How to ask questions on Sentinel-1 product performance?

The support to users of Sentinel-1 data and products is provided by the ESA for Copernicus products. This service can be contacted from the main page of the Copernicus Open Access Hub

This service may request support to the SAR Mission Performance Cluster (SAR-MPC) for questions related to the Sentinel-1 product performance. Below is a list of frequently asked questions.

Questions related to product performance

 


Where can I find list of products impacted by performance degradation?

The SAR-MPC web site contains a list of Quality Disclaimers

Each quality disclaimer describes the type of product impacted by the performance degradation, the cause of the anomaly, and when possible, the list of product names impacted by the product anomaly.

Please notice that only the most impacting anomalies are listed here, and that the list is not exhaustive.  For instance, there is no exhaustive list of products impacted by Radio Frequency Interference (RFI).

 


How to interpret the RFI annotations?

Since deployment of the SAR processor IPF 3.40 on the 4th of November 2021, each Sentinel-1 L1 product contains a set of annotation related to the Radio Frequency Interference (RFI) mitigation process.

This annotation can be used to spot products impacted by RFI. The way to interpret this specific annotation is explained in a dedicated document: "Sentinel-1: Using the RFI annotations"

However, please consider that the RFI mitigation implemented in the SAR processor may not be able to detect and mitigate all of them.

 


Why is there a missing file in a Sentinel-1 product?

A Sentinel-1 product is composed of a manifest file referencing annotation, support files, and data files.

The SAR processor makes such that all the required files are generated, and a set of quality control tools are operated online (just after the production of the products) and off line (with delay) to ensure the products complies to their specification and contains all the required files.

The Level 1 and Level 2 products made available to the end-users are provided together with a small PDF report containing the list of basic QC tests performed online, including their completeness.

However, some issues may occur between the production of the products and their dissemination to the data access hubs (scihub). This may be associated to missing files in some products.

In such situation it is recommended to contact the ESA User Support and EO Helpdesk (refer to the link on top of this page)

 


Availability of a burst ID Map

Since deployment of the SAR processor (S1 IPF) in version 3.40 on 4th November 2021, the Sentinel-1 SLC products for EW and IW modes contain a specific annotation of burst ID. To sets of bursts ID are provided corresponding to absolute and relative burst ID. Those ID are designed to support the users of SLC products, with each ID corresponding to the acquisition over a specific location, with a specific sub swath. A burst ID can be useful inter alia for indexing of the bursts, and requesting the bursts by ID, which requires to use a global map of burst ID.

Currently, such map of burst ID is not available. This map is under preparation and will be made available through this site once available.

Please note that some products are impacted by improper annotation of burst ID (refer to quality disclaimers number 77 and 78) due to invalid annotation of date of stop of acquisition as time since ascending node crossing.

 

Other questions / topics

 

One product is missing at a specific period

The Sentinel-1 SAR instrument is not operated during complete orbits of the spacecraft. The data are only acquired for specific areas for which predefined acquisition modes are operated. The Observation Scenario implements a baseline pre-defined mission observation scenario, making optimum use of the SAR duty cycle within the technical constraints of the overall system. This observation scenario evolves with time. Some products may not be acquired during a specific period due to changes of the scenario.

 


One Level 1 (or Level 2) product is missing while the Level 0 is available

The level 1 (and Level 2) products are generated by the Sentinel-1 IPF based on the SAR Level 0 products. The Level 0 products correspond to the RAW data acquired by the SAR instrument.

The Level 0 products may be impacted by anomalies associated to issues with the instrument or with issues with the downlink to the ground. This includes for instance missing data, data gaps, corrupted data, etc

The SAR processor (S-1 IPF) can to accommodate for Level 0 products impacted with a certain level of such anomalies. However, if the number of corrupted elements in the Level 0 products is too high, the SAR processor will not succeed in generating the corresponding Level 1 data and hence the Level 2 data. In such situation the Level 0 product may be available to the users, while the corresponding Level 1 and Level 2 products are not available.

 


My image is flipped in SNAP

 

SNAP displays by default the SAR images with time increasing in both range and azimuth directions corresponding to the sensor observation geometry. This does not correspond to a north-south, west-east projection of the scene.

For any question related to the usage of SNAP, we recommend having a look to the Step Forum for Sentinel-1

 


I have a specific question on product performance

 

The support to users of Sentinel-1 data and products is provided by the ESA for Copernicus products. This service can be contacted from the main page of the Copernicus Open Access Hub

The questions related to product performances will be forwarded to SAR Mission Performance Cluster