science

Sentinel-1

Sentinel-1 is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Sentinel-1 rather than just read about it. In short: Sentinel-1 is the first of the Copernicus Programme satellite constellations for Earth observation operated by the European Space Agency (ESA). Data collected via the satellites are used e.g. for marine and land monitoring, emergency response to environmental disasters, and economic applications.

Key takeaways

Sentinel-1 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Sentinel-1 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Sentinel-1 from memory before moving on to harder problems.

Reference excerpt

Sentinel-1 is the first of the Copernicus Programme satellite constellations for Earth observation operated by the European Space Agency (ESA). Data collected via the satellites are used e.g. for marine and land monitoring, emergency response to environmental disasters, and economic applications.

Overview The mission was originally composed of a constellation of two satellites, Sentinel-1A and Sentinel-1B, which shared the same orbital plane. Sentinel-1B was retired following a power supply issue on 23 December 2021, which left Sentinel-1A the only satellite of the constellation to be operating, until Sentinel-1C was successfully launched on 5 December 2024. Sentinel-1D launched in November 2025. 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. Sentinel-1D is in development. An equipment failure on Sentinel-1B in December 2021 accelerated work on Sentinel-1C, which has been successfully launched in December 2024. 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 693 km (431 mi) altitude, with 3-axis altitude stabilization. On 10 June 2026, ESA awarded Thales Alenia Space a contract to lead the development and build for two Copernicus Sentinel-1 Next Generation satellites. The new generation will have significantly larger coverage and improved resolution. 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.

Spacecraft

Sentinel-1A

Sentinel-1A was launched on 3 April 2014.

Sentinel-1B

Sentinel-1B was launched on 25 April 2016. Unavailable due to a power issue since 23 December 2021. Mission end declared on 3 August 2022.

Sentinel-1C

Development contract signed with Thales Alenia Space of Italy in December 2015. It was launched on 5 December 2024.

Sentinel-1D

Development contract signed with Thales Alenia Space of Italy in December 2015. It was launched on 4 November 2025.

Background 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). 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. The C-SAR instrument is the responsibility of Astrium Gmbh. Sentinel-1A was constructed in Rome, Italy. 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.

Instruments

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). The single C-SAR instrument with its electronics provides 1 dB radiometric accuracy with a central frequency at 5.405 GHz. This instrument has a spatial resolution down to 5 m (16 ft) and a swath of up to 410 km (250 mi). The data collected in C-SAR was made to be continuous after the termination of a previous mission (Envisat mission). 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.

Operational modes 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. The four operational modes offered by Sentinel-1 are:

Strip Map (SM) Mode, which features 5-by-5-metre (16 by 16 ft)spatial resolution and an 80 km (50 mi) 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 5-by-20-metre (16 by 66 ft) spatial resolution and a 250 km (160 mi) 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 20-by-40-metre (66 by 131 ft) spatial resolution and a 400 km (250 mi) 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 5-by-5-metre (16 by 16 ft) resolution and a low data rate. It produces 20 by 20 km (12 by 12 mi) sample images along the orbit at intervals of 100 km (62 mi). This is the main operational mode over open ocean, with data offered only in single (HH or VV) polarization.

Data products 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

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Sentinel-1

Start with the simplest possible case. Write down what Sentinel-1 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Sentinel-1 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Sentinel-1 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Sentinel-1

In research: Sentinel-1 appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Sentinel-1 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Sentinel-1 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Earth imaging satellites, Earth observation satellites of the European Space Agency, Sentinel satellites, so understanding it makes those chapters shorter.
In everyday life: Look for Sentinel-1 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Sentinel-1 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Sentinel-1 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Sentinel-1 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sentinel-1 in simple terms?

Why does Sentinel-1 matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Sentinel-1?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Sentinel-1.