The European Space Agency ESA is to select the next major satellite program. Researchers at Stockholm University are behind one of the four main candidates.
The ECO satellites’ instruments measure all radiation from horizon to horizon plus about 100 km more so you are sure to include most of the atmosphere. There are four identical instruments in each satellite, one that looks down at Earth, one that looks up and observes the Sun, and two that are in reserve. The backup instruments only measure occasionally, and in this way you can keep track of whether the active instruments deteriorate over time.
Over the years, the European Space Agency’s ESA’s Earth Explorer program has sent five research programs (or “missions” as they are called) into space to contribute important research data, and there are six more programs at various stages of development. At the beginning of 2023, a twelfth call for proposals was made for the program. 17 applications were received and recently ESA decided to allow four of these to proceed to the next stage of the process where the program proposals will be scrutinized more closely. In 2029, one of these research programs will be selected as ESA’s twelfth Earth Explorer.
One of the four programs selected by ESA for the second round is the Earth Climate Observatory (ECO), which will measure the Earth’s radiation balance.
– We want to measure the earth’s radiation balance directly from space, that is, the relatively small difference between incoming solar radiation and reflection plus infrared radiation from the earth. It is something that has not previously been successful, says Thorsten Mauritsen, lecturer at the Department of Meteorology, Stockholm University and one of the three researchers who are main applicants for ECO.
The radiation balance key to understanding climate change
The radiation balance is the key to understanding where climate change is headed. The imbalance occurs due to increasing greenhouse gases, which in turn leads to heat accumulating in the atmosphere and oceans. Global warming in turn leads to, among other things, heat waves, extreme precipitation, drought, changing climate zones and rising sea levels.
When the countries of the world are trying to keep the Earth’s temperature below two degrees, it is crucial to have a system in space that can quickly and reliably say whether the measures have had the desired effect before it is reflected in the temperature trend in the coming decades. You can also learn a great deal about how the climate system works by having long, uninterrupted time series of the radiation balance.
Thorsten Mauritsen
Photo: Malin Mauritsen
– As a climate scientist, there is also a slight concern that we are completely wrong in our forecasts for the future. The widespread view among climate scientists, which I share, is that global warming will stop at roughly the level of warming reached a few years or a decade after fossil fuel use is phased out. But even if the risk is extremely small, there are concerns that feedback mechanisms may continue to fuel global warming afterwards. We could detect such a horror scenario early on with ECO and you would then have more time to react, says Thorsten Mauritsen.
Reduce the uncertainty in the measurements
He says that current and planned American satellite systems have too little accuracy to measure the fine imbalance, the focus there is instead on high resolution.
– In ECO, we intend to go in the other direction to achieve our goal. We will use instruments that measure reflection and radiance from horizon to horizon seen from the perspective of the satellite, as well as similar instruments to measure solar radiation. We also have a double set of instruments. In this way, we can reduce the uncertainty and achieve very stable measurements over time, even if the harsh space environment were to wear down the instruments, says Thorsten Mauritsen.
Measurements night and day everywhere on earth
Technical sketch of what an ECO satellite might look like. The instruments are in the box at the top of the picture, red instruments are radiometers and green and yellow are different cameras that will look down on the earth. On the back of the instrument box are two more radiometers that measure incoming solar radiation. The bottom box contains everything needed to keep the satellite in orbit, including a small rocket motor, fuel, gyros, batteries, computer, navigation and communications
To measure the radiation balance, measurements need to be made day and night, and everywhere on earth. The researchers at Stockholm University have shown that this can be done if you have at least two satellites that travel in special orbits over or near the poles.
– These tracks are so cleverly aligned that at different times of the year, they are measured at different times of the day. The more common is to use sun-synchronous orbits where you always measure at the same times of the day, usually around lunch and at midnight. But the diurnal cycle in the radiation balance is enormous, so if such orbits were used, at least six functioning satellites would have been needed, which would have been very expensive, says Thorsten Mauritsen.
Tough thinning process
Up to and including 2029, there will now be a tough selection process to select the mission ESA will choose. In the meantime, the researchers at ECO will carry out a series of tests to ensure that the system will work. ESA will also investigate whether European companies can build the satellites as intended and whether something needs to be changed. After 2029, the satellites will be built and the launch is planned for 2036.
What do you hope to achieve with ECO?
– We hope that we can show the value in keeping track of global warming from space and that the ECO mission will be followed up so that future generations can keep better track of the climate, says Thorsten Mauritsen.
Researchers from six countries behind apply
In addition to Stockholm University, the main applicants for ECO are researchers from Brussels and Toulouse. From Stockholm University, Linda Megner and Jörg Gumbel, both at the Department of Meteorology, are also included in the application, and much of the research has been carried out by PhD student Thomas Hocking. A total of twelve researchers from Sweden, Belgium, France, Germany, Great Britain and Switzerland are behind the application. The budget framework from ESA’s side for the project is EUR 550 million. In the current stage, the four programs are allocated a smaller sum which will mainly go to industrial studies of how the mission could be realized.
The other projects moving forward are CryoRad, Hydroterra+ and Keystone.
Read more on ESA’s website about the four projects
Tags: Stockholm researchers step closer major satellite project
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