In this contribution, we provide an overview of the EMM (Earth and Mars Research Network) research infrastructure, outlining its main components and the potential scientific products that can be derived through its use. The presentation delves into selected aspects in greater detail, particularly where they resonate with the multiple scientific and technological challenges associated with the FORUM mission.

The observations acquired during the full mission of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument, aboard the European Space Agency Environmental Satellite (Envisat), have been analysed with version 8.22 of the Optimised Retrieval Model (ORM), originally developed as the scientific prototype of the ESA level-2 processor for MIPAS observations. The results of the analyses have been included into the MI- PAS level-2 version 8 (level2-v8) database containing atmospheric fields of pressure, temperature, and volume mixing ratio (VMR) of MIPAS main targets H2 O, O3 , HNO3 , CH4 , N2 O, and NO2 , along with the minor gases CFC- 11, ClONO2 , N2 O5 , CFC-12, COF2 , CCl4 , CF4 , HCFC-22, C2 H2 , CH3 Cl, COCl2 , C2 H6 , OCS, and HDO. The database covers all the measurements acquired by MIPAS in the nominal measurement mode of the full resolution (FR) part of the mission (from July 2002 to March 2004) and all the observation modes of the optimised resolution (OR) part (from January 2005 to April 2012). The number of species included in the MIPAS level2-v8 dataset makes it of particular importance for the studies of stratospheric chemistry. The database is considered by ESA the final release of the MIPAS level-2 products.The ORM algorithm is operated at the vertical grid coincident to the tangent altitudes of the observations or to a subset of them, spanning (in the nominal mode) the alti- tude range from 6 to 68km in the FR phase and from 6 to 70 km in the OR period. In the latitude domain, FR profiles are spaced by about 4.7o, while the OR profiles are spaced by about 3.7o. For each retrieved species, the auxiliary data and the retrieval choices are described. Each product is characterised in terms of the retrieval error, spatial resolution, and "useful" vertical range in both phases of the MIPAS mission. These depend on the characteristics of the measurements (spectral and vertical resolution of the measurements), the retrieval choices (number of spectral points in- cluded in the analyses, number of altitudes included in the vertical retrieval grid), and the information content of the measurements for each trace species. For temperature, water vapour, ozone, and nitric acid, the number of degrees of freedom is significantly larger in the OR phase than in the FR one, mainly due to the finer vertical measurement grid. In the FR phase, some trace species are characterised by a smaller retrieval error with respect to the OR phase, mainly due to the larger number of spectral points used in the analyses, along with the reduced vertical resolution. The way of handling possible caveats (negative VMR, vertical grid representation) is discussed. The quality of the retrieved profiles is assessed through four criteria, two providing information on the successful convergence of the retrieval iterations, one on the capability of the retrieval to reproduce the measurements, and one on the presence of outliers. An easy way to identify and filter the problematic profiles with the informa- tion contained in the output files is provided. MIPAS level2- v8 data are available to the scientific community through the ESA portal (https://doi.org/10.5270/EN1-c8hgqx4).

Riporta i principali risultati ottenuti nell'ambito del progetto: "Support to MIPAS Level 2 processor Verification and Validation - Phase F", Contratto ESA 4000112093/14/I-LG, cioe' la messa a punto del codice ORM_V8 da utilizzare per la rianalisi di livello 2 dell'intera missione di MIPAS/ENVISAT, il dataset processato, i test di verifica e di validazione dei prodotti di Livello 2 generati.

his report forms the basis for the selection of the ninth Earth Explorer mission within ESA's Earth Observation Programme. Two competing 'Fast Track' candidates, the Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission and the Surface ocean KInematics Multiscale (SKIM) mission. Each have each undergone a rapid and compressed Phase A feasibility study. This report covers the FORUM mission.

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a limb-viewing infrared Fourier transform spectrometer that operated from 2002 to 2012 onboard the ENVISAT satellite. The maintenance and the upgrade of both L1 and L2 ESA processors are accomplished by the Quality Working Group, where a fruitful collaboration among Level 1, Level 2 and validation teams can be exploited. Recently both ESA L1 and L2 processors have been updated, as well as the spectroscopic database and some absorption cross-sections. In addition to the products already present in the current release (V7) of ESA MIPAS data (temperature and the VMR of H2O, O3, HNO3, CH4, N2O, NO2, CFC-11, CFC-12, N2O5, ClONO2, HCFC-22, COF2, CF4, HCN and CCl4), the VMR of six additional species (OCS, CH3Cl, HDO, C2H2, C2H6, COCl2) will be provided in V8 dataset. In preparation of V8 full mission reprocessing, three Diagnostic Datasets have been generated to check the performances of all L1, L2 processors and the new auxiliary data.The analysis of these Diagnostic Datasets and the comparison with previous full mission dataset V7 will be used to perform a first assessment of the quality of the new V8 products. In the paper special focus will be given to the new species.

New remote sensing satellite sensors for the measurements of atmospheric radiation offer the advantage of very high spectral resolution and spectral and/or spatial and temporal coverage. The analysis of these measurements often requires a forward model (FM) for the simulation of the radiation collected by the sensor. The FM should model all the processes affecting the radiance, such as absorption and scattering by molecules and particles. Despite the advancement in sensor technology, the radiative transfer solvers are almost the same since several decades. Among these, the DISORT solver is still one of the most widely used. The DISORT code was developed 30 years ago, and while the code is maintained and updated regularly, the improvements are more geared towards new features than to a revision of the original setup. While the implementation was the best possible at the time, the memory constrains and language limitations of the time are nowadays considerably changed. On the other hand there is still the need of NRT retrievals, and the computing time of the multiple scattering needed in cloudy sky conditions is still the bottleneck of the FM calculation. We modified the DISORT algorithm in three directions: 1) Language improvements. Making use of dynamical assignment and modularity of modern fortran reduces execution time. 2) Algorithm improvements. By approaching the delta-m transformation on a per-layer basis, many computations were saved, expecially when the cloud pattern does not cover all the atmospheric range. 3) Numerical analysis improvements. While these improvements do not shorten the computational time, they improve the precision of the solution of the eigenvalue sub-problems that arises in the multiple scattering calculations. The modifications in the DISORT solver produce an improvement in calculation performances of a factor 3 with respect to the original version. The new solver is named as fast-DISORT (fDISORT).

MIPAS on ENVISAT performed almost continuous and global measurements of atmospheric temperature and composition from June 2002 to April 2012. These data are very useful for understanding atmosphere climatology from the upper troposphere to the mesosphere, including trends in composition and variability, as a reference for middle atmosphere ozone and general circulation as well as improvement of tropospheric composition retrievals. The ESA Level 2 processor, based on the Optimized Retrieval Model (ORM), originally designed for the Near Real Time analysis and developed by an European Consortium led by IFAC, is currently improved and used for the reanalysis of the full MIPAS mission. The maintenance and the upgrade of the ESA processor are made in the frame of the MIPAS Quality Working Group, where a fruitful collaboration among Level 1, Level 2 and validation teams is exploited. This collaboration is essential to improve the accuracy of the products and their characterization. This paper is meant to describe the most recent upgrades in the MIPAS processor, in particular the full mission was recently reprocessed with L1 V7 and L2 V7 processors, containing significant improvements with respect to previous version 6, and further improvements are in preparation, that will be collected in version 8 of the ESA processor. The improvements include both L1 and L2 processors, as well as the auxiliary data. In the L1 processor the correction of the instrumental drift caused by the ageing of the detectors has been implemented in order to reduce the non negligible systematic error in the trend estimation. Furthermore, the measured daily gain instead of the weekly gain is now used for the radiometric calibration that allows to better take account for the discontinuities in the gain that occasionally occur in MIPAS band B. Improvements in the L2 processor include a different approach for retrieving atmospheric continuum, the use of an a posteriori regularization with altitude dependent constraint, a better approach for handling interfering species, a reduced bias in CFC-11, the handling of horizontal inhomogeneities and the use of ECMWF altitude/pressure relation to determine more accurate altitudes. Improvements in the auxiliary data consist in the use of microwindows with larger information content, an improved spectroscopic database and diurnally varying climatological dataset. Furthermore, additional species are provided in the new processors, leading to a total of 22 retrieved species by the L2 version 8 processor. Each of these changes has a different impact on the Level 2 products. The individual contributions, as well as the cumulative effects, will be evaluated with a comparison with previous versions of MIPAS products and corresponding results of validation. Improvements in the trend determination will also be evaluated, as well as the quality of the new retrieved species.

MIPAS on ENVISAT performed almost continuous measurements of atmospheric composition for approximately 10 years, from June 2002 to April 2012. ESA processor, based on the algorithm ORM (Optimized Retrieval Model), originally designed for the Near Real Time analysis and developed by an European Consortium led by IFAC, is currently used for the reanalysis of the full MIPAS mission. The maintenance and the upgrade of the ESA processor are made in the frame of the Quality Working Group, where a fruitful collaboration among Level 1, Level 2 and validation teams can be exploited. This collaboration is essential to pursue improvements in the accuracy of the products and their characterization. This paper is meant to describe the most recent upgrades in the ESA processor performed to improve the quality of ESA products. In particular, the full mission was recently reprocessed with L1 V7 and L2 V7 processors, containing significant improvements with respect to previous version V6, and further improvements are in preparation, that will be collected in version 8 of the ESA processor. Improvements involve both L1 and L2 processors, as well as the auxiliary data. Improvements in the L1 processor consist in a correction of the instrumental drift, improved spike detection algorithm and new Instrument Line Shape, as well as the use of measured daily gain instead of weekly gain. Improvements in the L2 processor include a different approach for retrieving atmospheric continuum, the use of an a posteriori regularization with altitude dependent constraint, a better approach for handling interfering species, a reduced bias in CFC-11, the handling of horizontal inhomogeneities and the use of ECMWF altitude/pressure relation for determining more accurate altitudes. Improvements in the auxiliary data consist in the use of microwindows with larger information content, new spectroscopic database and diurnally varying climatological dataset. Furthermore, with each new version additional species are provided, leading to 20 the number of retrieved species by the L2 V8 processor. Improvements in the V7 products will be revised on the light of the results of the validation with correlative measurements, and, by comparing the first new L2 V8 products with the L2 V7 ones, a preliminary assessment of the performance of the new V8 processor will be performed.

We present the results of the algorithm modeling the horizontal gradients in the ESA retrieval of MIPAS data ORM v8.

MIPAS on ENVISAT performed almost continuously measurements of the atmospheric composition for almost 10 years, from June 2002 to April 2012. These ten years cover a period when the first effect of the dismiss of the emission of the CFCs after the Montreal protocol ratification in 1987can be measured. Even if ten years constitute a short period to derive trends, it has been proven that useful information on time variation of atmospheric constituents can be derived from the analysis of these measurements. However, previous versions of MIPAS on ENVISAT dataset were characterized by an instrumental drift due to the fact that some detectors used by MIPAS were affected by non-linearities, which change with time due to the ageing of the detectors and this was cause of a non negligible systematic error in the trend estimation. The new full mission reprocessed dataset V7 that will be released very soon uses L1 files where the impact of the ageing of the detectors on non-linearities has been corrected. Furthermore, also the L2 processor has been upgraded with new functionalities improving the performances of the processor. We present the results of study of trends derived from the analysis of the new MIPAS V7 products on several MIPAS target species including ozone depleting species, like CFC-11, CFC-12, CCl4 and HCFC-22.

MIPAS measurements on ENVISAT represent a unique database for the study of atmospheric composition and of the time variation of atmospheric constituents. For trend studies it is important that instrumental drifts are reduced. Some of the MIPAS spectral bands are affected by time-dependent non-linearity which have been recently corrected. In addition to this non-linearity correction, the forthcoming new version of MIPAS products (Version 7) contains several other improvements: a new approach for handling continuum capable of making the retrieval more stable, a new selection of spectral intervals selected for the analysis of the full resolution measurements aimed to reduce the bias between full resolution and optimized resolution measurements, the regularization of the H2O profiles, the products of five new species (HCFC-22, CFC-14, HCN, COF2, CCl4), which makes equal to 15 the total number of retrieved species. The latest improvements implemented in the ESA processor and some of the results on trend will be presented and discussed.

MIPAS measurements on ENVISAT represent a unique database for the study of atmospheric composition and of the time variation of atmospheric constituents.For trend studies it is important that instrumental drifts are reduced. Some of the MIPAS spectral bands are affected by time-dependent non-linearity that have been recently corrected.In addition to this non-linearity correction, the forthcoming new version of MIPAS products (Version 7) contains several other improvements: a new approach for handling continuum leading to a more stable retrieval, a new selection of spectral intervals for the analysis of the full resolution measurements aiming to reduce the bias between full resolution and optimized resolution measurements, the regularization of the H2O profiles. Furthermore, the implementation of the retrieval of five new species (HCFC-22, CFC-14, HCN, COF2, CCl4) leads to a total of 15 species in ESA products.The latest improvements implemented in the ESA processor, the results of the validation of the products and some preliminary results on the trend of some ozone depleting substances will be presented and discussed.

The ESA-ESRIN contract no. 21719/08/I-OL covered the activities performed between April 2008 and July 2014 by the L2 sub-group of the MIPAS Quality Working Group. The main objective of this project was to monitor the quality of MIPAS L2 products, to improve the performances of the L2 ESA processor, used for both the near real time analysis during ENVISAT mission and for the off-line analysis, and to enlarge the list of retrieved species. In particular, three different versions of the MIPAS operational processor were finalized: IPF V5, ML2PP V6 and ML2PP V7, leading to significant improvements in the quality of the products and in their diagnostics, to an increase of the number of processed scans, and to an enlargement of the list of provided products. With respect to IPF V4.1&2, used to process only the first two years of MIPAS measurements (2002-2004, Full Resolution (FR) measurements) and validated with respect to correlative measurements (Ridolfi et al., 2006, Cortesi et al., 2007, Wang et al., 2007, Payan et al., 2009, Wetzel et al., 2007, Wetzel et al., 2013, all contained in the MIPAS special issue), IPF V5: o performs the analysis of the full mission (both FR and Optimized Resolution (OR) measurements, characterized by a reduced spectral resolution but finer spatial resolution) after the introduction of an a posteriori regularization with self-adapting threshold aimed to reduce instabilities of the retrieval with measurements of the OR phase (due to sampling intervals finer than the instantaneous field of view of the instrument and the choice of using a retrieval grid aligned with the vertical sampling of the measurements); o provides as output Averaging Kernel (AK) for each scan. Products of ML2PP V6 are very similar to the ones of V5 in terms of bias, but are characterized by: o an improved diagnostics, since the Covariance Matrix and the AK matrix are computed taking into account all iterations performed during the retrieval (this is needed if the final Marquardt parameter is different from zero). Furthermore, horizontal AKs are provided for each latitude band and each season. o additional four new species, namely CFC-11, CFC-12, N2O5 and ClONO2. MIPAS ESA processor products V7 are characterized by: o reduced time dependent calibration error due to non-linearities (coming from using new L1 data, V7); o availability of retrieval altitude grid characterized by a very small bias after correction with ECMWF pressure/altitude relationship; o new microwindows for FR measurements with an increased information content and leading to a reduction of the detected bias in the FR measurements for CH4, N2O and CFC-12; o larger stability, given by the new approach for retrieving continuum (the continuum transmission is fitted instead of the continuum cross-section), and new regularization with altitude dependent regularization strength; o lower bias of CFC-11, due to proper handling of COCl2 interfering species in the retrieval o better representation of the measurements, proven by the fact that a smaller chi-square is obtained for most of the species; o better handling of diurnally varying interfering species, coming from the use of diurnally varying Initial Guess profiles; o products of five new species (HCFC-22, CFC-14, COF2, CCl4 and HCN) available. Concerning V7 products, preliminary verifications have been performed only on the diagnostic dataset V7, including more than 4000 orbits: the Non-Linearity correction performed in the L1 files introduces a drift in V7 profiles with respect to previous versions, that corrects for the instrumental drift present in previous datasets. Some problems have also been identified: V7 FR Temperature profiles in polar and midlatitude regions presents a negative bias of about 0.5-1K with respect to both V6 products and correlative measurements coming from the Non-Linearity correction. In the tropics in general V7 Temperature has a positive bias with respect to previous versions, for both FR and OR measurements, and this seems to come from the new approach for handling continuum. A new version of the spectroscopic database has been finalized, with improvements in H2O, HNO3, COCl2 and C3H8. The new version of the spectroscopic database will be used for the final reprocessing of the whole MIPAS mission in the frame of the subsequent contract. A large effort was spent for improving the quality of the MIPAS L2 products, but further improvements have been identified as needed to reduce some systematic errors of the products and to fully exploit the information contained in MIPAS measurements. One of the main problems identified so far is the error due to the horizontal inhomogeneities that are not currently taken into account by the algorithm. The quality of the retrieval is affected by the horizontal gradients but from the analysis of single scans no enough information is contained in the measurements to retrieve the gradients. Considering that the code will be used only for a reanalysis, the choice has been to take advantage of the information on horizontal gradients of both temperature and target species from previous reprocessing or ECMWF reanalysis and to modify the forward model in order to handle the externally provided gradients. Another important objective is the full exploitation of MIPAS measurements that implies the retrieval of weaker and weaker species, whose interference from other species cannot be disentangled. To this purpose the possibility of performing a multi-target retrieval is crucial. Furthermore, we have to consider that the vertical profile retrieval of weak species requires the use of some constraint for the attainment of a fast and useful product and it can be useful to have the possibility of tuning or removing it as needed during the average procedure. To this purpose Optimal Estimation seems to be more apt than the current approach where the constraint is determined with a self-consistent method, difficult to rebuild. For very weak species a posteriori averages of retrieved profiles after removing a priori constrain, as studied in the frame of this project, can be also considered. Validation of ML2PP V7 and further investigations aimed to solve these open issues will be completed in the frame of the subsequent contract.

MIPAS measurements on ENVISAT represents a unique database for the study of atmospheric composition and of the time variation of atmospheric constituents and trends, in combination with other data. With the end of the ENVISAT mission, the importance of this decadal set of measurements justifies any efforts for their full exploitation. The maintenance and the upgrade of the ESA processor are made in the frame of the Quality Working Group, where a fruitful collaboration between L1, L2 and validation teams can be exploited. This collaboration is essential to pursue improvements in the accuracy of the products and their characterization. Recently a new version of the Level 2 processor (ML2PP V7) has been finalized, containing a new approach for handling continuum capable of making the retrieval more stable, a new selection of spectral intervals selected for the analysis of the full resolution measurements aimed to reduce the bias between full resolution and optimized resolution measurements, the regularization of the H2O profiles, the products of five new species (CFC-22, CFC-14, HCN, COF2, CCl4). The addition of these 5 species leads to 15 the number of species processed by the operational processor, but the list of retrieved species can be further enlarged. The latest improvements implemented in the ESA processor and the results of the feasibility studies for additional upgrades will be presented and discussed.

In this paper we analyze the performance of the three MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) observation modes that sound the Upper-Troposphere/Lower-Stratosphere (UT/LS) region. The two-dimensional (2-D) tomographic retrieval approach is assumed to derive the atmospheric field of geophysical parameters. For each observation mode we have calculated the 2-D distribution of the information load quantifier relative to the main MIPAS targets. The performance of the observation modes has been evaluated in terms of strength and spatial coverage of the information-load distribution along the full orbit. The indications of the information-load analysis has been validated with simulated retrievals based on the observational parameters of real orbits. In the simulation studies we have assessed the precision and the spatial (both horizontal and vertical) resolution of the retrieval products. The performance of the three observation modes has been compared for the MIPAS main products in both the UT/LS and the extended altitude range. This study shows that the two observation modes that were specifically designed for the UT/LS region are actually competitive with the third one, designed for the whole stratosphere, up to altitudes that far exceed the UT/LS. In the UT/LS the performance of the two specific observation modes is comparable even if the best performance in terms of horizontal resolution is provided by the observation mode that was excluded by the European Space Agency (ESA) from the current MIPAS duty cycle. This paper reports the first application of the information-load analysis and highlights the worthiness of this approach to make qualitative considerations about retrieval potential and selection of retrieval grid.

We present a multi-year database of atmospheric fields of the upper troposphere, stratosphere and lower mesosphere retrieved from satellite measurements adopting a 2-dimensional tomographic approach. The full mission of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument, on board the European Space Agency ENVISAT satellite, is analyzed with the Geofit Multi-Target Retrieval (GMTR) system to obtain the MIPAS2D database with atmospheric fields of pressure, temperature and volume mixing ratio of MIPAS main targets H2O, O3, HNO3, CH4, N2O, and NO2. The database covers both the MIPAS nominal observation mode measured at Full Resolution (FR) from July 2002 to March 2004 and the nominal observation mode of the new configuration, measured at Optimized Resolution (OR) and introduced in 2005. Further to the main targets, minor species N2O5, ClONO2, COF2, CFC-11, and CFC-12 for the FR mission only have been included in MIPAS2D to enhance its applicability in studies of stratospheric chemistry. The database is continuously updated with the analysis of the ongoing measurements that are planned to last until the end of 2013 and extended to other targets. The GMTR algorithm is operated on a fixed vertical grid coincident with the tangent altitudes of the FR nominal mode, spanning the altitude range from 6 to 68 km. In the horizontal domain, FR measurements are retrieved on both the observational grid and an equispaced 5 latitudinal-degrees grid which is made possible by the 2-dimensional retrieval algorithm. The analysis of MIPAS OR observations is operated on the same altitude-latitude fixed retrieval grid used for the FR measurements. This choice provides a database with a homogeneous altitude and latitude grid, over the whole globe, covering to date about seven years of measurements. The equispaced latitude grid provides a new and convenient layout for the much needed synergetic studies of data from various instrumental and modeling sources. MIPAS2D is available to the scientific community through the two web sites http://www.mbf.fci.unibo.it/mipas2d.html, and http://www.isac.cnr.it/~rss/mipas2d.htm