The New Horizons instrument named Ralph is a visible/near infrared multispectral imager and a short wavelength infrared spectral imager. It is one of the core instruments on New Horizons, NASA's first mission to the Pluto/Charon system and the Kuiper Belt. Ralph combines panchromatic and color imaging capabilities with SWIR imaging spectroscopy. Its primary purpose is to map the surface geology and composition of these objects, but it will also be used for atmospheric studies and to map the surface temperature. It is a compact, low-mass (10.5 kg) power efficient (7.1 W peak), and robust instrument with good sensitivity and excellent imaging characteristics. Other than a door opened once in flight, it has no moving parts. These characteristics and its high degree of redundancy make Ralph ideally suited to this long-duration flyby reconnaissance mission.
The instrument named Ralph is a visible/NIR imager and IR hyperspectral imager that would fly as one of the core instruments on New Horizons, NASA's mission to the Pluto/Charon system and the Kuiper Belt. It is a compact, power efficient, and robust instrument with excellent imaging characteristics and sensitivity, and is well suited to this longduration flyby reconnaissance mission.
Evidence is reported of spontaneous vibrations of a deployable spacecraft structure at optical levels of motion under mechanical loads. In these experiments a truss was mechanically loaded while in a thermally and vibrationally stabilized test environment. The applied loads were smaller, by a factor of 20, than the load that would have caused gross slippage in the frictional interfaces of the structure. Even so, results indicate that infrequent, spontaneous vibrations occurred. Most of these vibrations occurred after the application and removal of a mechanical load. The response spectra of the vibrations occurred in narrow bandwidths around the dominant modal frequencies of the structure. The vibrations ranged in amplitude from 4 to 20 nm and in velocity from 2 to 8 鹿/s. Potential error sources are eliminated, including unmeasured environmental excitations and sensor errors. These vibrations are presumed to arise from the sudden release of strain energy stored in the hysteretic mechanisms and materials of the structure. An analysisbased on this hypothesis shows that the amplitudeof the observed vibrations is quantitatively consistent with this theory.
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