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LORAAS
Low Resolution Airglow and Aurora Spectrograph
LORAAS is the first of a series of 6 identical UV limb scanning sensors that
will fly during the period 1999-2010 produced by NRL. The other 5 sensors,
named Special Sensor Ultraviolet Limb Imager (SSULI) 1-5, will fly as part of
the Defense Meteorological Satellite Program (DMSP). The combined data
retrieved from these UV spectrographs will provide a long-term dataset for
studying thermosphere and ionosphere structure, composition, climate, and space
weather over the upcoming solar activity cycle.
Design Features
 | Summary
 | f/3 0.25-m near-Wadsworth configuration spectrograph |
| 80-170 nm passband |
| 1.8 nm spectral resolution |
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| Scan mirror
| Plane mirror 8.1 cm X 11.7 cm |
| SiC reflective coating |
| Motor drive and resolver controlled |
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| Collimator
| Mechanical grid collimator |
| 70 mm square aperture |
| 23 stacked grids |
| Roughly pyramidal effective aperture function |
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| Grating
| Spherical concave grating, 250 mm focal length |
| 1600 lines/mm blazed for 110 nm |
| 9.8 cm X 9.4 cm zerodur blank |
| SiC reflective coating |
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| Detector
| Windowless, with clamshell vacuum door mechanism |
| CsI photocathode |
| 40 mm diameter microchannel plate z-stack |
| Low sensitivity region in center of detector
 | photocathode masked, leaving bare microchannel plate |
| reduces 121.6 and 130.4 nm emission |
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| wedge & strip anode |
| 256 dispersion axis pixels |
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| Field-of-view
| 0.15-degree (FWHM) vertical resolution (5 km) |
| 2.4 degree (FWHM) horizontal field-of-view (120 km) |
| Normal scan zenith angles 100-127 degrees (750-50 km) |
| Extended scan zenith angles 5-140 degrees (800 km - disk) |
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Scientific Features
| Focuses on the F-region of the ionosphere |
| Measures daytime electron and neutral densities |
| Measures nighttime electron densities. |
| Continuous global measurement of space weather |
| Part of a long-term monitoring monitoring program |
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