HORIBA Helps NASA Discover Icy Mountains on Pluto
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Pictures of mountains show this geological activity occurred less than 100 million years ago. Areas of carbon monoxide ice, methane, nitrogen were detected. The Pluto's atmosphere consists mainly of nitrogen. However, Pluto’s small mass allows hundreds of tons of atmospheric nitrogen to escape into space each hour leading scientists to try to answer this question, “Where does all the nitrogen come from?”
The New Horizons probe is equipped with seven scientific instruments: three optical instruments, including the ALICE spectrograph, two plasma detectors, a solar wind sensor and a radiometer. The probe was launched January 19, 2006, from Florida and on July 14 was close to the dwarf planet. The spectrograph ALICE works in the ultraviolet (500.1800 Å) range, and is equipped with a HORIBA Jobin Yvon diffraction grating. Alice is a light spectrograph (4.5 kilograms) of low power (4.4 watts) developed by SWRI (Southwest Research institute) for the study of the atmosphere: determination of atomic and molecular compounds and their relative abundances.
The key optical component of the ALICE instrument is the toroidal holographic replica diffraction grating manufactured by HORIBA Jobin Yvon in 2005. The development of this grating batch was the result of collaboration between the SWRI in the US, and HORIBA Jobin Yvon’s team in France.
The ALICE diffraction grating, with a groove density of 1600 gr/mm, made on a metallic material substrate to minimize the weight, was optimized to work in a Rowland Circle type imaging spectrograph. Thanks to the holographic recording and space-qualified (TRL 9) replication process, the ALICE grating exhibited low stray light and no ghost. The active grating area is 35 mm in the dispersion direction by 20 mm in the spatial dimension. The spectrograph uses the first diffraction order through the full spectral bandpass of 70 nm – 205 nm. The spectral resolution was measured between 0.98 and 1.25 nm with a spectral resolving power of 55-200.
