Sentinel-3

A constellation of 2 identical satellites — Sentinel-3A and Sentinel-3B — following each other on the same sun-synchronized orbit.

Mission Objective

Sentinel-3 aims to provide accurate, reliable, and accessible environmental data. It focuses on measuring sea-surface topography, sea and land surface temperature, and ocean and land colour.

Mission Significance

The mission is crucial in ocean and land monitoring and contributing to climate change studies. Moreover, it provides essential data for weather forecasting and environmental management.

Source: ESA

Engineering Challenges

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

1. Stable calibration for ocean parameters monitoring – requires precise optical alignment, severe thermal control, and materials that minimize stray light.
2. Harsh space environment operation – requires overcoming high UV exposure, radiation degradation, and contamination.
3. Large bright surface observations (clouds, oceans, etc.) – requires high spatial uniformity to ensure that the light is measured correctly.

Instrument’s Components and Characteristics

The pioneering payload includes the following instruments:

• Sea and Land Surface Temperature Radiometer (SLSTR): Measures global sea and land surface temperatures.
• Ocean and Land Colour Instrument (OLCI): Provides detailed observations of ocean and land surface colour.
• Synthetic Aperture Radar Altimeter (SRAL): Measures sea-surface height, significant wave height, and wind speed.
• Microwave Radiometer (MWR): Provides atmospheric water content measurements, correcting SRAL data.
• Precise Orbit Determination (POD): Ensures high precision in the satellite’s positioning.

The constellation of the mission’s two satellites allows collaborative work and the maximization of data collection and coverage. The conjunction of both satellites enables OLCI to image the Earth at least once every two days and at the equator at least once per day.

Source: ESA

Acktar’s Solution

To meet Sentinel-3’s demanding optical and thermal requirements, Acktar supplied its Magic Black coatings over multiple instrument subsystems. These coatings offer extremely low reflectance, acting almost like internal black body surfaces and eliminating parasitic reflections that could impact ocean-color and thermal-infrared measurements. By combining high optical absorption with mechanical durability, Acktar helps ensure Sentinel-3’s long-term radiometric accuracy, enabling high-quality global measurements of oceans, land, and atmosphere.

Impact

During its mission, the satellites tracked and monitored various environmental parameters to meet the mission’s goals. This led to interesting and important discoveries:

• Sea-Level Rise: The precise data on sea-level changes contributed to a better understanding of global sea-level rise and its impacts.
• Phytoplankton Blooms: The monitoring of the phytoplankton blooms was crucial for understanding ocean health, marine ecosystems, and the global carbon cycle.
• Ocean Circulation Patterns: Tracking ocean parameters led to a greater understanding of ocean circulation patterns, which is vital for weather prediction and the creation of climate models.

Sentinel-3 is expected to continue its mission into the late 2020s, with plans to launch follow-on satellites—Sentinel-3C and Sentinel-3D—to ensure the continuity of the mission. The amplifications will improve data accuracy and expand observation capabilities, ensuring the mission’s continued contribution to Earth observation.

________________________________________________________________________________________________

 ACKTAR PARTS: