SUSIM
type: Concept
in scheme: instruments
definition: The main objective of the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) experiment was to measure with high precision full-disk solar fluxes and their changes over a solar activity cycle in the 120-400 nm wavelength region. The SUSIM experiment on all three Atmospheric Laboratory for Applications and Science (ATLAS) missions flew concurrently with another SUSIM experiment onboard the Upper Atmosphere Research Satellite (UARS) and was able to provide correlative measurements and calibration checks. The goals of the SUSIM experiment are (1) to improve the absolute accuracy of solar continuum irradiance measurements in the 140-400 nm region to plus or minus 6 to 10 % (wavelength-dependent), (2) improve the absolute accuracy of solar emission line irradiance measurements in the 120-400 nm region to plus or minus 6 to 10% (wavelength-dependent), (3) measure with high accuracy the intensities of the continuum below 208 nm relative to the intensities of the continuum above 208 nm to plus or minus 1%, (4) measure with high accuracy the intensities of solar emission lines below 208 nm relative to the stable solar continuum above 208 nm to plus or minus 1 to 5 % (wavelength-dependent), (5) measure the degree of correlation of the solar flares in the 120-400 nm region with ground observations. The instrument consists of two identical double-dispersion scanning spectrometers, seven detectors (five photodiodes and two photon counters), a UV calibration source, and a Sun sensor. The spectrometers and detectors are sealed in a canister filled with 1.1 atm of argon gas to eliminate contamination of the optics. One spectrometer is used continuously to measure the solar intensities while the other monitor is used once a day to track the stability of the first spectrometer. The two photon counters obtain a spectral resolution of 0.15 nm while the photodiodes obtain a spectral resolution of 5 nm. A deuterium lamp transfer standard is built into the instrument for calibration of…

Ultraviolet Instruments
type: Concept