Sentinel-2

A constellation of 2 identical satellites — Sentinel-2A and Sentinel-2B — following each other on the same orbit and phasing at 180 degrees to one another.

Mission Objective

The twin satellites are in a sun-synchronized orbit and are designed to deliver data about agricultural monitoring, emergency management, land cover classification, and water quality. 

Mission Significance

Sentinel-2 plays a crucial role in environmental management due to its high-resolution optical imagery of the Earth’s surface.

Source: ESA

Engineering Challenges

There are several technological challenges that arise from the satellites’ requirements:

• Consistent radiometric performance across a wide spectral range – requires stable calibration and stray light suppression.
• Overcoming high thermal variation along the orbit – requires specified materials with high endurance for heat and radiation.
• Harsh space environment operation – requires overcoming high UV exposure, radiation degradation, and contamination.
• Large bright surface observations (deserts, oceans, etc) – requires high spatial uniformity to ensure that the light is measured correctly.

Instrument’s Characteristics

The Sentinel-2 mission relies on the MSI (Multispectral Instrument), which captures high-resolution imagery across 13 spectral bands from visible to SWIR. As mentioned above, both satellites are identical and share the same characteristics:

Field of View: 290 km
Weight: 1.2 tones

Acktar’s Solution

To support the satellites’ imaging requirements, Acktar provided the black coatings – Magic Black, Fractal Black, and Vacuum Black. These micro-structured coatings achieve extremely low reflectance across wide spectral bands, acting like internal black body absorbers that reduce stray light and maintain radiometric accuracy. Acktar’s coatings also offer stable emissivity and minimal blackbody radiation, promoting thermal uniformity within the MSI.

Image captured by Sentinel-2 of Lake Balaton Hungary. Source: ESA

Impact

The Sentinel-2 mission has been orbiting around the Earth to provide the most accurate and updated data for environmental management. Over the years, its data has greatly improved the efficiency and the work quality of many aspects of our environment. In addition, this data is being used to conduct wide research about climate change and its global impact. Here are the main subjects and challenges it has been able to aid in:

Agriculture Monitoring: optimization of irrigation, reduction in fertilizer use, yield growth.
Deforestation and Forest Management: illegal logging activities track, forest health assessment, conservation efforts support.
Disaster Response: provides real-time data during natural disasters, such as floods, wildfires, and hurricanes, and aids in damage assessment and rescue operations.
Coastal and Marine Monitoring: fisheries management, coral reefs protection.
Urban Planning: sustainable development, management of natural resources in urban settings.

The Sentinel-2 twin is planned to end its life around 2025, after a decade of dedicated high-resolution imagery. However, the show must go on! Therefore, Sentinel-2C and Sentinel-2D will be sent to space to support the environment’s needs and enhance the mission’s abilities.

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