MERLIN: A French-German Space Lidar Mission Dedicated to Atmospheric Methane

Abstract

Abstract:The MEthane Remote sensing Lidar missioN (MERLIN) aims at demonstrating the spaceborne active measurement of atmospheric methane, a potent greenhouse gas, based on an Integrated Path Differential Absorption (IPDA) nadir-viewing LIght Detecting and Ranging (Lidar) instrument. MERLIN is a joint French and German space mission, with a launch currently scheduled for the timeframe 2021/22. The German Space Agency (DLR) is responsible for the payload, while the platform (MYRIADE Evolutions product line) is developed by the French Space Agency (CNES). The main scientific objective of MERLIN is the delivery of weighted atmospheric columns of methane dry-air mole fractions for all latitudes throughout the year with systematic errors small enough (<3.7 ppb) to significantly improve our knowledge of methane sources from global to regional scales, with emphasis on poorly accessible regions in the tropics and at high latitudes. This paper presents the MERLIN objectives, describes the methodology and the main characteristics of the payload and of the platform, and proposes a first assessment of the error budget and its translation into expected uncertainty reduction of methane surface emissions.

Introduction of Water‐Vapor Broadening Parameters and Their Temperature‐Dependent Exponents Into the HITRAN Database: Part I—CO2, N2O, CO, CH4, O2, NH3, and H2S

“…Following water vapor and carbon dioxide, methane is also one of the most significant greenhouse gases in the atmosphere, and its warming potential is almost 23 times that of carbon dioxide over a 100‐year cycle (Solomon et al, ). Therefore, monitoring methane in the terrestrial atmosphere is one of the main objects in many remote‐sensing missions including GOSAT (Kuze et al, ), SCIAMACHY (Frankenberg et al, ), MERLIN (Ehret et al, ), CarbonSat (Buchwitz et al, ), and TROPOMI (Butz et al, ). For the purpose of reducing the uncertainties in the retrieval of atmospheric methane column amounts, it requires one to model the absorption cross sections of methane with an extremely high accuracy (to even subpercent).…”

“…Note here the grey-shaded area in the top panel corresponds to the transitions with N ″ = 1 that were not included in our fitting procedure. objects in many remote-sensing missions including GOSAT (Kuze et al, 2009), SCIAMACHY (Frankenberg et al, 2011), MERLIN (Ehret et al, 2017), CarbonSat (Buchwitz et al, 2013), and TROPOMI (Butz et al, 2012). For the purpose of reducing the uncertainties in the retrieval of atmospheric methane column amounts, it requires one to model the absorption cross sections of methane with an extremely high accuracy (to even subpercent).…”

Potential of Spaceborne Lidar Measurements of Carbon Dioxide and Methane Emissions from Strong Point Sources

“…and decreasing above following a climatological average. We use two different suitable CO2 absorption line positions that were selected for the ESA A-SCOPE IPDA Lidar satellite mission [27], and the CH4 line position foreseen for the upcoming MERLIN mission [20,25], all listed in Table 1. We investigated possible interference by other plume exhaust gases by scanning the HITRAN database [28] for the occurrence of absorption lines of other gases in the vicinity of the wavenumbers of Table 1.…”

“…We limit our Lidar sizing analysis to pulsed, direct detection systems with two wavelengths (on-and offline), using knowledge gained during the planning and design phase of airborne [18] and spaceborne IPDA Lidars [20,24,25,27,33]. Alternative Lidar methodologies might likewise be applicable [19,22,34].…”

“…It is appropriate now to assess the feasibility of global Lidar observations of point sources that could complement the current and future observation systems, and to discuss the implications for a novel space-borne IPDA Lidar which goes beyond the systems currently being designed and developed [19][20][21][22][23]. In this initial feasibility study we first introduce the IPDA method focusing on plume detection sensitivity in Section 2, and use a Lidar performance model to assess the required size of a satellite Lidar for plume detection in Section 3.…”