The spectral variation of FUV airglow observed by the STSAT-1

This study presents the results of FUV airglow observations made from the dual band FUV spectrograph, FIMS, on STSAT-1 at an altitude of 685 km during the period from November 2003 to August 2004. The bandwidths of FIMS are 900-1150 A for the S-band with 2 A spectral resolution and 1340-1750 A for the L-band with 3 A spectral resolution. The combined nighttime airglow emission observed both in the up-looking and down-looking directions shows mostly hydrogen and atomic oxygen lines such as Lyman beta, Lyman gamma and OI 989 A while the daytime airglow includes atomic/ionic and molecular nitrogen lines, in addition. FIMS also made daytime limb observations in two occasions. The results clearly show the variations of nitrogen and oxygen lines according to the depth of the atmosphere along the line of sight. We have estimated the volume emissivities of the emission lines as a function of altitude and compared them with those from the AURIC model. We also compare the airglow lines with those of diffuse auroras.