NOMAD LNO solar spectrum (April 2016)
This graph is of measurements made with the Limb, Nadir and Occultation (LNO) channel of the NOMAD instrument on the ExoMars Trace Gas Orbiter, during the near-Earth commissioning (NEC) in April 2016.
This LNO solar spectrum shows 6 diffraction orders measured consecutively during NEC. The LNO channel can make measurements from 2.2 to 3.8µm (4550 - 2630 cm-1), but to achieve high spectral resolution only one diffraction order (approximately 24 cm-1) is imaged at any one time.
Solar absorption lines - which are used to calibrate the channel - appear as sharp features in the continua, whereas the curved arches are produced by the transmission function of the instrument.
The ExoMars Trace Gas Orbiter was launched on 14 March 2016. During the NEC solar spectra were obtained for calibration purposes.