ASCENDS: Past, Present and Future

Abstract:

ASCENDS: Past,Present and Future by Berrien Moore III (University of Oklahoma) and Ken Jucks (NASA) with The ASCENDS Science Working Group

The Active Sensing of CO₂ Emissions over Nights,Days,and Seasons (ASCENDS) mission was recommended by the National Research Council’s Decadal Survey,and it is considered the scientific and technological next step following Japan’s Greenhouse gases Observing SATellite (GOSAT) and NASA’s Orbiting Carbon Observatory (OCO).Space agencies are commitment to CO₂ observations:GOSAT-2:Japan is proceeding with its development;OCO-2:NASA has launched it into the A-Train;TanSat:China’s CO₂ mission is in development,and CarbonSat is being considered by ESA.Using a laser,ASCENDS will make uninterrupted CO₂ observations in high-latitudes,nighttime observations,and measurements in partly cloud conditions.ASCENDS expands the sampling of the atmosphere and may avoid some of the potential biases of passive systems.An issue for any mission is the linkage of observations to information regarding the subject of interest—in this case,surface fluxes of CO₂.ASCENDS and the other low-Earth orbiting CO₂ missions are difference from most missions in which the subject of interest is directly observed.In the case of these missions,the purpose of the atmospheric measurement is to determine surface fluxes that are distant from where the atmosphere is observed.This distinction between the subject observed and the subject of interest places added importance on the mission’s observational requirements that governs the specifications of the mission and instrument.We discuss the challenge of establishing these mission requirements and present quantitative information on mapping observations with their uncertainties to information regarding terrestrial and oceanic surface fluxes of CO₂.Results from the ASCENDS Science Working Group that the link measurement requirements to flux determination (or flux uncertainty reductions) are highlighted.We discuss modeling challenges that are coupled with this next generation of space-based CO₂ observations and review the history of ASCENDS and its current status.