Sentinel-1
NASA’s provision of the complete ESA Sentinel-1 synthetic aperture radar (SAR) data archive through the ASF DAAC is by agreement between the U.S. State Department and the European Commission (EC). As part of the Earth-observation Copernicus program, the Sentinel mission will provide scientists with accurate, timely, and easily accessible information to help shape the future of our planet. Content on ASF’s Sentinel web pages is adapted from the ESA Sentinel-1 website.
Overview
The Sentinels are a fleet of European Space Agency (ESA) satellites designed to acquire measurements from multiple sensor types that will provide information necessary to meet Europe’s Copernicus program objectives.
The first mission in the series, the Sentinel-1 constellation, includes twin satellites that each carry C-band synthetic aperture radar (SAR) which together provide all-weather, day-and-night imagery of Earth’s surface.
Sentinel-1A was launched on 3 April 2014, and Sentinel-1B on 25 April 2016. They orbit 180° apart, together imaging the Earth every six days.
In December 2021, an anomaly in the power supply of Sentinel-1B caused the SAR sensor to stop working. Attempts to restore power to the sensor failed, and the mission officially ended on August 3, 2022.
| Dataset Property | Value |
|---|---|
| Temporal Coverage | 12 Days |
| Spatial Coverage | Global |
| Beam Mode | Strip Map (SM) Interferometric Wide (IW) Extra-Wide (EW) Wave (WV) |
| Center Frequency | C-band at 5.405 GHz |
| Polarization | Single Polarization (HH or VV) Dual Polarization (HH+HV or VV+VH) |
| Spatial Resolution | SM – 5 x 5 m IW – 5 x 20 m EW – 20 x 40 m WV – 5 x 5 m |
| Swath Width | SM – 80 km IW – 250 km EW – 410 km WV – 100 km |
| Off-Nadir Angle | SM – 18.3° to 46.8° IW – 29.1° to 46.0° EW – 18.9° to 47.0° WV – 21.6° to 45.1° and 34.8° to 38.0° |
| Download info | https://asf.alaska.edu/how-to/data-basics/asf-services-data-discovery/ |
| File format | SAFE |
| Provider | European Space Agency |
| Date published: | 3 April 2014 |
The loss of one of the Sentinel-1 satellites means that the frequency of observations and global coverage will be significantly reduced until the launch and commissioning of Sentinel-1C. This is predicted to be completed in the third quarter of 2023. Sentinel-1B will be deorbited at this time.
The Sentinel-1 constellation benefits numerous services, such as monitoring of Arctic sea-ice extent, routine sea-ice mapping, and surveillance of the marine environment. Applications include oil-spill monitoring and ship detection for maritime security; monitoring land-surface for motion risks; mapping for forest, water, and soil management; and mapping to support humanitarian aid and crisis situations.
Updated August 22, 2022
International Collaboration
Sentinel-1 is the result of close collaboration among ESA, the European Commission, industry, service providers, and data users.
NASA’s provision of the complete ESA Sentinel-1 SAR data archive through the ASF DAAC is by agreement between the U.S. State Department and the European Commission (EC). As part of the Earth-observation Copernicus program, the Sentinel mission will provide scientists with accurate, timely, and easily accessible information to help shape the future of our planet.
Content on ASF’s Sentinel web pages is adapted from ESA’s Sentinel website.
User Guide/Technical Information
Sentinel-1A and Sentinel-1B satellites carry C-band SAR instruments to provide an all-weather, day-and-night supply of imagery of Earth’s entire surface every 6 days.
Instrument information
Launches:
- Sentinel-1B: Soyuz rocket, launched 25 April 2016, from Kourou, French Guiana
- Sentinel-1A: Soyuz rocket, launched 3 April 2014, from Kourou, French Guiana
Orbit: Polar, sun-synchronous at an altitude of 693 km
Revisit time: Six days with two-satellite constellation of Sentinel-1A and 1B. Before 1B launched, revisit time for Sentinel-1A alone was 12 days.
Instrument: C-band synthetic aperture radar (SAR) at 5.405 GHz
- Interferometric wide-swath (IW) at 250 km and 5×20 m resolution, using TOPSAR
- Wave (WV) images of 20×20 km and 5×5 m resolution (at 100 km intervals)
- Stripmap (SM) at 80 km swath and 5×5 m resolution
- Extra wide swath (EW) of 400 km and 20×40 m resolution, using TOPSAR
- Supports operation in single polarization (HH or VV) and dual polarization (HH+HV or VV+VH)
- Polarization implemented through one transmit chain (switchable to H or V) and two parallel receive chains for H and V polarization
- SM, IW and EW are available in single (HH or VV) or dual polarization (HH+HV or VV+VH)
- WV is single polarization only (HH or VV)
Receiving stations: SAR data: Svalbard, Norway; Matera, Italy; Maspalomas, Spain; and via laser link through EDRS (European Data Relay System)
Telemetry, tracking and command: via Kiruna, Sweden
Main applications: Monitoring sea ice, oil spills, marine winds and waves, land-use change, land deformation, and to respond to emergencies such as floods and earthquakes
Mission: Developed, operated, and managed by various ESA establishments
Life: Minimum of seven years
Satellites: 2.8 m long, 2.5 m wide, 4 m high with 2×10 m-long solar arrays and a 12 m-long radar antenna
Mass: 2300 kg (including 130 kg fuel)
Funding: ESA Member States and the European Union Prime contractors: Thales Alenia Space, Italy, for the satellite; Airbus Defence and Space, Germany, for the SAR instrument
Content on ASF’s Sentinel web pages is adapted from the European Space Agency (ESA) Sentinel website.
SAR Modes
Links in the table below open to ESA’s website for more information.
| SAR Mode | Extra Wide Swath (EW) | Interferometric Wide Swath (IW) | Stripmap (SM) | Wave (WV) |
|---|---|---|---|---|
| Details | Acquired with TOPSAR using 5 sub-swaths instead of 3, resulting in lower resolution (20m-x-40m). Intended for maritime, ice, and polar-zone services requiring wide coverage and short revisit times. | Acquired with TOPSAR. Default mode over land; 250km swath width; 5m-x-20m ground resolution. | Used in rare circumstances to support emergency-management services, 5m-x-5m resolution over an 80km swath width. | Default mode over oceans; VV polarization. Data acquired in 20km-x-20km vignettes, 5m-x-20m resolution, every 100km along the orbit. |
Image Quality
Users of Sentinel data may see quality issues similar to those below. Users are encouraged to submit examples of image-quality issues to [email protected].
Browse images affected by map projection
When an image granule is located above 65° latitude, the browse image can appear to be oriented and shaped differently than its outline in Vertex. The browse image is a geocoded JPEG displayed in a polar stereo map projection at latitudes above 65° in either hemisphere. The Vertex map always displays a granule in a Mercator projection. The examples show a Vertex map outline of a granule in the Arctic Ocean and an associated browse image. The browse image also is an example of stepped ends.
Images from data close to the noise floor
Images that contain a great deal of noise have often been processed close to the noise floor (the data closest to the point where it is too noisy to be useful). The noise can look like repeating lines across an image, something like horizontal window blinds, as in the left image below. Those repeating lines are not the same as the bright spots in these images, which appear in the image below and to the right as a line of repeated bright spots or bursts. Those bright bursts are image anomalies that are not yet well understood. Also visible in these images are beam seams (see the next section).
Beam seams
When one image is made up of several beams, the seams can show, particularly in dark data. Beam seams are visible in many of the images on this page, including the one to the right.
Offsets between channels
Beams that seem to have noisy or missing data at one end, such as the dark blue edge at the top of the image, have been processed in one channel more than another (such as the HV or VH channels).
Stepped edges
Stepped ends, as in this image, are an artifact of the multi-beam scanning technology of TOPSAR and the way that ESA “slices” a data take into discrete, manageable units.
Bright burst
Bright bursts are processing anomalies that are not well understood. Bright bursts are in the upper left corner of the image below at left and in the light stripe across the image below right. Also visible in the image on the left are noise (window-blind effect), beam seams, and a bit of blue on the far left that may indicate an offset between channels.
Sentinel-1 Documents
| Name | Description |
|---|---|
| Product Specification Document, ASF | Defines the ISO-compliant XML metadata for ESA’s Sentinel-1A data. |
| Sentinel-1 SAR User Guide Introduction | High-level description of instrument modes and products. Also introduction to relevant application areas, information on data distribution, product formatting, and software tools available from ESA. |
| Sentinel-1 Technical Guide | Covers an in-depth description of the mission’s products and algorithms as well as details of the SAR instrument and its performance. |
| Sentinel High Level Observation Plan, Issue 2, Revision 1 | Provides the top-level operations plan of the Sentinel missions, including space and ground segments. |
| Sentinels POD Service File Format Specifications | Useful for InSAR. Users who consult this document may also want Precision State Vectors, available from ASF from 3 September 2015. The product handbook describes the products generated as part of the provisioning of the Copernicus POD Service. |
| Sentinel Document Library | The full document library is available on the ESA website. |
Sentinel-1 Tools
| Name | Description |
|---|---|
| Sentinel-1 Toolbox (S1TBX) | Processing tools, data product readers and writers, and a display and analysis application to support the large archive of data from ESA SAR missions, including Sentinel-1, ERS-1 and -2, and Envisat, as well as third-party SAR data from ALOS PALSAR, TerraSAR-X, COSMO-SkyMed and RADARSAT-2. |
| ESA Sentinel App, for iOS and Android. | Powerful visualization of Sentinel product availability. Track the satellites in real time over a 3D globe, see the last and next time they have been and will be over the user’s location, and more. |
| PolSARpro | The Polarimetric SAR Data Processing and Educational Tool facilitates the accessibility and exploitation of multi-polarised SAR datasets. A wide range of tutorials and comprehensive documentation provides a grounding in polarimetry and polarimetric interferometry necessary to stimulate research and development of scientific applications; the toolbox of processing functions offers users the capability to implement them. |
| Other Tools | Other tools include a basic radar altimetry toolbox (BRAT), a data browser capable of exploring many product types in their native form (Derby), and more. |
Naming Convention
The figure below illustrates the Sentinel-1 granule naming convention. For more information, see the Sentinel-1 Technical Guide. Additional resources are listed under the Documents and Tools tab below.
Orbit Files and Auxilliary Data Files
Notes:
- The Precise Orbit Determination (POD) service for Sentinel-1 provides orbit ephemerides files in the form of Precise Orbit Ephemerides files (available 20 days after data acquisition), Restituted Orbit files (available a few hours after data acquisition). Flight Operation Segment (FOS) Predicted Orbit files (available seven days prior to data acquisition), and Instrument Processing Facility (IPF) auxiliary files L1 Processor Parameters, L2 Processor Parameters, Instrument, Calibration, and Simulated Cross Spectra Auxiliary Data are also available.
- Users of these vectors may want to refer to the Sentinels POD Service File Format Specifications available on the Documents and Tools tab below
Sentinel-1 Orbit Files at ASF
Sentinel-1 Orbit Files at ESA
ESA Sentinel-1 Quality Control page.
Guide to File Names
| IPF Auxiliary Data Files | Name |
|---|---|
| L1 Processor Parameters | aux_pp1 |
| Calibration Auxiliary Data | aux_cal |
| Instrument Auxiliary Data | aux_ins |
| L2 Processor Parameters | aux_pp2 |
| Orbit Files | Name |
|---|---|
| FOS Predicted Orbit | mpl_orbpre |
| POD Precise Orbit Ephemerides | aux_poeorb |
| POD Restituted Orbit | aux_resorb |
| POD Restitude Attitude | aux_resatt |
Content on ASF’s Sentinel web pages is adapted from the European Space Agency (ESA) Sentinel website.
Citing Sentinel-1 Data & Imagery
Sentinel-1 Data
Cite datasets in publications such as journal papers, articles, presentations, posters, and websites. For more information, see Terms and Conditions. Please send copies of, or links to, published works citing data, imagery, or tools accessed through ASF to [email protected] with “New Publication” on subject line.
| Type | Format | Example |
|---|---|---|
| Primary Data | Copernicus Sentinel data [year of data acquisition]. Retrieved from ASF DAAC [day month year of data access], processed by ESA. | Copernicus Sentinel data [year of data acquisition]. Retrieved from ASF DAAC [day month year of data access], processed by ESA. |
| Modified Data | [creator credit, year created], contains modified Copernicus Sentinel data [year of data acquisition], processed by ESA. | ASF DAAC 2015, contains modified Copernicus Sentinel data 2015, processed by ESA. |
Sentinel-1 Imagery
Include appropriate credit with each image shown in publications such as journal papers, articles, presentations, posters, and websites.
| Type | Format | Example |
|---|---|---|
| Primary Data | Copernicus Sentinel data [year of data acquisition], processed by ESA. | Copernicus Sentinel data 2015, processed by ESA. |
| Modified Data | [creator credit, year created], contains modified Copernicus Sentinel data [year of data acquisition], processed by ESA. | ASF DAAC 2015, contains modified Copernicus Sentinel data 2015, processed by ESA. |
Sentinel legal notice with Terms and Conditions
European Space Agency Legal Notice on the Use of Copernicus Sentinel Data and Service Information
The access and use of Copernicus Sentinel Data and Service Information is regulated under EU law.1 In particular, the law provides that users shall have a free, full and open access to Copernicus Sentinel Data2 and Service Information without any express or implied warranty, including as regards quality and suitability for any purpose.3
EU law grants free access to Copernicus Sentinel Data and Service Information for the purpose of the following use in so far as it is lawful4 :
(a) reproduction;
(b) distribution;
(c) communication to the public;
(d) adaptation, modification and combination with other data and information;
(e) any combination of points (a) to (d).
EU law allows for specific limitations of access and use in the rare cases of security concerns, protection of third party rights or risk of service disruption.
By using Sentinel Data or Service Information the user acknowledges that these conditions are applicable to him/her and that the user renounces to any claims for damages against the European Union and the providers of the said Data and Information. The scope of this waiver encompasses any dispute, including contracts and torts claims, that might be filed in court, in arbitration or in any other form of dispute settlement.
Where the user communicates to the public or distributes Copernicus Sentinel Data and Service Information, he/she shall inform the recipients of the source of that Data and Information by using the following notice5 :
- ‘Copernicus Sentinel data [Year]’ for Sentinel data; and/or
- ‘Copernicus Service information [Year]’ for Copernicus Service Information.
Where the Copernicus Sentinel Data and Service Information have been adapted or modified, the user shall provide the following notice:
- ‘Contains modified Copernicus Sentinel data [Year]’ for Sentinel data; and/or
- ‘Contains modified Copernicus Service information [Year]’ for Copernicus Service Information.
The users’ rights on their personal data are protected under European law6. Such data will only be used by the European Commission and the providers of the said Data and Information for providing services to the user and for statistical as well as evaluation purposes.
1 Regulation (EU) No 377/2014 and Commission Delegated Regulation (EU) No 1159/2013.
2 In agreement with the Copernicus Sentinel Data Policy, ESA/PB-EO(2013)30, rev. 1.
3 See in particular Art. 3 and 9 of Regulation 1159/2013.
4 See in particular Art. 7 of Regulation 1159/2013.
5 See in particular Art. 8 of Regulation 1159/2013.
6 Directive 95/46/EC of the European Parliament and of the Council of 24 October 1995 on the protection of individuals with regard to the processing of personal data and on the free movement of such data; Regulation (EC) No 45/2001 (EC) No 45/2001 of the European Parliament and of the Council of 18 December 2000 on the protection of individuals with regard to the processing of personal data by the Community institutions and bodies and on the free movement of such data.
Discover Sentinel-1 data
Alaska Satellite Facility (ASF) DAAC
ASF maintains a complete archive of processed Sentinel-1 data, available within three days of acquisition. Registration is required, and terms and conditions apply.
European Space Agency (ESA)
Sentinel-1 data are available from ESA from a Rolling Archive that delivers data within 24 hours of acquisition and maintains recent months of data. Registration is required, and terms and conditions apply.
| Data Discovery Tool | Link |
|---|---|
| ASF Vertex Data Search | Vertex |
| Python Search Module | asf_search |
| ASF Search API | ASF Search API |
| NASA Earthdata Search | Earthdata Search |
Learn more about ASF data discovery services
Note:
Search results for Sentinel granules are bundled, so regardless of the processing level of the original search granule (RAW, SLC, GRD or OCN), all other related granules are shown as well. The search result list for any selected granule includes the ground range detected (GRD) product, because the associated GRD browse image, when available, provides the user with the most accurate information about the data coverage.