JSC (AV) - Skylab 4 - General Purpose IVA Telecast - TV 77 - Gibson Explains Ultraviolet Part 1

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FR #A218 SKYLAB 4 KINESCOPE TAPE 7, PART 3 of 3 correction to a number which I handed in yesterday (garble) perihelion (garble) standby. Just gone through one of the most dynamic phases of its lifetime. It's just passed at its closest point to the sun, which we call the perihelion, October 28th, and at that time received a maximum amount of heat from the sun (garble) and also the tail was forced to swing from one orientation around to another (garble) particles from the sun which we call the solar wind pushed it around so that (garble) over from the sun. Now however it was moving along at a pretty good clip this time - was moving about a quarter of one million miles an hour and at that rate, it will be able to get to the moon from the earth in about one hour rather than the customary three days which it had taken us in the lunar program, and it was relatively close to the sun - was about a little over 13 million miles. Now we have seen a fairly pronounced change during this period of time and I think we have recorded a fair amount of words, sketches and certainly with the ATM data. Okay, we'll break here now and go on in and pick up the remainder of this discussion of the ATM instruments. Perhaps one of the most useful experiments essentially that we have onboard to learn about Comet Kohoutek is the XUV flint spectrograph Segment which is a rather long title. What it does is to look at a very small/of the comet and determine what is various colors of lighting in it - in the extreme ultraviolet range. Of course, (garble) colors which you and I cannot see but which the instrument can. Now what's so particularly good about this instrument is that it's able to resolve the colors to a refined detail. We call it spectral resolution - it's able to tell what one wavelength is from another very accurately and that allows us to look at the (garble) of light put out by the atoms - each atom putting out its own particular signature and wavelength (garble) and thereby (garble) understanding of what the comet composition is. The XUV (garble) instrument is controlled from this portion of the panel and another word perhaps is that unlike the previous instrument we've talked about, it doesn't take a picture of the sun - it only looks at a very narrow slit, something perhaps resembling the geometry of that pencil. It's one earth minute long which is a fiftieth of a degree in terms of what is seen and very much narrower (garble) across - that's about one-thirtieth a slice. So it sees a very small element of space which is most useful to us on the sun and we hope it will be in resolving features on the comet. A218 Page 2 We have another instrument on board which does something of a solar nature. We call it the scanning polychromator spectroceliometer. Now all those big words put together go together with this instrument and let me try to explain it. It's a bit like the TV that we're using right now. The TV takes a look at a picture, one little small element (garble) across and moves down another row and traces across and then that line, in that way, builds up the picture. Now this instrument does the same thing, and it's able to do it at the extreme ultraviolet wavelength and ultraviolet - mostly in the ultraviolet. But it's also able to do something else. It's also able to choose the frequency or the wavelenght that will make those observations. It's also able to sit still with a very small element of space and scan across all of the wave lengths it has at its disposal. So, in that way, we can perform two functions - it has six different detectors, all working at the same time, so you can build up either six pictures at the same time or learn a little bit more about the spectrum with several detectors. Like a TV camera, it does not record its information on film but records it on the way of electronic data which can be sent down to the ground rapidly, and in that way, we can analyze in one day and change the very procedures the following day. This is most useful to us observing the sun and we'd hoped it would be observing the comet. So far, what it's told us is that the strongest emission we see from the comet is from a hydrogen line, call it hydrogen lime (garble) very primary emissions from hydrogen - we expected to see that - we have not seen a great deal of any other limes, of strong emission, however, we do realize that this instrument was built for observing the sun which is many, many times stronger intensity that the comet. Two other instruments we have onboard which we use to study the sun and learn quite a bit about, and which we turn now on comet Kohoutek are the x-ray instruments. We have x-ray telegraphs - or excuse me - the x-ray telescope - on this portion of the panel, and the x-ray spectroheliograph - another big word - meaning that this also gets a little bit of information about the wave lengths and x-rays as well as just a picture of the sun in x-ray and in this case, we are trying to learn something about the comet in x-rays. Now we don't expect much emission, if at all, in the way of x-rays of the comet - it's far too cold for that. But there is an outside chance that we have a major flare from the sun that the x-rays from this flare will cause the comet to flouresce. By that, we mean that the high-energy emissions from the sun wll stimulate the gas around the comet and in that way, cause it to emit radiation at a little #A218 Page 3 bit lower intensity, which is also in the x-rays and can tell us something about this comet's position. Now another thing we can learn from x-rays is absorption. Absorption of x-rays from stars behind the comet. Hopefully, there have been some x-rays' sources behind the comet and during very long time exposures, we will be able to observe what the stars look like with the comet's tail up in front of it, and then at later times, observe what the stars are like when the comet is not in front of it, and in that way, learn a little bit about the composition of the material in between - that is the composition material in the tail, which is absorbed in the x-rays. All in all, the ATM has proved to be a very versatile set of observing instruments. We found that just because they were built with extreme capabilities, all (garble) to resolve very faint light - the white light coronagraph - weren't able to resolve extremely fine detail in terms of color or wavelength. The XUV slit spectrograph (garble) spectrograph - giving us a very good picture of the comet in ultraviolet, and perhaps the x-ray instruments and the scanning spectrometer as we call it for short - all of these instruments combined together, although originally intended for study of the sun, have given us we feel an excellent tool for learning about the comet. Now we'll go on down into the lower portion of the space station, and we'll look at what we have in the way of observing instruments out of the scientific airlock. Okay, we're now down here in the forward area of the orbital workshop and I'd like to show you some of the equipment and describe a little bit about how it works. Now the main part of it all is the articulated (?) mirror system. What we essentially have right here on my right hand side is a hole in the wall, if you will, and a way of putting instruments up against that hole in the wall which we have a door for on the outside. We put instruments up against that hole and we're able to take observations from the outside. The door I want to just check that, I got to ask a question - lost my train of thought. Okay, I'll pick this up and try it again. We're down here in the forward area of the OWS and I'd like to show you a little bit of the equipment that we're planning on using and have used for observing the comet out of the scientific airlock. Now airlock is for us - just a term for a hole, which is cut in the wall - and which we can put instruments up against and use that hole to allow the instruments January 31, 19/4 #A218 Page 4 access to outside - for observations. Now the heart of most all of the observations that we'll discuss right now is the articulated mirrow system. Without it, we'd be at a loss to really make a large number of the observations we have been able to do. Essentially, what it is a way which we can take observations of almost any point over hemisphere of the sky, or this whole area which we can look out here - without moving the spacecraft around. We do that with a mirror system which is inside, is projected out and then this being a mirror, it's able to reflect light back in. For example, if we wanted to reflect light back in from here, to there, we put the mirror at this angle. We're able to rotate it around like so, and we're able to rotate it in this direction also. In this way, we're able to make observations here and still have the spacecraft (garble) still planing at the sun, which we need for electrical power and for the solar observations. The first instrument which I think is an excellent instrument for the types of observations we've been making, is a far ultraviolet electronographic camera. And that's this instrument here. The real attribute of this is that it can take pictures - both what the emissions are and the ultraviolet - at extremely faint intensities. It's about 20 times more intense - ore 20 times more sensitive than the normal camera. It uses the high energy source - high voltage at least - 20,000 volts, and when looking out of the scientific airlock, it's got about 9 degrees field of view that you can see. And we've taken it out on the last EVA, in fact, the last two, and made some good observations with an EVA WHERE it can see a much larger part of the sky. We have a way of aligning what we want to look at, if you will, and that's been most useful also in conjunction with the mirror system, and understanding a little about the comet in ultraviolet, as well as in the optical - or in the visible range. So, all told, we have a plentiful complement of observing capabilities on Skylab, and when we get back I'm sure there's going to be lots of people, including ourselves, interested in looking at the data, and learning an awful lot more about comet Kohoutek. Thank you. Bill, would you cut the VTR please?...Okay, now you're able to see some of the far UV electronographic camera, the sights which we've used for aiming, and one thing I really ought to mention about this is the first time this was used in a space program was in Apollo 16 - it was taken to the moon and directed back to earth, learned a little bit more about the oxygen and hydrogen which is in the upper atmosphere of the earth. Here is a closeup of the UV stellar Januarv 31. 1974 A218 Page 5 astronomy experiment, and like all of these experiments, I'm sure they appear to be just boxes to you, all of the action of course is on the inside. It does seem to appear like boxes, too, but when we make the observations, there are certain things we have to do in order to achieve the best data possible. Some require a fair amount of judgment, some technical skill, but it all involves knowing fairly intimately what's inside of these boxes. The last part of the observations which I'd like to

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