Protecting Earth from Asteroid Impacts
by Louise Good
It’s crowded out there: the orbits of over 1,000 known potentially hazardous asteroids that are over 140 meters across and will pass within 4.7 million miles (7.5 million km) of Earth. Credit: NASA, JPL-Caltech.
If you could literally save the world, would you? For former NASA astronaut Ed Lu, the answer is a resounding “yes.” Lu, now head of the B612 Foundation, gave a Sheraton Waikiki Explorers of the Universe public lecture, “Protecting Earth from Asteroids, or How Astronomy Saves the World,” at the UH Mānoa Kennedy Theatre on August 15. He said there is a 30 percent chance that an asteroid large enough to destroy a large city (about 40 yards across) will hit Earth in a person’s lifetime. Such an asteroid would explode with a force 200 times that of the bomb that destroyed Hiroshima. Such an asteroid did hit Tunguska in Siberia in 1908, destroying an area bigger than the Los Angeles basin or larger that the island of Hawai‘i. Larger asteroids can do even more damage, but collide with our planet less frequently.
Founded in 2002 by former Apollo astronaut Rusty Schweickart and Lu, the B612 Foundation is working to detect and deflect asteroids headed for a collision with Earth. At first, the group concentrated on researching methods to deflect asteroids. It turns out that is the easy part. With Earth traveling 65,000 mph (100,000 km/hr), it is only necessary to change the speed of an asteroid by 1 millimeter per second, about the speed an ant walks, if you do it many years before the collision would take place. This could be achieved by crashing a spacecraft into the asteroid and then sending another spacecraft called a “gravity tractor” to hover near the asteroid for many years. But finding the asteroids long before they collide with Earth is a more difficult proposition. Although NASA has paid for projects that have discovered an estimated 90 percent of the very large near-Earth asteroids (NEAs) that could end civilization, it is not doing enough to find the smaller ones that could still do serious damage, according to Lu.
A couple of years ago, Lu explained, he gave a talk at Google, and afterward a man asked him, “How do you find all these things?” Lu explained that the best way to find almost all NEAs would be to put an infrared telescope (“a giant set of night-vision googles”) into orbit around the Sun. The man asked him how much it would cost. Lu estimated that if a nongovernment entity did it, it would cost about a third of a billion dollars. The man explained how he had helped to raise $450 million dollars to add a wing to the San Francisco Museum of Modern Art, and he encouraged Lu to raise the money to build and launch the satellite.
So that is what the B612 Foundation is doing— raising money to build, launch, and operate an infrared space telescope called Sentinel to discover the great majority of NEAs. This is not totally unprecedented, Lu explained. Several ground-based observatories, such as the W. M. Keck Observatory on Mauna Kea, Lick Observatory in California, and Lowell Observatory in Arizona were built with private funds. Lu said they hope to launch Sentinel on July 20, 2018, into a Venus-like orbit around the Sun.
According to the B612 Foundation website, the telescope has been designed and will be built by Ball Aerospace, the same people who built the Kepler and Spitzer space telescopes and the Deep Impact spacecraft. It will be launched by SpaceX on a Falcon 9 rocket. NASA will support the mission with its Deep Space Network for communications, navigation, and tracking, and will aid in asteroid orbit calculation and threat assessment.
Someone in the audience asked Lu what will happen if Sentinel finds an asteroid headed for Earth. “Governments … are very, very good at confronting threats that are known,” he answered.
Video of Lu’s talk