SENTINEL-2B

Sentinel-2B is a European Earth-observation satellite operated by the European Space Agency (ESA) as part of the broader Copernicus Programme, the EU's flagship initiative for environmental monitoring from space. Launched on 7 March 2017 and built by Airbus DS GmbH, the spacecraft carries a high-resolution multispectral optical imaging instrument designed to systematically capture wide-area imagery of Earth's land surface, coastal waters, and vegetation. It was assigned NORAD catalog ID 42063 and international designator 2017-013A upon reaching orbit, where it continues to function in a near-circular sun-synchronous trajectory.

Mission and Purpose

The primary role of Sentinel-2B is to deliver consistent, high-quality optical imagery of Earth's surface to support a wide variety of civil and governmental applications. The satellite is the second of the Sentinel-2 series and operates in coordination with its predecessor, Sentinel-2A, which was launched approximately a year and a half earlier. Rather than simply duplicating coverage, Sentinel-2B was inserted into an orbit phased 180 degrees apart from Sentinel-2A, meaning the two spacecraft are positioned on opposite sides of the planet at all times. This arrangement effectively doubles the revisit frequency compared to what either satellite could achieve alone, allowing any given area on Earth's surface to be imaged far more often than a single spacecraft would permit.

The satellite's imager captures data across 13 distinct spectral bands, spanning the visible light spectrum through to shortwave infrared wavelengths. This multispectral capability is central to the mission's utility: different wavelengths of reflected light reveal different physical and chemical properties of the surface below. Vegetation stress, water content in soils, changes in land cover, the health of crops, and the extent of urban development can all be assessed with varying combinations of spectral bands. Agricultural applications are among the most prominent uses of Sentinel-2B data. By tracking how fields change over a growing season — and comparing those observations against historical records — analysts can estimate crop vigor, identify signs of drought or disease, and generate projections of regional yields before harvest. Similar approaches are applied to managed forests, where the satellite can help track deforestation, detect bark beetle infestations, and monitor reforestation efforts.

Beyond agriculture and forestry, Sentinel-2B data supports emergency response operations. After natural disasters such as floods, wildfires, or landslides, rapid acquisition of imagery over the affected area is essential for coordinating relief efforts, assessing damage, and planning recovery. The high revisit frequency enabled by the dual-satellite Sentinel-2 constellation makes this kind of near-real-time monitoring practical at a global scale. Coastal zone management, soil monitoring, and inland water body tracking are additional operational domains served by the mission.

All data from Sentinel-2B are made freely and openly available under the Copernicus data policy, without commercial restrictions. This open-access approach is a deliberate policy choice by ESA and the European Union, intended to maximize the uptake of satellite data across public institutions, research organizations, and private enterprises alike.

Orbit and Tracking

Sentinel-2B operates in a sun-synchronous orbit (SSO), a specialized type of low Earth orbit in which the orbital plane precesses at a rate that keeps it aligned with the Sun throughout the year. This means the satellite always crosses any given latitude at approximately the same local solar time on each pass, ensuring that lighting conditions in acquired images remain broadly consistent from one revisit to the next. Consistent solar illumination is not merely convenient — it is scientifically important, because it reduces the variability in how surface features appear and makes it easier to compare images taken weeks or months apart.

As of current catalog data, Sentinel-2B maintains an apogee of 794 km and a perigee of 792 km, giving it a nearly circular orbit with very little eccentricity. This consistency in altitude is characteristic of well-controlled operational missions, where onboard propulsion systems are used to counteract the slow orbital decay caused by atmospheric drag at low Earth altitudes. The orbital inclination is 98.6°, which is the retrograde inclination typical of sun-synchronous missions at this altitude range. The satellite completes one full orbit approximately every 100.6 minutes, meaning it circles the Earth roughly 14 times per day. At this altitude and revisit cadence, and operating alongside Sentinel-2A, the constellation achieves a global land surface revisit time that enables dense time-series analysis useful for change-detection studies.

For observers and researchers interested in tracking Sentinel-2B, the satellite can be located using its NORAD ID 42063 in standard satellite-tracking databases and prediction tools. Its orbit is relatively stable and predictable, making pass predictions straightforward for any ground location. The satellite's altitude — roughly 793 km above the surface — places it well above the densest part of the atmosphere, contributing to its orbital longevity.

Design and Operator

Sentinel-2B was manufactured by Airbus DS GmbH under contract to ESA, as part of the broader industrial effort to develop and build the Sentinel series of satellites for the Copernicus Programme. The spacecraft has a launch mass of 1,140 kg, which places it in the medium-weight class for Earth-observation satellites. At this mass, the satellite requires a dedicated or shared launch vehicle capable of reaching sun-synchronous altitude.

The Multispectral Instrument (MSI) aboard Sentinel-2B is the defining element of the satellite's technical profile. The instrument uses a push-broom scanning approach, in which a linear array of detectors captures an entire cross-track swath of imagery simultaneously as the satellite moves forward along its orbital track. This architecture allows the instrument to achieve a wide swath width while maintaining relatively high spatial resolution across its spectral bands. The 13 spectral bands it captures are distributed across different resolutions depending on their intended application — finer spatial detail is provided in the bands most relevant to land-cover mapping and vegetation monitoring.

ESA, headquartered in Paris, France, is both the operator and the owning organization for Sentinel-2B. ESA's Earth Observation directorate manages the Copernicus programme in partnership with the European Commission. While ESA develops and operates the space segment, the Copernicus programme as a whole is a joint undertaking between ESA and the EU, with service delivery and data utilization coordinated through designated Copernicus services covering areas such as land, atmosphere, marine environment, climate change, and emergency management.

Significance and Current Status

The Sentinel-2 constellation, of which Sentinel-2B is one half, has become one of the most widely used sources of freely available optical satellite imagery in the world. The systematic, open-access approach to data distribution has enabled a generation of researchers, government agencies, non-governmental organizations, and commercial users to incorporate satellite observation into work that would previously have required purchasing costly commercial imagery or going without. Academic literature in fields ranging from agricultural science to urban planning has expanded considerably on the basis of Sentinel-2 data availability.

In climate-related research, the fine spectral resolution and regular revisit cadence of the Sentinel-2 constellation provide a valuable tool for tracking indicators linked to land-use change and ecosystem health — both of which are closely connected to the global carbon cycle and to assessments of compliance with conservation policies. In the context of global food security, the ability to monitor crop conditions across large agricultural regions — including in countries where ground-based reporting infrastructure is limited — gives analysts and policymakers a layer of objective, geographically consistent data that was not previously accessible at this scale or this cost.

Sentinel-2B was launched with a design lifetime that would allow many years of operational service, and as of the data reflected in the current tracking catalog, the satellite remains in orbit and has not been given a decay or reentry date. The health and operational status of the satellite are not recorded in the public orbital catalog. However, the mere fact that it maintains its characteristic near-circular orbit at the expected altitude is broadly consistent with continued station-keeping and normal operations.

Looking beyond the current constellation, ESA has been developing the Sentinel-2 Next Generation (Sentinel-2 NG) program to provide continuity of service as the original pair of satellites age. The existence of such a follow-on effort underscores the degree to which the Sentinel-2 data stream has become embedded in operational services that governments, institutions, and commercial entities now depend upon on a routine basis. The legacy of Sentinel-2B is therefore not limited to its own operational lifespan but extends into the infrastructure and practices it has helped to normalize around the systematic, open monitoring of Earth's surface from orbit.