Lindley Johnson spent 23 years in the U.S. Air Force keeping his eyes above the skies. He helped identify and tackle a growing risk to human space activity—the sheer volume of stuff orbiting the planet—in addition to helping manage and monitor military assets in orbit. In 1982, the Air Force set up a space command to coordinate its activities, not the least of which was making sure the then-new Space Shuttle fleet wouldn’t have a tragic encounter with spacefaring material.
In the early 1990s, Johnson’s focus turned to natural threats to the planet from near-Earth asteroids, now a large and growing class of rocks that scientists track both for their potential impact risk and to study the solar system. About 1,500 new objects are discovered every year. Since retiring as a lieutenant colonel several years ago, he’s become the founding head of NASA’s Planetary Defense Coordination Office, overseeing a network of ground-based telescope surveys for new asteroids and working with other agencies to prepare for the unlikely event of a direct hit. His job title—no pressure—is Planetary Defense Officer.
A sign on the credenza in his office reads, “Every Day is Asteroid Day,” he said.
Q: So we can just take out asteroids with nukes, right?
A: That’s Hollywood fantasy. First of all, it would be too late just to send an ICBM with a nuclear warhead on it. These things are moving at speeds like the equivalent of about 12 miles a second. They would be difficult to intercept on an impact trajectory in the last few moments. Second, you’re not going to stop anything at that point. All that mass is still going to come down on us and if anything spread it over a wider area. So that’s not really a viable option.
What we need to do is find them well in advance, several years in advance, so we can send a spacecraft out into interplanetary space. If you are able to catch them many years in advance, you prevent them from being an impactor by changing their velocity by just a little bit.
Was there an initial event that hooked you? Somebody spring into your office and say, “Hey, any asteroids coming at us?”
The hazard has always been there. It’s just that we began to realize it and understand it more as we were finding asteroids in orbit that came close to Earth orbit. They are very rare, but they can still happen. That realization came around in the late ’80s early ’90s, in parallel with the Alvarez paper on the demise of the dinosaurs probably being caused by impact from a large asteroid.
I was at the Air Command and Staff College and participated in an Air Force-led study called SpaceCast 2020. We were studying the capabilities the Air Force might need in the year 2020. I chose the topic of protecting the Earth from asteroids, after a University of Arizona professor had gotten me kind of interested in the problem.
Seems like a no-brainer.