Sentinel-1

The first satellite, Sentinel-1A, launched on 3 April 2014, and Sentinel-1B was launched on 25 April 2016. Both satellites lifted off from the Guiana Space Centre in Kourou, French Guiana on a Soyuz rocket.{{Cite news |url=http://www.arianespace.com/vehicle/soyuz/ |title=Soyuz overview |publisher=Arianespace |access-date=21 March 2018}} Sentinel-1D is in development.{{cite web |last=Foust |first=Jeff |url=https://spacenews.com/esa-considering-moving-up-radar-satellite-launch-after-sentinel-1b-malfunction/ |title=ESA considering moving up radar satellite launch after Sentinel-1B malfunction |work=SpaceNews |date=18 January 2022 |access-date=19 January 2022}} An equipment failure on Sentinel-1B in December 2021 accelerated work on Sentinel-1C,{{cite web |url=https://www.romsenter.no/Aktuelt/Siste-nytt/Oppdraget-over-for-radarsatellitten-Sentinel-1B |title=Oppdraget over for radarsatellitten Sentinel-1B |trans-title=Mission over for the Sentinel-1B radar satellite |work=Norwegian Space Agency |date=12 August 2022 |access-date=14 September 2022 |language=norwegian |archive-date=13 August 2022 |archive-url=https://web.archive.org/web/20220813011327/https://www.romsenter.no/Aktuelt/Siste-nytt/Oppdraget-over-for-radarsatellitten-Sentinel-1B |url-status=dead }} which has been successfully launched in December 2024.[https://webapps.itc.utwente.nl/Sensor/getsat.aspx?name=Sentinel-1C Sentinel-1C]

The satellites have a Sun-synchronous, near-polar (98.18° inclination) orbit. Their orbits have a 12-day repeat cycle and complete 175 orbits per cycle (having a 98.6 minute orbital period). The satellites operate at {{convert|693|km|mi|abbr=on}} altitude, with 3-axis altitude stabilization.

The European Space Agency and European Commission's policies makes Sentinel-1's data easily accessible. Various users can acquire the data and use it for public, scientific, or commercial purposes for free.

{{Technical|date=May 2024|section}}

Sentinel-1 spacecraft are designed to carry a C-band synthetic-aperture radar (C-SAR) instrument which provides a collection of data in all-weather, day or night, as well as an SDRAM-based Data Storage and Handling Assembly (DSHA).{{cite web |url=https://sentinel.esa.int/web/sentinel/missions/sentinel-1/instrument-payload |title=Sentinel-1: Instrument Payload |series=Sentinel Online |publisher=European Space Agency |access-date=7 March 2017}}

The single C-SAR instrument with its electronics provides 1 dB radiometric accuracy with a central frequency at 5.405 GHz.{{cite journal |url=http://www.esa.int/esapub/bulletin/bulletin131/bul131a_attema.pdf |title=Sentinel-1: The Radar Mission for GMES Operational Land and Sea Services |journal=Bulletin |first1=Evert |last1=Attema |first2=Piere |last2=Bargellini |first3=Peter |last3=Edwards |first4=Guido |last4=Levrini |first5=Svein |last5=Lokas |first6=Ludwig |last6=Moeller |first7=Betlem |last7=Rosich-Tell |first8=Patrizia |last8=Secchi |first9=Ramon |last9=Torres |first10=Malcolm |last10=Davidson |first11=Paul |last11=Snoeij |display-authors=1 |volume=131 |pages=10–17 |date=August 2007|bibcode=2007ESABu.131...10A }} This instrument has a spatial resolution down to {{Convert|5|m|ft|abbr=on}} and a swath of up to {{Convert|410|km|mi|abbr=on}}.{{Cite web |title=User Guides - Sentinel-1 SAR - Extra Wide Swath - Sentinel Online |url=https://copernicus.eu/user-guides/sentinel-1-sar/acquisition-modes/extra-wide-swath |access-date=2023-04-26 |website=Sentinel Online |language=en-US }}{{Dead link|date=December 2024 |bot=InternetArchiveBot |fix-attempted=yes }} The data collected in C-SAR was made to be continuous after the termination of a previous mission (Envisat mission).{{Cite web |title=Sentinel-1 - ESA EO Missions - Earth Online - ESA |url=https://earth.esa.int/web/guest/missions/esa-operational-eo-missions/sentinel-1 |access-date=2020-03-05 |website=earth.esa.int}}

The DSHA has an active data storage capacity of about 1,443 Gbit (168 GiB), receiving data streams from SAR-SES over two independent links gathering SAR_H and SAR_V polarization, with a variable data rate up to 640 Mbit/s on each link, and providing 520 Mbit/s X-band fixed-user data-downlink capability over two independent channels towards ground.

File:Sentinel-1B’s first image ESA359682.jpg over the Barents Sea. The Svalbard archipelago is visible on the left side.]]

Sentinel-1 has four operational modes and four types of data products available. All data levels are publicly available for free online within 24 hours of observation.{{Cite web |title=Sentinel-1 - Data Distribution Schedule - Missions - Sentinel Online |url=https://sentinel.esa.int/web/sentinel/missions/sentinel-1/data-distribution-schedule |access-date=2020-03-05 |website=sentinel.esa.int}}

The four operational modes offered by Sentinel-1 are:{{Cite web |url=https://sentinel.esa.int/web/sentinel/user-guides/sentinel-1-sar/acquisition-modes |title=User Guides - Sentinel-1 SAR - Acquisition Modes |series=Sentinel Online |publisher=European Space Agency |access-date=12 March 2018}}{{Cite web |url=https://sentinel.esa.int/documents/247904/1653440/Sentinel-1_Data_Access_and_Products |title=Sentinel 1 Data Access and Products |publisher=European Space Agency |date=March 2015 |access-date=11 March 2018}}

• Strip Map (SM) Mode, which features {{convert|5|by|5|m|ft|adj=on}} spatial resolution and an {{convert|80|km|mi|abbr=on}} swath. The sole uses of SM are to monitor small islands as well as emergency management for extraordinary events upon request. Data products are offered in single (HH or VV) or double (HH + HV or VV + VH) polarization.
• Interferometric Wide Swath (IW) Mode, featuring {{convert|5|by|20|m|ft|adj=on}} spatial resolution and a {{convert|250|km|mi|abbr=on}} swath. IW is the main operational mode over land and accomplishes interferometry through burst synchronization. Data products are offered in single (HH or VV) or double (HH + HV or VV + VH) polarization.
• Extra Wide Swath (EW) Mode, featuring {{convert|20|by|40|m|ft|adj=on}} spatial resolution and a {{convert|400|km|mi|abbr=on}} swath. EW is used mainly to monitor wide coastal areas for phenomena such as shipping traffic and potential environmental hazards like oil spills or changes in sea ice. Data products are available in single (HH or VV) or double (HH + HV or VV + VH) polarization.
• Wave (WV) Mode, which features {{convert|5|by|5|m|ft|adj=on}} resolution and a low data rate. It produces {{convert|20|by|20|km|mi|abbr=on}} sample images along the orbit at intervals of {{convert|100|km|mi|abbr=on}}. This is the main operational mode over open ocean, with data offered only in single (HH or VV) polarization.

The four types of data products offered by Sentinel-1 are:

• Raw Level 0 data
• Processed Level 1 Single Look Complex (SLC) data, which consists of complex images with phase and amplitude of specified areas
• Ground Range Detected (GRD) Level 1 data, which is only systematically distributed multi-looked intensity
• Level 2 Ocean (OCN) data, consisting of systematically distributed data of the ocean's geophysical parameters

File:Irish mosaic ESA358799.jpg land cover derived from Sentinel-1A data]]

There are a wide range of applications for the data collected via the Sentinel-1 mission, including marine and land monitoring, emergency response to environmental disasters, and economic applications. A major goal of the mission was to provide C-Band SAR data. Sentinel-1 provides continuity of data from the ERS and Envisat missions, with further enhancements in terms of revisit, coverage, timeliness and reliability of service. Recently, Sentinel-1 has worked in conjunction with SMAP to help achieve a more accurate measure of soil moisture estimates.{{Cite journal |last1=Lievens |first1=H. |last2=Reichle |first2=R. H. |last3=Liu |first3=Q. |last4=De Lannoy |first4=G. J. M. |last5=Dunbar |first5=R. S. |last6=Kim |first6=S. B. |last7=Das |first7=N. N. |last8=Cosh |first8=M. |last9=Walker |first9=J. P. |date=2017-06-27 |title=Joint Sentinel-1 and SMAP data assimilation to improve soil moisture estimates |journal=Geophysical Research Letters |volume=44 |issue=12 |pages=6145–6153 |bibcode=2017GeoRL..44.6145L |doi=10.1002/2017gl073904 |issn=0094-8276 |pmc=5896568 |pmid=29657343}} Observations from both instruments show them to be complementary of each other as they combine data of soil moisture contents.

A summary of the main applications of Sentinel-1 include:{{Cite web |url=https://sentinel.esa.int/web/sentinel/user-guides/sentinel-1-sar/applications |title=User Guides - Sentinel-1 SAR - Applications |series=Sentinel Online |publisher=European Space Agency |access-date=22 March 2018}}

• Marine monitoring: Sea-ice levels and conditions, oil spills, ship activity, and information about marine winds
• Land monitoring: Agriculture, forestry, and land subsidence
• Emergency response: Flooding, landslides, volcanoes and earthquakes

The C-SAR instrument is capable of measuring land subsidence through the creation of interferometric synthetic-aperture radar (InSAR) images. The analysis of phase changes between two or more synthetic aperture radar images taken at different times is able to create maps of the digital elevation and measure the land surface deformation of an area. High spatial (20m) and temporal (6 days) resolutions allow Sentinel-1 to improve on current InSAR techniques and provide systematic continuity to the data.{{Cite journal|last1=Cian|first1=Fabio|last2=Blasco|first2=José Manuel Delgado|last3=Carrera|first3=Lorenzo|date=March 2019|title=Sentinel-1 for Monitoring Land Subsidence of Coastal Cities in Africa Using PSInSAR: A Methodology Based on the Integration of SNAP and StaMPS|journal=Geosciences|language=en|volume=9|issue=3|pages=124|doi=10.3390/geosciences9030124|bibcode=2019Geosc...9..124C|doi-access=free}}

Shortly after the August 2014 South Napa earthquake, data collected by Sentinel-1A was used to develop an interferometric synthetic-aperture radar, or InSAR, image of the affected region. The Sentinel-1 satellites are expected to make analysis of earthquakes using InSAR techniques quicker and simpler.{{cite news |url=https://www.bbc.com/news/science-environment-29012588 |title=Sentinel system pictures Napa quake |work=BBC News |first=Jonathan |last=Amos |date=2 September 2014 |access-date=2 September 2014}}

File:Antarctic Peninsula ice flow ESA360217.jpg created from Sentinel-1A data]]

The prime contractor of the mission is Thales Alenia Space Italy, with whole system integration and also with production of platform Spacecraft Management Unit (SMU) and payload Data Storage and Handling Assembly (DSHA). Sentinel-1A was constructed in Rome, Italy. Other technologies such as the T/R modules, the C-band synthetic-aperture radar antenna, the advanced data management and transmission subsystems, and the on-board computer, were developed in L'Aquila and Milan.{{cite web |url=https://www.thalesgroup.com/en/worldwide/space/press-release/sentinel-1a-arrives-launch-site-french-guiana |title=Sentinel-1A Arrives at Launch Site in French Guiana |publisher=Thales Group |date=24 February 2014 |access-date=15 March 2018}} The C-SAR instrument is the responsibility of Astrium Gmbh.

The ground segment prime contractor is Astrium with subcontractors Telespazio, WERUM, Advanced Computer Systems and Aresys. Final test verification of the satellite was completed at Thales Alenia Space's clean rooms in Rome and Cannes.

• Sentinel-1A – launched on 3 April 2014
• Sentinel-1B – launched on 25 April 2016, unavailable due to a power issue since 23 December 2021, mission end declared 3 August 2022
• Sentinel-1C – development contract signed with Thales Alenia Space of Italy in December 2015; the launch was scheduled for April 2023{{cite web |url=http://www.airpressonline.it/8562/decolla-la-space-economy-italiana/ |title=Decolla la space economy italiana |trans-title=Take off of the Italian space economy |publisher=Airpress |language=it |access-date=15 December 2015|date=2015-12-15 }} but was delayed due to a launch failure of Vega-C in December 2022.{{cite news |title=Carbon component blamed for Vega rocket loss |url=https://www.bbc.co.uk/news/science-environment-64838254 |access-date=4 August 2023 |work=BBC News |date=3 March 2023}} It was launched on 5 December 2024.{{cite web |last1=Foust |first1=Jeff |title=Europe considers launching Copernicus satellite on Falcon 9 |url=https://spacenews.com/europe-considers-launching-copernicus-satellite-on-falcon-9/ |website=SpaceNews |access-date=19 June 2024 |date=12 January 2024}}
• Sentinel-1D – development contract signed with Thales Alenia Space of Italy in December 2015. In November 2022, launch scheduled for the second half of 2024.{{cite press release |url=https://www.arianespace.com/press-release/arianespace-supporting-the-european-unions-copernicus-programme-with-vega-c/ |title=Arianespace supporting the European Union's Copernicus programme with Vega C |date=29 November 2022 |access-date=29 November 2022 |work=Arianespace}} In January 2025, ESA has signed a contract with Arianespace to launch the satellite in the second half of 2025 on Ariane 6.{{Cite web |title=Ariane 6 to take Sentinel-1D into orbit |url=https://www.esa.int/Applications/Observing_the_Earth/Copernicus/Sentinel-1/Ariane_6_to_take_Sentinel-1D_into_orbit |access-date=2025-04-06 |website=www.esa.int |language=en}}

Examples of images produced from Sentinel-1 data.

File:Thunderstorms over Estonia on a Copernicus Sentinel-1 synthetic aperture radar image.jpg|Thunderstorms over Estonia. False colour RGB image of VV-, VH- and VV+VH-polarisation backscatter.

File:Lake Success, California ESA373671.jpg|Lake Success region, California. False colour RGB image of scans from two different dates.

File:Alert, Canada ESA375402.jpg|Ice movement in Alert, Canada. False colour RGB image of scans from three different months.

File:Ground Deformation from Chilean Volcanic Eruption Shown by Satellite Radar Image.png|InSAR image displaying the ground deformation after the eruption of Calbuco volcano in Chile.

File:Larsen-C crack interferogram ESA376365.jpg|Interferometry reveals a crack in the Larsen Ice Shelf, Antarctica.

{{reflist}}

{{Commons category}}

• [https://sentinel.esa.int/web/sentinel/missions/sentinel-1 Sentinel-1] at ESA's Sentinel Online
• [https://earth.esa.int/web/guest/missions/esa-operational-eo-missions/sentinel-1 Sentinel-1] at ESA's Earth Online
• [http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-1 Sentinel-1] at ESA's Observing the Earth
• [https://web.archive.org/web/20150119143859/https://scihub.esa.int/ Sentinel-1 Scientific Data Hub] by ESA
• [http://copernicus.eu/sites/default/files/documents/Copernicus_Factsheets/Sentinel-1_fiche.pdf Sentinel-1 fact sheet] {{Webarchive|url=https://web.archive.org/web/20180413214452/http://copernicus.eu/sites/default/files/documents/Copernicus_Factsheets/Sentinel-1_fiche.pdf |date=2018-04-13 }} by the European Union
• [http://www.copernicus.eu/ Copernicus Programme]
• [https://dataspace.copernicus.eu/ Copernicus Dataspace]: visualize and download data from Sentinel-1 and other ESA satellites.

{{Copernicus programme}}

{{European Space Agency}}

Category:Copernicus Programme

Category:Earth observation satellites of the European Space Agency

Satellites

Category:Earth imaging satellites