SENTINEL-2A

Sentinel-2A is a European Earth-observation satellite operated by the European Space Agency (ESA) and built by Airbus DS GmbH. Catalogued under NORAD ID 40697 and international designator 2015-028A, the spacecraft was launched on 22 June 2015 and remains operational in a sun-synchronous orbit. It forms the observational backbone of the European Commission's Copernicus Programme — the world's largest civilian Earth-observation initiative — providing freely accessible, high-resolution multispectral imagery of the planet's land surfaces on a regular revisit schedule.

Mission and Purpose

Sentinel-2A's primary role is systematic, wide-area optical imaging of Earth's land surfaces, coastal zones, and inland waterways. The satellite carries a Multispectral Instrument (MSI) capable of capturing data across 13 distinct spectral bands, spanning the visible, near-infrared, and shortwave-infrared portions of the electromagnetic spectrum. This breadth of spectral coverage enables the satellite to support a remarkably wide range of environmental and humanitarian applications from a single orbiting platform.

Among the most prominent uses of Sentinel-2A data is vegetation monitoring. By comparing reflectance across specific spectral bands, analysts can assess crop health, detect stress in agricultural fields, and monitor the condition of forests at regional and continental scales. This information feeds directly into European agricultural policy assessments and food-security planning efforts. Similarly, the satellite's data are used extensively in land-cover mapping and change-detection — tracking how urban areas expand, how forests are cleared or regenerate, and how coastlines shift over time.

Sentinel-2A also plays a meaningful role in disaster response. During flood events, wildfires, landslides, or industrial accidents, the satellite's imagery can be rapidly tasked and delivered to emergency responders through ESA's emergency management frameworks. The satellite's relatively short revisit time — a consequence of its orbit and swath width — means that updated imagery of an affected area can be acquired within days, or in combination with other Sentinel-2 satellites, even faster. Water quality monitoring is another established application: differences in spectral reflectance allow scientists to detect algal blooms, suspended sediment, and pollution plumes in lakes, rivers, and coastal waters.

The Copernicus Programme, under which Sentinel-2A operates, was designed from the outset on a principle of open and free data access. All imagery collected by Sentinel-2A is made available without charge to users worldwide, which has dramatically expanded the scientific and operational communities that rely on the satellite's observations.

Orbit and Tracking

Sentinel-2A occupies a sun-synchronous orbit (SSO), a class of near-polar orbit in which the orbital plane maintains a nearly constant angle relative to the Sun throughout the year. This geometry ensures that the satellite passes over any given point on Earth's surface at approximately the same local solar time on every revisit, which is critical for Earth-observation missions: consistent lighting conditions make it far easier to compare imagery acquired on different dates and detect genuine changes on the ground rather than artifacts introduced by shifting shadows or illumination angles.

The satellite's current orbital parameters place its apogee at approximately 794 km and its perigee at approximately 792 km above Earth's surface — a very nearly circular orbit, as the minimal difference between the two figures indicates. The orbital inclination is 98.6°, consistent with a sun-synchronous configuration, which requires an inclination slightly greater than 90° so that the slow westward precession of the orbital plane keeps pace with Earth's motion around the Sun. The orbital period is approximately 100.6 minutes, meaning the spacecraft completes roughly 14 full orbits of the Earth each day.

At an altitude of roughly 793 km, Sentinel-2A is well above the densest part of the low Earth orbit debris environment and experiences only minimal atmospheric drag, contributing to its long-term orbital stability. The spacecraft has remained in orbit since its 2015 launch with no recorded decay or reentry, and continues to operate from this orbit at the time of writing.

For satellite trackers and enthusiasts, Sentinel-2A is trackable using standard two-line element (TLE) sets distributed by space-surveillance networks. Its NORAD catalog ID 40697 can be used to retrieve current positional data and generate ground-track predictions through any major tracking platform, including this site. The satellite's nearly circular orbit makes its ground track and overpass times relatively predictable.

Design and Operator

Sentinel-2A was designed and manufactured by Airbus DS GmbH under contract to the European Space Agency. The spacecraft has a launch mass of 1,140 kg, placing it firmly in the category of medium-sized Earth-observation satellites. Its central instrument, the Multispectral Instrument, provides a wide imaging swath — enabling large areas to be captured in a single pass — at spatial resolutions that vary by spectral band, with the highest-resolution bands intended for detailed land-surface analysis.

The European Space Agency, headquartered in Paris with major technical facilities across Europe, serves as both the operator and institutional owner of the satellite. ESA developed the Sentinel series of satellites specifically to serve the data needs of the Copernicus Programme, which is funded and directed by the European Commission. Within this arrangement, ESA is responsible for spacecraft development, launch procurement, and routine mission operations, while the European Commission oversees the broader program and the downstream data services that rely on Sentinel imagery.

The satellite was launched on 22 June 2015, making it the first of the Sentinel-2 series to reach orbit. Sentinel-2A was subsequently joined by a second satellite of the same design, Sentinel-2B, which entered orbit in early 2017. The two spacecraft are positioned in the same orbital plane approximately 180° apart, which effectively halves the revisit time for any given location compared to operating a single satellite. This two-satellite constellation configuration was planned from the program's inception as a means of maximizing temporal coverage without requiring a more complex multi-spacecraft arrangement.

Significance and Legacy

Sentinel-2A occupies a notable place in the history of civilian Earth observation. At its launch, it represented one of the most capable open-access optical imaging satellites ever placed in orbit, and the European Commission's commitment to distributing its data freely set it apart from many commercial and government systems that restrict access through licensing or cost barriers. The resulting democratization of high-resolution land-surface imagery has had measurable effects on environmental science, agricultural research, humanitarian response, and policy-making at national and international levels.

The data archive accumulated since 2015 has grown into a significant scientific resource. Researchers can access a continuous, multi-year time series of multispectral imagery covering the entire land surface of the Earth — a record that enables studies of long-term land-cover change, vegetation phenology, glacier retreat, urban growth, and many other phenomena that require observations sustained over years or decades. This archive continues to grow with each passing orbit.

Sentinel-2A also helped establish a template for subsequent ESA Sentinel missions, demonstrating the value of dedicated, purpose-built Earth-observation spacecraft operating as components of a larger, coordinated observation infrastructure rather than as standalone instruments. The Copernicus Programme has since expanded to encompass Sentinel satellites for atmospheric monitoring, ocean observation, radar imaging, and other applications, but the Sentinel-2 series remains among the most widely used by the global scientific and operational community.

The satellite's longevity — now a decade in orbit and still operational — speaks to the durability of its design and the continuing relevance of its observational capabilities. Planning for future-generation Sentinel-2 satellites, intended to eventually succeed the current pair, has been underway within ESA, ensuring that the data continuity established by Sentinel-2A will be maintained into the coming decades.

How to Spot It

Sentinel-2A is a medium-sized satellite orbiting at roughly 793 km altitude, and under favorable conditions it can be visible to the naked eye as a steady, moderately bright point of light moving steadily across the sky. It does not flash or blink — unlike tumbling rocket bodies or debris — and will appear to move at a pace consistent with a low Earth orbit object, crossing the visible sky in roughly two to four minutes depending on the pass geometry.

The best opportunities to observe it occur during twilight passes, when the observer on the ground is in darkness but the satellite is still illuminated by sunlight — typically within one to two hours after local sunset or before local sunrise. At its inclination of 98.6°, Sentinel-2A passes over virtually all latitudes, so observers across nearly the entire globe can expect periodic overpass opportunities. Using the NORAD ID 40697 with any satellite-tracking application or the tools available on this site, you can generate precise pass predictions for your location, including the time, direction, and elevation of each upcoming overpass.