Long-term analysis of GOME in-flight calibration parameters and instrument degradation

Since 1995, the Global Ozone Monitoring Experiment (GOME) has measured solar and backscattered spectra in the ultraviolet and visible wavelength range. Now, the extensive data set of the most important calibration parameters has been investigated thoroughly in order to analyze the long-term stability and performance of the instrument. This study focuses on GOME in-flight calibration and degradation for the solar path. Monitoring the sensor degradation yields an intensity decrease of 70% to 90% in 240–316nm and 35% to 65% in 311–415 nm. The spectral calibration is very stable over the whole period, although a very complex interaction between predisperser temperature and wavelength was found. The leakage current and the pixel-to-pixel gain increased significantly during the mission, which requires an accurate correction of the measured radiance and irradiance signals using proper calibration parameters. Finally, several outliers in the data sets can be directly assigned to instrument and satellite anomalies

The Global Ozone Monitoring Experiment: Review of in-flight performance and new reprocessed 1995-2011 level 1 product

The Global Ozone Monitoring Experiment (GOME) on-board the second European Remote Sensing satellite provided measurements of atmospheric constituents such as ozone or other trace gases for the 16 year period from 1995 to 2011. In this paper we present a detailed analysis of the long-term performance of the sensor and introduce the new homogenized and fully calibrated level 1 product which has been generated using the recently developed GOME Data Processor level-0-to-1b (GDP-L1) Version 5.1. By means of the various in-flight calibration parameters we monitor the behavior and stability of the instrument during the entire mission. Severe degradation of the optical components has led to a significant decrease in intensity in particular in channels 1 and 2 covering the spectral ranges of 240–316 nm and 311–405 nm, respectively. Thus, a soft correction based on using the sun as a stable calibration source is applied. Revision and optimization of other calibration algorithms such as the wavelength assignment, polarization correction, or dark current correction resulted in an improved and homogeneous level 1 product that can be regarded as the European satellite reference data for successor atmospheric composition sensors and that provides an excellent prerequisite for further exploitation of GOME measurements

SCIAMACHY: The new Level 0-1 Processor

SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) is a scanning nadir and limb spectrometer covering the wavelength range from 212 nm to 2386 nm in 8 channels. It is a joint project of Germany, the Netherlands and Belgium and was launched in February 2002 on the ENVISAT platform. After the platform failure in April 2012, SCIAMACHY is now in the postprocessing phase F. SCIAMACHY�s originally specified in-orbit lifetime was double the planned lifetime. SCIAMACHY was designed to measure column densities and vertical profiles of trace gas species in the mesosphere, in the stratosphere and in the troposphere (Bovensmann et al., 1999). It can detect a large amount of atmospheric gases (e.g. O3 , H2CO, CHOCHO, SO2 , BrO, OClO, NO2 , H2O, CO, CH4 , among others ) and can provide information about aerosols and clouds. The operational processing of SCIAMACHY is split into Level 0-1 processing (essentially providing calibrated radiances) and Level 1-2 processing providing geophysical products. The operational Level 0-1 processor has been completely re-coded and embedded in a newly developed framework that speeds up processing considerably. In the frame of the SCIAMACHY Quality Working Group activities, ESA is continuing the improvement of the archived data sets. Currently Version 9 of the Level 0-1 processor is being implemented. It will include An updated degradation correction Several improvements in the SWIR spectral range like a better dark correction, an improved dead & bad pixel characterisation and an improved spectral calibration Improvements to the polarisation correction algorithm Improvements to the geolocation by a better pointing characterisation Additionally a new format for the Level 1b and Level 1c will be implemented. The version 9 products will be available in netCDF version 4 that is aligned with the formats of the GOME -1 and Sentinel missions. We will present the first results of the new Level 0-1 processing in this paper

The FDR4ATMOS Project

The FDR4ATMOS project has two main tasks. The focus of task A is to update the SCIAMACHY processing chain for better Ozone total columns. After the full re-processing of the SCIAMACHY mission with processor versions 9 (Level 1) and version 7 (Level 2), the comparison with ground-based data showed that the total Ozone column showed a downward trend of nearly 2% from the beginning of the time series to its end. This trend is an artefact and is likely caused by changes made to the calibration algorithms in the Level 1 processor (the DOAS retrieval algorithm for Ozone was not changed). The most likely reason are changes in the degradation correction that lead to subtle changes in the spectral structures that in the retrieval are interpreted as an atmospheric signature. In task A we will update the Level 0-1 processor with the final aim of a mission re-processing. The second task in the FDR4ATMOS project is to develop a cross-instrument Level 1 product for GOME-1 and SCIAMACHY for the UV, VIS and NIR spectral range with a focus on the spectral windows used for O3, SO2, NO2 total column retrieval and the determination of cloud properties. Contrary to other projects, FDR4ATMOS does not aim to build a harmonised time series on Level 2 products but on Level 1 products, i.e. radiances and reflectances. The GOME-1 and SCIAMACHY instrument together span 17 years of spectrally highly resolved data. The goal of the FDR4ATMOS project is to generate harmonised data sets that allow the user to use it directly in long term trend analysis, independent of the instrument. Since this was never done for highly resolved spectrometers, new methods have to be developed that e.g. take into account the different observation geometries and observation times of the instrument without impacting the spectral structures that are used for the retrieval of the atmospheric species. The resulting algorithms and the processor should also be as generic as possible to be able to transfer the methodology easily to other instruments (e.g. GOME-2, Sentinel-5p) for a future extension of the time series. The FDR4ATMOS started in October 2019 and is currently in phase 1. We will present the goals of the project and first results

Level 1-to-2 Data Processor Version 3.0: A Major Upgrade of the GOME/ERS-2 Total Ozone Retrieval Algorithm,

Abstract The Global Ozone Monitoring Experiment (GOME) was launched in April 1995, and the GOME Data Processor (GDP) retrieval algorithm has processed operational total ozone amounts since July 1995. GDP Level 1-to-2 is based on the two-step Differential Optical Absorption Spectroscopy (DOAS) approach, involving slant column fitting followed by Air Mass Factor (AMF) conversions to vertical column amounts. We present a major upgrade of this algorithm to Version 3.0. GDP 3.0 was implemented in July 2002, and the 9-year GOME data record from July 1995 to December 2004 has been processed using this algorithm. The key component in GDP 3.0 is an iterative approach to AMF calculation, in which AMFs and corresponding vertical column densities are adjusted to reflect the true ozone distribution as represented by the fitted DOAS effective slant column. A neural networkensemble is used to optimize the fast and accurate parameterization of AMFs. We describe results of a recent validation exercise for the operational version of the total ozone algorithm; in particular, seasonal and meridian errors are reduced by a factor of two. On a global basis, GDP 3.0 ozone total column results lie between -2% and +4% of ground-based values for moderate solar zenith angles lower than 70°. A larger variability of about +5% and -8% is observed for higher solar zenith angles up to 90°. Copyright OCIS codes 01

SCIAMACHY: Level 0-1 Processor V9 and Phase F Re-processing

SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) is a scanning nadir and limb spectrometer covering the wavelength range from 212 nm to 2386 nm in 8 channels. It is a joint project of Germany, the Netherlands and Belgium and was launched in February 2002 on the ENVISAT platform. After the platform failure in April 2012, SCIAMACHY is now in the postprocessing phase F. Its originally specified in-orbit lifetime was double the planned lifetime. SCIAMACHY was designed to measure column densities and vertical profiles of trace gas species in the mesosphere, in the stratosphere and in the troposphere (Bovensmann et al., 1999). It can detect a large amount of atmospheric gases (e.g. O3 , H2CO, CHOCHO, SO2 , BrO, OClO, NO2 , H2O, CO, CH4 , among others ) and can provide information about aerosols and clouds. The operational processing of SCIAMACHY is split into Level 0-1 processing (essentially providing calibrated radiances) and Level 1-2 processing providing geophysical products. The operational Level 0-1 processor has been completely re-coded and embedded in a newly developed framework that speeds up processing considerably. In the frame of the SCIAMACHY Quality Working Group activities, ESA is continuing the improvement of the archived data sets. Version 9 of the Level 0-1 processor includes - An updated degradation correction - Improvements to the polarisation correction algorithm - Improvements to the geolocation by a better pointing characterisation - Several improvements in the SWIR spectral range like a better dark correction, an improved dead & bad pixel characterisation and an improved spectral calibration The new format for the Level 1b and Level 1c will be netCDF V4. We will present the verification results and the results of the mission re-processing

FDR4ATMOS (Task A): Improving SCIAMACHY Level 1 and add calibrated lunar data

The project FDR4ATMOS (Fundamental Data Records in the domain of satellite Atmospheric Composition) has been initiated by the European Space Agency (ESA). Task A of the project covers the improvement of the SCIAMACHY Level 1b degradation correction, with the aim to remove ozone trends from the SCIAMACHY Level 2 data set that were introduced during the development of baseline version 9 (both data sets not released). We will also, for the first time, add calibrated lunar data to Level 1, covering the whole spectral range of SCIAMACHY and the full mission time. The SCIAMACHY processing chain for better Ozone total column data: After the full re-processing of the SCIAMACHY mission with the updated processor versions, the validation showed that the total Ozone column drifted downward by nearly 2% over the mission lifetime. This drift is likely caused by changes in the degradation correction in the Level 1 processor, that led to subtle changes in the spectral structures. These are misinterpreted as an atmospheric signature. We updated the Level 0-1 processor accordingly and a full mission re-processing was done. As a major improvement we additionally incorporated calibrated lunar data in the SCIAMACHY Level 1b product. In the new Level 1b product we will provide the individual scans of the moon as well as disk integrated and calibrated lunar irradiance and reflectance. The instrument performed regular lunar observations building up a unique 10 year data set of lunar spectra from the UV to the SWIR with moderately high spectral resolution. SCIAMACHY scanned the full lunar disk and over the ten year mission time made 1123 observations of the moon. Most satellites can only observe the moon under very specific geometries due to instrument-viewing and orbit restrictions. SCIAMACHY, however, with a two mirror pointing system was much less constrained and was able to observe the moon under an extreme large variation of geometries (especially during dedicated lunar observation campaigns), allowing it thus potentially to tie different satellites and geometry observations together. During the individual lunar observations, SCIAMACHY only saw a small slice of the Moon and scanned over the moon in order to obtain data for the full disk. We combined the individual calibrated scans, correcting for scan speed and the fact the Moon does not fill the entire slit length. The calculation of distance-normalized lunar reflectances did not require an external solar spectrum, but used solar measurements of SCIAMACHY itself. This version of Level 1 will also be the first one that replaces the ENVISAT byte stream format with the netCDF format that is aligned with the product format of other atmospheric sensors like the Sentinels The paper will present the improvements of the Level 1 product, the results of the quality control and validation

Collimation for the LHC high intensity beams

The unprecedented design intensities of the LHC require several important advances in beam collimation. With its more than 100 collimators, acting on various planes and beams, the LHC collimation system is the biggest and most performing such system ever designed and constructed. The solution for LHC collimation is explained, the technical components are introduced and the initial performance is presented. Residual beam leakage from the system is analysed. Measurements and simulations are presented which show that collimation efficiencies of better than 99.97 % have been measured with the 3.5 TeV proton beams of the LHC, in excellent agreement with expectations.peer-reviewe