The third imaging photometer is equipped with filters and a photocathode for observations at vacuum-ultraviolet wavelengths, in particular emissions of the Lyman-Birge-Hopfield band of molecular nitrogen at about 140 to 170 nm. Imaging at these wavelengths allows coverage of the auroral oval in both the dark and sunlit ionospheres. The filter array for the vacuum-ultraviolet imaging photometer also includes filters for atomic hydrogen Lyman alpha at 121.6 nm and oxygen lines at 130.4 and 135.6 nm.
Filters included in this dataset for observations of the aurora and
geocorona are the shown in the following table.
VACUUM-ULTRAVIOLET IMAGING PHOTOMETER C Filter# Name Lp,nm dL,nm Tp Sp S(Lya) Principal function ------- ---- ------ ----- ---- ---- ------ ------------------------ 1 136W 150 43 0.21 1.65 N2(LBH) band 2 123W 131 32 0.30 3.08 OI lines 3 120W 125 30 0.36 3.10 2.18 H Lya line 4 140N 156 34 0.18 1.27 N2(LBH) band (narrow dL) 5 136W 150 41 0.25 2.05 N2(LBH) band 7 123W 128 30 0.30 3.08 OI lines B 117N 120 11 0.14 0.91 0.79 H Lya line (narrow dL) C 117A 130 47 1.00 10.5 7.0 H Lya line Lp is wavelength of peak transmission for filter. dL is passband FWHM. Tp is transmission at Lp and +15 deg C. Sp is sensitivity at Lp in units of counts/(kilorayleigh-pixel). S(Lya) is sensitivity at L121.6 in units of counts/(kilorayleigh-pixel).