Rollable Thin Shell Composite-Material Paraboloidal Mirrors

An experiment and calculation have demonstrated the feasibility of a technique of compact storage of paraboloidal mirrors made of thin composite-material (multiple layers of carbon fiber mats in a polymeric matrix) shells coated with metal for reflectivity. Such mirrors are under consideration as simple, lightweight alternatives to the heavier, more complex mirrors now used in space telescopes. They could also be used on Earth in applications in which gravitational sag of the thin shells can be tolerated. The present technique is essentially the same as that used to store large maps, posters, tapestries, and similar objects: One simply rolls up the mirror to a radius small enough to enable the insertion of the mirror in a protective cylindrical case. Provided that the stress associated with rolling the mirror is not so large as to introduce an appreciable amount of hysteresis, the mirror can be expected to spring back to its original shape, with sufficient precision to perform its intended optical function, when unrolled from storage

Optical testing

Optical testing is one of the most vital elements in the process of preparing an optical instrument for launch. Without well understood, well controlled, and well documented test procedures, current and future mission goals will be jeopardized. We should keep in mind that the reason we test is to provide an opportunity to catch errors, oversights, and problems on the ground, where solutions are possible and difficulties can be rectified. Consequently, it is necessary to create tractable test procedures that truly provide a measure of the performance of all optical elements and systems under conditions which are close to those expected in space. Where testing is not feasible, accurate experiments are required in order to perfect models that can exactly predict the optical performance. As we stretch the boundaries of technology to perform more complex space and planetary investigations, we must expand the technology required to test the optical components and systems which we send into space. As we expand the observational wavelength ranges, so must we expand our range of optical sources and detectors. As we increase resolution and sensitivity, our understanding of optical surfaces to accommodate more stringent figure and scatter requirements must expand. Only with research and development in these areas can we hope to achieve success in the ever increasing demands made on optical testing by the highly sophisticated missions anticipated over the next two decades. Technology assessment and development plan for surface figure, surface roughness, alignment, image quality, radiometric quantities, and stray light measurement are presented

Fabrication Of Large RZ Glass Discs

QC 351 A7 no. 03The problems connected with the utilization of large high -resolution telescopes are concentrated into two principal areas. The first concerns the physical properties of the mirror disc; the second involves the pro- cessing of the mirror in the optical shop. This technical report concerns, 1) the design of a new type of opti- cal polisher, one with a stationary mirror platform, and, 2) the casting of large discs made up of a new type of glass. This new glass, designated type RZ by Owens -Illinois, has a zero coefficient of thermal expansion at 25° Centigrade. A proposal for research in these two areas has already been made. This research has been supported, in part, under Contract ONR -2173- (12) by the Advanced Research Projects Agency and administered by the Office of Naval Research.This title from the Optical Sciences Technical Reports collection is made available by the College of Optical Sciences and the University Libraries, The University of Arizona. If you have questions about titles in this collection, please contact [email protected]

A NEW DESIGN CLASS OF WIDE-FIELD CAMERA FOR WIDE PASS-BAND USES

QC 351 A7 no. 09Meinel and Shack recently devised a three-element reflective optical system for a specific astronomical application that appears to offer rather general uses for fast, wide-field cameras. A three-element system is mathematically elegant in that this is the minimum number of surfaces necessary to provide zero third-order spherical aberration, coma, and astigmatism for any distribution of spacings and powers.. Two-element configurations of surfaces, such as the Schwarzschild and Couder, in general, leave one of the above aberrations uncorrected. The maximum speed and field of good definition of two- mirror designs are also quite limited. The Meinel-Shack three-mirror system provides much superior performance since the degrees of freedom afforded through the use of aspheric deformations on all surfaces permits the exact solution for the fifth -order aberrations astigmatism 5, coma 5 and spherical 5 to be eliminated along with astigmatism 3, coma 3 and spherical 3. Moreover, it is possible to design practical systems with zero Petzval sum yielding a flat focal surface, and achieve an excellent balance of the remaining fifth -order aberrations, elliptical coma and oblique spherical aberration. The ultimate optical performance is governed by the resulting balance of any remaining higher - order aberrations. A preliminary report of the design approach used by Meinel and Shack is given in Optical Sciences Technical Report No. 6, appended to this report.This title from the Optical Sciences Technical Reports collection is made available by the College of Optical Sciences and the University Libraries, The University of Arizona. If you have questions about titles in this collection, please contact [email protected]

An F/2 Focal Reducer For The 60-Inch U.S. Naval Observatory Telescope

QC 351 A7 no. 07The Meinel Reducing Camera for the U. S. Naval Observatory's 60-inch telescope, Flagstaff, Arizona, comprises an f /10 collimator designed by Meinel and Wilkerson, and a Leica 50-mm f/2 Summicron camera lens. The collimator consists of a thick, 5-inch field lens located close to the focal plane of the telescope, plus four additional elements extending toward the camera. The collimator has an efl of 10 inches, yielding a 1-inch exit pupil that coincides with the camera's entrance pupil, 1.558 inches beyond the final surface of the collimator. There is room between the facing lenses of the collimator and camera to place filters and a grating. The collimated light here is the best possible situation for interference filters. Problems of the collimator design work included astigmatism due to the stop's being so far outside the collimator, and field curvature. Two computer programs were used in development of the collimator design. Initial work, begun in 1964, was with the University of Rochester's ORDEALS program (this was the first time the authors had used such a program) and was continued through July, 1965. Development subsequently was continued and completed on the Los Alamos Scientific Laboratory's program, LASL. The final design, completed January 24, 1966, was evaluated with ORDEALS. This project gave a good opportunity to compare ORDEALS, an "aberration" program, with LASL, a "ray deviation" program. It was felt that LASL was the superior program in this case, and some experimental runs beginning with flat slabs of glass indicated that it could have been used for the entire development of the collimator. Calculated optical performance of the design indicated that the reducing camera should be "seeing limited" for most work. Some astigmatism was apparent, but the amount did not turn out to be harmful in actual astronomical use. After the final design was arrived at, minor changes were made to accommodate actual glass indices of the final melt, and later to accommodate slight changes of radii and thicknesses of the elements as fabricated. An additional small change in spacing between two of the elements was made at the observatory after the reducing camera had been in use for a short time. The fabricated camera is working according to expectations. Some photographs are included in the report to illustrate its performance and utility.This title from the Optical Sciences Technical Reports collection is made available by the College of Optical Sciences and the University Libraries, The University of Arizona. If you have questions about titles in this collection, please contact [email protected]