New European satellites study oceans, vegetation, and climate.
Europe is launching the new Earth observation missions Sentinel-3C and Flex tomorrow morning. The satellites will ‘rocketpool’ a Vega-C rocket into space. In the coming years, they will contribute to weather and climate research. They will also provide insights into the health of Earth’s vegetation.
No one could have missed it this summer: weather in Europe is becoming more extreme due to climate change. We are seeing higher temperatures, prolonged droughts, and heavy downpours that can lead to flooding. ‘Ocean waters have been warming up over the past few decades,’ says Ad Stoffelen of the Royal Netherlands Weather Institute (KNMI). ‘This affects the Earth’s average temperature, which, at 21.1 degrees Celsius, is higher than ever.’
Oceans play a crucial role in temperatures over land. However, there is still considerable uncertainty regarding the precise nature of this relationship. The Sentinel-3C satellite aims to find answers. Its ocean and land color instrument monitors the ocean and land surface throughout the day and estimates the presence of aerosols and clouds in the atmosphere, while a temperature radiometer measures water and land temperatures day and night.
Sentinel-3C is the fifteenth satellite in the Copernicus Earth observation programme. It continues the measurements of its predecessors, 3-A (2016) and 3-B (2018), which are nearing the end of their operational lives. This timely succession is crucial, explains Catharina Bamps of the Copernicus programme: “Reliability and continuity of measurement data are incredibly important when you want to study the health of the Earth over the long term.”
In addition to climate research, Sentinel 3-C also provides data that is immediately used by countless users worldwide. For example, for water quality research and precision agriculture, or to detect wildfires early. Users can apply ready-made data from one of the Copernicus diensten or search for raw satellite data in databases like WEkEO and CDSE.
Stage and igniters
The Dutch space industry contributed to the Vega C rocket, which is launching Sentinel-3C and Flex into space from Kourou, French Guiana, at 3:21 a.m. Dutch time on Tuesday morning. Airbus Netherlands, based in Leiden, built the ‘interstage’ that connects the first and second stages of the 35-meter-tall rocket. Aerospace Propulsion Products (APP), based in Brabant, built igniters for the Vega’s three solid-fuel motors.
Plants emit light
Sentinel-3C is not the only satellite being launched into space early tomorrow morning. ESA’s Earth Explorer mission, FLEX, is on the same rocket. And that is no coincidence, explains Frank de Bruin of ESA. The FLEX mission requires measurement data from Sentinel-3 satellites to function properly; specifically, data on atmospheric conditions such as clouds, aerosols, and water vapor, as well as data on the land surface, including land cover type and ground temperature. “FLEX flies six to fifteen seconds behind a Sentinel-3 satellite, ensuring that they always measure the same location on Earth under the same conditions.”
FLEX is ESA’s photosynthesis mission. Everyone is familiar with photosynthesis: plants use sunlight to convert water and CO2 into sugars and oxygen. Under ideal conditions, plants convert all the energy into sugars. However, in extremely dry conditions, for instance, plants emit excess energy as heat or light. FLEX can measure the latter as fluorescence from space using the FLORIS instrument (Fluorescence Imaging Spectrometer). De Bruin explains: ‘This mission gives us insight into vegetation health and helps establish a link with stressors such as drought, heat, and pesticides.’
Flex is a small satellite, though De Bruin prefers to describe it as ‘compact and elegant’. It is the size of a large laundry machine and weighs four hundred kilograms. Over the next five years, it will produce a complete fluorescence map of the world every 27 days, with a resolution of 300 by 300 meters.
Autonomous Earth observation
And there is another reason for launching Flex, says Christiaan van der Tol of the University of Twente: ‘We use global climate models, which we also compare with one another. Take, for example, the reports from the UN climate panel, the IPCC. However, these models still contain significant uncertainties. With the global fluorescence measurement data from Flex, we can reduce some of these uncertainties.’
Collecting reliable data autonomously on a global scale, including in remote or inaccessible areas, is the reason Europe is building Earth observation satellites, says Jasper van Loon of the Netherlands Space Agency, who also chairs ESA’s Earth Observation Programme Board. ‘This data is invaluable for the safety of the Netherlands, the climate, and our society. That is why we are investing in our own scientific and meteorological satellites through the EU, ESA, and EUMETSAT.’
