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This is about science produced by the California Institute of Technology and originally broadcast by station KPCC Pasadena California. The programs are made available to this station by a national educational radio. This program is about a surveyor with host Dr. Robert McGrath and his guest Dr. Leonard Jaffe surveyor project scientist for Cal Tech's Jet Propulsion Laboratory. Here now is Dr. McGregor. I have heard it said by a good many of the professionals in the field during the last two weeks following the fabulous surveyor success that this particular mission was without doubt the most gratifying and satisfying experience in there. Space careers before talking about this experience and perhaps some of the ideas and facts that have come out of it I think it might be helpful if we reviewed briefly AP historical background of the surveyor
project. You remember Leonard that the surveyor project persay began in the early days of NASA's career perhaps. I guess it was in the early 60s and it was one of the very first missions conceived to undertake scientific exploration of the moon. Do you remember the particular circumstances in which some of that thinking went for it. Well this was a time where we had tried some preliminary flyby missions of the moon 20 years three and for art they were intended to make it only were a survey of the moon from space measuring radiation and possibly taking a photograph or two. There was such an attempt as Ira Yes we didn't get any photographs we did get some radiation measurements of the Earth's radiation belts and in fact discovered the outer radiation balladeer it but we didn't. It
turned out come close enough to the moon at that time to really learn very much new about it. But that time plans began to be made. For the first landing on the moon which was the Rangers first American landing intended initially as hard landings. This was Crash sequences on the moon taking pictures as we went carrying a variety of other scientific experiments. It was hoped to make measurements as we approach the moment I recall that even that set of missions was changed markedly as the program developed and certain experience was acquired. It eventually ended up by providing pictures on the way in so to speak a 40 impact actually took place but it was surveyor then that literally was designed to attempt a gentle landing if you like and perhaps even undertake some measurements at the service. A surface.
Comparison of those original ideas with what we've come up with and this most recent experience. How did the original surveyors compare with what we've actually flown. When regional surveyors were intended to carry a great many scientific instruments and surveyor one carried their intended to have a payload of about 200 pounds of scientific instruments that was based However at that time on a launch vehicle capability which was expected to be somewhat more than actually materialized. That's right. The one trick I use here is the Atlas same tour and as time went on from the first planning the expectations as to what the Atlas Centaur could actually carry to the moon. Decreased somewhat in order to say it was necessary to reduce the payload. They also reduced the spacecraft weight as I recall the day not right. Go to a light oh yes indeed. And then there is no intent was to get the scientific information. Do you recall
some of the experiments that were proposed at the time the kind of measurement that was going to be attempted. Well there was such things as an X-ray diffract time with it to make measurements of mineral type a gas chromatograph to make measurements of any. Guesses it might be present on the surface or Obama from the surface by heating our variety of eye measurements that might be made not only on the surface but several feet down. My drawing of her on the surface and placing instruments in the hole. So the original plan was fairly ambitious by my recent experience. This I suspect so. Then there's the experience as it developed with the spacecraft design evolving and the launch vehicle capable capability becoming more definite. We eventually came a couple of years ago to the present program definition and the present definition and description
and detailed configuration of the spacecraft in the payload. What is the actual mission content as we have it today. Oh I think it should be remembered that there are basically two kinds of surveyors currently planned. One is an engineering survey. And another is a scientific what we had in surveyor one was an engineering model and this was really intended to check out the spacecraft to verify that it would indeed function as we hoped that we could really carry out a soft landing on the moon. Get a camera operating here and prove out the equipment nor what concepts of a spacecraft and its operation as well as the boost to a goal that went with it. Beyond this we hope to have some scientific flights which will carry a payload of scientific instruments
including such things as two television cameras a seismometer a micrometeoroid experiment an alpha scanning experiment which is intended to measure the chemical composition of the surface a soil mechanics surface sampler and a touch down dynamics experiment. But these are all in these later scientific models. But for seven as currently planned our our engineering models. So the combination of the elements in this payload that would give us what kind of information about the business and he cameras for example working together what would they do that a single TV camera would not normally think of. Give us stereo viewing of the surface and this would mean much better data on exact distances of objects from the spacecraft. This will help us considerably in preparing a map of the nearby terrain.
How about the seismometer. What kind of information with us give us about what this would tell us something about the interior of the moment. None of the other experiments really do that. Hopefully if we detect any seismic activity and the mome resulting from internal motions in the moon or possibly from large external disturbances such as meteorite hits we can get some information about transmission of sound waves seismic waves through the rocks inside the moon and this in turn should tell us quite a bit about this internal structure at the moment. So perhaps from this we can determine whether or not there's a core as we have it here. Yes this is one of the current scientific questions. Is there indeed a car on the moon. Is that separated internally in any way into.
Rich regions and rock regions of the earth. We believe it is separated in this way. The scientific missions would be planned for what two or three or four years and a few two or three years ahead. I suppose that the present plan then is to continue with these engineering missions at the moment yes. The premise that we've gained a great deal of experience and confidence in the spacecraft and launch vehicle system with this single success what would be the purpose of these later so-called engineering missions where they have particular scientific merit. Well they are meant primarily for scientific purposes and certainly hope to get more scientific information from them just as we did from surveyor run them and what I would say they were originally conceived primarily to verify the operation of the spacecraft but also to provide some useful information for Project Apollo.
How would that get in right. Naturally it's desirable to minimize the risk to humans in the Apollo flights and therefore to reckon the way to go any site I see so that from day. Non-plan of the interesting landing sites for Apollo One could then deploy several surveyors that we have gone on into the next year or so into the science to get a particular type of right nation concept is basically a first exploration of the landing site with a surveyor. This way you're not risking you with it if it seems right from one surveyor sends back in the way of information then presumably we could go ahead and risk an Apollo landing in that general area. Mattresses talk a little bit more about the kind of information we actually acquired from a surveyor one. You indicated that there was scientific merit to
the accomplishment of tikus Arab amount from comets that have been made first. How does this compare with the Soviet Luna 9 mission which landed. I've heard a comparison made but from what little I know of Luna 9 there appear to be specific distinctions of the type of vehicle used the kind of coverage and detail that was acquired. What is your understanding of that mining. Well first as to the type of way only the family of the mine was around where I would consider it for some of the later Rangers. Like the survey on landing that with that second series of Ranger right there was a later series of Rangers which was considered at one time that would provide a so-called rough landing something between a g a crash leaning in any really soft One such a surveyor rut accomplish. However a decision was made some while ago not to
proceed with these later ranges because it appeared that surveyor would be available fairly soon and could do an even better job. Now what Luna nine dead and what these letters Rangers would have done. Rise up land that we capsule. Fairly softly on the lunar surface but not actually break it down the way for a smooth landing to read it break it. I'm not using a large retro rocket engine so there would not be completely destroyed by impact and then release it from the main spacecraft on the surface at a low enough philosophy so that the shock absorbing material around the capsule read protect the instruments inside from destruction. So we have every reason to think that the Luna 9 vehicle landed much harder than the severe one somewhat
harder it may not have been a great deal harder it rather looks from the data that the Russians ham released that their weenie was not very much higher. Just how gently did surveyor 1 land about 10 feet per second. Now during this landing process of survey airline as I recall there was a good deal of instrumentation onboard a spacecraft both engineering and scientific which was intended to give us information during the landing process itself just as the feet pads touch down. What were some of the things that were actually accomplished. Well the instruments were not really placed primarily for scientific reasons they were on their work as they were needed for the operation of the spacecraft itself. But we are of course trying to get I was scientific information we can out of the data that have been received. Of course it was recognized that one could glean such information. Oh yes indeed yes. The first kind of information
chronologically that would be returned. That should be of scientific interest would be. Information on the trajectory of a spacecraft between the neighborhood the earth and the moon. And this should give us information about the mass of the moon the mass distribution inside of the moon. The exact position of the moon. This is something we do on every flight. Right it gives us a refinement each time and yes important astronomical constants. Right next as we came in from up to our landing we were using radars to guide the surveyor down to a soft landing. Now these radar data should be telling us something about the radar reflectivity and more generally about the electrical properties of the surface of the moon. You know we have received these data now and are analyzing them so that in addition to inferences about the electrical properties of a surface you get
other information about the surface from the radar echo. Well it is basically electrical property information that we have information on the strength of the radar return as a function of direction for example. In a small area this is not anything we had before. I can take you for example some indication of the roughness of the surface. Yes and that bit is available and yes being examined now. How about next in the sequence of events. Well next thing you happened perhaps major scientific interest is it we actually touched down mechanically and we were very interested in measuring the forces at all lunar surface exerted on the spacecraft during this touchdown. We have information of this kind from strain gauges which essentially measure the forces in the three legs of the spacecraft. At the
moment they were touching in during the whole process of the touchdown during the second or so that it took for this spacecraft to touch and bounce some so that I got to work around there. Yes so actually from the strain gauge measurements one can infer something about the stiffness or hardness of the surface. That's correct. Next what would be the. You had another coming round I was going to add also it gives a certain information about how Rabelais area is simply from the times at which the three legs touched it turned out that touched down times on the three legs were the same. Within a few hundredths of a second. So he made a fine three point landing. We made a fine three point landing when the first light touched the other two legs were only an inch or two off the surface. So we know our spacecraft was quite level with the surface and the surface itself was fairly level. We do have other information on that too I think were there any other
measurements that were made during the touchdown process or did we go right to the pictures from there. I think the next information we got back was essentially the pictures. How about the thermal balance the temperature balance in the spacecraft did that with any information or did that come to equilibrium at some later time. Well right as rain or a slower process we don't start getting useful information back from the thermal measurements untold. Some hours let's say after touchdown it takes that long to really get any useful information concerning the surface temperatures or other thermal properties. Yes I remember that back in the design days that some of the staff worried at great length about what would be the thermal balance of course this is a critical design parameter and this would be dependent somewhat greatly upon the character of the surface itself. The inner surface itself so there is hope that one might infer something about at least direct computations where this is correct. Has this been paying off the data must be
available in some sort by yes. In general the predictions seem pretty good. One point that came out very strongly in analyzing the data is that the radiation of the thermal radiation of heat coming off the lunar surface depends strongly upon direction that the radiation back towards the sun is considerably greater than the radiation off the same spot of surface in a direction away from the sun. Yes. Also our thermal measurements on the spacecraft itself were interesting in that they indicated we had not kicked up such a cloud of dust on landing that we covered the P-8 and and metal surfaces of the spacecraft with dust. This would have greatly changed the temperatures of those services and this did not occur.
Then we went into this picture taking sequence starting with that first very marvelous shot of the one of the landing legs. I remember seeing in the laboratory photographs and the material that's been published the disturbance of the surface. Have we been able to draw very many conclusions yet about the character of the surface from that type of photograph. Oh yes indeed I think this is the most valuable information we have received back concerning this nature of the surface itself. First of all it was obvious even looking at the very first picture that the surface had been disturbed by the landing pad as it came down. And since it didn't come down very hard it was clear that the surface was by no means hard rock. It was obviously soft enough to be disturbed by it not very. Violent push on it. And so it must be a fairly soft material of some kind.
Just a first glance but certainly not a deep layer of dust as has been suggested in some quarters. Well this depends on what you mean by the red dust I suspect. The scientists such as Thomas goes who have suggested that there's a lot of dust on the moon did not suggest that it was really like the dust under the bed. I think their feeling was that while this might be a material made of very fine particles of the prodigal's would be stuck together to some extent and would have some strength. Therefore there was a cohesive structure side cohesive structure. This is right and going down a sort of frothy character to it maybe or. Well I think it's been said I really know that the material might behave something like snow when I think this is still running a fairly good description. Clearly it isn't snow but its mechanical properties are perhaps not so very different. The
later pictures of the pan which gave us. Very fine detail and showed the area the surface kicked up by the pit and showed clearly that this was not a a from off really that it was made actually of separate protocols. It was less like a soil or sand or gravel right by well not gravel a very fine particles apart those were a twentieth of an inch or smaller. For the most part. Oh well they were under quite a few larger ones but the basic bulk of the material was fairly fine it was hard to see even with the resolution we had in those pictures. But it's clear it wasn't all one piece the surface it was like a psychotic thought it wasn't a slab of rock or a seer even a slab a price right. We took pictures for the entire lunar day two weeks or so that was available. But on each of the earth days in which we were
in command it was of course clear that using the antennas at Goldstone the prime command and as that we had only a third of the day in which to take pictures. But even with this the more limited time period of observation and sending and receiving of information we got a large number of pictures. I've seen a number something like 10000 pictures of that right number. This gave us a good many hundreds a day a few thousand back nearly a thousand day. How was it. We were so interested in taking the same scene over and over again I should think there would be a repetition here. Literally this is a consideration of sun angle. Well there were two reasons are one wise. We did this in color. So this essentially meant first taking the pictures in black and white then going back in taking it three times through three different color
French's. So this meant as a minimum we wanted to take each area four times also in probably more important really was at the sun angle or as moving as the moon went around the Earth to the lunar day progress right. So the shadow pattern changed and this changes the appearance of the surface very greatly it adds enormously to our information. If we look at a given spot as the shadows change over it we can get much better information as to the slopes. Of the local terrain following the shadows. Yes a parking question you get is that when you look at the pictures in High Noon lunar new on the surface appears to be somewhat flatter does it not. Right and then he get towards early early in a day or late day it looks much coarser on a fine scale. This is true also.
You can get certain types of information best at certain sunny angles for example for a color comparison. You don't want shadows in there particularly like sort of full sun high stuff so you want a high side right for for details of the slopes and elevations of the surface. You do want long shadows but checking whether there is any Or again whether they were any rocks for example which were sitting on the surface with clear space between them and the surface part of the under part of them and as you would like to have the sun right overhead to see if there's any shadows at high noon. Yes there were and then of course there is also the question of resolution. You had two different focal lengths that writes correct focal length and holes that were available to you. Among the things that were seen. Which would you mention as being of most striking and exciting. Well to me frankly the most striking shot was the one of the pay ad
in the high resolution fine detail which showed as I said earlier that the surface arises so I am composed of separate particles quite fine that the prodigals didst tend to stick together. They were lumpy. They want a Lucy and. Also by measuring the depth to which that pad penetrated and going through suitable analysis using the force data from the strain gauges were able to get a pretty good number for the strength of the soil. So that I think was perhaps the most interesting picture. I'm the ones that seem to me were quite striking were the ones of the rock fields in the distance which showed a large number of rocks a yard or more across literally fields of them.
Was this in immediate proximity of major crater area. Yes roof I think could you make such an I don't know. Well it's not major in the sense that you could see them from or if the graders were by no means that large but the craters of perhaps 100 yards or a few hundred yards across which are a little too small to see from Earth. As I recall there was also some pictures that were shown which showed a horizon with a hill in the distance. What was the relationship between that scene and the terrain local terrain that we're know from the lunar maps. Robin Room to make an identification as related to what we thought would be a rather smooth area inside of an almost buried crater of which only the rim is showing about the general lunar terrain and the particular place we landed we were about 12 miles away from the north west corner of this large
crater area and inside of it and we could see that portion of the rooms projecting over the horizon and you could use this signing information on it to provide a better identification of our landing site by triangulating on these mountain peaks in the distance. So that was the old ram of that old crater. Right well this certainly has been. An exciting period for us all. There is a tremendous wealth of information here and even with the so-called engineering shots as you referred to that we've obtained a large amount of scientific data. We look forward very much then to the scientific missions which you've mentioned Leonard and maybe in a year or two years or three years whatever the time scale is will have even greater breath of knowledge of what goes on to characterise surface and something about its chemistry. This was about science with host Dr. Robert Mugabe and his guest
About science
About Surveyor
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California Institute of Technology
KPCC-FM (Radio station : Pasadena, Calif.)
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University of Maryland (College Park, Maryland)
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Episode Description
This program focuses on the science behind the Surveyor program that sent spacecraft to the Moon. The guest for this program is Dr. Leonard Jaffe, Surveyor Project Scientist, Jet Propulsion Laboratory.
Series Description
Interview series on variety of science-related subjects, produced by the California Institute of Technology. Features three Cal Tech faculty members: Dr. Peter Lissaman, Dr. Albert R. Hibbs, and Dr. Robert Meghreblian.
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Guest: Jaffe, Leonard
Host: Hibbs, Albert R.
Producing Organization: California Institute of Technology
Producing Organization: KPCC-FM (Radio station : Pasadena, Calif.)
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University of Maryland
Identifier: 66-40-13 (National Association of Educational Broadcasters)
Format: 1/4 inch audio tape
Duration: 00:28:30
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Chicago: “About science; About Surveyor,” 1966-11-21, University of Maryland, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC, accessed January 30, 2023,
MLA: “About science; About Surveyor.” 1966-11-21. University of Maryland, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC. Web. January 30, 2023. <>.
APA: About science; About Surveyor. Boston, MA: University of Maryland, American Archive of Public Broadcasting (GBH and the Library of Congress), Boston, MA and Washington, DC. Retrieved from