large space telescope. The decision as to how man should be used, depending partly upon man's capability in space and partly upon such matters as economics, will influence the whole design of the telescope. Astronomical Hardware Goals What are the specific astronomical hardware goals that we can visualize? The longrange goal is an essentially permanent astronomical facility, which astronomers have designated the Large Space Telescope (LST). We have specified that this LST should have the equivalent resolving power of a 120-inch, diffraction-limited telescope but that the actual aperture might be as great as 150 to 180 inches, depending primarily on the technology and on the diameters of the available launch vehicles. In order to achieve this goal, there might be two such telescopes launched, one as an engineering model and the other as the final instrument. The intermediate steps between where we are now and this long-range facility are somewhat more controversial. Although I have no specific suggestions to make, I would like to suggest two particular requirements. First, any intermediate facility must be an astronomically significant device. If it is not, it will be very difficult to get astronomers to devote the blood, sweat, and tears that are needed if these astronomers are to contribute any input to this system. If I were asked, as an astronomer, to spend an amount of time. comparable to that which I have spent working on the Orbiting Astronomical Observatory (OAO) on an instrument that was an interesting engineering prototype but did not provide key astronomical data, I am sure I would find other areas in which to devote my interests. The second requirement I suggest is that any intermediate step should advance some of the areas of technology that are crucially important for the large space telescope. I would not suggest that an intermediate step must advance all phases of technology needed for the LST. If a too-ambitious intermediate step would result in launch only a year or two before the large space telescope, it would mean that such an intermediate program would have very little influence on the LST itself. My experience with the space field suggests that the group which designs the large space telescope will probably be a different group from that which has designed an intermediate telescope. If any one thing can be predicted, it is that any one group of engineers is likely to want to change any design decisions made by any other group; hence, to make an intermediate instrument a detailed scale model of the large space telescope would make no practical sense at all. To answer basic technological questions in the areas that will be important to the LST is the more useful and important goal. One possible way of looking at an intermediate step is as a smaller instrument that would involve high spatial resolution and high spectroscopic resolution. This would get us involved in the problems of the high resolution mirror, where possibly we could consider segmented optics and some figure control system. It would also give us further experience in acquisition and guidance and would provide an important introduction to the problems of detailed thermal design in a high-resolution instrument. In addition, such a smaller instrument would be used for astronomical research with some of the same detectors that we hope to use in the large space telescope. The main uncertainty I have in envisioning this intermediate step is whether we would use man or not. This depends entirely upon what the NASA Office of Manned Space Flight recommends that man be used for. If man can be used in a minimum way for EVA maintenance, I hope this technique can be worked into the intermediate step. On the other hand, if man is going to make use of a large enclosed space in orbit, it is very doubtful that it would make sense economically to apply this technique to any instrument smaller than the full-scale large space telescope. Technology Objectives and Plans Frank J. Sullivan NASA, Office of Advanced Research and Technology I represent the group that tries to create and push forward what is often referred to as the "state of the art." For those of you not familiar with the NASA, I am referring to the Office of Advanced Research and Technology, more commonly known as OART. Because Bruce Lundin, Acting Associate Administrator for OART, could not be present at this workshop, he has asked me to convey to you three important points: 1. We are very interested in telescope technology; 3. We need your inputs to help identify the major problems and how we should approach their solution. Astronomy has been, and continues to be, one of the NASA's most promising fields of activity. We in the Office of Advanced Research and Technology look forward to having the opportunity to sponsor and to support the technical disciplines that will further observational astronomy - one of the most venerable scientific fields and yet in its infancy from the point of view of new productivity. Some of the technology problems associated with astronomy seem amenable to solution within our present level of capability and are presently being worked on. Examples of these are active optics and figure sensors, which have been developed and demonstrated in the laboratory but which are, in a sense, crutches or partial engineering solutions to take care of another class of problems. These are the problems that we do not know how to solve or which do not seem likely to be soluble. One example is the construction and figuring of a 2- or 3-meter, monolithic, diffraction-limited, primary mirror suitable for operation in space. Such a mirror would solve many reliability and long-life problems and would probably save a great deal of money. To solve a problem such as this, we normally pursue two avenues - the array of partial solutions and the search for ideal materials - at levels based upon their relative likelihood of success. We intend to follow such a procedure in this particular case. There is still another aspect of our program that makes life and decision-making interesting, namely, the problem which will be solved by someone else and handed to us on a platter, sometimes right in the middle of a development program. An example is the availability of man for maintenance, for equipment changing, and also, unfortunately, for contaminating the space through which we view astonomical objects. In such cases, we try to plan for all eventualities within the availability of funds, space, and weight and hope that our tradeoffs fit the final facts of life. The state-of-the-art is, of course, constantly changing; this is demonstrated in the series of talks prepared for this workshop. It is our aim to try to make these changes fit the needs of science, of the nation, and of mankind. In the area of astronomy and technology, no one knows these needs better than you who are taking part in this workshop. We look forward with great interest to the results of your deliberations and assure you they will be used in the most practical and profitable way to forward the state of the technical art related to astronomy. |