ALTIUS Symposium

2 May 2017, 08:30 → 3 May 2017, 22:10 CET

 

The Royal Belgian Institute for Space Aeronomy (BIRA-IASB) is inviting you to the

First International ALTIUS Symposium

on May 2-3, 2017 at the Museum of Natural Sciences, Brussels, Belgium.

ALTIUS (Atmospheric Limb Tracker for Investigation of the Upcoming Stratosphere) is a satellite mission proposed by the Royal Belgian Institute for Space Aeronomy, aiming at the remote sensing of key atmospheric constituents at high vertical resolution. Its primary objective is the retrieval of ozone concentration profiles with a global coverage by the combination of limb-scatter measurements with solar, stellar, and planetary occultations. Secondary objectives focus on aerosols, NO2, H2O, CH4 and other trace gases. ALTIUS will be a component of the ESA/EO Earth Watch Programme.

The symposium aims at the establishment of an ALTIUS community of partners and users, and is dedicated to recent scientific advances in satellite remote sensing, data retrieval and atmospheric research relevant to the ALTIUS mission.

 

Brussels, Grand-Place

We invite all symposium participants to take note of the list of scientific topics open for collaboration. It can be found here: Download

 

 

Tuesday, 2 May

08:30 → 09:00 Registration

09:00 → 10:40 ALTIUS: Mission objectives and status

Conveners: Didier Fussen (IASB), Emmanuel Dekemper (Belgian Institute for Space Aeronomy)

09:00 Introduction: Welcome word, objectives of the workshop, and logistics

Speakers: Christine Bingen (BIRA-IASB), Didier Fussen (BIRA-IASB), Martine De Mazière (BIRA-IASB)

09:20 The ALTIUS mission

Belgium has proposed the ALTIUS (Atmospheric Limb Tracker for the Investigation of the Upcoming Stratosphere) mission to ESA as a stratospheric ozone profiler with complementary scientific objectives. It has now been approved as an EarthWatch mission in the ESA-Earth Observation programme. It will be operated from a micro-satellite of the PROBA class orbiting in a 700 km heliosynchronous orbit. The instrument will combine three 2D spectral imagers observing the Earth’s atmospheric bright limb from the ultraviolet to the NIR spectral range at moderate resolution (1-10 nm). The platform agility will allow for multi-mode observations by performing solar and stellar occultation observations, across the terminator and in the eclipse. The spectrometer principle is 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 has presently completed its Phase B1, with a successful intermediate design review for the payload and a preliminary design review for the platform. The design will soon enter a consolidation phase. So far, the ALTIUS expected performance is fairly compliant with requirements for an operational ozone monitoring (with global stratospheric ozone monitoring as a target) mission and aims at several scientific objectives with expected retrievals of NO2, H2O, CH4 concentration profiles, aerosol extinction profiles and PSC/PMC detection. The symposium aims at presenting the concepts and the objectives of ALTIUS, at summarizing the status of the mission developments and at triggering scientific collaboration to the project.

Speaker: Dr Didier Fussen (BIRA-IASB)

09:40 ALTIUS as part of the Belgian Earth observation strategy

Earth observation is since a long time a priority for Belgium. In 1984 our Country was already associated with France on the SPOT optical imaging system for the observation of the earth with a focus on the agriculture. In the same period Belgium launched its national earth observation programme still financing universities and research institutions. Later, other Spot satellites have embarked "Belgian platforms": Vegetation (in 1998) and PROBA V (2013). The goal of these sensors is to provide the international user community with time series of the world vegetation at 1km spatial resolution. The result of these investments by our Country is a recognized community of companies and scientists with very diverse competence in earth observation. During the last ESA Ministerial Council held in December 2016 the most important budgetary contribution of Belgium was again assigned to earth observation. The major Belgian mission for the next years is Altius. This mission should provide the scientists around the world with crucial data over the ozone (and other potential chemical components) at the stratospheric level. In this presentation we would like to explain why Belgium decided to support the Altius mission and why this mission is so important for our Country.

Speaker: Mr Jean-Christophe Schyns (BELSPO)

10:00 ALTIUS, an Earth Watch mission

Speaker: Dirk Bernaerts (ESA)

10:20 Discussion - Session 1

Speaker: Didier Fussen (IASB)

10:40 → 11:00 Coffee break and poster session

11:00 → 13:00 System concept and measurement methods

Conveners: Didier Fussen (BIRA-IASB), Emmanuel Dekemper (BIRA-IASB)

11:00 ALTIUS instrument and operations concept

ALTIUS relies on the sucessful heritage of pioneering, though sucessful UV-VIS-NIR limb missions (OSIRIS, SCIAMACHY, SAGE-III, or GOMOS among others). They have demonstrated the possibility of retrieving atmospheric trace species concentration profiles from limb-scattered solar light, or from directly transmitted light from celestial bodies. To achieve this, most of them have sampled the light field (the bright limb, or the Sun) layer by layer, experiencing a strong sensitivity to pointing knowledge error,a nd a critical need for accurate pointing calibration. Thanks to recent advances in spectral imaging techniques (mainly with AOTFs and Fabry-Prot interferometers), ALTIUS was designed as a true hyperspectral imager recording monochromatic images of the scene with and unprecedent vertical and horizontal sampling (< 1km), and a moderate spectral resolution (1-10nm). Combined with the good attitude control of the micro-satellite platform, the instrument concept allows for easier pointing calibration, and much simpler control during occultations (by inertial pointing instead of dynamic tracking). During this talk, we will present the main features of the ALTIUS mission. We will show how to exploit at best the capabilities of a true hyperspectral imager in limb geometry, not only in pure measurement conditions, but also during in-flight calibration or special observation campaigns. An overview of the current payload and platform design will be given, while some typical measurement scenarios will be explored.

Speaker: Dr Emmanuel Dekemper (Belgian Institute for Space Aeronomy)

11:20 PROBA Autonomy in Practise: Challenges in a Changing Operational Context

The PROBA satellite series, developed by QinetiQ Space for the European Space Agency’s, represent a benchmark in the small satellites domain. Meanwhile, the PROBA platform accumulated over 25 years in orbit, without failure on any of the launched satellites. With the latest mission, PROBA-V, QinetiQ Space also demonstrated the platform has evolved to a fully operational platform; after its successful commissioning, PROBA-V now serves as an operational Earth observation mission to provide continuity in vegetation data, which were previously delivered by CNES’ SPOT 4 and SPOT 5. One of the salient features of the PROBA satellites is that they are constantly at the technology forefront in the implementation, to unprecedented levels, of onboard autonomy in platform and payload management, as well as of automation in the platform and payload ground management and operations. The level of autonomy implemented in the satellites onboard software in payload, mission and system resource management functions and in GNC (Guidance, Navigation and Control), has increasingly demonstrated, across the last 15 years, to allow onboard detailed planning and execution of operational scenarios. This eliminates the need for detailed onground mission planning and for hundreds of commands to be sent to the flight segment only to perform nominal scientific observations. These functions include the capability of complex reconfigurations in case of system non-nominal behaviours, maximising the availability of the platform and the mission scientific return with no need for ground intervention and with extended periods without contact with the control centre. With a total of more than 25 years of PROBA combined operations experience (against a total combined originally expected lifetime of 5-8 years), the PROBA satellites have redefined the meaning of autonomous operations proving that, applying onboard and onground autonomy also complex, high-demanding missions can be performed by a small satellite, with a required mission operations effort strongly reduced with respect to more classical approaches.

Speaker: Mr Joris Naudet (QinetiQ Space)

11:40 Preliminary design of the ALTIUS payload

In the past decade, there has been a significant reduction in the number of atmospheric sounders with a high vertical resolution in space. This impacts the monitoring of long-term trends for essential atmospheric species, such as Ozone. In this frame, the ALTIUS (Atmospheric Limb Tracker for the Investigation of the Upcoming Stratosphere) mission was proposed by the Belgian Institute of Space Aeronomy to contribute to remote atmospheric trace gas monitoring with a high vertical resolution. For the ALTIUS mission, QinetiQ Space will be supplier of the satellite and mission prime while OIP will be the industrial prime-contractor for the instrument. The ALTIUS mission will consist of a 2D spectral imager, on-board a PROBA satellite, flying at an altitude of approximately 700 km SSO. The ALTIUS payload will allow observation of the Earth’s atmospheric bright limb in an extended spectral region from the Ultraviolet to the NIR. In addition, the ALTIUS instrument will perform solar and stellar occultation observations in the dark limb. The ALTIUS payload will be based on the use of dedicated Acousto-Optic Tuneable Filters (AOTFs) in the Visible (450-800nm) and NIR (900-1800nm) range, while in the UV (250-400nm) spectral filtering will be done by a stack of Fabry Perot interferometers. By this way, the ALTIUS payload will perform observations with a spectral resolution better than 10 nm over the complete operational spectral-range. During the previous phase of instrument design, initiated by BELSPO and ESA, some critical aspects of the instrument design and performances have been investigated. In particular the following development have been undertaken. - Elaboration of the instrument concept, focused on opto-mechanics for each channel, and preliminary integration with the platform. - UV-channel spectral filter concept trade-off selection - Preliminary thermal and structural analyses - Instrument performances budgets and engineering budgets. The status of design achievements at the end this last phase will be presented, focusing on the instrument design and performances. The resulting thermal and structural analyses will also be presented.

Speaker: Dr Ludovic Aballea (OIP N.V)

12:00 Use of Fabry-Perot technology in the ALTIUS payload

ALTIUS UV channel is intended for spectral imaging measurements in the wavelength range 250 – 400 nm at FWHM resolution around 2.5 nm. The UV channel entrance pupil diameter is 12.3 mm for bright limb channel and 50 mm for stellar occultation channel. The image size of the UV detector is 4.25 mm x 4.25 mm. The UV FPI assembly based tunable filter is placed in the optical chain in a collimated beam with the field stop placed between the 2nd and 3rd FPI module. The optics design is based on 14 mm clear aperture of each of the four FPI modules. In this presentation we will describe the space heritage of VTT piezo-actuated FPI technology from the Finnish Aalto-1 Cubesat spectral imager (AaSI) built in the ESA “Contract No. 4000106267/12/NL/CP – MEMS Fabry-Perot Interferometer Technology for Miniaturized Hyperspectral Imagers and Microspectrometers” and from the PICASSO VISION instrument built in the ESA GSTP project RFQ/3-14170/14/NL/MH – “CUBESAT Technology Pre-Developments, QB-50: PICASSO Mission & VISION Miniaturized Hyperspectral Imager”. We will also present preliminary results from nationally funded HyperGlobal project on ship SO2 emission measurements based on UV FPI hyperspectral imager for the wavelength range 300 – 325 nm. The second part of the presentation describes the present status of the ALTIUS UV FPI assembly design based on Hafnium Oxide – Silicon Dioxide Bragg mirrors. VTT has developed in its internal development project cascaded UV FPI assembly laboratory prototype based on FPIs designed for 300 – 360 nm and 345 - 395 nm spectral ranges. Preliminary characterization results of this assembly will be shown.

Speaker: Dr Heikki Saari (VTT Microspectrometers)

12:20 ALTIUS Payload Data Ground Segment

The ground segment (GS) is a corner-stone element of any space mission. The objective of this presentation is two-fold. In a first part we will present the key elements that have a major impact on the design of the ALTIUS ground-segment: mission context, timeliness constraint, data volume and main operational concepts. The second part will then set the focus on the design of the payload data ground segment (PDGS).

Speakers: Mr Didier Pieroux (BIRA-IASB), Dr Jan Thoemel (BIRA-IASB), Mr Michel Kruglanski (BIRA-IASB)

12:40 Discussion - Session 2

Speakers: Didier Fussen (BIRA-IASB), Emmanuel Dekemper (BIRA-IASB)

13:00 → 14:00 Lunch break

14:00 → 15:40 Radiative transfer in limb observation geometry

Conveners: Filip Vanhellemont (BIRA-IASB), Ghislain Franssens (BIRA-IASB)

14:00 Radiative transfer and retrieval in limb viewing geometry: the potential and challenges in transferring SCIAMACHY experience to the ALTIUS mission.

As one of a few scientific groups in the world dealing with the radiative transfer modeling and the interpretation of measurements of the scattered solar radiation in the limb viewing geometry, the science team at the University of Bremen has a comprehensive 30 years long experience in this field. During the preparation (1984-1990), pre-launch (1990-2002), operation (2002-2012), and post-operation (2012-) phases of the SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY) mission, the GOMETRAN/SCIATRAN radiative transfer model was developed and extended to address all atmospheric effects relevant for modelling measurements of the scattered solar light in the limb viewing geometry. State of the art retrieval algorithms have been developed to obtain trace gas distributions (O$_3$, NO$_2$, BrO, OClO, H$_2$O, Na, Mg, Mg$^+$) as well as cloud and aerosol characteristics from limb scattering measurements. Although the measurement principle and observation geometry of the ALTIUS mission are similar to those of SCIAMACHY, several significant differences in the measurements and their calibration (e.g. sparse wavelength sampling, a lack of an absolute radiometric calibration) require that they are specifically accounted for when transferring the retrieval approaches developed for SCIAMACHY observations to those of ALTIUS. Although the retrieval approach is generic, a thorough investigation is required to optimize the forward model and retrieval environment used when applying the SCIAMACHY inversion technique to different limb data. Such a transition has been successfully achieved and the data of OMPS are now used to retrieve vertical profiles of atmospheric constituents. This presentation will focus on the potential application of the knowledge gained from the SCIAMACHY heritage for use in the retrieval of trace constituents within the ALTIUS mission. The most important issues specific for use with ALTIUS data with respect to the radiative transfer modeling and the retrieval strategy and their impact on data products will be addressed.

Speaker: Dr Alexei Rozanov (University of Bremen)

14:20 Radiative transfer modelling with SIRO

The radiative transfer program Siro solves limb and and nadir scattering radiance by the backward Monte method. In this talk we present a few selected results from Siro studies in the past. We also propose possible roles for Siro in the Altius project.

Speaker: Prof. Erkki Kyrölä (Finnish Meteorological Institute)

14:40 Radiative transfer modelling with SASKTRAN

The SASKTRAN radiative transfer model was originally developed for operational processing of retrievals of stratospheric trace gas and aerosol from the OSIRIS limb scattered sunlight measurements. Initially designed to solve the radiative transfer equation through successive orders of scattering in a spherical atmosphere, the model has evolved to an extensive framework of modules to set the atmospheric state in multiple dimensions, specify optical properties of species, and select various methods of solution of the radiative transfer equation for various limb, nadir, and occultation measurement configurations. This talk will present details on the various options available to the SASKTRAN user, with a focus on the potential for analysis of ALTIUS measurements, including simulation of the polarized radiance, optimized two-dimensional analytic weighting functions, and efficient multiple scattering. Benchmark accuracy and computational requirement for retrievals on OSIRIS and OMPS limb scattering data will be discussed.

Speaker: Prof. Adam Bourassa (University of Saskatchewan)

15:00 ARTIS - The Altius Radiative Transfer In-flight Simulator

The Altius Radiative Transfer In-flight Simulator (ARTIS) is a software tool, developed at BISA, to simulate the light observed by the ALTIUS instrument on its orbit around the Earth. Current key functionalities of this program are: (i) simulation of the movements of relevant planets in the solar system (including Earth), (ii) vectorial radiative transfer calculation in an oblate spheroid atmosphere, (iii) including refraction, single Rayleigh scattering, absorption by gases (1D), single scattering and absorption by aerosols (1D), (iv) calculation of Jacobians, (v) satellite orbit simulation based on osculating Kepler parameters and (vi) realistic time and space awareness. Over the last year, another (parallel) effort was started to develop a standalone software library of core RT and related algorithms, called the Altius RTLib, in order to extend the functionality of ARTIS and to support the design of retrieval algorithms. The goal is to let RTLib evolve into a central algorithm repository and to move core algorithms currently in ARTIS to RTLib, so that then ARTIS, retrieval modules and possibly other software components can call on the functionality in RTLib. Current features of RTLib are: (i) vectorial multiple Rayleigh scattering, (ii) efficient production of lookup tables and (iii) the calculation of Jacobians for gases. To be included later this year: (i) a general albedo treatment, (ii) refraction (taken from ARTIS), (iii) vectorial multiple scattering by aerosols and (iv) support for line-absorbers in the IR (contribution by Nina Mateshvili). Special care went into the design of the multiple Rayleigh scattering algorithm, trying to make it both accurate and fast, while respecting the spherical geometry of the atmosphere. The development of a broadband model for IR line-absorbers, based on the correlated-k method, is also nearing completion. A brief overview of both these algorithms will be given in the talk.

Speaker: Dr Ghislain Franssens (BISA)

15:20 Discussion - Session 3

Speakers: Filip Vanhellemont (BIRA-IASB), Ghislain Franssens (BIRA-IASB)

15:40 → 16:00 Coffee break and poster session

16:00 → 17:40 Retrieval algorithms

Conveners: Emmanuel Dekemper (BIRA-IASB), Filip Vanhellemont (BIRA-IASB)

16:00 Ozone, Aerosol, and Cloud Data Products from Suomi NPP OMPS Limb Profiler

The Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP) instrument is currently flying on the Suomi NPP satellite, and has collected more than 5 years of regular data since its launch in October 2011. LP limb scattering hyperspectral measurements simultaneously cover a spectral range between 290 nm and 1015 nm with variable spectral resolution (0.8-30 nm), and an altitude range between 0 km and 80 km with 1 km sampling. Level 1 sun-normalized radiance data created from these measurements are available to create multiple products. OMPS LP ozone profiles represent a continuation of the Aura MLS high resolution data record, providing profiles covering the altitude range from cloud top to 52.5 km with ~1.8 km vertical resolution. We are creating a reprocessed LP Version 2.5 (V2.5) ozone product that incorporates improved altitude registration information and stray light correction in the Level 1 data set, and a simplified aerosol correction using LP aerosol profiles in the Level 2 retrieval, and a reduced set of wavelengths for both UV and visible retrievals. This ozone product has reduced bias relative to MLS in the tropical upper stratosphere/lower stratosphere, and typically agrees to within ±5% in the stratosphere. OMPS LP Version 1.0 (V1.0) aerosol extinction profiles extend the stratospheric aerosol data record available from SAGE II and OSIRIS, providing extinction coefficient profiles from cloud top to 30-35 km. The spatial and temporal sampling of LP enables extensive observation of volcanic eruption plumes and stratospheric dynamics. We have also developed a cloud height product to supply lower boundary information for the ozone and aerosol retrievals. Future LP algorithm development will include a 2-D approach to address line-of-sight inhomogeneity effects that affect all limb-viewing measurements.

Speaker: Mr Matthew DeLand (Science Systems and Applications, Inc. (SSAI))

16:20 Treasures of the Limb: past, present, and booty to come

Limb observations from orbiting sensors have a rich history. The cold space background, long optical paths, and limb geometry provide formidable advantages for achieving calibration, sensitivity and vertically resolved geophysical parameters. The measurement of limb ray refraction also provides temperature and pressure profiles, unburdened by spectral calibration, leading to reliable long-term trends. This talk reviews those advantages and successes, including recent achievements of the SOFIE instrument on the AIM satellite. It then lists advances in calibration, sensitivity, profile fidelity, downlink data rate, and future synergy of limb sensors with nadir sounders. This is now possible thanks to modern FPAs, ADCS, and GPS. Finally, we suggest that advances in weather forecasting and climate observation will be strongly dependent on limb observations and analysis techniques pioneered and perfected by teams designing and operating sensors such as ALTIUS.

Speaker: Mr Larry L. Gordley (GATS)

16:40 ACE-MAESTRO retrieval and validation

In February 2017, the Canadian-led Atmospheric Chemistry Experiment (ACE) satellite mission completed its thirteenth year of measurements. The long lifetime of ACE has provided a valuable time series of composition measurements that contribute to our understanding of ozone recovery, climate change and pollutant transport. The SCISAT/ACE mission uses infrared and UV-visible spectroscopy to make its solar occultation measurements. This presentation will focus on the ACE-MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation). This instrument is a dual UV-visible-NIR spectrophotometer which was designed to extend the ACE wavelength coverage to the 280-1030 nm spectral region. From these measurements, altitude profiles of atmospheric trace gas species are retrieved. In addition to the mission and instrument status, a review of retrieval methods, validation and scientific results from ACE-MAESTRO will be presented.

Speaker: Prof. Kaley Walker (University of Toronto)

17:00 The ALTIUS retrieval algorithm

The ALTIUS instrument observes the atmosphere in several modes: limb scatter, solar/lunar and stellar/planetary occultation. Furthermore, Level 2 data delivery splits in two separate lines: a near real-time ozone product and a collection of offline scientific products. Both aspects lead to a data processing chain that is a bit more complex than is usually the case. In this overview, we will present the Level1 processing from raw to geolocated and calibrated data, and the subsequent Level 2 processing to gas concentration and aerosol extinction profiles for each observation mode separately, highlighting the main physical/mathematical aspects that need to be taken into account. The current status, ongoing work and unresolved issues will also be discussed.

Speaker: Dr Filip Vanhellemont (Royal Belgian Institute for Space Aeronomy)

17:20 Discussion - Session 4

Speakers: Emmanuel Dekemper (BIRA-IASB), Filip Vanhellemont (BIRA-IASB)

17:40 → 19:00 Cocktail and poster session

19:00 → 21:00 Walking dinner

Wednesday, 3 May

09:00 → 10:40 ALTIUS geophysical product validation

Conveners: Daan Hubert (BIRA-IASB), Jean-Christopher Lambert (BIRA-IASB)

09:00 ALTIUS Geophysical Validation Methodology

Proposed by BIRA-IASB as an Earth Watch element of ESA’s Living Planet Programme, Atmospheric Limb Tracker for Investigation of the Upcoming Stratosphere (ALTIUS) will continue the long-term and global-scale measurement of ozone, aerosols, and several reactive gases and greenhouse gases carried out so far by satellite missions reaching now their end of life (Fussen et al., AMTD 2016). On board of the agile PROBA micro-satellite to be launched in 2021 on a mid-morning polar orbit, this UV/visible/near-infrared hyperspectral imager will alternate measurements of limb-scattered sunlight with solar, stellar and planetary occultations, from which the vertical distribution of target trace gases and aerosols will be retrieved with the global sampling and at the vertical resolution required to improve numerical predictions of weather and climate, to assess environmental policy impacts, and to better understand connections between changes in atmospheric composition, transport and climate. In order to assess the performance of the mission, to ensure proper use of the ALTIUS data, and to enable candidate users to readily evaluate the fitness-for-purpose of the data, a dedicated validation programme has to be organized, which is the subject of this introductory talk. While part of the quality assessment of satellite data consists classically in monitoring the outputs of the data production system, another part, referred to as independent validation, consists in checking the satellite data and their associated uncertainties against reference measurements provided by well-documented ground-based and balloon-borne systems, e.g., those in use in ground-based monitoring networks contributing to WMO’s Global Atmosphere Watch (GAW) like NDACC, SHADOZ, and TCCON. Direct intercomparison with other satellite data can be valuable in documenting mutual consistency with other sounders, and it extends usefully ground-based validation results to the more global domain. The lower altitude range of ALTIUS data on ozone, NOx, CH4, water vapour and aerosols could also be validated against aircraft measurements by the IAGOS/MOZAIC in-service system. The fact that ALTIUS is part of ESA’s Earth Watch element, which aims at facilitating the delivery of Earth observation data to operational services, adds operational and interoperability constraints beyond the scientific and research objectives of the mission, which will be discussed too.

Speaker: Dr Jean-Christopher Lambert (Royal Belgian Institute for Space Aeronomy (IASB-BIRA))

09:20 Validation from ground-based measurements

During this presentation we present recent developments within the international NDACC (network for the detection of atmospheric composition change) and TCCON (total carbon column observing network) as well as each network's strenghts and weakenesses with respect to validation purposes. The EU NORS, QA4ECV and GAIACLIM projects have improved the networks internal consistency of selected targets, specifically wrt the reporting of measurement uncertainties. The EU Copernicus program will support NDACC for rapid delivery of measurement data for selected instruments and targets for use in operational model and satellite validation. Likewise TCCON is continuously improving its network, retrieval strategy and delivery mode.

Speakers: Dr Bart Dils (BIRA-IASB), Dr Bavo Langerock (BIRA-IASB)

09:40 Towards Unified Reporting of Errors

Towards Unified Error Reporting (TUNER) has been selected as an emerging SPARC activity. Its goal is to make error estimates of existing satellite observations of atmospheric temperature and constituent profiles intercomparable. Error estimates of measurements of atmospheric state variables are essential to judge whether differences between estimates of the atmospheric state can be explained or if they hint at unknown problems. While many recipes exist to calculate the error budget of an observation, the data user is faced with the problem that errors reported by various instrument groups are rarely consistent. In this talk, the following problems will be tackled: (a) which error components should be included in the error budget; (b) how should the content of prior information in the retrievals be dealt with; (c) how can retrievals be characterized which were not produced via an optimal-estimation-like formalism and thus do not provide the usual diagnostics; (d) how can error estimates which were generated using different approaches be made comparable, and (e) what is to be considered when comparing with direct (non-remote) measurements. An action plan towards unified error reporting will be suggested.

Speaker: Dr Thomas von Clarmann (KIT/IMK)

10:00 Use of data assimilation for ALTIUS validation

BIRA-IASB is involved in data assimilation (DA) of stratospheric chemical observations since almost 20 years. This is done though the development of the Belgian Assimilation System of Chemical ObsErvations (BASCOE). In this presentation, we will discuss the capabilities of DA methods to validate (1) the measurement concept of ALTIUS and (2) the ALTIUS observations. For the first case, an Observing System Simulation Experiment (OSSE) of ALTIUS ozone data has been performed based on a BASCOE analysis of the Microwave Limb Sounder. With this OSSE, we will evaluate the measurement concept of ALTIUS (limb and occultations – solar, stellar, planetary and Moon), especially during the polar night where limb observations are missing. In the second case, we will describe the ALTIUS level 3 data product – i.e. the ALTIUS analysis by BASCOE that will be delivered operationaly – and how this product will be useful to validate ALTIUS level 2 profiles.

Speaker: Dr Quentin Errera (BIRA-IASB)

10:20 Discussion - Session 5

Speakers: Daan Hubert (BIRA-IASB), Jean-Christopher Lambert (BIRA-IASB)

10:40 → 11:00 Coffee break and poster session

11:00 → 13:00 Data usage and applications

Conveners: Quentin Errera (BIRA-IASB), Simon Chabrillat (BIRA-IASB)

11:00 ECV datasets for the ESA Climate Change Initiative

Observations from space are essential to assist the successful understanding and management of climate change, one of the biggest challenge facing mankind in this century. Establishing the necessary accurate long-term data records requires coordinated activities involving all relevant parties, i.e. environmental and space agencies, climate science community and measurement experts. Over the last few years new programmes addressing the needs for climate data records have been initiated, e.g. in Europe the ESA Climate Change Initiative (CCI) and more recently the Copernicus Climate Change Service (C3S). We report on ongoing efforts within these programmes to build harmonised and well characterised long term data records of vertically-resolved ozone concentration, which constitute one of the primary atmospheric Essential Climate Variables. More specifically we discuss the current state-of-the-art and the challenges to ensure continuity in time and data quality, with a view on requirements for future ozone observational systems.

Speaker: Dr Michel Van Roozendael (BIRA-IASB)

11:20 CAMS and ECMWF applications for ALTIUS data

ECMWF has been entrusted to operate the Copernicus Atmosphere Monitoring Service (CAMS) on behalf of the European Commission until the end of 2020. CAMS provides continuous data and information on atmospheric composition. The global service combines a state-of-the art transport and chemistry model with satellite data from various sensors to provide global daily analyses and 5-day forecasts of 3-dimensional fields of atmospheric composition including ozone, carbon monoxide, nitrogen dioxide, sulphur dioxide, and aerosols. More details about CAMS can be found on http://atmosphere.copernicus.eu/. In this talk we will give some background information about CAMS and show which atmospheric composition observations are being assimilated routinely in the near-real time system. We will also demonstrate the benefits of assimilating height resolved observations, for example O3 profiles from MIPAS and MLS and how ALTIUS data could fill the gap that will be left if the MLS instrument dies.

Speaker: Dr Antje Inness (ECMWF)

11:40 Global ozone: past, present and future

This talk will describe the evolution of global ozone including ozone in the polar regions. Conclusions will be largely based on the WMO/UNEP Scientific Assessment of Ozone Depletion: 2014. There are now several indications that the ozone layer is beginning to recover from ODS-induced depletion. Nonetheless, the Antarctic ozone hole will continue to occur at least until mid-century. Occasional large Arctic ozone depletion, such as that in spring 2011 and 2016 is also possible in coming decades. Recovery of polar ozone could be delayed by increases in stratospheric aerosol that could be caused by injection of sulphur by large volcanic eruptions or geoengineering. Upper stratospheric ozone declined during the 1980s and early 1990s, and has clearly increased by about 5% since 2000. The ozone decreases until the mid-1990s were dominated by ODS increases. However, from 2000 to 2013 the decline in ODS abundances and the cooling by increased carbon dioxide are both estimated to have made comparable contributions to the observed upper stratospheric ozone increases. In the mid-latitude lower stratosphere (15 to 25 km altitude), ozone exhibited a long-term decline through the 1980s and early 1990s. Since 2000, ozone at these altitudes has remained approximately stable. Tropical ozone is strongly dependent on transport, in particularly tropical upwelling. Observations of changes in temperature and ozone over the past three to five decades are suggestive of increased upwelling of air in the tropical lower stratosphere. Therefore, in the future, a decrease of tropical column ozone is conceivable.

Speaker: Dr Rolf Müller (Forschungeszentrum Jülich)

12:20 The SPARC Data Initiative - Setting standards for future observations

The last few decades represent a “golden age” of stratospheric composition measurements that were crucial in advancing our understanding of atmospheric processes and their role in climate. The SPARC Data Initiative carried out a comprehensive inter-comparison of these observations obtained from up to 18 multi-national satellite instruments and including 25 different chemical trace gas species and aerosol. This assessment, presented in the newly available SPARC report no. 8, offers a documentation of these observations, knowledge on retrieval, performance, and measurement issues, and also summarises our state of knowledge on measurement uncertainty and on the atmospheric state more generally. In this contribution I will highlight the key results of the report, and provide some examples of how these measurements still help to solve science puzzles related to the state of the ozone layer and climate more generally.

Speaker: Dr Michaela Hegglin (University of Reading)

12:40 Discussion - Session 6

Speakers: Quentin Errera (BIRA-IASB), Simon Chabrillat (BIRA-IASB)

13:00 → 14:00 Lunch break

14:00 → 15:50 ALTIUS in space: synergies with other instruments

Convener: Michel Van Roozendael (BIRA-IASB)

14:00 OMPS measurement challenges and potential solutions

Data collected by the limb scattering instrument within the Ozone Mapping and Profiler Suite (OMPS) has taught us a great deal about the performance peculiarities of imaging limb sensors. Like ALTIUS, OMPS images the vertical extent of the Earth's limb using a 2-dimensional detector. In the case of OMPS the vertical coverage is approximately 100 km. This approach has advantages when accounting for diffuse upwelling radiation, but there are equally drawbacks, among them signal dynamic range and internally-scattered stray light. The OMPS limb instrument also shares problems common to all limb scatter sensors, namely telescope stray light and tangent height registration. In this presentation we will outline our mostly successful attempts to mitigate these issues through a combination of pre-launch characterizations and post-launch empirical techniques. The OMPS flying on the Suomi National Polar-orbiting Partnership (SNPP) spacecraft since 2011 is the first of four instruments planned through 2038. The more than 10 years between the launches of the first and second limb instruments has provided an opportunity for some design improvements, which we will briefly describe.

Speaker: Dr Jaross Glen (NASA)

14:20 Status of the Sentinel-5 Precursor, Sentinel-4 and Sentinel 5 Missions

Sentinel-5 Precursor (S-5P) is the first of a series of atmospheric chemistry missions to be launched within the European Commission’s Copernicus (former GMES) Programme. With the current launch window of summer 2017 and a nominal lifetime of 7 years, S-5P is expected to provide continuity in the availability of global atmospheric data products between its predecessor missions SCIAMACHY (Envisat) and OMI (AURA) and the future Sentinel-4 and -5 series. S-5P will deliver unique data regarding the sources and sinks of trace gases with a focus on the lower Troposphere including the planet boundary layer due to its enhanced spatial, temporal and spectral sampling capabilities as compared to its predecessors. The S-5P satellite carries a single payload, namely TROPOMI (TROPOspheric Monitoring Instrument) that was jointly developed by The Netherlands and ESA. Covering spectral channels in the UV, visible, near- and short-wave infrared, it measures various key species including tropospheric/stratospheric ozone, NO2, SO2, CO, CH4,CH2O as well as cloud and aerosol parameters. These data sets will be extended by the Sentinel-4 (S-4) and Sentinel-5 (S-5) missions, which are hosted instruments on EUMETSAT geostationary and polar orbiting platforms to be launched during 2021.This paper includes descriptions and the status of the S-5P, S-4 and S-5 missions.

Speaker: Dr Claus Zehner (ESA)

14:50 Stratospheric chemistry with IASI and possible synergies with ALTIUS

The Infrared Atmospheric Sounding Interferometers (IASI) are a suite of nadir sounders onboard the European MetOp platforms. The first instrument was launched on MetOp-A in 2007 and is still in operation. It was followed by IASI-B in 2012, and a third instrument is schedule for launch in 2018. Overall the IASI program will thus provide an unprecedented record of atmospheric measurements of 20 years, which will be continued for another 15 years at least with the IASI-NG mission on EPS-SG. Although IASI had atmospheric composition only has a side objective, it has rapidly proven being a key element of the Earth observing system for all aspects related to the chemistry of the lower atmosphere. This talk will briefly review some of the main achievements of IASI for monitoring the troposphere and the stratosphere. It will then focus on the monitoring of the stratospheric system with the measurements of ozone and nitric acid columns; the presentation will in particular put emphasis on the analysis of the available 10-years time series of the two species and will show how these allow identifying the processes responsible for their stratospheric variability at different latitudes, and assessing trends. The presentation will in addition introduce the methodology developed for determining the longwave radiative effect of stratospheric ozone and show first results also of its time evolution. The results will be put in the perspective of possible synergies and combined analysis with the high-vertical resolution measurements ozone and NOx species with ALTIUS.

Speaker: Dr Pierre Coheur (Université Libre de Bruxelles)

15:10 SAGE III on ISS and Beyond

The Stratospheric Aerosol and Gas Experiment (SAGE) III is a fifth generation occultation instrument from NASA Langley Research Center. Launched onboard a SpaceX Falcon 9 rocket on February 19, 2017 and installed on the International Space Station (ISS), SAGE III will utilize solar occultation, lunar occultation, and limb scanning techniques to observe Earth’s stratosphere and upper troposphere to measure ozone, aerosol, and other trace gases. Currently in the commissioning phase, SAGE III on ISS is undergoing preliminary testing and characterization while also beginning routine operations. Early results will be discussed and a short introduction to the future of SAGE will be presented.

Speaker: Robert Damadeo (NASA)

15:30 Discussion - Session 7

Speakers: Jean-Christopher Lambert (BIRA-IASB), Michel Van Roozendael (BIRA-IASB)

15:50 → 16:10 Coffee break and poster session

16:10 → 17:15 General Discussion

Convener: All chairmen

16:10 Summary of the discussion; open questions, collaborations, recommendations

Speaker: All chairmen

17:00 Initiation of an ALTIUS User Community: start web page

Speaker: Didier Fussen (IASB)

17:05 Closing session

Speaker: Didier Fussen (IASB)