Global-scale observations of the limb and disk mission implementation: 1. Instrument design and early flight performance

GOLD employs an instrument with two identical ultraviolet spectrographs that make observations of the Earth's thermosphere and ionosphere from a commercial communications satellite owned and operated by Societe Europeenne des Satellites (SES) and located in geostationary orbit at 47.5 degrees west longitude (near the mouth of the Amazon River).

They make images of atomic oxygen 135.6 nm and N-2 Lyman-Birge-Hopfield (LBH) 137-162 nm radiances of the entire disk that is observable from geostationary orbit and on the near-equatorial limb. They also observe occultations of stars to measure molecular oxygen column densities on the limb. Here, we provide an overview of the instrument and compare its prelaunch and early flight measurement performance.