Future Mission Session

In the last decade, the number of satellite-borne atmospheric sounders with a high vertical resolution has dropped significantly with a detrimental impact on the monitoring of long term trends for essential atmospheric species like ozone.

As an answer to this critical situation, the Belgian Institute for Space Aeronomy is presently developing two LEO missions based on new concepts and/or technologies.

The ALTIUS (Atmospheric Limb Tracker for the Investigation of the Upcoming Stratosphere) mission will be designed from a micro-satellite of the PROBA class orbiting in a 700 km heliosynchronous orbit. The payload will consist of three 2D spectral imagers capable of observing the Earth’s atmospheric bright limb from the ultraviolet to the NIR spectral range. Being a very agile platform, ALTIUS will also promote the concept of multi-mode observations by performing solar and stellar occultation observations, across the terminator and in the dark limb region.

The spectrometric technique will be based on Acousto-Optic Tunable Filters (AOTF) and Fabry-Pérot interferometers. The imaging capacity is an essential method to solve the major difficulty associated with the accurate determination of the tangent altitude of the sensed atmospheric region.

ALTIUS is presently at the end of a Phase B1, on its way to a full PDR review. The mission objectives are both operational (with global stratospheric ozone monitoring as a target) and scientific with expected retrievals of NO₂, H₂O, CH₄ concentration profiles, aerosol extinction profiles and PSC detection.

As a little brother, PICASSO is aiming at a very different goal: to demonstrate that atmospheric limb remote sensing is feasible from pico-satellites. This miniature platform will restrict its observation mode to solar occultations acquired in inertial pointing mode whereas the wavelength domain is focussed on the Chapuis band with a miniaturized Fabry-Pérot spectrometer in the visible domain. Vertical profiles of refraction angles will also be derived from refractive dilution of solar intensity. Solar images will be analyzed on board due to restricted downlink capacities. PICASSO is funded by ESA and also at the PDR level with a target launch in 2016.

The Sentinel-4 (S4) mission, together with Sentinel-5 (S5) and the Sentinel-5 Precursor (S5P) missions, is part of the Copernicus Space Component dedicated to monitoring atmospheric composition. The primary objective of the geostationary S4 mission is to provide hourly tropospheric composition data in support of the air quality applications of the Copernicus Atmosphere Monitoring Services. The Low Earth Orbit (LEO) missions S5 and S5P provide atmospheric composition data with daily global coverage for air quality, climate, and ozone/surface UV applications.

The S4 instrument is a Ultra-violet Visible Near infrared spectrometer (UVN) designed to measure Earth radiance and solar irradiance. Key features of the UVN instrument are the spectral range from 305 nm to 500 nm with a spectral resolution of 0.5 nm, and from 750 nm to 775 nm with a spectral resolution of 0.12 nm, in combination with a low polarization sensitivity and a high radiometric accuracy. The instrument observes Europe with a revisit time of one hour. The spatial sampling distance varies across the geographic coverage area and takes a value of 8 km at the reference location at 45°N. The S4 products include key air quality parameters such as tropospheric amounts of NO₂, O₃, SO₂, HCHO, CHOCHO, and aerosols. Preparatory activities for Level-2 product generation are underway. Two S4 UVN instruments will be embarked on the sequence of two geostationary Meteosat Third Generation-Sounder (MTG-S) platforms. The Flight Acceptance Review of the first MTG-S satellite is expected to take place in the first quarter of 2021. The expected S4 mission lifetime spans 15 years.

An overview of the S4 mission and the implementations status will be presented. The potential for synergetic exploitation of observations from the geostationary S4 mission and from the LEO missions S5 or S5P will be highlighted.

In the frame of the European Copernicus programme, two series of satellites are dedicated to the monitoring of atmospheric parameters: Sentinel-4 will focus on tropospheric constituents with relevance for European air quality with hourly temporal resolution; Sentinel-5 will observe atmospheric composition on a daily basis with full global coverage. The latter will have a precursor mission Sentinel-5p carrying a slightly simplified instrument.

The purpose of the Sentinel-5 mission is to provide long-term (2022-2040) global coverage of data on atmospheric composition. These will address the information needs of Copernicus services related to air quality, climate forcing and stratospheric ozone / surface UV irradiation.

The Sentinel-5 mission will be accomplished by flying spectrometers in the UV – visible – near infrared – short-wave infrared spectral regions (UVNS) on Eumetsat’s Metop-SG series of satellites, and utilising the relevant data from three other instruments on the same platforms, namely the infrared sounder IASI-NG, the multi-spectral imager Metimage and the polarisation imager 3MI. EUMETSAT is responsible for the operational processing and dissemination of UVNS data products.

The UVNS instrument will observe spectral features suitable for retrieval of O3, NO2, SO2, HCHO, CHOCHO, BrO, OClO and surface UV irradiation in the range 270-500nm, H2O and cloud in the range 685-773 nm, CH4 between 1590-1675 as well as 2305-2385 nm, and CO and H2O in the latter band. Aerosol information will be available in all spectral bands. With a swath width of 2600 km, near-global coverage will be reached within a day at a spatial resolution of 7 km at nadir (except stratospheric ozone: ~50km). Spectral resolution will be between 0.25 and 0.6 nm.

The observation requirements have been consolidated. The instrument is currently in the detailed design phase and approaching the preliminary design review. The selection of geophysical data products is being finalised.

This paper will provide an overview of the main characteristics and status of the Sentinel-5 mission.

Sentinel-5 leaves a gap in high vertical resolution measurements of atmospheric composition in the upper troposphere and stratosphere. These are needed to monitor the climate impact of radiatively active gases and the evolution of the stratospheric ozone layer (including attribution), as well as to support NWP and improved tropospheric ozone data for air quality. Activities to detail the observation requirements for such a mission are ongoing.

EarthCARE (Earth Clouds, Aerosols and Radiation Explorer) is aiming at the quantification of the relationship between clouds, aerosols and radiation for the improvement of climate and weather models. In this context the mission will provide detailed information on the vertical distribution of aerosols, liquid water and ice on a global scale.

The EarthCARE mission is part of ESA’s Earth Explorer programme and is implemented in cooperation with the Japan Aerospace Exploration Agency (JAXA). The satellite payload consists of two active and two passive instruments. The Atmospheric Lidar (ATLID) operates at 355 nm and is equipped with a high-spectral resolution receiver and depolarisation channel that separates molecular from particulate backscatter distinguishing cloud and aerosol types. The Japanese Cloud Profiling Radar (CPR) is a highly sensitive W-band Doppler radar (94GHz) that measures cloud profiles, precipitation and vertical motion within clouds. Due to its significantly higher sensitivity as compared to CloudSat, it will detect substantially thinner ice clouds and stratocumulus. The Doppler observation will provide novel information on convection, precipitating ice particles and raindrop fall speed.

A Multi-Spectral Imager (MSI) with a 150 km wide swath and seven channels in the visible, near-IR, short-wave IR, and thermal IR, will provide scene context information and allows the reconstruction of three-dimensional atmospheric scenes when combined with lidar and radar retrievals. A Broad-Band Radiometer (BBR) observing solar and thermal radiation reflected and emitted from the Earth in three fixed field of views (forward, nadir and backward) will make collocated measurements of the outgoing reflected solar and emitted thermal radiation.

The synergistic exploitation of the four instruments will provide 3D cloud-aerosol-precipitation scenes, with collocated broad-band radiation data, over a mission lifetime of three years. The satellite acceptance review is scheduled for October 2017. 

during the discussion seed questions proposed by the chairs will be discussed with the audience.

Theme: Future Mission Session

The ESA Earth Explorer Atmospheric Dynamics Mission (ADM-Aeolus) shall demonstrate the potential of high spectral resolution Doppler wind lidars for operational measurements of wind profiles and their use in Numerical Weather Prediction (NWP) and climate modelling. Spin-off products are profiles of cloud and aerosol optical properties. ADM-Aeolus carries the novel Doppler wind lidar instrument ALADIN.

The ALADIN instrument will measure the zonal component of the wind field from the surface up to 30 km in clear and particle-rich air (aerosol layers and transparent clouds), and down to the top of optically dense clouds. It will also deliver backscatter and extinction profiles and lidar ratios. From these parameters, it is possible to retrieve cloud and aerosol information such as cloud-top height, multi-layer clouds and aerosol stratification, cloud and aerosol optical depth, and some limited information on cloud/aerosol type. The satellite will fly in a polar dusk/dawn orbit, providing a global coverage of ~16 orbits per day. The wind measurements (Level 1b) will be delivered near-real-time (NRT) together with a stand-alone Level 2 processor. The L2b wind profiles will be further ingested into the operational Integrated Forecasting System (IFS) at ECMWF. ECMWF will also produce an assimilated 2-D wind profile product (L2c).

Recently the two ALADIN laser transmitters were successfully qualified and delivered for further instrument integration. The instrument delivery will follow later this year and the satellite qualification and launch readiness is scheduled for 2016.

Impact studies have shown that the largest impact of ADM-Aeolus is expected in regions with few other direct wind profile observations, e.g. over the oceans, in the Tropics and in the Southern Hemisphere. Climate monitoring based on reanalysis data are expected to benefit from ADM-Aeolus observations through improvements of NWP analyses. One example is the detection of wind driven circulation changes in Arctic regions. Climate model processes involving wind dynamics, such as convectively coupled tropical waves, El Niño circulations and Monsoons, could be validated with tropical wind profiles from ADM-Aeolus.

In February 2015, the first Aeolus Science and CAL/VAL Workshop was held in ESA-ESRIN, Frascati, Italy. A summary of the workshop high-lights will be given.

In May 2015, a joint ESA-DLR-NASA airborne campaign in Iceland will provide a unique opportunity for the preparation for the ADM-Aeolus in-orbit airborne calibration and validation (CAL/VAL). The airborne Aeolus Airborne Demonstrator (A2D) will be flown together with another high spectral resolution direct detection wind lidar and two coherent wind lidar systems. Calibrations, science measurements, formation flying and satellite under flights will be performed and evaluated. First quick-look results from the campaign will be presented.

The status of the ADM-Aeolus mission and its data products will be presented together with results from impact studies, the pre-launch campaigns, and the CAL/VAL and science exploitation preparations.