Career profile: Daniel Esteban-Fernandez on developing the SWOT satellite at JPL

Daniel Esteban-Fernandez is a radar engineer. From flying through hurricanes with radar sensors (see him posing with one of the airplanes above) to hatching new ideas for satellites on paper napkins, he now manages the division at NASA’s Jet Propulsion Laboratory responsible for deep space and planetary communications, navigational tracking, and active radio frequency remote sensing.

Was engineering always a childhood dream?

Apparently I told my mother I wanted to be an engineer when I was 11. And that’s what I became. I was very intrigued by electronics. I was the type of kid who would disassemble things to understand what was inside and how they worked – radios and things. That sense of curiosity was there.

How did you end up flying through hurricanes?

During my PhD at the University of Massachusetts, Amherst, we built a radar that was flown through hurricanes by NOAA for reconnaissance. The radar was designed to measure high wind speeds. Flying through a hurricane is an experience like no other. I’ve experienced turbulence on regular flights, but this is multiplied by 10 or 15. If something happens and you go down, then good luck. But the crew and pilots are very professional and have been doing this for decades, so you have to trust that everything will be done properly. The planes we flew were good-sized propeller planes. With them, we were able to fly straight through the hurricane, gathering measurements the whole time. We tried to avoid the pockets of highest wind, but sometimes you get surprised and the plane shakes like crazy. Everything is strapped down, for good reason, but sometimes you see a pencil flying around, or someone’s sandwich that they just took out to eat. Going through the eye wall is the most intense and dramatic part. You feel that you are levitating, like there’s no gravity. The plane pulls up and down, up and down. All of a sudden you have twice the gravity pulling you down, then the next second you feel like there’s no gravity. Some people get nauseated from this, but I was lucky and it didn’t really bug me. It was definitely intense, but fun.

Why did you want to join JPL?

Daniel Esteban-Fernandez poses for a headshot
Daniel Esteban-Fernandez since starting his work at JPL

JPL is obviously very strong in building radars. I wanted to have the experience of building the radar instruments, and then actually using them, and there’s very few places where you can do that. In most places, you analyze data or design the instrument, but you don’t put the nuts and bolts together. Most places outsource that part. So JPL is a very unique place, and that’s what attracted me, that you also get to build things.

Tell us about SWOT, the satellite you’ve helped develop at JPL.

Back in 2007 or 2008, I was making sketches on paper napkins with a small group of people for a new satellite we had in mind. We wanted to merge two science communities and build a single satellite for both of them: those who study oceans and those who study rivers and lakes. Eventually, our satellite got the green light to proceed to development, and it got named SWOT (Surface Water and Ocean Topography). SWOT will be a step up in terms of what we can see in the oceans, and no other satellite has provided so much information on lakes and rivers. It will have two antennas, which are like two eyes that can gauge depth and distance. It will really be revolutionary.

The SWOT satellite is a joint activity between JPL and the French space agency CNES. The idea for this new satellite that can study oceans, rivers, and lakes first came about from the community-driven 2007 "Decadal Survey", an opportunity for scientists and engineers lay out the most important scientific endeavors for the decade ahead. NASA was able to follow through with their recommendation and fund it. Read more about how SWOT can help us here.

How do you prepare the satellite for the harsh conditions in space?

After we build individual radar pieces and put them together, we do a lot of testing. Then, we go to a special building at JPL where we put the radar into a vacuum chamber. For SWOT, this happened in the middle of the pandemic, so it was a far more difficult ordeal to arrange than usual, in terms of needing to limit how many people were involved and making sure it was safe for everyone.

When the satellite is out in space, sometimes it will see the Sun, and sometimes it will be on the other side of Earth, exposed to cold, dark space. We have to test to make sure the instrument can withstand that entire range of conditions and temperatures, including the launch from Earth, and the subsequent orbit around Earth.

How did it feel to finish building the radar, and then pass your “baby” over to another group to handle?

There’s two parts to the process. First, seeing the transformation from a paper concept to the piece of equipment is just a phenomenal thing to observe. To see how paper sketches on napkins 10 years ago are now actually a huge piece of equipment is a very rich and humbling experience. And part of that is getting to the finish line, completing all the tests, showing it’s going to work and perform as we expect, and then, yes, you hand it over. That’s the second part of the process. You hand it over to the next set of people and it’ll continue its journey. But even though my role had ended, I still felt fine, because most of the team who built the radar moved on to the next part. It’s a radar that’s highly complex and very sensitive, and so it’s important that the next set of people to exercise and test it understand what to do. That’s typically how we do it at JPL, so that we don’t run into problems. It made my transition to my next role, as manager, perfectly trouble-free.

Developing and launching satellites is incredibly complicated. What’s it like when a failure occurs?

Most recently, that happened with SMAP (a satellite that measures soil moisture). It had two instruments on board that shared a 20-foot spinning antenna, but a month or so after the launch, one of them stopped transmitting. Thankfully, the second instrument – a radiometer – kept working along with the antenna. So the overall SMAP mission could continue.

When there’s an instance of failure like that, a lot of things happen – a lot of work to understand what has happened and if you can recover it. Then there’s a whole investigation, and a failure review board, and all these processes kick off. But I think that the next thing being a success helps. We’re good at that at JPL – not getting stuck in the past, but using failure to move forward and be successful the next time around. Since the beginning of NASA and JPL, failure was at the core of how we learned. There’s always more to learn, and we take failure extremely seriously to improve from it.