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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) and 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.

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.

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.

Learn more about Sentinel-1

Type

Earth Observation Satellite

Data Center

ASF DAAC

Launch

Sentinel-1A - April 3, 2014
Sentinel-1B - April 25, 2016

Objective

Land and Ocean Monitoring
Dataset PropertyStrip Map (SM) modeInterferometric Wide (IW) modeExtra Wide (EW) modeWave (WV) mode
Temporal Coverage12 Days12 Days12 Days12 Days
Spatial CoverageGlobalGlobalGlobalGlobal
Center FrequencyC-band at 5.405 GHzC-band at 5.405 GHzC-band at 5.405 GHzC-band at 5.405 GHz
PolarizationSingle Polarization (HH or VV)
Dual Polarization (HH+HV or VV+VH)		Single Polarization (HH or VV)
Dual Polarization (HH+HV or VV+VH)		Single Polarization (HH or VV)
Dual Polarization (HH+HV or VV+VH)		Single Polarization (HH or VV)
Dual Polarization (HH+HV or VV+VH)
Spatial Resolution5 x 5 m5 x 20 m20 x 40 m5 x 5 m
Swath Width80 km250 km410 km100 km
Off-Nadir Angle18.3° to 46.8°29.1° to 46.0°18.9° to 47.0°21.6° to 45.1° and 34.8° to 38.0°
File formatSAFESAFESAFESAFE
ProviderEuropean Space AgencyEuropean Space AgencyEuropean Space AgencyEuropean Space Agency
Date published:2014201420142014

 

Instrument NameOperational Date(s)Spectral ResolutionType of Instrument
Sentinel-1 C-band synthetic aperture radar (SAR)20141 nm-180nmImaging Radar
SAR ModeInterferometric Wide Swath (IW)Extra Wide Swath (EW)
DetailsAcquired with TOPSAR. Default mode over land; 250km swath width; 5m-x-20m ground resolution.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.

Users of Sentinel data may see quality issues similar to those below. Users are encouraged to submit examples of image-quality issues to uso@asf.alaska.edu.

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.

[image]

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).

[images]

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.

[image]

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).

[image]

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.

[image]

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.

The figure below illustrates the Sentinel-1 granule naming convention. For more information, see the Sentinel-1 Technical Guide.

Graphic showing the various elements of granule naming.

Sentinel-1 granule naming convention

Orbit Files and Auxilliary Data Files

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) and Restituted Orbit files (available a few hours after data acquisition). Flight Operation Segment (FOS) Predicted Orbit files (available seven days before data acquisition), Instrument Processing Facility (IPF) auxiliary files, L1 Processor Parameters, L2 Processor Parameters, Instrument, Calibration, and Simulated Cross Spectra Auxiliary Data are also available.

Access to Sentinel-1 ephemeris files and documentation:

Guide to File Names

IPF Auxiliary Data FilesName
L1 Processor Parametersaux_pp1
Calibration Auxiliary Dataaux_cal
Instrument Auxiliary Dataaux_ins
L2 Processor Parametersaux_pp2
Orbit FilesName
FOS Predicted Orbitmpl_orbpre
POD Precise Orbit Ephemeridesaux_poeorb
POD Restituted Orbitaux_resorb
POD Restitude Attitudeaux_resatt

Frequently Asked Questions

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