Keynote Address*

DR. S. FRED SINGER Professor of Physics, University of Maryland

INTRODUCTION G. C. TEWI:\KEL, Past President, .ISP

Our Convention is honored this year in having as its guest speaker Dr. S. Fred Singer, Professor of Physics, University of Maryland. [ rnld that his work has been associated with such nebulous topics as: The Upper Atmosphere; High Altitude Sounding Rookets; Geophysical Re­ search with Artificial Satellites; Primary Cosmic Rays and their Origin; Environment in Space Vehicles; Orbits of Rockets and Space Vehicles; Theory of Relativity; Origin of Meteorites; [on 0­ spheric Currents; Magnetic Storms and Aurora; and R.adiation Belts. Dr. Singer has earned for himself distinction as one of the most brilliant of our space scientists. He designed satellites before there were any. He pre­ dicted the existence of radiation belts which later were discovered by Dr. Van Allen. Dr. Singer was commended by President Eisen­ hower for outstanding achievement in the develop­ ment of satellites for scientific purposes. He was the recipient of the Distinguished Alumnus DR. S. FRED SINGER :\ward by Ohio State University in 1958. He was selected as olle of the Ten Outstanding Young excltI11g problems that exist in outer space, Men of 1959 by the U. S. Jr. Chamber of Com­ merce. particularly in connection with the planets. It is my pleasure and honor to present to you lI·hat their scientific importance is, and why Professor Singer of the University of Maryland. it is so vital that measurements be made. The start "'ill be the Moon-our nearest INTERESTING PROBLEMS IN neighbor-sometimes called a satellite of the OUTER SPACE Earth, because it in fact revolves around the RESlDEKT Tewinkel, President Karo, Earth. But sometimes it is also called a twin P Ladies and Gen tlemen of the Consecu ti ve planet of the Earth. Meeting, r am very pleased and honored to The origin of the Moon is unknown. There be invited to deliver thir Keynote Address are generally two types of theories. One is that today. the Moon was captured by the Earth but was After spending consideyable time in think­ formed independently. The other is that the ing about the subject I decided that since very Moon was formed close to the Earth, within soon you will have finished explori ng the its gravitational lield. Later I will tell you Earth, there then will be only one place to go, how careful measurements of the features of and that is out into space. Therefore, I will the Moon make possible deciding between touch on some of the interesting problems these two. possibilities. For historical reasons that exist in outer space for photogramme­ it should be men tioned that there are also trists, surveyors, cartographers and mappers; theories which claim that the Moon came out in other words, for people who have the back­ of the Earth after it had been formed; I fear ~round and professional interest "'hich you those theories do not stand up very well under have. the lall's of physics. I am not an expert in many of the new in­ rt seems fair to start with the problem of struments and new techniques. but [ can talk t he back side of the i\loon-the hidden side­ about what I personally think are some of the because therein lies theonl)' photogrammetric

* Presented at the !\SP-l\CSi\1 Gellcral .\ssenlhly, The Shoreham Ilotel, Washing-Lon, D. C, i\larch 22, 1%I. 371 372 PI1UTU(;H.\~1 ~[ETR[l' ENGINEEHING achievement made in space so far. As you Unfortunately their techniques were not know, it was made by a Russian scientific perfect. In the first place, from reading over group in one of the lunik rockets, October 7, their original paper, it appears that the nega­ 1959. They were able to photograph the back tives themselves were not particularly good; side of the Moon using a camera with two there were little imperfections in the film; focal-lengths, 200 and 500 millimeters. They the development may not have been carried were able to obtain pictures of 10 millimeters on properly; the contrasts were not always and 25 millimeters in diameter, which they right. took on 35 millimeter film. Secondly, there was radio interference. It is a very important achievement. But While pictures were transmitted several from a technical point of view, the measure­ times from the probe to the Earth, there was ments were not ideal. In the first place, the radio interference; as a result noise was intro­ distance to the Moon was quite large--of the duced into the picture. order of 65,000 kilometers-during the time I think it extremely interesting how they that the camera was operating. And secondly finally reduced the data which they received -and this is probably the most serious­ on the Earth. I will spend a little time on that, they made their observations when the back because I am sure the action will interest side of the Moon was fully illuminated by the you. Sun. Therefore,- no shadows could be ob­ They took the precaution of having the served. it is extremely difficult to observe analysis made by three separate, independ­ any surface detail of the Moon when it is ent groups-one in Leningrad, one in Mos­ viewed under full illumination. cow, one in Kharkov. These groups did not The spectacular lunar pictures which you communicate with each other. They only always see are those taken during half-moon, compared their final results. This is quite im­ because then the craters and the mountains portant in order to get a completely unbiased throw shadows, and the relief stands out picture. particularly well. In fact, the most successful I mentioned before that not much surface picturing of the Moon that I know of is a detail is visible because the Sun was shining composite, the two halves of the Moon taken full on the Moon. They could however see with the Sun first on one side, and then on the surface detail very well near the edge-actu­ other side. When joined together, the whole ally the northwest rim-where many of the of the Moon surface is seen in relief. lunar features were already known. In spite of the fact that these pictures were You are probably aware of the fact that taken under fairly unfavorable conditions, the Moon "librates," so that we can see a they did achieve some results which they little around one edge of the Moon when it is analyzed. I should briefly discuss the tech­ turned one way, and then around the other nique because it has not been too well ex­ edge when turned the other way. They were pounded. It has only recently been released able to observe the edge features of the Moon by the Russians in a Russian journal. Also, quite well, and showed that the features it was discussed at a conference which the continued around into its hidden side. Russians organized last December in Lenin­ But then they ran up against the following grad. problem. There are on the Moon, roughly As I mentioned, the pictures were taken on speaking. two types of features. These are the 35 millimeter film. They were developed in so-called maria. the oceans-of course they the vehicle itself using very much standard are not really oceans. but are so-named-and types of processing techniques. The negatives the mountains. The contrast between them is were dried, and then scanned with a slow quite large. They have different reflecting television type of scanner. This has the ad­ powers. Furthermore, there are also small vantage of getting the resolution of the photo­ features on the Moon which have a rather graphic process without having to recover the low contrast. pictures. You can transmit them to the Their first problem was reducing the ex­ ground by telemetering. A further advantage treme contrast without destroying the moder­ is that you can take your time about trans­ ate contrast. They went about this in a very mission. Because you can scan as slowly as fine way. Essentially the need is a dynamic you like, you can get fairly high resolution. compression of the picture. They pre­ In other words, the resolution of the tele­ pared what is called a photographic mask. vision system, while of course not as good as The technique is quite new to me; per­ the photographic resolution, is better than haps it has been used by others, but I suspect televising directly. not. They then constructed a positive which KEYNUTE ADDRESS 373 was washed out, and purposely blurred it by But perhaps I should make clear that printing out-of-focus. They made it with very all of the back side of the Moon has not yet low con trast. Then they superimposed this been photographed. There is still an u nex­ positive on the negative and produced plored region which has not yet been seen. another print. In this way they were able There is still tremendous need for looki ng at to reduce the dynamic range-the con­ the back side of the Moon with much better trast range of the picture. They could reduce resolution and at a time when the Sun is so the extreme contrast without destroying the si tuated that one can see the relief and the moderate contrast. details much better than in the past. This technique worked well but unfor­ Leaving this problem for a moment, I tunately they had other problems. would like to discuss another one, concerned I mentioned the noise ,in the transmission. with the Moon. That is how does one prepare The only way they could get rid of that was a con tour map? This has just been done, by superposition of many of the transmissions. incidentally, by Baldwin who wrote a book They superimposed some dozen of these called "The Face of the Moon." He is re­ on each other, and wel;e then able to see publishing it with new data. which features of the Moon survived. Those If you want to know the altitude of a point that survived were believed to be real fea­ on the Moon, in order to construct a contour tures; those that did not survive were sus­ map, there are two ways of doing this, in pected to be noise introduced into the trans­ principle. One is to study what is called the mISSIOn. terminator. That is, you look at the line The third technique which they finally where the illuminated portion ends and the used is also interesting. da,'k portion begins-this is the terminator I mentioned that the pictures were trans­ line. Of course, you will see shadows. You mitted by radio techniques to the ground measure the length of these shadows. where they were recorded on magnetic tape. You know the altitude of the Sun. Therefore, So essentially what they had on the ground you can estimate the heights of various sur­ was a magnetic tape record of the pictures. face features. This method has been found to Instead of turning this record back into be quite unsatisfactory and of very little light, as before, they trkated the magnetic accuracy, because, as you probably know tape electronically. They decided to work better than I, the terminator line is very at a particular level of intensity correspond­ indistinct. due to the low altitude of the ing to light intensity, and then amplify Sun. the magnetic tape signal around this level. A much more precise method is the one Thus they increased the contrast at a based on the libration of the Moon. I touched particular density region. Of course, every­ on this earlier. thing that was very bright got brighter Because of the lunar bulge, the Moon does and showed no resolution at all; and every­ not show us the same face all the time; it ac­ thing that was dark got darker. But this did tually oscillates slightly. This oscillation not matter, because the~ had the magnetic amounts to about 14 degrees. So one can tape available and could \'un it over and over really see more than half of the Moon. again. So gradually they increased the con­ If the Moon were a perfect sphere, and if trast at each level. They were able to resol ve you picked a point on it-let us say one things of extremely low cdntrast by this proc­ marked by a small crater-you could calcu­ ess of electronic amplification. late exactly where this point is going to be I mention these factors to indicate that a during the libration. If the Moon is not a considerable amount of effort went into anal­ perfect sphere, then this point, as it librates, yzing these pictures. They were able to re­ will not be at the exact place that you ex­ solve something like 250 surface features of pect. the Moon. Of the total they considered per­ This, brieRy, is the principle of measuring haps 200 to be reliable and the rest of dOli btful altitude, or deviation from the spherical sur­ validity. face, using the libration. Unfortunately, this effort while very fine You must pick a lot of very good surface and pioneering, did not settle any funda­ features on the Moon, observe them carefully mental problems about the Moon. It showed, and mark their position as the Moon librates. as expected, that the bacr side of the M 0011 Then you have to make a lot of calculations. is more or Jess like the fl1ont; that there are This in fact has been done quite recently. craters, maria, and all the features that \Ve now have a contour plot of the front side we know exist on this side of the Moon. of the Moon. I would say it is good to maybe 374 PIIUT()GR"\M~IWrRIC ENGINEERING

a thousand foot altitude. It shows, in fact, and "frozen in" because the Moon is not per­ that the maximum depressions occur, as you fectlyelastic. would expect, in the maria-the so-called If the craters were formed a long time ago, oceans-and the maximum altitudes occur on you would expect to observe an ellipticity and the mountains. The difference between that the axis of this ellipse would point to­ these tll'o--the maximum range---is of the wards the tip of the bulge. order of 30,000 feet. which is a consider­ Think of the Moon as a sphere with circular able distance. craters on it. If you pullout a point on it, so It is interesting that the altitude resolution as to create a bulge, the craters will be­ is now about as good as the resolution of sur­ come distorted. Therefore, it is very importan t face detail on the Moon. to look for their distortion. This is what was Lea\'ing this problem, and going on to a done, and it was found that the ellipticity is perhaps more exciting problem-the craters. very, yery small and may in fact be zero. They tell us something of the history of the I suggest that here is a yery good job for 1\/oon. photogrammetry, and it is a very important I believe the paramount view today, and job, too, because the presen t photographs do the one which I think is the correct one, is not establish at all whether or not this el­ that most, if not all, of the craters originate lipticity exists. I would like to point out for through the impact of large bodies, such as you the consequences of the presence or meteorites or asteroids, which hit the Moon, absence of this ellipticity. As they hi t they prod uce an explosion II-hich If the ellipticity pointed to the bulge really blows off material and generates a crater. exists, this would indicate that the craters One mystery about the craters is that they were formed at a time when the Moon was seem to be nearly circular. \Vhy is that? The still very much closer to the Earth than now fact that they are circular led people earlier -some billions of years ago. If you trace the to think that these were extinct volcanoes. Moon's history, going back in time, it comes But now we know that meteorite impacts will closer and closer to the Earth. And this has also produce circular craters. The reason, I been done first by Sir George Darwin and think, is quite interesting. It has nothing to more recently by a German astronomer who do with the idea that the meteorite may has calculated that some four billion years come in nearly yertically. Even if at a ago the Moon must have been about three fairly large angle, it will still produce a Earth radii away instead of today's sixty circular crater. The reason is that the Earth radii. Going back still further, he calcu­ meteorite is quite small compared to the size lated that the Moen was then captured by of the crater. The Arizona meteor crater, for the Earth gravitationally-it was just an in­ example-the meteor body itself-may be dependent body which came along. This was only of the order of one per cent of the size of a rather complicated process which we do not the crater. This crater is due to a large explo­ need to go into now. Eventually its orbit was sion which essentially does not depend on the changed into a circle and then this orbit he­ direction of the meteorite's momentum as it gan to expand. That is where it is today. comes .j n. The explosion, therefore, always You can see that at three Earth radii, the leaves a circular crater. Earth's tidal force on the Moon would have But are the craters really quite circular? been very, very much greater than it is today. This matter has just been studied by a col­ In fact, if you calculate the effect of this tidal league of mine at the University of Maryland, force, you can figure the deformation of the Professor Ernst Opik. He seems to detect a Moon to be so great that all of the craters slight ellipticity. I will try to explain \\"hy he would have been broken up and destroyed. undertook this study. Yet we see today that all the craters are qui te The Moon is not a perfect sphere. Its libra­ perfect; they have a nice, smooth ri m. tion tells us that. In fact, the 1\100n has a This leaves one of two conclusions. Either bulge, which points towards the Earth. It is the Moon did go through this kind of capture a so-called triaxial body. The bulge is pro­ process, some four billion years ago, and the duced by the tidal force of the Earth's attrac­ craters were all formed afterwards, so that tion. The Moon at one time was very much they came out to be nice and smooth. Or the closer to the Earth. The tidal force therefore Moon was never captured at all. In order to II-as then much stronger. This bulge may he a decide between these two possibilities, one fossil bulge that was prorluced when it was needs to measure the ellipticity of these close to the Earth, some billions of years ago, crat"en,. KEYNOTE ADDRESS 375

Let me go Ilack (0 (he first possibilily again, fac(, Ihey do cover the maria, bu ( (hcsl' da rk (0 shmy \I'hal' is \\"rong \I'ilh it. II \\"ould seem areas secm 10 come back again ano again. So "ery strange fOt, the i\loon to b(' caplured by Ihey Illlls1 Ila,'l' somc kind of regcnerative the Earth and not to have any craters on it at power, the sort of pOII'er one associates Idth all until after the capture and the Moon had hardy plan ts, such as lichens-a sort of com­ gone out for some distance. Therefore. it bination of moss, fern, and algae. It is there­ seems a little more reasonable to think that fore no\\" believed quite widely that lichens the Moon was actually formed from loose ma­ do in fact exist on Mars. There may be other terial \I'hich happened to be going around the ,·egetation. Earth at a distance of five to eight Earth An additional piece of evidence which I radii; that it coalesced into a body; then that might mention is spectroscopic. People have this coalescence process-the last part of it­ measured the infra-red spectrum of Mars and actually produced the present craters, he­ found the absoqHion bands in it which cor­ cause the impacts \I'ould have been energetic respond to the bands in organic molecules, enough to give them. thereby indicating that some kind of organic To be consistent with this picture, which, molecules do exist on Mars. These absorp­ as I mentioned, was put fonvard by my col­ tions come from the maria; they seem to be league Prof. Gpik, one would expect these definitely associated with these dark areas. craters to have a very small ellipticity di­ The topography on Mars is fairly smooth. rected to\l'ards the bulge. There are no violent mountains and no deep I think that I may have talked enough ridges. as lye have on the 1\loon. But there about the Moon. Of CO~lrse, one could talk may be quite large difTerences in level. \\'e do about it for hours. I only wanted to illustrate not knOll'. \\'e cannot apply the techniques some of the problems, to show that they are that \I'e use for the Moon to measure the con­ really basically interesting and intriguing, tours of Mars. and that they demand a great deal of techni­ There seem to be interesting little spots. cal and scientific skill for their solution. white spots, on Mars. These may be due to Perhaps I should say a few words abou t the \I'ater vapor. \I'hich is condensed hoar frost, planet Mars. There the problems are quite in other words. Frost would tend to condense different. out from lower regions, so there must be some Mars has an atmosphere. It has some modulation in the plateau. Maybe there are water vapor. I t has erosion. It is a planet low regions and high regions. The maria are which resembles the Earth much more than thought to be depressions in low regions. the Moon does, and therefore it will be more You probably have heard about the haze familiar to some of you and will be more on Mars. Actually there are three types of amenable to the techniques that are used on hazes, or clouds. There is the so-called blue the Earth. haze; it is not blue at all; it is a type of smoky There are several features about the Mar­ haze. I n the blue region of the spectru m you tian surface \\"hich r \I·ill mention very quickly. cannot see till" surface of Mars. To see the Like the Moon there are regions which are surface, you must lise red light. And since called the "maria"-the oceans-but they we al\l'ays use sunlighl, which contains red are certainly not filled wilh water. Then we light, you can see Mars best if you lise a red have "continents," which are higher than filter. So much for the "bllle" haze. Thl' the maria. And white polar caps. The con­ yellow haze. of course, is due to dust storms. tinents are generally reddish-yellow, the It is of quite a different origin than the blue. maria seem to be dark grey, and the polar The white haze, when and if it does exist, caps, white. probably consists of ice crystals. Tt occurs I t is though t tha t the maria-the depres­ very rarely. It always occurs near the ter­ sions-derive their COI01' from either Iheir minator line. It may indicate jusl the freezing peculiar soil or from vegetation. The argu­ out of the little bit of water vapor which is in ments which favor the hypothesis of vegeta­ the Martian atmosphere. tion, to \I'hich I also subscribe, are the follow­ These are the main problems that we are ing. There are tremendous dust storms on going to run into on observing lhe surface of Mars-not all the time, but quite often. You Mars. would expect that after some time this yellow Perhaps I should close this discussion of dust should have covered the maria, so that Mars with one remark about the famous they would be filled up, so to speak, and their canals. I think there is no doubt that such surface features would have disappeared. In things as narrow black markings really exist. 376 PHOTOGRAMMETRIC ENGINEERING

They radiate from circular features \\'hich arc planet, hut from fairly close to it and with C

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