Observations of far-ultraviolet (FUV) dayglow by the Global-scale Observations of Limb and Disk (GOLD)
mission provide a new opportunity to monitor relative composition changes in the upper atmosphere as well as
solar extreme ultraviolet (EUV) variability. Relative composition changes are measured through ΣO/N,
which is the column density ratio of atomic oxygen to molecular nitrogen, while Q provides
a measure of the solar EUV energy flux below 45 nm into the upper atmosphere. This
spectral range provides the ionizing radiation which ultimately results in FUV airglow emission
produced by photodissociation and photoelectron impact. The quantities ΣO/N and
Q are derived from GOLD FUV observations through lookup tables that are constructed using a first-principles photoelectron
transport model. The two FUV emission features used are O I 135.6 nm and N Lyman-Birge-Hopfield
(LBH) bands as functions of solar zenith angle. We present an overview of the theoretical basis for the
algorithms and practical considerations for application to GOLD data. The effect on derived products
from uncertainties in electron impact cross sections, off-nadir viewing, and instrument artifacts are
reviewed. We also discuss GOLD Level 1C DAY and Level 2 ON2 and QEUV data products and present
representative samples of each.