEFENDER useful is its playing of the offense against the defense. (Discussion off the record.) 30-741-64-pt. 5-10 NUCLEAR TEST DETECTION (VELA ) If I could turn to the VELA program, this is a cutaway of one of two spacecraft which were launched the middle of October last year. They are highly complex spacecraft. The most striking thing, 1 think, about them was the fact that the first launch was a complete success. It may be that the next ones will not be so successful, but at least the first launch of this pair was completely successful. By that I mean that the spacecraft were put into nearly circular orbits at about 50,000 nautical miles from the surface of the earth on opposite sides of the earth. Mr. FLOOD. With reference to the Equator, where were they? Dr. SPROULL. They are in tipped orbits with respect to the Equator that it, the plane of the orbits is the plane tipped with respect to the Equator. Mr. FLOOD. Where were they fired from? Dr. SPROULL. From Cape Kennedy. They were fired together with the same ATLAS-AGENA rocket, separated after they were in the transfer elliptical orbit. The rocket of the first one was fired at apogee to make the ellipse go into a circle, later the other was fired at apogee to make its ellipse go into a circle but at different times so that one is on one side of the earth and one on the other. They are about 180 degrees apart now and varying only very slowly their relative positions, so that between the two of them they see practically the entire surface of the earth. They could detect, in fact, an explosion of the order of anywhere in the space that is of a radius equal to the distance from here to the sun. If one took the entire space with the earth at the center with about a 100-million-mile radius, one could see explosion anywhere in that region. a Mr. FORD. What is the life expectancy? Dr. SPROULL. The life expectancy at the beginning of our project was about 6 months. We expected to make launches every Now these two birds have been there for just about 5 months. Both of them are still working properly. One of them had a slight suspicious defect which, however, is intermittent. Also there is a backup or redundant circuit for that particular element. It has not been necessary to use the redundant circuit. We still have a complete backup system available for that. We do not really know the answer to your question, Mr. Ford. It is at least 5 months, maybe a great deal longer. The other spacecraft has one battery that is a little suspicious, but again the spacecraft is working on its original batteries and it has not been necessary to transfer to the spare set. Mr. FLOOD. What is the purpose of the solar cell panel? Dr. SPROULL. That keeps charging the batteries. The batteries are needed because from time to time Mr. FLOOD. The source of power is the solar cell panels? Dr. SPROULL. That is right. From time to time the spacecraft is eclipsed by the earth. The earth comes between it and the sun, although the eclipse is not very long because the orbit radius is over 10 times the earth's radius. Mr. FLOOD. They are storage batteries? Dr. SPROULL. That is right. The principal detectors are these Xray detectors and the idea is to measure the background within which a detection system would have to work. This is not intended to be an inspection system. It is intended to do the R. & D. on which you could design a detection system. Mr. FLOOD. What do you do with the information you collect there? Dr. SPROULL. It goes into the Air Force Center, Sunnyvale, Calif., and some of it is read out in real time and some of it is stored and read out every 6 hours. It tells us, for example, what the maximum of coincidences was among these X-ray detectors. If you had an explosion, you would expect that all of the detectors on the same side of the spacecraft would show a large signal at one time. If you just have background from residual radioactivity or from a cosmic ray hitting or something like that, you would expect only one or at most two or three of the X-ray detectors to show a signal. We have never seen more than a fourfold coincidence. Mr. FLOOD. Aren't you in the area of the old and new radiation belts? Aren't you about in the area? Dr. SPROULL. No. We are just above the radiation belts. In fact, that is the reason why we have chosen this particular orbit of about 50,000 nautical miles. Mr. FLOOD. What about the new one they dusted off last week? Dr. SPROULL. There is still some radiation at this height. It is tapering off gradually. It never comes exactly to zero. Of course, there is the solar wind, so there is a considerable background but it is much less at this altitude than it is at lower altitudes. That is also probably part of the reason that the solar cells seem to be functioning so well at this altitude. We chose the altitude to get the background low and we have found that the background is agreeably low, and that means that if we did detect a five or six or so coincidence among the X-ray detectors it would be a very significant event. There are other detectors other than these. There are gamma ray and neutron detectors Mr. FLOOD. What does that mean? Dr. SPROULL. To make a detection system in space one would have to set his threshold of significance adequately above the background level so that the false alarms would be if possible zero, but certainly Mr. FLOOD. It would be an arbitrary line. Dr. SPROULL. Yes. It looks as if now we can set that line, with this kind of system, at just above fourfold coincidence of the X-ray detectors. I just wanted to point out that detection is only one of the problems of a system like this. One would also like to find out as much about a suspicious event as he could, how big it was, where it was, whether there was anything about it that tells you what the purpose of the test was, whether it was for developing of an ABM weapon or for just proof testing of a weapon, et cetera. Mr. FLOOD. What about natural phenomenon, explosions in the ionosphere, space atmosphere and natural disturbances? How does this pigeon react to these? Dr. SPROULL. The principal natural disturbances are those coming from the sun, solar flares, and the principal background of X-ray detectors is the solar flares, but the neutron detectors and the gamma ray detectors do not have as large a background from that source. They respond more to cosmic rays, but when you look at all the de tectors together, since they respond differently to natural events, then the combination would respond to an atomic explosion. We feel we can distinguish an explosion from the natural background. But it is exactly the kind of thing that you are asking that makes it desirable to carry on experiments like this with the natural background. Mr. FLOOD. What metal is in that hardware? Dr. SPROULL. It is mostly aluminum, most of the things are, to hold it together. There is a fair amount of magnesium, too. The solar cells are silicon and covered with a very thin layer of glass to keep the micrometeorites from damaging the surface. The rocket motor down through the center is now, of course, not there any longer. That was burned out to put it into the orbit to begin with. Mr. MAHON. Does this spacecraft maintain a certain attitude as it proceeds through space? Dr. SPROULL. Yes. I am sorry I did not mention that, Mr. Chairman. These were spun, the pair of the spacecraft were spun, so as to give them a high angular momentum about a particular axis so that axis would maintain itself in space in the orbit, even in the presence of small disturbances like micrometeorites. So it was spun out like a rifle bullet to stabilize it against small perturbations. Mr. MAHON. So it does not just proceed through space in a topsy-turvy way? Dr. SPROULL. No. It is going in its regular orbit that is very nearly a circle, remarkably close to a circle and in its orbit it is spinning. In fact, it is quite the analogy of the earth going around the sun, spinning on its axis at the same time it goes through space. Mr. FLOOD. There is considerable stability then? Dr. SPROULL. That is right. It has a very high angular momentum due to the spin, compared to the disturbances that can be given to it by the light particles coming in and hitting it. Mr. FLOOD. That lends itself to the reflection of information. Dr. SPROULL. Yes. We know which detectors are illuminated. Mr. FLOOD. Where they are. Dr. SPROULL. Yes. (Discussion off the record.) Again, we do not expect to see such with this device, but we expect to find the background. Mr. FLOOD. Do those elements all arrive from the same sources? Dr. SPROULL. I am sorry Mr. FLOOD. Does the X-ray arrive from the same source, kind of thing, a projection? the same Dr. SPROULL. If it were a nuclear explosion it certainly would, yes, but from the background the solar flares of course extend over a large region of space, hundreds of thousands of miles. Mr. FLOOD. If it were a nuclear it would clearly be narrowed to point "X." Dr. SPROULL. That is right. Do you have a few more minutes? Mr. MAHON. Yes. REMOTE AREA CONFLICT (AGILE) Dr. SPROULL. I would like to turn to a LASER project in our Project Agile, then, that is a quite different thing from the thing that Dr. Brown was talking about, because he was talking about our LASERS. Incidentally, ARPA has about a program in LASERS as part of the program, the overall program he mentioned to you, but in addition to that work that ARPA is doing, with the possible implications for I thought you would be interested in seeing an application of quite a low-power LASER to the remote area conflict. Mr. FLOOD. Are you using your LASERS to any degree at all in Dr. SPROULL. No, we are not. The LASER is a line of sight device as far as we can tell and it is not, as Dr. Brown also mentioned, an all-weather device. Mr. FLOOD. I thought radar was too, until you fellows started bending it. Dr. SPROULL. Yes, but we are talking here in the over-the-horizon work of radars, in the order of the electromagnetic waves can be reflected. They are actually bent as they go into it but it adds up to a reflection by a layer of electrons. At high frequencies. as you go to higher frequencies Mr. FLOOD. I know, but you would be surprised how a very few short years ago one of your predecessors, fully qualified, insisted this bending of radar could never be done. Now you say LASER has no potential. Dr. SPROULL. I would like to make my remarks more quantitative and then I will express my opinion at the end, if I may. Mr. MAHON. All right. Proceed without interruption for a while. Dr. SPROULL. The over-the-horizon radar we are talking about is about and if you look at the electron density in the ionosphere that is necessary to bend that, it turns out to be quite modest, the electron densities. As you go from 10,000 megacycles, which is X-band radar, the electron density in the ionosphere is nowhere large enough to bend it. Those rays go right on out. Now it is conceivable that at least locally one could make very much higher densities of electrons, but it is a very large project. In lasers, what we are talking about is many orders of magnitude higher frequency still. We are clear through the radio frequency, the microwave frequency region into the infrared, where we are talking about 10th-to-the-14th cycles per second, not just times the frequency and so the electron densities one would need to bend a laser beam are the sort of electron densities that you get in a metal, where of course you can make a reflector. But it is very difficult for me to see, and I will end there-I am not saying it is impossible. It is very difficult for me to see how you could get that kind of electron densities in any atmospheric situation. This, as I say, So we are something like is done with the here-and-now state-of-the-art of lasers. It is just put together to see if we could get a device that would be useful in counterinsurgency. (Discussion off the record.) |