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 through Copernicus EO Support.

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 may not be exhaustive.

For instance, we perform a systematic screening of the Sentinel-1 quicklooks to report the ones with residual Radio Frequency Interference (RFI). However, some weak RFI with small geographic extension may not be part of this reporting.

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 (Copernicus Data Space Ecosystem). 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. Two 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.

A reference map of burst ID is available on this site [here].

Please note that some products are impacted by improper annotation of burst ID (refer to quality disclaimers number 77 and 78 and follow on) due for instance to invalid annotations of date of stop of acquisition as time since ascending node crossing or other issues in the processing.

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

Other questions / topics

The following questions refers to the production rules and the usage of specific tools to manipulate Sentinel-1 products.

What is the instrument configuration ID (ICID) ?

The onboard configuration of Sentinel-1 SAR instrument is tuneable. This onboard configuration is named "instrument configuration", and each version of it has a specific identifier called "Instrument Configuration ID" (ICID) corresponding to a specific number. The change of ICID is motivated for instance by the activation of a redundancy, the redesign of the antenna pattern, or a change of FDBAQ configuration. Sentinel-1A used successively its ICID numbers 1 to 7 (at the date of July 2024), while Sentinel-1B used its ICID number 1 to 2 until its decommissioning. A change of ICID on one Sentinel-1 unit is not necessarily linked to a change of ICID on other Sentinel-1 units.

The latest update of ICID (at the date of July 2024) was related to an optimisation of the WV2 Elevation antenna applied both for S1A (leading to a change of ICID from 6 to 7 on 28 February 2019) and for S1B (leading to a change of ICID from 1 to 2 on 14 May 2019).

The details of the onboard SAR configuration are not public. However, the key parameters required for the processing of RAW data are part of the Sentinel-1 processor auxiliary data files (ADF), and more specifically to the AUX_INS, AUX_CAL, AUX_PP1, etc. Once a new processing configuration (new set of ADF) is defined, it is then endorsed by SAR-MPC for the various ICID it refers to. The set of processor ADF is available inter alia in the SAR MPC web site and as well accessible from a dedicated ADF REST API or from the Copernicus Data Space Ecosystem API.

The selection of the most appropriate processing ADF for a given Sentinel-1 RAW product is as follows:

If the ADF is not specific to a Sentinel-1 unit, it is prefixed by S1_ not annotating the unit (A, B, C, D), like for instance AUX_SCS:
1. Then the selection of the ADF is only based on the validity date of the RAW data vs the validity date and generation date of the available ADF
If the ADF is specific to a Sentinel-1 unit, it is prefixed by the S1A, or S1B, or S1C, etc, and the selection shall consider:
1. the Sentinel-1 unit: the Sentinel-1A ADF shall not be used for Sentinel-1B processing ;
2. the ICID matching the one of the RAW data ;
3. the ADF selection rule based on both the validity date and the generation date of the ADF. Each ADF may be assigned to a specific selection rule. For what concerns the AUX INS/CAL/PP1/PP2/ML2, the selection rule is called LatestValCover (status on July 2024), meaning that among the ADF having a start validity date before the start of the RAW product acquisition, the latest generated one shall be considered.

The SAR-MPC ADF REST API provides a way to select the proper ADF knowing the ICID and the validity date of a RAW product.

The SAR-MPC pages on ADF diffusion (for instance for AUX_PP1) allow selecting ADF for a given unit (S1A, S1B...), instrument configuration ID, validity date and an "active" flag. The ADF not marked as "active" are considered as outdated as they cannot be selected for the processing considering the selection rules exposed above and the set of ADF available at the date of today.

The ICID assigned to a given RAW product can be found in its manifest by looking for the following element:

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