We investigated the contributions of the hydroxyl (OH) airglow to the illumination of resident space objects.
During nighttime, in a moonless sky, the airglow is the largest contributor to the sky brightness in the visible
(vis), the near-infrared (NIR) and short-wave infrared (SWIR) spectral region. The dominant contributors to
the airglow are vibrationally excited hydroxyl radicals, OH(ν). The radicals are formed in vibrational states
up to υ=9 by the reaction of hydrogen atoms with ozone. The strong emissions, known as Meinel emissions,
are sequences with σν= 1-6. Emissions with υ = 3, 4, 5 and 6 occur in the visible and NIR between .4 and 1.0
µm. From 1.0 to 2.5 µm there are very strong emissions from the δν= 2 sequences. The σν= 1 emissions
extend into the thermal infrared to 4.5 μm. In this work, we considered four band passes, a vis-NIR band
pass, two SABER band passes centered at 1.6 and 2.0 μm, respectively, and a broad band pass around 2.7
µm. SAMM2 was utilized to compute spectra and line of sight radiances. We used line of sight (LOS)
radiances to compute the irradiance on a space object that was taken as a flat plate with a Lambertian surface
reflectance. Profiles of irradiance versus orientation were calculated. The OH airglow will illuminate a facet
even if it is pointing somewhat upward. However, the irradiance in the 2.7 μm band pass comes almost
entirely from the atmosphere in the low altitude and the earth emission.