SARINvatore for CS-2

PROVIDER

ESA/ESRIN

SARINvatore (SARIN Versatile Altimetric TOolkit for Research and Exploitation) for CryoSat-2 is a Software Processor Prototype developed by ESA/ESRIN (REF1) to experiment with SARin processing from L1A (FBR) to L2 using the SAMOSA retracking model. It can be used over open ocean or coastal zones, as well as over more difficult targets such as rivers, lakes, and sea-ice. This toolkit is made available to the user community as EarthConsoleTM P-PRO Service. The toolkit takes in input Cryosat-2 SARin FBR data products and produces in output geophysical L2 products in standard NetCDF format. This output can be manipulated and visualized with BRAT (the Broadview Altimetry Radar Toolbox).

EarthConsole^® P-PRO SARINvatore for CRYOSAT-2 Software Prototype User Manual

Introduction

The P-PRO SARINvatore (SARIN Versatile Altimetric TOolkit for Research and Exploitation) for CryoSat-2 service is a web platform that provides the capability to experiment with SARin processing from L1A (FBR) to L2 using the SAMOSA retracking model.

The service is based on the SARvatore Processor Prototype that has been developed entirely by Salvatore Dinardo in the scope of the EOP-SER Altimetry Team (Salvatore Dinardo, Bruno Manuel Lucas, Jerome Benveniste) at ESA-ESRIN.
The processor has been further upgraded (SARINvatore) to accept in input L1a (FBR) SARIN data products and build SARIN Level-2 geophysical data products as well.

The processors will make use of the EarthConsole P-PRO distributed computing platform to deliver timely the output data products.

These output data products are generated in standard NetCDF format (using CF Convention), and they are compatible with BRAT (Broadview Radar Altimetry Toolbox) and other NetCDF tools.

List of option entries and adoped conventions

The processor prototype is versatile in the sense that the users can customize and adapt the processing, according their specific requirements, by setting a list of configurable options. The configurable options are divided according to the processing level they refer to (L1b and L2). Here, you find them listed with a basic description of their significance.

L1b Processing Options:

Option Name	Option Value	Option Description
[Pre-Processing] Filter out Duplicated CryoSat-2 Products during the processing time	Enable Disable	Enable to filter out duplicated products during the processing. If activated, duplicated products (from different baselines) will not be processed: only the product with highest baseline rank will be processed.
Data Posting Rate 20Hz/80Hz	20 Hz 80 Hz	Flag to set the data posting rate: 20 Hz (canonical posting rate) or 80 Hz (finer posting rate). 20 Hz corresponds to a distance between samples of about 320 m and 80 Hz to about 80 m.
Hamming weighting Window	Apply only in coastal zone Yes, apply it No, do not apply it	Users can decide here whether to apply or not a Hamming weighting window on the SAR burst data or to apply it only for surface locations in coastal area (more info in REF2).
Beam-Forming	Approximated Exact	Users can decide here whether to operate an exact Beam-Forming or an approximated Beam-Forming (more info in REF2).
FFT Zero-Padding	Yes, apply Zero-Padding No, don’t apply Zero-Padding	Users can decide here whether to operate the Zero-Padding prior to the range FFT (section 4.8 in REF2). Zero-Padding is indicated for coastal zone and sea-ice analysis.
Radar Receiving Window Size	512Range Bins 1024 Range Bins	Users can select here the size of the radar receiving window: 512 range bins (standard) or 1024 range bins (extended). Extended window is indicated for coastal zone analysis.
Antenna Pattern Compensation	NO YES	Flag to activate the antenna pattern compensation on the Stack Data.
Dump SAR Stack Data in output	NO YES, with only power YES, with power and phase	Users can choose here to post in output SAR/SARIN Stack Data Products for each selected pass. Beware: SAR/SARIN Stack Data Products are quite bulky (usually one GB for medium-size product); we recommend to process SAR/SARIN Stack Data singularly or max 5 passes ata time: contact the P-PRO team for a massive production of SAR/SARIN Stack Data.

L2 Processing Options:

Option Name	Option Value	Option Description
Restrict the re-tracking on specific surfaces	Process all Process only open sea points Process only water points	Users can decide here whether to process the whole pass, only points in open sea or only water points (i.e., points in open sea, coastal zone and inland water).
PTR width alphap parameter	LUT Constant	Users can decide here whether to use a LUT (Look-Up Table) or a constant for the PTR (Point Target Response) alphap parameter.
SAMOSA Model Generation	Use SAMOSA 2 Use SAMOSA 3 Use SAMOSA+	Users can decide here which SAMOSA retracking model to use in the processing (SAMOSA 2 or SAMOSA 3 or SAMOSA+). The SAMOSA 3 is a truncated version of SAMOSA 2 (only zero-order term); more info in REF3. SAMOSA+ is the SAMOSA2 model tailored for inland water, sea ice and coastal zone domain; more info in REF4.
Single-Look or Multi-Look Model	Single-Look Multi-Look	Users can decide here to retrack the waveform with the multi-look waveform model or the single-look waveform model.. Single-Look option is indicated for quick runs over sea ice and inland water while Multi-Look is the most accurate and is advised for ocean applications.
Dump RIP in output	NO YES	Flag to append Range Integrated Power (RIP) in the output NetCDF data product.
Dump SAR Echo Waveforms in Output	NO YES	Users can choose here to append the SAR Echo Waveforms in the output product.
Choose the Default Tide Model	FES2004 FES2014b TPXO8 TPXO9	Flag to command the Default tide model used in the product (choose between FES2004, FES2014b, TPXO8, TPXO9).
Choose the Default Mean Sea Surface Model	DTU15 DTU18 CLS-CNES15	Flag to choose the Default mean sea surface model used in the product (choose between DTU15, DTU18, CLS-CNES15).

Adopted Conventions

The Reference Time for the TAI Datation is 01/01/2000 00:00:00
The Vertical Datum for altitude reference is the WGS84 Ellipsoid
The Curve Best-Fitting Scheme, used in the re-tracking stage, is a Bounded Levenberg-Marquardt Least-Squares Estimation Algorithm (LEVMAR-LSE).
The SAR Power Return Waveform Model, used in the re-tracking stage, is the SAMOSA Model (REF3)
Static bias has been applied to the range, sigma nought and antenna mispointing measurements. The values of the static biases are reported in the output NetCDF data products.
The orbital altitude has been corrected for a Time Tag Bias. The value of the applied time tag bias is reported in the output NetCDF data products.
The measurements are posted both at rate of 20 Hz/80 Hz and of 1 Hz.
The sea state bias correction has not been applied to the sea level anomaly estimates.
All the default geophysical path corrections are from the CryoSat-2 FBR products; refer to CryoSat-2 mission handbook to know the exact source of these corrections
No a priori data editing has been applied to the 20 Hz/80 Hz measurements.
The misfit between SAR Waveform Model and SAR Waveform Data has been computed as:

sqrt( 1/128*sum(residual)^2 )*100

where residuals are the differences between model’s waveform power and data’s waveform power, normalized for the waveform power’s maximum value.

Output Formats

The L2 data products generated in output are in standard NetCDF format (CF-convention), fully compatible with BRAT.

The file naming convention for those files is :

RES_FBR_INPUT_FILENAME.nc

where:

FBR_INPUT_FILENAME is the filename of the SAR FBR data file given in input

(for more details on the input filename, please check the product specification)

The NetCDF format is self-explanatory with all the data field significance described in the attributes.

Along with the NetCDF file, it is provided in output a .png picture of the radar data image (Radar Echogram) and a .kml file of the satellite pass ground-track.

Selecting the corresponding option, users can decide to post in output also the SAR Stack Data Products, still in NetCDF format.

The naming convention for those stack data products is :

STK_FBR_INPUT_FILENAME.nc

They will be held in the STACK folder inside the .tgz output package.

Opening SARvatore products in BRAT

SARvatore products can also be opened in the Broadview Radar Altimetry Toolbox (BRAT). However, when products are loaded, the track is not correctly displayed on the BRAT map and an error is reported:

Broadview Radar Altimetry Toolbox (BRAT).

The toolbox is able to read:

all altimetry data from official data centres (from ERS-1 and 2, Topex/Poseidon, Geosat Follow-on, Jason-1, Envisat, Jason-2, Cryosat and Sentinel-3, from Sensor Geophysical Data Record to gridded merged data);
any NetCDF file.

In the latter case, a small edit is needed to correctly visualize the track associated with the input products.

Considering SARvatore products, the NetCDF file is associated with the NETCDF_CF / Generic NetCdf Variant 1 format:

Broadview Radar Altimetry Toolbox (BRAT) 2

Therefore, to correctly display the track on the BRAT map, users shall close the program, open the bratXX/bin/data folder:

Broadview Radar Altimetry Toolbox (BRAT) Folder

and edit the aliases.xml file as follows in the Generic NetCdf Variant 1 section:

change the latitude to latitude_1Hz ;
change the longitude to longitude_1Hz;
change the time to time_counter_1Hz (or those at 20Hz);

Broadview Radar Altimetry Toolbox (BRAT) 3

Once the track is loaded again in BRAT, it will be correctly displayed and no error will be reported:

Broadview Radar Altimetry Toolbox (BRAT) 4

More information can be found in Chapter 5 of the BRAT user manual available here.

Afterwards, SARvatore products can be processed in BRAT using the Advanced option in the Operations menu.

Broadview Radar Altimetry Toolbox (BRAT) 5

To learn how to use BRAT, please consider the material available at the following links:

https://youtu.be/PdnSalcOUHA
https://www.youtube.com/watch?v=PdnSalcOUHA
or, equivalently, the material associated with the lesson: “SARvatore & BRAT Demos“.

Acronyms and References

Acronyms

SAR: Synthetic Aperture Radar
SARIN: Synthetic Aperture Radar Interferometry
WGS: World Geodetic System
EOP-SER: Earth Observation Programmes: Science, Exploitation, Research
CF: Climate & Forecast
FBR: Full Bit Rate
LUT: Look-Up Table
L1a: Level 1a
L1b: Level 1b

References

REF1: Dinardo S. and Benveniste J. (2013): Guidelines for the SAR (Delay-Doppler) L1b Processing; European Space Agency/ESRIN Report, issue 2.3, XCRY-GSEG-EOPS-TN-14-0042, available at: https://wiki.services.eoportal.org/tiki-download_wiki_attachment.php?attId=2540

REF2: Guidelines for the SAR (Delay-Doppler) L1b Processing, ESA, 2013, available here.

REF3: (SAMOSA Model Paper) Ray, Chris & Martin-Puig, Cristina & Clarizia, M.P. & Ruffini, Giulio & Dinardo, Salvatore & Gommenginger, Christine & Benveniste, Jerome. (2015). SAR Altimeter Backscattered Waveform Model. Geoscience and Remote Sensing, IEEE Transactions on. 53. 911-919. 10.1109/TGRS.2014.2330423

REF4: Dinardo, Salvatore & Fenoglio, Luciana & Buchhaupt, Christopher & Becker, Matthias & Scharroo, Remko & Joana Fernandes, M & Benveniste, Jérôme. (2017). Coastal SAR and PLRM altimetry in German Bight and West Baltic Sea. Advances in Space Research. 62. 10.1016/j.asr.2017.12.018.

How to request the service

To benefit from our services, we first invite you to register on the EarthConsole^® Webapp and thoroughly fill-in the P-PRO service request form. Note that in the service request form you are required to specify whether you want to request ESA sponsorship or not. Your selection will imply that you are choosing one of the following options:

Option 1 “Sponsorship Request via ESA NoR”

If you have a research, development or pre-commercial project, you may be eligible to submit a sponsoring request via the ESA NoR portal. If the sponsorship request will be approved, this would cover partially or totally the cost of the P-PRO service. To guide you through the sponsoring submission procedure, we have prepared this Step-by-Step Manual.

Once your sponsoring request will be approved by ESA, we will be able to activate your P-PRO service.

We encourage you to let us know in case you need administrative assistance at info@earthconsole.eu as we can help you fill-in the form. In any case, when you will submit your sponsoring request to ESA we recommend to keep support@earthconsole.eu, altimetry.info@esa.int and info@earthconsole.eu in cc to speed-up the evaluation process.

If you are not eligible to apply for a sponsorship via the NoR portal or in case of rejection, option n° 2 is always available.

Option 2 “Unsponsored Service Activation”

Following the request of the desired service via the EarthConsole^® Webapp, we will send you a quotation of the service for your approval together with the instructions to proceed with the payment.
The prices available in this pricing list cover most of the typical users’ requests. 15% discount is applicable to research, development, pre-commercial and educational projects. Special discounts can be applied in the case of requests for subscription plans. Ad-hoc quotations are available on-demand.

Contact Us

For any question, bug-reports or support on the processor, please contact the ESA Altimetry Team at: altimetry.info@esa.int.
For EarthConsole^TM P-PRO specific questions please contact: support@earthconsole.eu.

PROVIDER

SARINvatore for CS-2

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