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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 05 Nov 2018

Research article | 05 Nov 2018

Review status
This discussion paper is a preprint. A revision of the manuscript was accepted for the journal Atmospheric Measurement Techniques (AMT).

The OCO-3 mission; measurement objectives and expected performance based on one year of simulated data

Annmarie Eldering1, Tommy E. Taylor2, Chris W. O'Dell2, and Ryan Pavlick1 Annmarie Eldering et al.
  • 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109, USA
  • 2Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO, 80521, USA

Abstract. The Orbiting Carbon Observatory-3 (OCO-3) is NASA's next instrument dedicated to extending the record of the dry-air mole fraction of column carbon dioxide (XCO2) and solar-induced fluorescence (SIF) measurements from space. The current schedule calls for a launch in the first half of 2019 via a Space-X Falcon 9 and Dragon capsule, with installation as an external payload on the Japanese Experimental Module Exposed Facility (JEM-EF) of the International Space Station (ISS). The nominal mission lifetime is 3 years. The precessing orbit of the ISS will allow for viewing of the earth at all latitudes less than approximately 52°, with a ground repeat cycle that is much more complicated than the polar orbiting satellites that so far have carried all of the instruments capable of measuring carbon dioxide from space.

The grating spectrometer at the core of OCO-3 is a direct copy of the OCO-2 spectrometer, which was launched into a polar orbit in July 2014. As such, OCO-3 is expected to have similar instrument sensitivity and performance characteristics to OCO-2, which provides measurements of XCO2 with precision better than 1 ppm at 3 Hz with each viewing frame containing 8 footprints of approximate size 1.6 by 2.2 km. However, the physical configuration of the instrument aboard the ISS, as well as the use of a new pointing mirror assembly (PMA), will alter some of the characteristics of the OCO-3 data, compared to OCO-2. Specifically, there will be significant differences from day to day in the sampling locations and time of day. In addition, the flexible PMA system allows for a much more dynamic observation mode schedule.

This paper outlines the science objectives of the OCO-3 mission and, using a simulation of one year of global observations, characterizes the spatial sampling, time of day coverage, and anticipated data quality of the simulated L1b. After application of cloud and aerosol prescreening, the L1b radiances are run through the operational L2 full physics retrieval algorithm, as well as post-retrieval filtering and bias correction, to examine the expected coverage and quality of the retrieved XCO2 and to show how the measurement objectives are met. In addition, results of the SIF from the IMAP-DOAS algorithm are analyzed. This paper focuses only on the nominal nadir-land and glint-water observation modes, although on-orbit measurements will also be made in transition and target modes, similar to OCO-2, as well as the new snapshot area mapping mode.

Annmarie Eldering et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Annmarie Eldering et al.
Annmarie Eldering et al.
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Short summary
NASA's Orbiting Carbon Observatory-3 (OCO-3) is scheduled for a 2019 launch to the International Space Station (ISS). It is expected to continue the record of column carbon dioxide (XCO2) and solar induced chlorophyll fluorescence (SIF) measurements from space used to study and constrain the earth's carbon cycle. This work highlights the measurement objectives and uses simulated data to show that the expected instrument performance is on par with those from OCO-2.
NASA's Orbiting Carbon Observatory-3 (OCO-3) is scheduled for a 2019 launch to the International...