GreenHouse Observations of the Stratosphere and Troposphere (GHOST): a novel shortwave infrared spectrometer developed for the Global Hawk unmanned aerial vehicle

Abstract

ABSTRACT The tropospheric distribution of greenhouse gases (GHGs) depen ds on surface ux variations, atmospheric chem-istry and transport processes over a range of spatial and tempo ral scales. Accurate and precise atmosphericconcentration observations of GHGs can be used to infer surface ux estimates, though their interpretation relieson unbiased atmospheric transport models. GHOST is a novel, compa ct shortwave infrared spectrometer whichwill observe tropospheric columns of CO 2 , CO, CH 4 and H 2 O (along with the HDO/H 2 O ratio) during deploy-ment on board the NASA Global Hawk unmanned aerial vehicle. The pr imary science objectives of GHOST areto: 1) test atmospheric transport models; 2) evaluate satellite ob servations of GHG column observations overoceans; and 3) complement in-situ tropopause transition layer obs ervations from other Global Hawk instruments.GHOST comprises a target acquisition module (TAM), a bre slicer and feed system, and a multiple order spec-trograph. The TAM is programmed to direct solar radiation reecte d by the ocean surface into a bre opticbundle. Incoming light is then split into four spectral bands, selecte d to optimise remote observations of GHGs.The design uses a single grating and detector for all four spectral bands. We summarise the GHOST concept andits objectives, and describe the instrument design and proposed d eployment aboard the Global Hawk platform.Keywords: Greenhouse gases, shortwave infrared, grating spectrometer , airborne remote sensing