Launched on July 1 2025, aboard the MTG-S1 satellite from Cape Canaveral, Sentinel-4 is a groundbreaking initiative aimed at monitoring air quality across Europe. At the heart of the Sentinel 4 mission is an advanced Ultraviolet-Visible-Near-Infrared (UVN) spectrometer, for which NPL provided a key test facility used to verify its performance pre-launch.
This mission is part of the Copernicus Earth Observation Programme, into which the UK is a major contributor alongside our EU partners and marks a significant advancement in Europe’s ability to observe and respond to atmospheric changes in near real-time.
NPL provided the pre-flight alignment, integration and test (AIT) optical ground support equipment (OGSE) facility within a consortium led by Micos Engineering GmbH. NPL-provided facility comprises a series of light sources, lasers, and optical test cards that ensure the mechanical and optical performance of the instrument, during its assembly stage.Sentinel-4's primary goal is to deliver hourly data on key atmospheric pollutants, including ozone (O₃), nitrogen dioxide (NO₂), sulphur dioxide (SO₂), formaldehyde (HCHO), and aerosols.
This data will significantly enhance the capacity to track pollution, forecast air quality, and implement vital environmental policies including the UK Air Quality Strategy and the Zero Pollution Action Plan in the EU.
The Sential-4 AIT OGSE which will be utilized for all four flight models, a second Sentinel-4 instrument (B) is planned for launch in the 2030s aboard MTG-S2, with models C and D to follow in the 2040s, ensuring long-term continuity of atmospheric monitoring.
The Sentinel-4 AIT OGSE was the first such facility developed by NPL, more recently followed by the STAR-cc-OGSE facility used for the CNES/UKSA MicroCarb mission which successfully launched on 26 July 2025. STAR-cc-OGSE is currently being further developed to meet the requirements of the TRUTHS mission, together with the recent commissioning of its sister Small Satellite Calibration Facility (SSCF) dedicated to smaller commercial payloads.
Paul Green, Principal Scientist and Science Area Leader, said: Sentinel-4 is an ambitious mission to monitor air pollution to high accuracy, have high spatial and temporal resolution over Europe and beyond, a mission with direct & immediate health benefits for a continent. We’re proud to have been able to support the mission through NPL’s expertise in optical facility design and satellite sensor characterisation.
*The core project team, led by the Earth Observation Climate and Optical group’s Dr Paul Green, included John Mountford, Dr Paul Miller, David Gibbs, Victoria Montag, Mike Parfitt & Faye Lai, with support from colleagues in dimensional and electromagnetic measurement and the mechanical workshop.
28 Jul 2025