OBSERVER: Countdown to Sentinel-1C – Five powerful use cases from Europe’s top radar satellite mission
OBSERVER: Countdown to Sentinel-1C – Five powerful use cases from Europe’s top radar satellite mission
evan
Thu, 21/11/2024 – 10:19
For the last decade, Copernicus Sentinel-1 has been delivering a wealth of radar data for a wide range of applications to users around the world. Building on the legacy of pioneering European satellite missions such as ERS and ENVISAT, Sentinel-1 has provided invaluable data serving diverse sectors and many types of users in a variety of activities. Despite the early retirement of Sentinel-1B due to an anomaly in its instrument electronics power supply, the mission continues with Sentinel-1A still operational and Sentinel-1C soon to be launched.
In this week’s Observer, we explore the capabilities of Sentinel-1 through five visual examples showcasing what users can achieve with its data.
Full, free, and open radar data for numerous sectors worldwide
Copernicus Sentinel-1 is unique. It’s the only radar satellite mission whose data is available to users on a full, free, and open basis. Since its operations began in 2014, the mission has generated over 30 PB of data, with more than 14 million products made available to users to date. For context, that as much data as you would consume by streaming all 8 seasons of Game of Thrones in UHD (4K) every single day for nearly 36 years. Each month, more than 150,000 products based on Sentinel-1 data are published and made available to users. Given its scope and accessibility, it’s no surprise that data from this mission supports numerous sectors worldwide and one critical area where Sentinel-1’s impact is especially significant lies just beneath our feet.
Monitoring land use and movement
Sentinel-1 has created new opportunities for a vast array of land monitoring applications. The mission’s frequent revisits over the same areas enable close monitoring of land changes, which is particularly useful for applications such as urban planning, agriculture, and forest management.
In the following image, a combination of Sentinel-1 radar data from September, October and November 2023 helps us better understand when crops were most active in the landscape. The reddish areas indicate crops which were active in August, while the yellow areas show crops active during both August and September. Blue areas highlight crops that were active in October, and magenta areas represent crops active in both August and October.
Radar images are also important for tracking land subsidence and structural damage. The remote sensing technique known as Differential Synthetic Aperture Radar Interferometry (DInSAR) combines two or more radar images of the same area acquired at different times to detect changes occurring between acquisitions. This method enables the monitoring of even slight ground movements—down to just a few millimetres—across large areas with high spatial resolution. DInSAR helps us better understand the impact of earthquakes, landslides, volcanic activity, and other ground deformation events, as illustrated in this image of Haiti from 2021.
Safety on the high seas with Sentinel-1 radar and AIS
On the open seas, traditional methods of observing and tracking ships methods have significant limitations. Ground-based radar systems, for example, have a limited range, typically restricted to coastal areas, making them ineffective for monitoring vessels in remote ocean areas. To address this, two primary systems are used to track marine vessels: cooperative and non-cooperative tracking.
In cooperative tracking, ships actively share their identities and locations through specific tracking methods. One of the most widely used systems is the Automatic Identification System (AIS), which operates worldwide, enabling extended tracking capabilities. AIS relies on vessels to report their positions voluntarily by means of a transponder; therefore, if a ship chooses not to broadcast its location, it will not appear in the cooperative tracking system.
Sentinel-1A, on the other hand, uses radar to detect ships regardless of whether they are equipped with AIS or any other tracking system. In the following image, created by combining Copernicus Sentinel-1 radar data from January 2022 to December 2023, thousands of white dots, representing ships, are visible just off the Greek coast.
The Sentinel-1A approach is useful for identifying smaller fishing boats and vessels operating illegally, which may deliberately avoid cooperative tracking. However, to improve these tracking capabilities, Sentinel-1C will be equipped with an AIS signal antenna. This will complement the satellite’s ability to detect non-cooperative ships by adding the capability to track and identify cooperative vessels. AIS improves Sentinel-1’s ability to monitor the movement of ships, indicating their direction and speed, supporting efforts to detect illegal activities, and helping ships avoid collisions.
Near-real-time data for monitoring our oceans
In addition to helping vessel tracking on the open seas, Sentinel-1 plays a crucial role in monitoring our oceans. By processing radar data, the Copernicus Marine Service (CMEMS) generates a range of ocean products, such as sea ice thickness and sea ice velocity, which describe the lifecycle of floating ice in polar regions. These outputs are essential for those navigating Arctic waters, where safe travel depends on accurate ice condition forecasts.
Sentinel-1 also provides near-real-time data for monitoring of the open ocean, collecting information on wind and waves. This data helps improve our understanding of wave-current interactions and can be used to track the paths of harmful algal blooms (HABs), oil slicks, and other surface anomalies, as shown in the image below.
Timely radar data in support of disaster management
With its reliable Synthetic Aperture Radar (SAR) data, Sentinel-1 also supports emergency response and disaster management. By delivering 10-metre resolution images within hours of acquisition, the mission provides timely insights for assessing the impact of natural disasters.
SAR’s ability to penetrate cloud cover and capture imagery in all weather conditions, combined with Sentinel-1’s frequent revisit times, makes it invaluable for flood monitoring. The Copernicus Emergency Management Service (CEMS) uses Sentinel-1 data to produce flood maps which support emergency responders in managing crises. During the heavy monsoon rains in Pakistan in August 2022, for instance, CEMS prepared flood delineation maps and other products to assess the extent of flooding and assist rescue teams in the region.
Looking ahead to Sentinel-1C
The Sentinel-1 satellite mission continues to advance, bringing new features and capabilities to its wide range of applications. On Tuesday 3 December at 22:20 CET, Copernicus Sentinel-1C is scheduled to launch from Europe’s spaceport in Kourou, French Guiana with the Vega C Return-to-Flight launch.
Besides having an AIS signal antenna, Sentinel-1C’s GNSS (Global Navigation Satellite System) receivers will also be compatible with Galileo. The European Commission, in collaboration with the European Space Agency (ESA), will conduct a demonstration of the Galileo High Accuracy Service (HAS). This test will showcase the use of precise point positioning (PPP) enabled by Galileo’s E6 band, achieving onboard real-time accuracy of up to 0.2 metres. The demonstration will use Sentinel-1C’s advanced GNSS receivers and complete multiple orbits during the 6–7-hour test period.
Once operational, Sentinel-1C will ensure that Sentinel-1 returns to its nominal two-satellite constellation configuration. Sentinel-1D construction is also being finalised and will be ready for launch in the coming year, further securing the mission’s long-term future.
Thu, 21/11/2024 – 12:00
