Development and testing of a lightweight-kinematic optical mount with integrated passive vibration-and-shock
mitigation technologies and simple / robust optical alignment functionality is presented. Traditionally, optical mounts
are designed for use in laboratory environments where the thermal-mechanical environments are carefully controlled to
preserve beam path conditions and background disturbances are minimized to facilitate precise optically based
measurements. Today's weapon and surveillance systems, however, have optical sensor suites where static and dynamic
alignment performance in the presence of harsh operating environments is required to nearly the same precision and
where the system cannot afford the mass of laboratory-grade stabilized mounting systems. Jitter and alignment stability
is particularly challenging for larger optics operating within moving vehicles and aircraft where high shock and
significant temperature excursions occur. The design intent is to have the mount be suitable for integration into existing
defense and security optical systems while also targeting new commercial and military components for improved
structural dynamic and thermal distortion performance. A mount suitable for moderate-sized optics and an integrated
disturbance-optical metrology system are described. The mount design has performance enhancements derived from the
integration of proven aerospace mechanical vibration and shock mitigation technologies (i.e. multi-axis passive isolation
and integral damping), precision alignment adjustment and lock-out functionality, high dimensional stability materials
and design practices which provide benign optical surface figure errors under harsh thermal-mechanical loading. Optical
jitter, alignment, and wave-front performance testing of an eight-inch-aperture optical mount based on this design
approach are presented to validate predicted performance improvements over an existing commercial off-the-shelf
Delivery of Orbital Replacement Units (ORUs) to the International Space Station (ISS) and other on-orbit destinations is an important component of the space program. ORUs are integrated on orbit with space assets to maintain and upgrade functionality. For ORUs comprised of sensitive equipment, the dynamic launch environment drives design and testing requirements, and high frequency random vibrations are generally the cause for failure. Vibration isolation can mitigate the structure-borne vibration environment during launch, and hardware has been developed that can provide a reduced environment for current and future launch environments.
Random vibration testing of one ORU to equivalent Space Shuttle launch levels revealed that its qualification and acceptance requirements were exceeded. An isolation system was designed to mitigate the structure-borne launch vibration environment. To protect this ORU, the random vibration levels at 50 Hz must be attenuated by a factor of two and those at higher frequencies even more. Design load factors for Shuttle launch are high, so a metallic load path is needed to maintain strength margins. Isolation system design was performed using a finite element model of the ORU on its carrier with representative disturbance inputs. Iterations on the model led to an optimized design based on flight-proven SoftRide MultiFlex isolators. Component testing has been performed on prototype isolators to validate analytical predictions.
The Herschel Space Observatory (formerly known as FIRST) consists of a 3.5 m space telescope. As part of a JPL- funded effort to develop lightweight telescope technology suitable for this mission, COI designed and fabricated a spherical, F/1, 2 m aperture prototype primary mirror using solely carbon fiber reinforced polymer (CFRP) materials. To assess the performance of this technology, optical metrology of the mirror surface was performed from ambient to an intended operational temperature for IR-telescopes of 70K. Testing was performed horizontally in a cryogenic vacuum chamber at Arnold Engineering Development Center (AEDC), Tennessee. The test incorporated a custom thermal shroud, a characterization and monitoring of the dynamic environment, and a stress free mirror mount. An IR-wavelength phase shifting interferometer (IR PSI) was the primary instrument used to measure the mirror surface. From an initial surface figure of 2.1 microns RMS at ambient, a modest 3.9 microns of additional RMS surface error was induced at 70K. The thermally induced error was dominated by low-order deformations, of the type that could easily be corrected with secondary or tertiary optics. In addition to exceptional thermal stability, the mirror exhibited no significant change in the figure upon returning to room temperature.