Continuous ground-based multiwavelength airglow measurements

Abstract

[1] A new spectrograph instrument, called the Continuous High-resolution Instrument for Multiwavelength Echelle Spectroscopy (CHIMES), has been designed to make simultaneous and spatially overlapping ground-based measurements of the green line and red line airglow emissions (5577 A and 6300 A) continuously, 24 hours-a-day. The spectrograph uses a 50 mm long, 50 μm wide slit, and varies the exposure time at different times of day (daytime, twilight, and nighttime), from 2 s in daytime to 10 min at night. It utilizes an Echelle grating to achieve dispersion of 0.05 A/pixel at 5577 A. Daytime 6300 A and 5577 A airglow from this instrument are extracted by comparing the measured spectra to direct solar spectra and extracting small increases in flux in the Fraunhofer absorption lines at those wavelengths, after compensating for the Ring effect contribution. We present the first ground-based measurements of the daytime 5577 A airglow, as well as example measurements of daytime, twilight, and nighttime airglow signatures.