Hockey keeps Paco López-Dekker with both feet on the ground. There he hears: great that your satellites will soon fly into space, but your pass was just bad.
López-Dekker is the principal scientist at TU Delft on a satellite mission that the European Space Agency selected last September as the 10th Earth Explorer. These are missions with the purpose of monitoring how processes on Earth are changed by humans. López-Dekker is the first Dutch principal investigator of an Earth Explorer. Together with his team, he invented the Harmony mission and now leads its development.
Harmony is to be launched in 2029 from Kourou in French Guiana. Two new radar satellites will then enter orbit to observe climate-related processes alongside an existing ESA radar satellite: Sentinel-1. We meet in the geosciences building at TU Delft.
“In Europe, we are leaders in Earth observation, and the American space agency NASA is jealous of what we are doing here. We often feel that we already know the Earth well. This is not true.”
Hundreds of millions of people depend on meltwater from glaciers, but they are running out
What will Harmony teach us about Earth?
“Basically three things. He will monitor small shifts in the land surface that can lead to earthquakes, how glaciers flow, and how the coupling between the sea surface and the lower atmosphere works. Most of the Earth’s surface is ocean and 90 percent of the extra warm since the current climate changes have ended up there. The exchange of gases and heat between the ocean and the atmosphere has not yet been thoroughly studied. Heat and gases move via turbulence. These movements take place on a small scale, a few square kilometers. Previous satellites did not observe in detail enough to track these movements.”
Harmony will measure cloud movement, wind, waves and surface currents in high resolution by working with three satellites. To see where something is moving, a radar satellite sends pulses back to Earth in sequence and measures how fast they bounce back. The faster, the closer to that time. “With one radar satellite, you measure in one dimension: the direction of the satellite’s view. With three satellites looking from different angles, we have sufficient diversity in measurement directions so that we can reconstruct the movements in all directions.”
The versatile mission is a reflection of López-Dekker’s personality. “I was never focused on one thing; I was often commented that I had too many interests. As a principal investigator, I now bring different types of people together: scientists and engineers. I talk to both sides: What is technologically possible for the researchers, and what do the researchers want the technology to be able to do?”
How did the idea of monitoring movements on earth with three satellites come about?
“Ideas for new satellites arise when technological development and scientific questions meet. The technology behind Harmony is based on another mission I developed in 2015. It was also supposed to monitor movements on land and in glaciers. Hundreds of millions of people depend on meltwater from glaciers for their water supply, but they are running out due to climate change. We wanted to measure this in high resolution with new radar technology. But that mission was not chosen by ESA. There was no budget for it.”
We were in competition with two other missions, but they were quickly dropped because they turned out to be too expensive
Why was Harmony chosen?
“We added the question of the ocean’s role in climate change in 2018. How long the oceans can absorb the extra heat is a question that is now very relevant. And the execution of the mission is technologically feasible.
“The name Harmony arose in a conversation with my ten-year-old daughter. There were all kinds of mission proposals at ESA with names of male gods. I wanted a female Latin goddess. Concordia is the goddess of unity, but it was sensitive because of the Costa Concordia sinking in 2012. Harmony is the Greek version of Concordia.”
Four years of hard work and fun, you wrote on Twitter. How did the selection procedure go?
“Every three years, ESA issues a call for new ideas for satellite missions. Then teams submit proposals for missions that they think are scientifically interesting enough to spend money on. ESA selects a small number of them for a feasibility study. We were in competition with two other missions, but they were quickly dropped because they turned out to be too expensive. For a year and a half, we did tests with hundreds of people—for example, with airplanes over the Wadden Sea—and we did a lot of computer simulations. It’s a big risk, because the chance of the work not resulting in a mission after all was much greater than the chance of the satellite actually getting there.
“Then we stood on a stage with fourteen scientists and a few involved colleagues from ESA, and we had to convince the ESA advisory committee. The reactions were positive, but the final, redemptive email from ESA took months.”
For example, we will measure how hard the wind pushes on the water
What did you do when you heard that ESA wanted to run Harmony?
“Scientists are down-to-earth people. We met briefly with the science team online and then immediately began working on the challenges we still face with Harmony.”
What are the challenges?
“Well, the launch will of course be very exciting. In total, the mission is estimated to cost 420 million euros, and hundreds of people are working on it. During launch, the satellites go into the air at thousands of kilometers per hour. Everything can break.
“But: The really exciting thing is that we now have to ensure that Harmony actually helps scientists. It is important that we learn how to interpret the data. Our satellites measure indirectly. For example, we will measure how hard the wind presses on the water, because it says something about the exchange of heat and gases. But it is impossible to measure that pressure from space. But the harder the wind pushes, the harder the water. And you can measure roughness with radar: the rougher the more reflection. To understand and quantify all the connections, I am now modeling what Harmony’s observations will look like. Before it was just the selection for execution and launch that was a dot on the horizon, now we have to make sure that the satellites don’t just fly around, but do , what we have promised.”