The European Space Agency’s (ESA) Aeolus satellite was launched on 22 August 2018 from Centre Spatial Guyanais in Kourou, French Guyana. The Aeolus data has been extensively analysed by a number of meteorological centres and found to have a positive impact on NWP forecasts, particularly in the tropics and polar regions. These positive results, along with the successful in-orbit demonstration of the measurement concept and associated technologies utilised on Aeolus, resulted in a statement of interest from EUMETSAT in a future, operational DWL mission in the 2030 to mid-2040’s timeframe and a request to ESA to carry out the necessary pre-development activities for such a mission. This paper will describe the current status of instrument pre-development activities that are being performed in the frame of a potential Aeolus-2 mission. The main inputs for a future Doppler Wind Lidar (DWL) instrument that have been used are: lessons learned from the Aeolus development phases and the in-orbit operations and performance; initial inputs from EUMETSAT including a total mission lifetime of higher than 10-15 years utilizing 2 spacecraft (implying a lifetime of 5.5 years for each) with a launch of the first satellite in 2030, increased robustness and operability of the instrument, and an emphasis on reduction of recurrent costs; the maximum utilization of the demonstrated design heritage; and a number of recommendations for the requirements of a future DWL mission from the Aeolus Scientific Advisory Group (ASAG). These inputs have been collated and combined into a set of preliminary requirements which have been used as the basis for a dedicated Instrument Consolidation Study. An extensive review and trade-off of the above inputs by Airbus Defence & Space, ESA, and independent experts, resulted in the decision to baseline a bi-static instrument design. In addition, three instrument subsystem pre-development activities are currently running: two laser transmitter pre-developments and the pre-development of an improved detector. These developments have the aim to demonstrate that issues identified from the above are resolved and that the technology levels are sufficiently mature for the follow-on DWL mission. The status of these pre-developments will be summarise
AEOLUS underwent a long development led by Airbus Defence and Space both for the LIDAR instrument (ALADIN) in France, and the platform in the UK, and was successfully launched into a Sun-synchronous 320 km dawn-dusk orbit by a Vega launcher in August 2018.
The ALADIN Doppler wind LIDAR is pioneering the application of such kind of instrument in space and widens the field for space based LIDAR applications. Initially the mission was designed to be a demonstrator but can be actually considered as operational as the data are used routinely with positive impact on the Numerical Weather Predictions (NWP) models after less than one year of operations in-orbit.
After four years of operational lifetime, and also thanks to a strong support to in-flight operations, AIRBUS has learnt, together with ESA customer and scientist user teams, many things about ALADIN LIDAR instrument behavior and its performance monitoring in orbit.
While temperature and power telemetries monitoring are quite standard in post-delivery, the follow up of the instrument optical alignment and performance is less direct and lesson learnt show it can be however very profitable in particular for the first UV LIDAR in orbit.
The ALADIN architecture is recalled with its measurement principle, and its calibration mode and measurement mode, summarizing the available data for monitoring its behavior in orbit: this covers far field pattern from the atmospheric echo, or near field pattern from the atmospheric echo or internal calibration path; this allows to derive alignment stability of the transmitter and receiver part of the instrument. Also, spectral calibration curves trends allow to retrieve information’s about spectrometers stability. In addition, energy monitoring trend are presented with several means available, and linked lessons learnt are driven.
As an important contributor for ALADIN performances, the telescope stability is analyzed and thermal correlation presented with representative Earth albedo maps. The telescope stability is shown as a contributor to link budget but also to spectrometers systematic error limitation due to their sensitivity to variations of divergence and line of sight (angle of incidence).
As other key element, the CCD sensor "hot pixel" observation is described with the workaround solution operation at instrument allowing to remove their negative impact on measurement data.
Overall conclusion is driven with lessons learnt and perspective for a follow on instrument.
EarthCARE is the 3rd Earth Explorer Core Mission of the European Space Agency (ESA) Living Planet Program, with the fundamental objective of improving understanding of the processes involving clouds, aerosols and radiation in the Earth’s atmosphere [2] [3] [5] [6]. EarthCARE data products will be used to improve climate and numerical weather prediction. The data products include vertical profiles of aerosols, liquid water and ice, observations of cloud distribution and vertical motion within clouds, and will allow the retrieval of profiles of atmospheric radiative heating and cooling [4]. For above mission objective, the EarthCARE satellite hosts four complex instruments, the ATLID, (ATmospheric LIDAR from Airbus Toulouse), the CPR (Cloud Profiling Radar, from JAXA/NEC), the MSI (Multi Spectral Imager from SSTL) and the BBR (Broad Band Radiometer from TAS-UK). The instrument performance verification approach is based on (a) the full performance verification testing done on instrument level, and (b) on Instrument Performance Checks (IPCs) to be repeated periodically on instrument and satellite level. IPCs are designed to confirm that the core instrument performance as verified on instrument level does not degrade after integration on the platform and throughout the overall satellite AIT campaign until launch. Five ATLID IPCs have been defined in close cooperation between Airbus instrument and satellite prime teams, considering instrument performance verification needs as well as feasibility of IPC repetition in satellite AIT. This feasibility refers mainly to satellite AIT limitations for laser hazard protection measures, cleanliness (ISO8 environment), complexity of optical setups, need for limited test durations<1 day and more difficult instrument accessibility (instrument integrated at more than 3m height on the satellite). For the ATLID Lidar instrument, the following IPCs have been defined: (1) Transmit Laser Beam Line of Sight (LoS) stability, (2) Activation of Transmit Laser beam steering mechanism, (3) Laser pulse energy knowledge stability, (4) Overall Receive chain optical response check and (5) Detection chain total noise in darkness. IPC test definition as well as test results from instrument level and satellite level IPC testing will be presented. The trend of ATLID IPC test results is found stable along all test repetitions done until today. Additional presentation content can be accessed on the supplemental content page.
The global representation of aerosol, clouds, and their impact on the energy budget remains a major source of uncertainties in global models for climate predictions, but also strong weather events in numerical weather prediction. Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) mission, the sixth Earth Explorer Mission of the European Space Agency (ESA) Living Planet Programme, shall improve the understanding by three dimensional observations of global profiles of cloud, aerosol, precipitation and associated radiative properties. A major contribution will be provided by the ATmospheric LIDAR (Light Detection and Ranging), ATLID, being developed and tested by Airbus Defence and Space S.A.S in Toulouse. ATLID is a High Spectral Resolution-Polarization LIDAR and will provide vertical profiles of optically thin cloud and aerosol layers, the aerosol type, as well as the altitude of cloud boundaries. After the development, qualification and delivery of all units, ATLID integration has finally been completed and the self-standing instrument was successfully tested to demonstrate its performance under ambient and space environment conditions, in Toulouse and CSL/Liège respectively. All preliminary test results obtained up to now are very promising and indicate ATLID’s capability and compliance to all performance goals and specifications. The instrument has been now delivered, to Airbus Defence and Space GmbH Immenstaad, and integrated into the EarthCARE platform. Results of ATLID ambient test campaign, EMC, mechanical test campaign, and thermal balance test campaign, along with final performance and calibration test results shall be presented in this paper.
G. de Villele, J. Pereira do Carmo, A. Helière, A. Lefebvre, L. Barbaro, T. Belhadj, F. Chassat, B. Corselle, R. Evin, M. Feral, I. Levret, P. Lingot, F. Olivier, S. Pelletier, J. Pochet, A. Schaube, F. Varlet, P. Vlimant
The ATmospheric LIDar (Light Detection and Ranging), ATLID, is part of the payload of the Earth Cloud and Aerosol Explorer (EarthCARE) mission, the sixth Earth Explorer Mission of the European Space Agency (ESA) Living Planet Program. After the successful major step of optical and electrical integration, ATLID has started its performance and functional testing in Toulouse Airbus Defence and Space. The emission part of the instrument has been operated with both TxA (Laser transmitter units) delivered from Leonardo team: as major achievement the main performance of both flight lasers have been tested and confirmed with more than 40mJ UV emission @51Hz with operation via instrument control ACDM flight unit (ATLID control and data management). Tests are parallelized with on one side the EFM test (Electrical Flight Model), and on the other side the OFM tests (Optical flight model). The EFM tests aim at validating the functional and electrical architecture via functional testing on each nominal and redundant path with all the flight electronic units and laser sources. The OFM tests aims validating the receiver alignment from telescope input till fiber detectors, the field of view of the three detection channels and their radiometric performance. OFM vibration tests have been performed and have validated design stability against mechanical loads. End of OFM and EFM tests is planned at summer 2018 and will give go ahead for instrument assembly in its final ATLID PFM configuration with laser cooling system integration. After Ambient performance testing, the environmental test campaign immediately start with EMC, mechanical and thermal vacuum testing.
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