Abstract
ATLID (ATmospheric LIDar) is the atmospheric backscatter Light Detection and Ranging (LIDAR) instrument on board of the Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) mission, the sixth Earth Explorer Mission of the European Space Agency (ESA) Living Planet Programme. ATLID’s purpose is to provide vertical profiles of optically thin cloud and aerosol layers, as well as the altitude of cloud boundaries, with a resolution of 100 m for altitudes of 0 to 20 km, and a resolution of 500 m for 20 km to 40 km. In order to achieve this objective ATLID emits short duration laser pulses in the ultraviolet, at a repetition rate of 51 Hz, while pointing in a near nadir direction along track of the satellite trajectory. The atmospheric backscatter signal is then collected by its 620 mm aperture telescope, filtered through the optics of the instrument focal plane assembly, in order to separate and measure the atmospheric Mie and Rayleigh scattering signals. With the completion of the full instrument assembly in 2019, ATLID has been subjected to an ambient performance test campaign, followed by a successful environmental qualification test campaign, including performance calibration and characterization in thermal vacuum conditions. In this paper the design and operational principle of ATLID is recalled and the major performance test results are presented, addressing the main key receiver and emitter characteristics. Finally, the estimated instrument, in-orbit, flight predictions are presented; these indicate compliance of the ALTID instrument performance against its specification and that it will meet its mission science objectives for the EarthCARE mission, to be launched in 2023.
Highlights
The EarthCARE missionEarthCARE [1,2,3,4,5] is a joint collaborative mission of European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) with the objective to improve our understanding of the cloudaerosol-radiation interactions and Earth radiative balance, so that they can be modelled with better reliability in climate and numerical weather prediction models [6]
The instrument implements a co-alignment control loop, making use of a Beam SteerSteering Mirror (BSM) at transmitter chain level and a Co-Alignment Sensor (CAS) at ing Mirror (BSM) at transmitter chain level and a Co-Alignment Sensor (CAS) at receiver receiver chain level, in order to track and ensure that the emitted laser beam is aligned with chain level, in order to track and ensure that the emitted laser beam is aligned with the the receiver field of view
The OGSE does not emit any signal and ATmospheric LIDar (ATLID) is in dark current calibration (DCC) mode
Summary
EarthCARE [1,2,3,4,5] is a joint collaborative mission of ESA and Japan Aerospace Exploration Agency (JAXA) with the objective to improve our understanding of the cloudaerosol-radiation interactions and Earth radiative balance, so that they can be modelled with better reliability in climate and numerical weather prediction models [6]. The advanced payloads will provide aerosol-cloud and radiation and radiation measurements to further refine their modelling of direct and indirect effects measurements further[15]. A simple means of separating the backscattering contributions of aerosols and quently, a simple means of separating the backscattering contributions of aerosols and molecules consists of filtering the backscattered spectrum with a high spectral resolution molecules consists of filtering the backscattered spectrum with a high spectral resolution filter centred on the laser emitted wavelength. The operating wavelength in the extincUV was selected as the molecular scattering is high enough to measure more accurately spectral range was as the clouds molecular scattering high enough to measure(Nd:YAG more tion profiles andselected aerosols/thin thickness and is because laser technology accurately extinction profiles and aerosols/thin clouds thickness and because laser laser with frequency tripling conversion) is available for operation in this spectraltechregion.
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