Yannig Durand

The Airborne Demonstrator for the Direct-Detection Doppler Wind Lidar ALADIN on ADM-Aeolus. Part I: Instrument Design and Comparison to Satellite Instrument

Abstract The global observation of profiles of the atmospheric wind speed is the highest-priority unmet need for global numerical weather prediction. Satellite Doppler lidar is the most promising candidate to meet the requirements on global wind profile observations with high vertical resolution, precision, and accuracy. The European Space Agency (ESA) decided to implement a Doppler wind lidar mission called the Atmospheric Dynamics Mission Aeolus (ADM-Aeolus) to demonstrate the potential of the Doppler lidar technology and the expected impact on numerical weather forecasting. An airborne prototype of the instrument on ADM-Aeolus was developed to validate the instrument concept and retrieval algorithms with realistic atmospheric observations before the satellite launch. It is the first airborne direct-detection Doppler lidar for atmospheric observations, and it is operating at an ultraviolet wavelength of 355 nm. The optical design is described in detail, including the single-frequency pulsed laser and th...

Performance modeling for A-SCOPE: a space-borne lidar measuring atmospheric CO2

A-SCOPE (Advanced Space Carbon and Climate Observation of Planet Earth) has been one of the six candidates for the third cycle of the Earth Explorer Core missions, selected by the European Space Agency (ESA) for assessment studies. Earth Explorer missions focus on the science and research aspects of ESAs Living Planet Programme. A-SCOPE mission aims at observing atmospheric CO2 for a better understanding of the carbon cycle. Knowledge about the spatial distribution of sources and sinks of CO2 with unprecedented accuracy will provide urgently needed information about the global carbon cycle. A-SCOPE mission encompasses a new approach to observe the Earth from space based on an IPDA (Integrated Path Differential Absorption) Lidar. Based on the known principle of a differential measurement technique, the IPDA lidar relies on the measurement of the laser echoes reflected by hard targets as the ground or the top of the vegetation. Such a time-gated technique is a promising way to overcome the sources of systematic errors inherent to passive missions. To be fully exploited, it however translates into stringent instrument requirements and requires a dedicated performance assessment. In this paper, the A-SCOPE instrument concept is first presented, with the aim of summarizing some important outcomes from the industrial assessment studies. After a discussion of the mission requirements and measurement principles, an overview is given about the instrument architecture. Then the instrument performance is reported, together with a detailed discussion about sources of systematic errors, which pose the strongest technical challenges.

The EarthCARE mission: Mission concept and lidar instrument pre-development

The earth clouds, aerosols, and radiation explorer mission has been selected as the 6th earth explorer mission of ESAs living planet programme [1]. A suite of four instruments, active and passive, will be embarked on the same satellite to measure cloud and aerosol properties simultaneously with TOA radiances in order to derive TOA fluxes in relation to clouds and aerosols.

Performance of high-power laser diode arrays for spaceborne lasers

The adequacy of commercial quasi-continuous high-power laser diode arrays (HPLDAs) as pump sources for spaceborne lasers has been assessed by endurance tests up to 3 x 10(9) shots under various stress conditions, vacuum operation up to 0.36 x 10(9) shots, and proton radiation tests. Observations of the evolution of the electro-optic parameters and of the near-field patterns of the HPLDAs during endurance tests have revealed that some diode bars could reach the required lifetime of a multibillion shots, suggesting how to build long lifetime HPLDAs by proper selection of the diode bars. The robustness of the HPLDAs against the proton environment experienced in a typical low Earth orbit has been checked. Finally, high-power laser diode arrays have been operated under vacuum, showing a behavior similar to that of HPLDAs operating in atmospheric conditions.

Predevelopment of a direct detection Doppler wind lidar for ADM/AEOLUS mission

The Atmospheric Dynamics Mission (ADM-Aeolus) has been selected as the second of a series of Earth Explorer Core Missions. The payload aims at providing measurements of atmospheric wind profiles with global coverage. The key element of ADM-Aeolus is the Atmospheric Laser Doppler Lidar Instrument (ALADIN), a Direct Detection Doppler Lidar. The ALADIN instrument belongs to a completely new class of earth-observation lidar payloads with limited power requirements and high reliability over a three-year lifetime. Technological challenges are addressed in an early stage by the development of a Pre-Development Model (PDM), which is a functional representative model of the receiver of ALADIN. The PDM is being established to validate the technologies used in the ALADIN design, evaluate the flight-worthiness of its major subsystems and verify the instrument overall performances. The purpose of this paper is to present the latest results on the status of the ALADIN Pre-Development Model.

Results of the pre-development of ALADIN, the Direct Detection Doppler Wind Lidar for ADM/AEOLUS

Due for launch in late 2007, the Atmospheric Dynamics Mission (ADM-Aeolus) has been selected as the second Earth Explorer Core Missions within ESA Living Planet Programme. Its payload aims at providing measurements of atmospheric wind profiles with global coverage. The key elecment of ADM-Aeolus is the Atmospheric LAser Doppler Lidar INstrument (ALADIN), a Direct Detection Doppler Lidar in the ultra-violet spectral region operating with aerosol and molecular backscatter signals in parallel. The ALADIN instrument belongs to a completely new class of earth-observation payloads with limited power requirements and high reliability over a three-year lifetime. It will be the first European Lidar in space. Technological challenges are addressed in an early stage by a pre-development programme that consists of designing, manufacturing and testing a functional representative model of the receiver of ALADIN (the Pre-Development Model, PDM), and a breadboard of the transmitter. The pre-development programme is being established to validate the technologies used in the ALADIN design, evaluate the flight-worthiness of its major subsystems and verify the instrument overall performances. The purpose of this paper is to present the main achievements of the pre-development programme: environmental tests on the Pre-Development Model (thermal-vacuum and mechanical tests), development of the laser breadboards and assessment programme of the laser diodes.

MTG Flexible Combined Imager optical design and performances

Meteosat Third Generation is the next ESA Program of Earth Observation dedicated to Nowcasting and very short term Weather Forecasting (NWC), medium/short range Global and Regional Numerical Weather Prediction (NWP), and Climate and Air Composition Monitoring. The satellites will be operating from the Geostationary orbit using a 3 axes stabilized platform. The main instrument is called the Flexible Combined Imager (FCI), currently under development by Thales Alenia Space France (TAS-F). This instrument will provide full images of the Earth every 10 minutes in 16 spectral channels between 0.44 and 13.3 μm, with a ground resolution from 0.5 km to 2 km. The FCI is composed of a TMA telescope developed by Kayser-Threde (KT), which includes a Scan mirror, and a calibration mechanism with an embedded black body dedicated to accurate in-flight IR radiometric calibration and a Metallic Neutral density for dedicated VNIR Sun calibration. The image produced by the telescope is split into several spectral groups by a spectral separation assembly (SSA) with dichroïc beamsplitters. The output beams are collimated to ease the instrument integration, and reach the cold optics (CO-I) which focalize the optical beams onto the detectors. The cold optics and IR detectors are accurately positioned inside a common cryostat to improve registration between spectral channels. Spectral filters are integrated on top of the detectors in order to achieve the required spectral selection. This article will describe the optical design and the main optical performances of the FCI: image quality, very high line-of-sight stability, and an efficient stray-light rejection thanks to the implementation of dedicated baffles and a stringent control of contamination. The FCI currently under development is expected to exhibit a significant improvement of performances with respect to Meteosat Second Generation satellites.

The FCI on board MTG : optical design and performances

Meteosat Third Generation is the next ESA Program of Earth Observation dedicated to provide Europe with an operational satellite system able to support accurate prediction of meteorological phenomena until the late 2030s. The satellites will be operating from the Geostationary orbit using a 3 axes stabilized platform. The main instrument is called the Flexible Combined Imager (FCI), currently under development by Thales Alenia Space France. It will continue the successful operation of the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on Meteosat Second Generation (MSG) with improved performance. This instrument will provide full images of the Earth every 10 minutes in 16 spectral channels between 0.44 and 13.3 μm. The ground resolution is ranging from 0.5 km to 2 km. The FCI is composed of a telescope developed by Kayser-Threde, which includes a Scan mirror for the full Earth coverage, and a calibration mechanism with an embedded black body dedicated to accurate in-flight IR radiometric calibration. The image produced by the telescope is split into several spectral groups by a spectral separation assembly (SSA) thanks to dichroïc beamsplitters. The output beams are collimated to ease the instrument integration before reaching the cryostat. Inside, the cold optics (CO-I) focalize the optical beams onto the IR detectors. The cold optics and IR detectors are accurately positioned inside a common cold plate to improve registration between spectral channels. Spectral filters are integrated on top of the detectors in order to achieve the required spectral selection. This article describes the FCI optical design and performances. We will focus on the image quality needs, the high line-of-sight stability required, the spectral transmittance performance, and the stray-light rejection. The FCI currently under development will exhibit a significant improvement of performances with respect to MSG.

The flexible combined imager onboard MTG: from design to calibration

The Meteosat Third Generation (MTG) Programme is being realised through the well-established and successful cooperation between EUMETSAT and ESA. It will ensure the continuity with, and enhancement of, operational meteorological and climate data from Geostationary Orbit as currently provided by the Meteosat Second Generation (MSG) system. The industrial Prime Contractor for the Space segment is Thales Alenia Space (France) with a core team consortium including OHB-Bremen (Germany) and OHB-Munich (Germany. This contract includes the provision of six satellites, four Imaging satellites (MTG-I) and two Sounding satellites (MTG-S), which will ensure a total operational life of the MTG system in excess of 20 years. A clear technical baseline has been established for both MTG-I and MTG-S satellites, and confirmed through a rigorous Preliminary Design Review (PDR) process that was formally concluded during 2013. Dedicated reviews have been held for all the main elements including the core instruments (Flexible Combined Imager (FCI) and Infrared Sounder (IRS)), the Platform (which is largely common for the two satellites), the Lightning Imager (LI) and the MTG-I and MTG-S satellites as a whole. The satellites and instruments are at the moment in preparation for the Structural and Thermal Models (STM). The FCI is designed to provide images of the Earth every 10 to 2.5 minutes in 16 spectral channels between 0.44 and 13.3 μm, with a ground resolution ranging from 0.5 km to 2 km. The on-board calibration is based on the use of a Metallic Neutral Density (MND) filter for VIS/NIR channels and a blackbody for the IR channels. This paper introduces the overall FCI design and its calibration concept covering VIS/NIR and IR domains and it describes how the use of the MND makes it possible to accurately correct the medium and long term radiometric drifts of the IR3.8 μm channel.

Critical laser technology developments and ESA space qualification approach in support of ESA's Earth observation missions

In this paper, ESAs approach to lasers and detectors space evaluation and qualification will be explored. ESA has its own international qualification system, the ESCC system. This system guarantees reliability, assurance and quality of components, and hence a successful space mission. An overview of the ESCC (European Space Component Coordination) system, as well as the relevant ECSS (European Cooperation for Space Standards) related standards addressing components and hybrid qualification will be given. These standards are being constantly updated, through well structured working groups, constantly coming up with new ways of qualifying space components. These components are themselves constantly changing in terms of material, technology, and manufacturing processes. The development of advanced Lidar systems for space applications and their evaluation by airborne or ground based test campaigns is an important strategic element of the ESA Earth Observation Programme. These systems depend on robust and reliable lasers and detector at their core function. Since the early eighties, ESA has been supporting the development of the critical subsystems of any Lidar, i.e. lasers and detectors. Several missions, involving different kinds of lidars, provide the requirements to be addressed in the Lidar risk mitigation activities. They also present a challenge concerning their space qualification and reliability assurance. These missions are: ADM-Aeolus flying ALADIN a Doppler Wind Lidar; EarthCARE embarking ATLID an Atmospheric Backscatter Lidar; three missions studied for their feasibilities: WALES, A-SCOPE and ACCURATE, all using Differential Absorption Lidar in different ways to measure respectively profiles of water vapour, total column of CO2 and greenhouse gases in an occultation geometry.