Fig. 1
a Dayside 0.90-μm filter transmission (dashed curve: revised from Iwagami et al. 2011) with an expected scattered solar spectrum (solid curve) showing little interference due to Venus atmospheric gases. The peak transmission of the filter is as small as 0.29% because of one common detector and electronics for dayside and nightside. b 0.90-μm dayside filter blocking ability (after BARR Co.). Blocking is effective at 300–1150 nm except in the pass band around 900 nm showing optical density (OD) of seven or more. Note that transmission = 10−OD. c Nightside 0.90-, 0.97- and 1.01-μm filter transmissions (dashed curves: revised from Iwagami et al. 2011) with expected Venus thermal emission spectra (solid curves) with a 1-nm resolution. The three spectra are for H2O surface abundances of 15, 30 and 60 ppmv