# Sentinel-1

> model of synthetic aperture radar Earth observation satellite

**Wikidata**: [Q1147027](https://www.wikidata.org/wiki/Q1147027)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Sentinel-1)  
**Source**: https://4ort.xyz/entity/sentinel-1

## Summary
Sentinel-1 is a family of three European synthetic-aperture-radar (SAR) Earth-observation satellites built by Thales Alenia Space and Airbus Defence & Space for the European Space Agency’s Copernicus programme. Unlike optical satellites, Sentinel-1’s radar can image Earth’s surface day or night, through clouds, providing continuous land and ocean data for disaster response, environmental monitoring and security applications.

## Key Facts
- **Total produced**: 3 spacecraft (Sentinel-1A, 1B, 1C; 1B now out of service)
- **Operator**: European Space Agency within the Sentinel programme / Copernicus
- **Prime contractor**: Thales Alenia Space; subcontractor: Airbus Defence & Space
- **Instrument carried**: C-band synthetic aperture radar (SAR)
- **Subclass of**: synthetic aperture radar satellite
- **Website**: https://www.esa.int/Sentinel-1 (English)
- **Wikipedia presence**: articles in 10 languages; 19 Wikimedia sitelinks
- **Freebase ID**: /m/047f5bz (issued 28 Oct 2013)

## FAQs
### Q: What makes Sentinel-1 different from optical Earth-observation satellites?
A: Its C-band SAR instrument transmits its own microwave energy, so it records images regardless of daylight or cloud cover, enabling reliable, all-weather monitoring.

### Q: How many Sentinel-1 satellites are currently operational?
A: Two of the three built spacecraft—1A and 1C—remain in service; Sentinel-1B was declared out of service.

### Q: Who owns and operates Sentinel-1?
A: The European Space Agency owns the satellites and operates them as part of the European Union’s Copernicus environmental-monitoring fleet.

### Q: What kinds of data does Sentinel-1 provide?
A: High-resolution radar imagery used for mapping land deformation, sea-ice extent, oil spills, deforestation, and rapid disaster assessment.

## Why It Matters
Sentinel-1 extends Europe’s ability to monitor the planet continuously, independent of weather or time of day. Because radar penetrates clouds and darkness, governments and scientists receive reliable imagery during floods, volcanic eruptions, and ship-source pollution incidents when optical sensors are blind. The open-data policy makes these radar archives the largest of their kind, feeding climate-change research, crop-yield forecasting, and infrastructure-subsidence mapping worldwide. By guaranteeing frequent, free imagery, Sentinel-1 has become the de-facto standard for many civil-protection agencies, lowering the cost of Earth-observation applications and fostering a commercial downstream industry worth billions of euros.

## Notable For
- First operational, openly accessible C-band SAR constellation designed for routine global coverage
- Provides interferometric data that can detect millimetre-scale ground movement—vital for landslide and earthquake studies
- All-weather, day-and-night imaging capability, unique among the predominantly optical Sentinel fleet
- Data are delivered free and near-real-time, underpinning the EU’s Copernicus Emergency Management Service
- Constellation design allows repeat imaging of the same spot every 6–12 days, supporting time-series analysis

## Body
### Programme Context
Sentinel-1 is the radar component of ESA’s Sentinel programme, the space segment of the European Union’s Copernicus environmental-monitoring initiative. The programme’s goal is to supply operational, long-term Earth-observation data for land, ocean and atmospheric services.

### Spacecraft Generation
Three flight-model satellites have been manufactured under a Thales Alenia Space–led consortium, with Airbus Defence & Space as major subcontractor. Each spacecraft carries an identical C-band synthetic aperture radar, ensuring data continuity across the series.

### Imaging Capabilities
Operating at 5.405 GHz (C-band), the SAR instrument can scan in four exclusive acquisition modes, ranging from high-resolution (5 m × 5 m) to wide-swath (25 m × 100 m) imaging. The radar’s interferometric repeat-pass capability enables measurement of surface deformation on the order of millimetres.

### Data Access and Policy
All Sentinel-1 data are provided on a full, free and open basis, downloadable through the Copernicus Open Access Hub. Near-real-time products are available within three hours of sensing, supporting maritime-surveillance and emergency-mapping services.

### Operational Status
Sentinel-1A launched in April 2014; Sentinel-1B in April 2016 (retired 2022); Sentinel-1C is planned to ensure continuity. The constellation is designed for a 7-year operational lifetime per satellite, with overlapping launches maintaining service.

## References

1. [Source](https://www.esa.int/Applications/Observing_the_Earth/Copernicus/Sentinel-1/Facts_and_figures)
2. Freebase Data Dumps. 2013