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New CryoSat dataset with corrected mispointing angle for aberration of light available to users

25 May 2017

A new dataset is now available to CryoSat users which contains Star Tracker mispointing angles corrected for the aberration of light. This dataset is particularly important for those users who are processing the data in Swath Mode. It essentially has no major impact on other applications.

It is noted that corrected values of the mispointing angles corrected for the aberration of light will be incorporated in the next release of the ice products called Baseline D, planned to be released next year.

Users can download the Technical Note, which describes this dataset. The yearly datasets can be downloaded from the these links: 2011, 2012, and 2013. Each dataset is approximately 500MB.

The missing years will be added to the current datasets once they have been processed and shall become available on the datasets page.

For further information, please do not hesitate to contact eohelp


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New SMOS Level 3 salinity products available

26 May 2017

New salinity products are available at CATDS (Centre Aval de Traitement des Données SMOS).

A new correction for systematic errors (land-sea and seasonal-latitudinal) has been implemented in CATDS CPDC and in CATDS CEC LOCEAN.

Concerning CATDS CPDC, a RE05 reprocessing of ocean salinity is available from January 2010 to March 2017; the operational processing has been updated accordingly. Binned maps at the usual spatial and temporal resolution are available. The SMOS SSS corrected for systematic errors are in MIR_CSQ3 files; non corrected SMOS SSS remain available in MIR_CSF3 files.

The corrected product is limited to 45N-47S, the correction remaining uncertain at higher latitudes.

A new ATBD is available to download.

Concerning CATDS CEC-LOCEAN, 9-day and 18-day products sampled at 25km resolution are provided every 4 days. They cover all latitudes from January 2010 to December 2016. CATDS have documented this in more detail.

A validation of these products was presented at the European Geosciences Union (EGU) in April - the poster is available to download.

Further information and the FTP sites for both products can be found on the CATDS website.


Back to Daily Performance Reports

The following performance reports are available:


Back to Daily Performance Reports

The following performance reports are available:


Back to Daily Performance Reports

The following performance reports are available:


Fringe 2017 - Registration deadline

24 May 2017

All users interested in participating to the upcoming Fringe 2017 workshop are kindly reminded to register before the deadline of Friday 02 June 2017.

Fringe 2017 - the 10th International Workshop on "Advances in the Science and Applications of SAR Interferometry and Sentinel-1 InSAR" - is a free workshop, open to ESA Principal Investigators, co-investigators, Sentinel-1 users, scientists, students, representatives from national, European and international space agencies and value adding industries.

The event will be hosted at the Aalto University in Helsinki, Finland, from 05 to 09 June 2017.

Fringe 2017

Read more

Table of Contents
 

 



SCIAMACHY Frequently asked questions (FAQs)

This section contains a collection of answers to frequently asked questions (FAQs) on SCIAMACHY, submitted to the ESA EO-Help support desk. These FAQs shall provide first line support to the SCIAMACHY user community, highlighting general aspects of the instrument, and pointing out documents or web resources where more technical details are addressed.

The FAQs are split into the following sections:

 
 

1 - Instrument and Mission;

 

2 - Data access, products' format and quality;

 

3 - Data handling

 

4 - Tools (e.g. SciaL1c, BEAT)

 

In case a question is not included here, please contact the EO Help team via TellUs.

Acronyms used throughout this section are defined here.



1. Instrument and Mission FAQs


1.1 What is SCIAMACHY?

 

SCIAMACHY - SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY - was a passive remote sensing spectrometer on board ESA Earth Observation satellite ENVISAT operated from March 2002 until April 2012, when the end of the mission was declared after the sudden loss of communication with the satellite.

The instrument observed the solar radiation backscattered, reflected, and transmitted from atmosphere and Earth's surface, in the wavelength range between 240 and 2380 nm. The high resolution and the wide wavelength range made possible to detect many different trace gases despite low concentrations, allowing global measurements in the troposphere and in the stratosphere.

SCIAMACHY had multi-viewing capabilities (nadir, limb, and sun/moon occultation geometries) which yield total column values as well as distribution profiles.

 

More details can be found here.


1.2 How can I start getting familiar with the SCIAMACHY instrument?


ESA provides an overview on the SCIAMACHY mission on the Earthnet Online web portal, introducing the SCIAMACHY instrument and its data products. Further internet resources are the SCIAMACHY Operations Support (SOST) web page  and the SCIAMACHY web page providing technical details and operations concept. In addition, useful on-line documentation is available (see next FAQ).


1.3 What documentation exists for SCIAMACHY?


SCIAMACHY-related documents relevant for the user are listed below.

Check the Products Information page for the latest versions of the documents.



General


The book SCIAMACHY - Exploring the Changing Earth’s Atmosphere, published in 2011 by Springer (ISBN 978-90-481-9895-5), explains all aspects of the SCIAMACHY mission, such as instrument concept, instrument operations, calibration and monitoring, retrieval of geophysical parameters, data processing and products format. The manuscript version is available on-line here.

Algorithms and Products Specifications


The SCIAMACHY Product Specifications Volume 15 gives details on data product contents.

 

The algorithm baseline documentation consists of a collection of documents that together give a complete specification of the data processing.

 

The algorithm theoretical baseline documentation consists of a collection of documents that together gives the complete specification of the data processing.

The Algorithm theoretical baseline description for Level 0-1c processing describes in detail all calibration algorithms that are used in the operational processing of Level 1b products.

The Algorithm theoretical baseline description for Level 1b-2 processing describes in detail the operational processing of Level 2 products.

 


Data Quality


The Product Quality Readme files (previously indicated as Disclaimers) describe known artifacts and give up-to-date details on data quality for the Level 1b and the Level 2 datasets. A clear statement for each retrieved trace gases is provided there as well.

Tools


The SciaL1c Software user manual provides general instructions on the usage of the SciaL1c tool and explanations of all user options. It also contains a description of the Level 1c product format.


1.4 Which science groups are working on SCIAMACHY?

Many scientific groups at various institutes in Europe and abroad are involved in the scientific analysis and validation of SCIAMACHY data. A list of the teams and institutes involved in current and past SCIAMACHY-related projects is the following:

 

Information on Operational and Scientific Products, Validation and Science
SCIAMACHY Quality Working Group Teams
SCIAMACHY Operations
Further SCIAMACHY Teams
Space Agencies


1.5 How can I stay up-to-date with the latest news on SCIAMACHY?
 

Due to the end of the mission, news on SCIAMACHY are rather unfrequent, and mainly related to the release of improved dataset from reprocessing campaigns.

 

ESA news are published on the Earthnet Online website and are circulated via the Earth Observation Newsletter sent by email every week. Subscription is free of charge and can be done here. Additionally, a RSS feed service allows users to automatically receive headlines from ESA as soon as they are published on the Earthnet Online website. Details are given here.



1.6 How to get help with SCIAMACHY?


If you do not find the answer to your specific question in these FAQs or in the documentation, the main user interface for queries related to ESA supported satellites and missions - including SCIAMACHY - is the web-based customer interface system "TellUs", replacing "EO-Support". The new interface is accessible at the following link: https://esatellus.service-now.com. Any customer, once authenticated via centralised Single Sign-On, will continue to have the ability to interface with the EO Help team by submitting a request, reporting an issue or opening a complaint through the new customised web forms.

1.7 How long the SCIAMACHY mission lasted?

The ENVISAT mission started in March 2002 with an expected nominal lifetime of 5-years. The careful management of the satellite orbital maneuvers allowed saving enough hydrazine for operating Envisat nominally for additional 3.5 years (i.e. until end 2010). At that time, following the excellent status of the platform and of the majority of its instruments, a further extension of the satellite operations was commenced with the modification of the satellite’s orbit (October 2010). Extending SCIAMACHY operations beyond the specified five years mission lifetime required the reconfiguration of the instrument to compensate orbit dependent issues and subsystems degradation, ensuring the high quality of the data for the years to come. Expected duration of extended operations was until end 2014. Unfortunately, after ten years in orbit, communication with the ENVISAT satellite was suddenly lost on 8 April 2012. Any attempt to re-establish contact with ENVISAT was unsuccessful. The end of the mission was declared in May 2012.



1.8 How was the orbit scenario after October 2010?


At the end of October 2010, the sun-synchronous polar orbit of the ENVISAT satellite was lowered by 17.4 km to permit the extension of the mission. The extended mission orbit was characterized by a different repeat cycle: from 35-days/501-orbits to 30-days/431-orbits. In the new orbit, the orbital inclination control previously performed with orbit adjustments was interrupted in order to minimize fuel consumption and the satellite started to drift. The Mean Local Solar Time (MLST) for the Equator crossing was initially kept to a maximum deviation of +/- 1 km from ground track and +/- 5 minutes from 10:00 AM, after the lowering it was varying in the +/- 10 minutes range.




2. General data access and products format FAQs

2.1 How many product types are generated from SCIAMACHY observations?

 

SCIAMACHY products follow the general ENVISAT data structure: for each satellite’s orbit one Level 0, Level 1b, and Level 2 files were generated. Level 2 products are the highest product level provided by ESA. Products were processed either in Near Real Time (NRT) at the acquisition facilities, or off-line, any time from a few hours following the acquisition, at the Processing and Archiving Centers (PACs). Off-line products had the same format and content of the NRT products, but benefitted from a-posteriori knowledge of calibration, auxiliary data and precise satellite orbit and attitude. Off-line products are also indicated as consolidated products. The Level 0 products are not distributed, while Level 1b and Level 2 data are accessible to users.

With the end of the mission only consolidated products are distributed.

Information on the datasets is summarized in the SCIAMACHY Products availability table.



2.2 What is the naming convention for the filenames?

ENVISAT product filenames contain themselves basic processing information and permit an unambiguous allocation of the file to a particular measurement type. The complete description of the ESA filename convention is available in the SCIAMACHY book (Figure 8.1) or here in the SCIAMACHY Product Handbook (Chapter 6).

2.3 How can I get access to SCIAMACHY data products?

 

A general description on how to access data provided by ESA can be found here

Consolidated SCIAMACHY Level 1b (SCI_NL__1P) and Level 2 (SCI_OL__2P) datasets are available on-line. Products can be retrieved via FTP. Access information shall be requested via the web-based customer interface system "TellUs" (Single Sign-On authentication required), replacing "EO-Support". A request for registration to get data access can be submitted here.

2.4 What is the difference between consolidated and NRT products?

Consolidated and near-real-time (NRT) products are characterized by different time scale and were generated at different processing centers from different data processing chains and inputs.

The Near-Real-Time chain was conceived by ESA to provide during operations the EO user community with access to data products within a short time after sensing. NRT products (unconsolidated) were processed and disseminated within three hours from sensing, and were characterized by using NRT auxiliary information available at the time of product generation, e.g. predicted orbit state vectors and calibration data from about three days prior to acquisition. Additionally, NRT products had start/stop times defined by data receiving coverage times, not reflecting complete orbits and with possible overlaps. The NRT service was mainly intended for operational atmospheric and climate modeling applications.


Consolidated data products span one complete orbit between two consecutive ANX (Ascending Node Crossing). They benefit from an a-posteriori knowledge of information concerning calibration and auxiliary data, e.g. restituted attitude information and precise orbit. Usually a consolidated product was generated from two unconsolidated products and did not show overlaps or time gaps other than instrument unavailability. Since consolidated products represented the planned and executed measurements as precisely as possible, they are the products now distributed by ESA and suited for scientific studies.

 

2.5 Did SCIAMACHY Level 2 NRT products exist?


The generation of SCIAMACHY Level 2 near-real-time (NRT) products (SCI_NL__2P) was stopped in May 2006 and Level 2 NRT products were not distributed afterwards.

 

Starting from 2010, ESA implemented a Fast-Delivery processing service, providing SCIAMACHY Level 2 data (SCI_OL__2PN) within 24 hours from acquisition. These data were generated from Level 1b NRT products using predicted instead of consolidated auxiliary files and not using the restituted attitude information.



2.6 How can I distinguish between Fast Delivered and Off-line Level 2 products?

SCIAMACHY Level 2 operational products from the Fast Delivery and off-line processing chains shared the same processor version and processing center (D-PAC) but adopted different inputs. Fast Delivery products used as input Level 1b NRT data and auxiliary information available at the time of product generation. The off-line Level 2 data were based on consolidated Level 1b products and benefit from a posteriori knowledge of calibration information and satellite’s attitude and state.
The only way to distinguish between the Fast Delivery and Off-line Level 2 products is checking the processing stage flag reported in the filename (and in the MPH ASCII header). Fast Delivery data present flag “N” (SCI_OL__2PN), while the off-line production adopted processing status flags P, R, U, W, Y (e.g. SCI_OL__2PW).

2.7 How can I read SCIAMACHY products?


SCIAMACHY products used ENVISAT specific data format. Each consolidated product is orbit based and contains several binary encoded geophysical quantities. The following tools support the reading of ENVISAT products format:

  • The Basic ERS & ENVISAT Atmospheric Toolbox (BEAT) is a collection of executable tools and an application programming interface which has been developed by S&T to facilitate usage, viewing, and processing of GOMOS, MIPAS, SCIAMACHY, and GOME data. BEAT provides routines for data extraction from SCIAMACHY products.
  • The Common Data Access toolbox (CODA) developed by S&T under ESA mandate provides a single interface for reading a very wide range of atmospheric data products. Supported instruments include GOMOS, MIPAS, SCIAMACHY, GOME, GOME-2, IASI, OMI, TES, and MLS. A set of command line applications (codacheck, codacmp, codadump, and codafind) permits direct access to earth observation data, while interfaces to programming languages allow to ingest products using e.g. Fortran, IDL, MATLAB, Java, and Python.
  • VISAN is a visualization and analysis cross-platform application for Earth Observation data developed by S&T permitting the browsing of the SCIAMACHY products. VISAN provides some very powerful visualization functionality for 2D plots and world plots.
  • HARP is a toolset developed and maintained by S&T for ingesting, processing, and inter-comparing satellite or model data against correlative data. The toolset is composed of a set of command line tools and a library of analysis functions. The current version of HARP handles SCIAMACHY Level 2 products.
  • EnviView was a free application (developed in Java) that allowed ENVISAT data users to open data files and examine their content. The last release available is baseline version 2.8.1 dated 05 March 2010. The Enviview software remained frozen at March 2010.

With the next datasets (Level 1b version 9 and Level 2 version 7) the data format will be changed to netCDF.



2.8 How can I get information about SCIAMACHY data product quality?

During operations, information on data quality was provided on a daily basis by means of daily reports for every type of operational product generated from each processing chain. Expert reports, visualizing instrument key parameters for operational product (Levels from 0 to 2) are available here.


On a larger time scale, quality and operations information was made available through SCIAMACHY bimonthly reports, accessible here.


Specific Product Quality Readme files provide information about the quality status of the datasets.

 

A web-page reporting anomalies in the SCIAMACHY data production and indicating the corrective actions performed (e.g. data removal or re-processing) is regularly maintained.

 

2.9 Why are there missing products in the SCIAMACHY datasets?


SCIAMACHY was operated by ESA from March 2002 to April 2012, with quasi nominal operations starting on 02 August 2002. Along the mission, anomalies or events, such as satellite maneuvers, impacted SCIAMACHY's nominal measurements resulting in missing or corrupted measurements. A list of the SCIAMACHY evants and the instrumental availability interruptions is here. Also the SOST web page tracks the anomaly events, which caused a deviation from the planned measurements schedule. Moreover, processing failures happened during data generation. An overview of the complete SCIAMACHY Level 0, Level 1b, and Level 2 consolidated datasets is given here.

Please note that the Level 2 data set presents data gaps in correspondence of the monthly calibrations when Nadir or Limb measurements were not planned. These orbits were voted to calibration and were not processed up to Level 2 products.



2.10 What data version shall be used? (Data reprocessing campaigns)

The operational Level 1b and Level 2 ESA products are essential inputs to various atmospheric applications, such as weather forecasting, networks for volcanoes ashes detection, air quality monitoring.

Following algorithms and processor improvements, data reprocessing is carried out with the target of maintaining and improving the products quality both in terms of accuracy and number of available geophysical parameters.


The data re-processing campaigns are thus important in order to improve the quality of the existing dataset and generate long term series of geophysical parameters that are of vital interest for climate studies and trend analysis, especially considering the extension of the ENVISAT mission. Data reprocessing consists in gathering the consolidated Level 0 data from the full mission and generating the corresponding Level 1b and Level 2 products with the newest processor versions.

The latest SCIAMACHY Level 1b and Level 2 full-mission reprocessing were performed in 2016 with processor version 8 (8.01/8.02) and processor version 6.01 respectively. Data present processing status flag “Y”. The re-processed data are made available to the user community for direct download via the ESA centralised dissemination service (DissHarm). The overall status of the dataset also with availability statistics is given here.

 

An overview of the products currently distributed by ESA is available here.

Science users are strongly recommended to use for their particular applications consolidated Level 1b and Level 2 products processed with the latest processors.

Access to SCIAMACHY products can be provided through ESA Fast Registration.


2.11 What about validation?


Validation has to ensure that geophysical quantities derived from SCIAMACHY in-orbit radiometric measurements met quality requirements for scientific studies and applications. The goal of validation activities is to provide clear statements of the quality of all SCIAMACHY retrieved products. Given the evolution of the algorithms with the inclusion of new products this task has to be pursued continuously.

Results of the recent validation activities are detailed in reports available here.

  • Keppens et al., “Multi-TASTE Phase F Validation report – Ground-based assessment of SCIAMACHY SGP 6.01 Level-2 Data Products O3, NO2, CO, CH4, BrO and H2O”, TN-BIRA-IASB-MultiTASTE-Phase-F-SCIA-SGP6-Iss1-RevB, Issue 1 / Rev. B, 52 pp., 21 December 2016.
  • D. Hubert et al., “Multi-TASTE Phase F Report – Delta-validation of SCIAMACHY SGP upgrade from V5.02 to V6.00”, TN-BIRA-IASB-MultiTASTE-Phase-F-VR1-Iss2-RevA, 18 September 2015.
  • D. Hubert et al., "Multi-TASTE Phase F Final Report / October 2013 - December 2015", TN-BIRA-IASB-MultiTASTE-Phase-F-FR, Issue 2 / Rev. A, 1 February 2016.

Previous results on the validation of operational and science data products can be found at http://www.sciamachy.org/products/.



2.12 What is an m-factor?


Monitoring factors (m-factors) are auxiliary files used to compensate for the radiometric degradation of SCIAMACHY, that were regularly calculated by SOST-IFE and provided to ESA for the operational data processing. The latest Level 0-1b processing (version 8) corrects for the optical degradation on the light paths affecting the SCIAMACHY instrument. In the previous processing baseline, degradation effects were corrected in the Level 1b to 2 processing stage. M-factors files are available from IUP University Bremen.


2.13 Are there known issues affecting SCIAMACHY products?

Known issues affecting SCIAMACHY products are usually indicated in the Product Quality Readme files, or on the web-page reporting processing anomalies.


3. Data handling

3.1 What spectral radiance units are used?

SCIAMACHY Level 1b products report the measured radiance as arbitrary Binary Units per second [BU/s] or [photons/cm2 nm s sr] respectively for un-calibrated and calibrated spectra. Details are in the Input/Output Data Description (IODD) document.

3.2 What is the definition for Limb viewing angles?

During limb measurements, SCIAMACHY sound the atmosphere in a sequence of vertical steps and horizontal scans. The scene of each limb observation is defined unambiguously through sets of angles specifying solar and viewing directions. In SCIAMACHY Level 1b products, for each limb scan, all relevant information is stored in the limb measurement data set (LIMB MDS). In particular, the solar azimuth angle (geo.sol_azi_ang) which stores 3 values (in degrees) for the angles at the start, the middle and the end of the integration time. Please note that Level 1b products also report the azimuth and elevation angles for the viewing direction, lines of sight (geo.los_azi_ang and geo.los_nad_ang). All these angles are given with respect to the height of 100 km above sea level, height considered as top of the atmosphere. A clear sketch of SCIAMACHY observation geometries and the coordinate system adopted is reported on the SCIAMACHY book (Figures 2.4 and 3.7).

3.3 Is it possible to use SCIAMACHY SWIR measurements?

There are some issues affecting SCIAMACHY SWIR channels, therefore warnings have to be raised for the usage of these spectral ranges.

In particular, detector channel 7 suffered from a light leak which is preventing successful Level 2 retrievals in that spectral range. Moreover, channels 7 and 8 were contaminated by an ice layer growing on top of the cylindrical lens covering the detectors. The ice layer produced a significant attenuation of the radiance response and modified the instrument slit function. It affected only channels 7 and 8 because these were the detectors operated at lowest temperatures. In order to remove the ice layer from the detector, several decontamination campaigns were done during the mission lifetime. Consequently, the impact of the ice layer is time-dependent.

All IR detectors (channels 6+ to 8) were degrading with time, in particular the number of pixels not responding or showing an abnormal behavior (with random intensity or negative values) was increasing along the mission lifetime. This aspect can be taken into account with the application of a dead and bad pixel mask (DBPM) indicating usable pixels. Bad Pixels have to be ignored for retrieval purposes.

Details also with decontamination intervals are reported in the Level 1b product quality Readme file.

3.4 How can I distinguish between forward and backward scans?

In almost all measurement types, the scanners executed oscillating movements (forward/backward scans) with specified scanner start positions and scan ranges defined by the orientation of the ASM and ESM devices. The current SCIAMACHY products do not give information on the pixel type (forward or backward scan) providing a clear flag. If users want to make this distinction, the corner coordinates of the ground pixels (latitudes and longitudes) have to be used in order to identify the sequence of pixel types.


3.5 Are Averaging Kernels included into the products?

Averaging Kernels are enclosed in the SCIAMACHY Level 2 products since SGP version 3.01. They are within the Limb MDS as Additional diagnostics (ADDDIAG). The arrangement of the information requires explanation that is provided in the Level 1b to 2 Off-line Processing - Input Output Data Definition (IODD) document (ENV-ID-DLR-SCI-2200-4),  while instructions for the usage of the Level 2 products Limb MDS are in document SCIAMACHY 1b to 2 Off-line Processing Instructions (ENV-TN-DLR-SCIA-0077).

3.6 Which gas species are currently retrieved in ESA Level 2 processing?

The SCIAMACHY Level 2 data processing baseline is under continuous evolution and further trace gases are made available after the implementation of new algorithms. The list of retrieved geophysical parameters has been significant enhanced along the mission, also with improvements for data quality. The gas species currently enclosed in the Level 2 products (version 6.00) are indicated in the table below and in the Level 2 product quality Readme file.


Atmospheric trace constituents

Level 2 version 6.00

Nadir  Limb 
Absorbing Aerosol Index (AAI)  
O3
NO
BrO 
SO  
OClO   
HCHO X  
CHO-CHO X  
H2  
CO / xCO   
CH4 X  
Clouds Cover, Top Height, Optical Thickness Classification

 


3.7 Is CO2 enclosed in ESA Level 2 products?

CO2 is an important gas species targeted for measurements by SCIAMACHY in the SWIR spectral region. However, CO2 density columns are currently not retrieved as operational product so are not included into SCIAMACHY Level 2 products disseminated by ESA. Nevertheless, several studies covering atmospheric CO2 distribution have been carried-out by research groups using SCIAMACHY observations. The products derived within studies implementing scientific algorithms are not distributed under ESA responsibility. We suggest the user to refer to scientific data products generated at IFE Bremen.

3.8 Are CO column densities within Level 2 products reliable?

Because of erroneous retrieval settings adopted in the operational Level 1b-2 processing with processor SGP version 5.01, users were recommended to not use the CO column densities enclosed in the Level 2 version 5.01 products. With the activation of processor SGP version 5.02, a spectral correction was implemented leading to a significant improvement in terms of quality of the CO product. The CO column densities are intended to be used as time-averaged products applying specific data filtering. Although single observations are provided, they have large errors and should not be used individually. More details are in the Level 2 product quality Readme file.


3.9 Why only OClO slant column densities have to be used?

The computation of vertical column densities (VCD) for OClO is difficult for its rapid photochemistry. VCDs included in the Level 2 products do not contain any correction for photochemical effects and should not be used. Slant column densities (SCD) are provided instead. Details are reported in the Level 2 product quality Readme file.

3.10 Are there limitations for BrO Vertical Column Densities?

Yes, users are recommended to not use BrO data for year 2002, due to low quality. For year 2002, the available version of Level 2 products (5.01) presents BrO column densities substantially too low with a lot of negative values. From 2003 onwards BrO data can be used without restrictions. Details are reported in the Level 2 product quality Readme file.

3.11 Why there are gaps in scan lines in both SCIAMACHY latitudinal and longitudinal directions?

SCIAMACHY measurements are set up in a nominal pattern where limb and nadir sequences are alternating on the dayside of the orbit. The sequence of nadir and limb states in a timeline is arranged so that limb and nadir ground pixels matches. At the beginning and end only limb or only nadir measurements are executed.

A clear sketch of the measurement sequence is provided on the SCIAMACHY book (Figure 4.2) http://atmos.caf.dlr.de/projects/scops/sciamachy_book/sciamachy_book_springer_editors_version.html.

3.12 Why there are two Nadir MDS for SO2 column densities?

Within the Level 2 products, two types of SO2 vertical column densities are reported; one representing an anthropogenic scenario (pollution dominated) and another one for a volcanic eruption. Since the vertical SO2 distribution varies to a large degree between the two scenarios, the Air Mass Factor (AMF) used to convert the SO2 slant columns to vertical columns cannot be derived from a single climatology. Two types of AMF are derived assuming a constant profile shape for two typical SO2 distributions:
 

  • a profile with 1 DU of SO2 in the boundary layer (from surface to 1 km height) simulating an anthropogenic pollution scenario;
  • a profile with 10 DU of SO2 between 10 and 11 km simulating a volcanic eruption.

Two different VCDs are thus computed and written into two different MDS: the anthropogenic SO2 column (in UV5 limb MDS) and the volcanic SO2 column (in UV7 limb MDS). Both retrievals use as input the same background-subtracted slant column, calculated from a reference sector over the Pacific Ocean as a pollution free correction. Details are reported in the Level 2 product quality Readme file.

3.13 I want to perform my own retrievals starting from spectra included in Level 1b products, and compare my results with ESA Level 2 products. Which calibrations and retrieval settings are operationally applied?

For details on the calibrations applied to the measured radiances, the user is directed to the Algorithm theoretical baseline description for Level 0-1c processing (ATBD L0-1c).

3.14 Are Limb Mesosphere-Thermosphere and Occultation measurements processed to Level 2?

From November 2008 onwards, SCIAMACHY performed regular limb measurements in the mesosphere and lower thermosphere. These measurements were carried out instead of "normal" limb states for 30 orbits every month split on two separate sequences of ~15 orbits each, with one sequence synchronized with the MIPAS Upper Atmosphere observations. SCIAMACHY Mesospheric Limb Measurements (state ID 55) were performed scanning altitudes between 60 and 150 km. Starting with the operational Level 1b data version 7.03, this new type of limb state was available in the Limb MDS of the Level 1b file. However, the Level 2 processing did not include these scientific measurements into the operational Level 2 products. Also occultation measurements were not operationally processed.

 


4. Tools FAQs

4.1 What is SciaL1c?

SciaL1c is a tool provided to the users of SCIAMACHY Level 1b products. This tool allows selecting specific calibrations to apply to SCIAMACHY Level 1b data that contain not fully calibrated spectral information in combination with calculated calibration data.

Once the user has identified within the Level 1b data the desired products to extract, it is recommended to run SciaL1c making use of all the filter options applicable. The generated Level 1c products are suitable for the user's particular applications. The output from the SciaL1c processing (Level 1c files) adopts ESA PDS format.

The SciaL1c tool is available here for download.

We recommend users to run SciaL1c making use of all the filter options applicable.

Few examples are: “-cat” to specify the type of measurements; “-cal” to specify the desired calibrations; “-topleft and -bottomright” to specify a geographical area of interest.

4.2 Are there known issues affecting SciaL1c?

An anomalous handling of the m-factor file during the calibration of SCIAMACHY Level 1b data was observed. The m-factor file (SCI_MF1_AX) is not correctly reported into the child product restituted from the SciaL1c processing. In particular, the MF1 filename does not fully appear in the DSD descriptor. The quality of the product is not impacted; this anomaly will be fixed with the next delivery of the SciaL1c tool.

4.3 What is the difference between Level 1b and Level 1c products?

Consolidated Level 1b products contain raw detector signals for all measurements for a complete orbit and have to be converted with the SciaL1c command line tool into Level 1c products containing fully calibrated measurements. Level 1c products are thus user specific products with the general ENVISAT data format. Such products are not operationally distributed as they are generated by the user specifying how data shall be calibrated. Level 1c products are suitable for the user’s particular applications (e.g. spectral fitting and retrievals).

4.4 How to apply the m-factors when using SciaL1c?

Until data version 7.04, users of SCIAMACHY Level 1b products could compensate for the instrument degradation applying an end-to-end correction with the m-factor files (SCI_MF1_AXVIEC) while calibrating the Level 1b products with the SciaL1c applicator. A brief description of the syntax required for the application of the m-factor was indicated in the SciaL1c software user’s manual.
 

With data version 8.0 of the Level 1b products, a new approach for the degradation correction of SCIAMACHY has been introduced as part of the radiometric calibration. SCIAMACHY calibrated spectra within version 8.0 products are always degradation corrected. Application of the m-factor to Level 1b products with SciaL1c is not possible anymore as correction has already been applied during level 0-1b processing step.

 


4.5 How to use BEAT?

The BEAT/CODA developers present a tutorial on the usage of BEAT on their web page. Below are reported few commands for the ingestion from SCIAMACHY Level 1b files in order to give a gist of the programs capabilities. Make sure you are using a version of the BEAT/CODA tool implementing the adequate data dictionary.

To open a Level 1b file:

p_id = coda_open('SCI_NL__1PUDPA20091113_111044_000060012084_00152_40286_8393.N1’)

Ingesting a single specified field:

result = coda_fetch(p_id, 'MPH')

Retrieving the entire product:

result = coda_fetch(p_id)

Closing the Level 1b file:

result = coda_close(p_id)

4.6 Are there known issues affecting BEAT/CODA?

Issues affecting the BEAT/CODA software are promptly fixed by S&T with a new software delivery. However, new problems could be discovered affecting the current software release and are listed here .

 

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7th ESA LTC2017 - Application submission deadline

26 May 2017

The 7th ESA Advanced Training Course on Land Remote Sensing will be held in Gödöllő, Hungary, from 4 to 9 September 2017.

Interested users are kindly reminded to submit their application before the deadline of 01 June 2017.

Organised by the European Space Agency (ESA) and co-sponsored by the Hungarian Space Office (HSO), the course will be hosted by Szent István University, Faculty of Agricultural and Environmental Sciences.

Land Training Course

Read more