San Diego, CA, August 31, 2000 - Composite Optics, Inc. (COI) of San Diego, has recently completed fabrication and testing of the world's largest, lightest-weight, most dimensionally stable, all-composite mirror. The 2-meter aperture mirror (i.e., approximately 7 ft. across) is a prototype developed in partnership with NASA's Jet Propulsion Laboratory (JPL) for use in space-borne infrared astronomy. It was constructed entirely from Carbon Fiber Reinforced Polymer (CFRP) composite and weighs just 77 pounds.
The technology developed will enable production of the FIRST telescope. In comparison to the Hubble Space Telescope (HST), the 3.5-meter diameter FIRST composite telescope will provide two (2) times the collection area of the HST with a structure that weighs less than seven percent (7%) and costs less than ten percent (10%) of the HST. While the optical accuracy requirements for this mission are not as strict as they were for Hubble (6 micron RMS wavefront error), the potential for reaching that same level of quality with such weight and cost savings is now a realistic goal for future missions, specifically because of the developments on this program. NASA is slated to provide the European Space Agency (ESA) with a complete telescope structure, including primary and secondary mirrors and support struts, for their FIRST spacecraft which will help solve the mystery of how stars and galaxies are born.
"This revolutionary technology is a huge accomplishment for COI and is a critical technology step for future space missions," said Jim Gormican, COI's President and CEO. Tom Phillips, Caltech Professor of Physics and Director of the Caltech Submillimeter Observatory, stated, "The carbon fiber technique will be the enabling lightweight construction technology for large future space telescopes at wavelengths longer than 30 microns."
COI was challenged by JPL to produce a lightweight mirror that would meet the accuracy and stability requirements of ESA's FIRST Mission. These requirements included a surface accuracy of a few microns RMS at the cryogenic operational temperature of 80 degrees Kelvin (-315 degrees Fahrenheit) with first mode stiffness greater than 60 Hz, all in a substrate with areal density less than 20 kg/m2. Through innovations in engineering, tooling, and materials and processing, COI produced the 10 kg/m2, 2-meter prototype with an as-built surface accuracy of 2.1 microns RMS and first mode stiffness of 137 Hz. The surface accuracy of the prototype was also measured optically down to 70K. The extreme temperature caused a modest 3.9 micron RMS change in the mirror figure. The results not only meet the FIRST requirements, but have established a level of accuracy, stability, and low mass that is unparalleled in any other composite structure built to date.
NASA's commitment to small business research collaboration helped COI to achieve this recent milestone. COI's development of lightweight mirrors made from CFRP began in 1992 with a small grant from JPL at the end of the Precision Segmented Reflector (PSR) research program. COI pursued innovation in composite mirrors through funding from Small Business Innovative Research (SBIR) programs. Eventually, the success of the all-composite primary flight mirror for the Microwave Limb Sounder (MLS) instrument on JPL's AURA (EOS-Chem) Mission gave JPL and COI the vision that a larger, lightweight mirror could be developed to meet the demands of cryogenic operation for infrared-wavelength space astronomy missions. Additional Phase I and Phase II SBIRs helped to further evolve critical pieces of COI's CFRP mirror technology before the 2-meter mirror was produced under Phase A/B mission funding for NASA's support of ESA's FIRST program.
Though the 2-meter mirror is a significant milestone, COI understands that the new level of composite capability has far reaching benefits to future space instrument missions as well. These enabling technical innovations will permit new levels of structural stability to be utilized in missions such as NASA's Space Interferometry Mission (SIM), Next Generation Space Telescope (NGST), and the Terrestrial Planet Finder (TPF). These missions require optical level tolerances to be maintained across broad dimensions (8-11 meters) with very lightweight structures. Lightweight hybrid mirror substrates enabled with stable CFRP can reduce mission costs by reducing the weight of space telescopes. In addition, the technology demonstrated on the FIRST 2-m mirror shows how mirror segments can be replicated off a small mold, further reducing mission costs by eliminated time consuming and costly polishing of a large mirror surface. Ultimately, COI sees CFRP itself becoming viable as an optical quality surface, and is pursuing technologies to achieve that vision.
COI is a world leader in the design, engineering, manufacturing and testing of advanced composite products for the space and aerospace markets. Based in San Diego, California, COI is an employee-owned business with over 390 Associates and is the recent recipient of a NASA Public Service Medal for contributions to the Chandra X-Ray Observatory. Named by the U.S. Small Business Administration as the 1999 National Small Business Subcontractor of the Year, Composite Optics, Inc. has provided innovative products and services that utilize state-of-the-art composite materials since 1976.
