And other mind-bending remote sensing pursuits
By: Joe Gomez
“The reason I like talking about the sun is that it challenges our assumptions. It makes you question what is a surface? What is a map? Progress happens when we break assumptions and bring people together who view things from a different angle, like cartographers and astrophysicists.” -Bruno Sánchez-Andrade Nuño
At Locate — two days of all things maps, location data, and sensors — you’ll hear from Bruno Sánchez-Andrade Nuño, VP of Impact at Satellogic. His company is applying advances in machine learning and high-resolution, high-cadence satellite imagery to monitor changes to the planet in real time. The goal is to make those insights more accessible.
“There has been a huge gap between the pixel and the answer. Now we have more open data and better tools. We can fulfill this dream of democratizing access to answers so a small, independent farmer or an NGO can make smarter decisions.”
Bruno is Ph.D. Magna cum Laude in astrophysics and postdoc in satellite and rocket science. He was also a former Mapboxer, helping build out our Satellite team in the early days. If his resume isn’t interesting enough, part of his postdoc research was on mapping the sun. We sat down with Bruno to get a preview of his talk at Locate. Obviously we asked him about the☀️
Bruno, why map the Sun? What can we learn?
To understand how a star works, why not observe the closest one to us? On the Sun’s surface, you may see explosions thousands of times the size of Earth in seconds. Observing space weather, like solar wind, CME’s, and flares — these huge blasts of radiation — helps us understand their effects on assets in space and on Earth, including people.
And it’s just such a weird place that challenges so many of our assumptions. For example, what is the surface of the sun? Is it a place you can stand on? No, it’s gas. Ok, then how do we define and measure this surface when it’s in constant change and tension?
How do you map a constantly changing surface?
Well the sun is a gas and it’s rotating, and because of that, the equator moves faster than the poles. Any map you make needs to be dynamic. The maps I generated were about understanding the location where the Sun and Earth are, in a sense, connected. On Earth, we have relatively weak magnetic poles, but beyond the Sun’s surface, the magnetic field dominates gravity. Whenever you see the surface, all of the lines and shapes of the gas; these are really magnetic fields moving, or magnetohydrodynamics — it’s very strange.
Just like we can imagine an invisible radio connection between an antenna and a receiver, there’s a place where Earth is connected to the sun, and this location is moving all the time. There is a “magnetic line” from here to a place on the sun surface, like a highway. That means if you release an electron or proton from that location, it will follow the magnetic path directly to Earth. This is basically solar wind.
Just like any map, you had to project a massive sphere onto a flat plane.
Yes, to map the sun I used captured imagery from two opposing satellites looking at different sides of the Sun (the NASA STEREO mission), and then I merged the data to generate a combined map projection.
The model was running live at NRL Space Science Division in Washington, DC for many years. Every day it updated the combined maps of the sun’s atmosphere from the two satellites. As I mentioned earlier, the sun rotates. In the script, I actually removed that rotation from the data so you can view the surface as if it were a real map.
The highest resolution image of the sun surface we have is something like 70km per pixel. Even defining what the surface is gets challenging since most of the Sun is actually opaque — the atoms are opaque to the light. It gets less and less dense as you move to the exterior so then the light can escape to space, and that’s what you see; this is the surface.
And it takes a lot of time for light to escape the center. Today we are seeing the light created at about the early times of the Homo Sapiens, about 170,000 years ago. And then from the surface, it just takes about 8 minutes for light to reach Earth. We can only observe the surface, and there’s surprisingly a lot we still don’t understand.
What is the biggest mystery about the sun that we’ve yet to solve?
Well, the sun is very hot in the center, maybe 27 million degrees Fahrenheit (15 million degrees Celsius), and then as you’d expect, it gets cooler as you move toward the surface, about 10,000 Fahrenheit (5,600 Celsius). But the atmosphere of the sun, just above the surface, is way hotter, 1–2 million degrees, much hotter than the surface itself. It makes no sense that the atmosphere is hotter than the surface. We don’t really know why. It’s a whole place where physics works differently, and therefore, maps have to work differently as well.
How has your work mapping the Sun informed your work at Satellogic?
Map projections, calibration of instruments, sensors, cameras, going from a raw picture to rectified images — all of these tools for trying to understand the sun, are just as useful for looking down at Earth. To gain insights from satellite imagery has been a question of time, access, and input from experts. Much of this isn’t accessible to a small farmer in Botswana or governments of developing countries. Our challenge is how do we transform this data into knowledge, into wisdom, into good decisions.
There’s also more data now than ever coming from public sources like Landsat or Copernicus in Europe. I’m most excited for this future that combines more data of more types with machine learning. And we need not just people who understand the mechanics of satellites and algorithms, but more people who have a vision for how to apply it. How do we use these tools to solve the most pressing social and environmental challenges of our time?
We’ll be announcing more speakers like Bruno in the weeks to come, as well as interactive demos and code labs where you can get your hands on the latest mapping tech at Locate. Register for early bird tickets now to save your spot — the price increases soon. You can also sign up to race autonomous Robocars at the event. More details here.
Mapping the sun @ Locate was originally published in Points of interest on Medium, where people are continuing the conversation by highlighting and responding to this story.