As a child, Aaldert Van Amerongen often built with space Lego. He is now head of the Earth observation program at the Leiden space research institute SRON, where many of his colleagues still have space Lego on their desks. In recent years, Van Amerongen (46) helped build a Dutch measuring instrument, SPEXone, which is attached to NASA’s recently launched climate satellite PACE. SPEXone (14 million euros, 3.5 years development time) must measure small particles swirling around in the Earth’s atmosphere, aerosols, to refine climate models.
The satellite – with the Dutch instrument – was launched from Cape Canaveral in Florida on a Space X Falcon 9 rocket in the early morning of February 8. It was still pitch dark then. So dark that Van Amerongen and his colleagues could clearly see the fire of the igniting rocket engines from more than ten kilometers away. The bleacher benches they were sitting on were shaking. The Dutch engineers watched anxiously as their instrument took off into space, but the rocket soon disappeared behind the clouds.
The launch went smoothly. About fifteen minutes after departure, PACE arrived in an orbit around the Earth at an altitude of 677 kilometers. Another fifteen minutes later, the solar panels unfolded as planned.
And when, a week after the launch, the activation and testing of SPEXone with commandos from Maryland also went well, Van Amerongen was relieved, but not surprised. The Netherlands has a lot of experience in building optical measuring instruments such as microscopes and telescopes (such as SPEXone), he explains as he walks through the modern, square SRON building in Leiden. “We don’t make many mistakes anymore, we have done that in the past. Instead of being a little good at different things, we in the Netherlands are very good at one thing.”
The shiny aluminum model of PACE hangs from a wire on the ceiling of SRON, among other models of satellites that the Netherlands helped build.
PACE stands for plankton, aerosols, clouds and ocean ecosystem. These are the things the satellite will study to reveal something about Earth’s climate, Earth’s atmosphere and the health of the oceans. To do this, PACE has three scientific instruments on board.
One of those instruments is the Dutch SPEXone, which is mounted on the side. Once he arrives at his workplace at SRON, Van Amerongen takes a scale model of the instrument from a black suitcase. The metal block is slightly larger than a shoebox and five small telescopes protrude from the bottom.
As the satellite moves forward, those five telescopes measure at different angles how aerosols reflect sunlight back to the instrument. A beam of light consists of waves that ripple in different directions: horizontal, vertical and everything in between. That ripple direction is called polarization. The polarization, color and intensity of the reflected light say something about the properties of the aerosols.
Why aerosols?
“These particles form one of the largest uncertainties in climate models. Aerosols affect the Earth’s temperature in several ways. Some particles cooled the Earth by reflecting sunlight that would otherwise have warmed the Earth. Other aerosols actually cause warming by absorbing sunlight. Aerosols also influence the properties of clouds. The more aerosols, the whiter the cloud, the more sunlight the cloud reflects. That has a cooling effect. But it is not yet clear how strongly different types of aerosols influence the climate.
“By combining data on aerosols with information on clouds from another instrument on PACE and on global temperatures, we can learn something about the effect of different particles on the climate. We can then use this knowledge to refine our climate models.
“In addition, according to the World Health Organization, four million people worldwide die prematurely every year due to polluted air. If we know which types of aerosols are swirling around in a certain place, governments can make more targeted rules to reduce emissions of certain types of aerosols.”
How does building an instrument like SPEXone work?
“The most fun is the first phase, the preliminary design. For SPEXone we sat in a small room every day with about five people with different knowledge. If a mechanic wants to place a screw somewhere, an optician says no, that is not possible, because then the screw will block the light. Then came the testing phase. During the launch, SPEXone had to withstand severe vibrations and shocks. To check whether everything is properly secured, we place the instrument on a plate and bang a pendulum against that plate. We also tested whether the instrument worked well under extreme cold and heat. In space, a small radiator keeps SPEXone at room temperature, but if something goes wrong with the satellite and causes the radiator to fail, the side of the satellite facing the sun becomes very hot and the side facing deep space becomes extremely hot. cold.
“The funny thing is that I often had the instrument in my hands during construction. And now he’s flying there in space.”
Why is it important for the Netherlands to participate in international space travel?
“It is important to show that science funding has an impact. With space research, such as the development of SPEXone, we really add something concrete to climate science.”
Suddenly Van Amerongen jumps up from his chair. He happily gives two thumbs up to a colleague who walks past. Van Amerongen says that he heard a little earlier that SRON had been given the green light by the European Space Agency ESA to build two new satellites, TANGO. They must jointly measure greenhouse gas emissions from 2027.
The first Dutch satellites were intended for astronomy research, but nowadays more and more satellites look at the Earth. Why is that?
“In 1995, the first Earth observation satellite that the Netherlands helped build was launched. That satellite is called GOME and looked at ozone. More and more satellites are being added that look at the Earth, something that is happening worldwide. This is because we are increasingly realizing how useful satellites are in answering climate issues. My department has therefore received additional funding. With a satellite you can scan the entire world in a short time. Today, climate models are mainly fed with data from satellites.”
CV Quantum effects
Aaldert van Amerongen (Amsterdam, 1978) studied experimental physics at the University of Amsterdam. In 2008 he received his PhD from the same university on the quantum effects of atoms. He then started at SRON where he developed optical instruments.
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2024-03-10 21:46:55
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