The MSP is an innovative instrument, using a rotating mirror to scan along a line of the sky from North to South. Each scan takes sixteen seconds. Five channels are used, each coupled with a narrow bandpass filter. Due to temperature fluctuations the filters are mounted to a tilting frame, this allows for tilter-filtering; an inexpensive and fast way to calibrate the instrument without having to invest in a temperature controlling system. By tilting the filters from peak transmission position to an angle that transmits the base wavelength (which acts as the background emission) the background for each filter is obtained. The detector for the MSP is a photomultiplier. The output is given as a count of photons for each channel. The main observed channels use filters for 557.7, 630.0, and 844.6 nanometres, these are the emission lines of atomic oxygen. The other pair of filters uses the 427.8 nanometre line for molecular nitrogen and the 486.1 nanometre line for the Doppler emission profile for Hydrogen. The latter being the result of proton aurora. To obtain a background each filter is tilted from peak transmission to an angle that emits the base wavelength, which acts as a representative of the background emissions. However, the 844.6 and 486.1 lines were not active during the study.
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| The MSP |
The data can also be turned into keogram, which I think looks way cooler.
Next: All sky cameras
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