BIRC is a multispectral infrared imager designed to operate in 8 bandpasses between 2.5 and 5.0 μm utilizing a cryocooled
HgCdTe detector and Ø80 cm telescope. The instrument was flown on a ballooncraft platform and operated in a
near-space environment. BIRC was designed to measure the water and CO2 emissions from the comet ISON. The system
produces an f/4 image over a field of view of 3 arcminutes, and employs shift/co-add algorithms to observe dim objects.
An innovative thermal design holds the system components in separate vacuum and atmospheric zones which are
independent of the neighboring instrument deck. This paper summarizes the design, test and integration of the BIRC
instrument.
Precise knowledge of the instrument boresight was required over the gimbal range for the CRISM Instrument (Compact Reconnaissance Imaging Spectrometer for Mars), which will fly aboard the Mars Reconnaissance Orbiter. Vector metrology techniques were applied to measure both the optical axis and the axis-of-rotation of the instrument housing about its mount (gimbal axis). Boresight stability was quantified through comparison of pre-environmental and post-environmental alignment data. In addition, checks were made of the instrument internal alignment and field-of-view. Distillation of the boresight data into gimbal axis and optical axis offset knowledge allowed the calculation of the instrument boresight at all gimbal settings. Finally, alignment information was mapped into the instrument reference cube, ensuring proper instrument orientation during installation.
Bragg Gratings are waveguides, typically single-mode optical fibers, into which a periodic refractive index modulation has been imprinted by a patterned UV exposure. Fiber Bragg Gratings separate telecom frequency bands or compensate for optical dispersion in long-haul fiber networks, and also serve as strain sensors for civil engineering or geophysical studies and oil, gas or mining exploitation. A Bragg Grating writer is an interferometer for generating the UV exposure pattern. It is one of the unusual cases where an interferometer is a production tool, rather than a metrology instrument. In this paper, we review the most common Bragg Grating writing geometry and propose an opto-mechanical structure having minimal adjustment and very high mechanical stability.
Optical Fiber Bragg Grating (FBG) strain and temperature sensors were embedded into four carbon/epoxy, filament-wound 5.75' diameter Standard Testing and Evaluation Bottles (STEBs). These sensors were used to monitor temperature and strain during cure and pressurization of the pressure vessels. Preliminary to this work, micrographs were made of embedded fiber, showing good incorporation of the fiber into the material and no degradation of the optical fiber's acrylate coating. A survey was also made of different ingress/egress techniques to protecting the fiber as in enters the bottle and preventing attenuation and power fluctuation, with Tefzel tubing proving to be the most effective method. The FBGs were embedded parallel to the reinforcing fibers, in the hoop and helical directions, and also in the axial direction. The sensors showed close agreement with surface-mounted Resistance Strain Gages (RSGs),as well as finite element modeling. Sensors in the hoop direction embedded at mid-cylinder showed the closest agreement (-1.2%), while agreement for hoop- direction sensors embedded near the ends of the bottle (11%) was not as close. The agreement was also better for helically directed sensors embedded at mid-cylinder (-1.6%?) than for those embedded near the ends (-24%). Some preliminary impact testing was conducted that indicated FBG sensors would be appropriate for sensing impact damage.
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