This presentation will cover 64 years of experience with telescopes, optical components, optical coatings, large optics, optical fabrication, lasers and related subjects. It will focus on five topic areas paying special attention to critical lessons learned in these areas. Part 1 will cover contributions and inherent value of mentoring in optical and astronomical sciences. This will include specific personal experiences and valuable lessons learned from teachers and mentors going back to the beginning of the space age and the first satellites. It will also cover selected examples from the author’s mentoring and community optics and astronomy outreach efforts. Part 2 will delineate the lessons learned from the investigation and independent expert review and assessment of optical damage incidents over a period of five decades. It will also recount frequent optical misconceptions that have negatively impacted efficient system development and implementation over the years and how to avoid them. Part 3 will consist of a short tutorial on the tools, techniques, and the “how and why” of optical inspection. This will be interlinked with the previous optical damage and mistakes topic, where possible. Part 4 will consist of the author’s involvement and experiences in optical education with emphasis on the founding and early years of the University of Arizona Optical Sciences Center, now the College of Optical Sciences. Part 5 will cover the enduring issues and challenges for managers, planners and contributing scientists for large optics and telescope projects. This brief overview will follow up and expand upon the author’s presentation on this topic at the 1985 “SPIE Optical Fabrication and Testing Workshop: Large Telescope Optics”, Albuquerque, NM. Throughout all topic areas presented, the author will stress the lessons learned and the value of these lessons to the planning, management and successful execution of future optics projects and programs.
In a major effort to understand limitations on the performance of ground-based optical telescopes and gimbals, the Air Force Research Laboratory (AFRL) and a contractor support team measured the vibration and jitter of several large telescopes. These measurements were conducted over a ten-year period with high bandwidth accelerometers, angular position sensors, and seismometers attached to various locations on the telescopes, mounts, and bases. Measurements were taken over a 0.1 to 1000-Hz bandwidth and at angular tracking velocities between 0.001 and 18.5 degrees per second, single-axis. Jitter power spectral densities (PSD) and root-mean-square (rms) values and ranges were determined for both dynamic tracking and quiescent condition. Many telescopes exhibited near-noise-floor level jitter (i.e., about 10 nanoradians rms) under some conditions in certain bandwidth ranges. Under very high-speed single-axis tracking conditions (i.e., 10.5 - 18.5 degrees per second), jitter often rose to several micro-radians rms. This paper presents and discusses the overall mechanical jitter measurement results obtained for five telescopes with emphasis on two 3.5-meter aperture-class high-tracking rate instruments.
Lightweight, deployable space optics has been identified as a key technology for future cost-effective, space-based systems. The United States Department of Defense has partnered with the National Aeronautical Space Administration to implement a space mirror technology development activity known as the Advanced Mirror System Demonstrator (AMSD). The AMSD objectives are to advance technology in the production of low-mass primary mirror systems, reduce mirror system cost and shorten mirror- manufacturing time. The AMSD program will offer substantial weight, cost and production rate improvements over Hubble Space Telescope mirror technology. A brief history of optical component development and a review of optical component state-of-the-art technology will be given, and the AMSD program will be reviewed.
The Airborne Laser (ABL) program requires a large aperture, highly transparent window to allow the high energy laser beam to be focused on targets. This window presents many challenges as it is thin, large in diameter and very highly curved. Additionally, the window must be made from a material highly transparent at 1.315 micrometers, the chemical oxygen-iodine laser wavelength, have good transmission from the visible through 3 micrometers and be able to withstand the rigors of operations on a tactical aircraft. To manufacture this window, a unique partnership between two companies, Heraeus and Corning, was forged to demonstrate the process and manufacture the window blanks. Infrasil 302, a Heraeus product, is the only material with low absorption at 1.31 micrometers that can be produced in large enough quantities to make a window blank of the required size. Corning has developed the technology to flow- out and sag glass products to make highly curved optics without the need to machine them out of a cylindrical block. Using their experience and a common desire to support the ABL program, the two companies worked together to develop the processes that produce the window blanks. Contraves Brashear Systems of Pittsburgh will polish the blank in to its final form, with coatings applied by Optical Coating Laboratories, Inc. of Santa Rosa to maximize transmission.
The reflectivity and scatter of several large telescope mirrors have been measured immediately after coating and after various use times. Mirrors evaluated inside those of the AEOS 3.67-m Telescope and the SOR 3.5-m Telescope. Reflectivity and scatter measurements were made on the actual mirrors and witness samples using a (mu) Scan<SUP>TM</SUP> reflectometer/scatterometer, a Minolta 2002 hand-held spectro-reflectometer, and laboratory spectro-photometers and scatterometers. The reflectivity measurements made on coating witness samples were compared to measurements in round-robin tests by nationally recognized optical measurement laboratories. From the results of the round- robin measurements, correction factors were determined for the hand-held instruments and used to establish actual reflectivities of the large mirrors as a function of location on the mirror and time after coating deposition. Measurements of the reflectivity and scatter of the SOR 3.5- m primary mirror taken immediately after coating, nine months after coating, and 39 months after coating, and measurements of the reflectivity and scatter of the AEOS 3.67-m telescope primary mirror immediately after coating are presented and discussed. Correlations with coating data taken on other large mirrors are also presented. Depending on coating selection, initial coating quality, operational conditions, and cleaning procedures, coating lifetimes may vary from less than one to more than five years.
Packing, shipping, and handling procedures employed during several transportation activities for two large telescope primary mirrors are presented along with detailed shock recording results. Operations monitored included craning, forklifting, and shipping by air, sea, and land during all phases of manufacture and installation. The mirrors monitored were the SOR 3.5-m Telescope spun cast borosilicate primary mirror and the AEOS 3.67-m Telescope Zerodur thin meniscus primary mirror. Shock recording instrumentation included 2-, 5-, and 10-g Omni-G<SUP>TM</SUP> impact indicators, 10-g Impact o-graph<SUP>TM</SUP> 3-axis recording accelerometers, and high-resolution 3-axis accelerometers with Astromed Dash 8 eight-channel chart recorders and audio indicators. Shock results for some operations were monitored to the 0.01-g level. In-shipment temperature data are also presented and discussed. Effects of lifting operations, road conditions via truck, flight conditions via C-5B aircraft, and transportation via sea- going barge are discussed. Data are presented for three different crate designs and configurations and, in some cases, include mirror-in-cell shipping data. Shock results were observed from as low as a few hundredths-g to over 3- g's during various operations.