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

The tropospheric distribution of greenhouse gases (GHGs) depends on surface flux variations, atmospheric chemistry and transport processes over a range of spatial and temporal scales. Accurate and precise atmospheric concentration observations of GHGs can be used to infer surface flux estimates, though their interpretation relies on unbiased atmospheric transport models. GHOST is a novel, compact shortwave infrared spectrometer which will observe tropospheric columns of CO2, CO, CH4 and H2O (along with the HDO/H2O ratio) during deployment on board the NASA Global Hawk unmanned aerial vehicle. The primary science objectives of GHOST are to: 1) test atmospheric transport models; 2) evaluate satellite observations of GHG column observations over oceans; and 3) complement in-situ tropopause transition layer observations from other Global Hawk instruments. GHOST comprises a target acquisition module (TAM), a fibre slicer and feed system, and a multiple order spectrograph. The TAM is programmed to direct solar radiation reflected by the ocean surface into a fibre optic bundle. Incoming light is then split into four spectral bands, selected to optimise remote observations of GHGs. The design uses a single grating and detector for all four spectral bands. We summarise the GHOST concept and its objectives, and describe the instrument design and proposed deployment aboard the Global Hawk platform.

[1]  David Crisp,et al.  The Orbiting Carbon Observatory (OCO) mission , 2004 .

[2]  M. Buchwitz,et al.  Space‐based near‐infrared CO2 measurements: Testing the Orbiting Carbon Observatory retrieval algorithm and validation concept using SCIAMACHY observations over Park Falls, Wisconsin , 2006 .

[3]  Philippe Ciais,et al.  Weak Northern and Strong Tropical Land Carbon Uptake from Vertical Profiles of Atmospheric CO2 , 2007, Science.

[4]  Masakatsu Nakajima,et al.  Thermal and near infrared sensor for carbon observation Fourier-transform spectrometer on the Greenhouse Gases Observing Satellite for greenhouse gases monitoring. , 2009, Applied optics.

[5]  S. Dance,et al.  Estimating surface CO2 fluxes from space-borne CO2 dry air mole fraction observations using an ensemble Kalman Filter , 2009 .

[6]  Y. Sawa,et al.  Formation mechanisms of latitudinal CO2 gradients in the upper troposphere over the subtropics and tropics , 2009 .

[7]  Liang Feng,et al.  On the impact of transport model errors for the estimation of CO2 surface fluxes from GOSAT observations , 2010 .

[8]  S. Wofsy,et al.  HIAPER Pole-to-Pole Observations (HIPPO): fine-grained, global-scale measurements of climatically important atmospheric gases and aerosols , 2011, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[9]  Hartmut Boesch,et al.  Global Characterization of CO2 Column Retrievals from Shortwave-Infrared Satellite Observations of the Orbiting Carbon Observatory-2 Mission , 2011, Remote. Sens..

[10]  E. R. Polovtseva,et al.  The HITRAN2012 molecular spectroscopic database , 2013 .