Didymos and its small moon Dimorphos were the targets of the Double Asteroid Redirection Test
This article by David Barnhart of the University of Southern California originally appeared on Conversa and is republished here with permission.
In a world first, NASA has crashed a spacecraft into an asteroid in an attempt to push the rocky traveler off course. The Double Asteroid Redirection Test, or DART, is intended to test a potential approach that could prevent an asteroid from hitting Earth. David Barnhart is a professor of astronautics at the University of Southern California and director of the Space Engineering Research Center there. He watched NASA’s live broadcast of the mission’s success and explains what is known so far.
1. What do the pictures show?
The first images, taken by a camera on board DART, show the Didymos double asteroid system, about 2,500 feet (780 meters) in diameter, being orbited by the smaller asteroid Dimorphos, which is about 525 feet ( 160 meters) long.
As DART’s guidance algorithm locked on Dimorphos, the craft adjusted its flight and began heading toward the smaller of the two asteroids. The image taken 11 seconds before impact and 42 miles (68 kilometers) from Dimorphos shows the asteroid centered in the camera’s field of view. This meant that the targeting algorithm was quite accurate and the craft would hit right in the center of Dimorphos.
The penultimate image, taken two seconds before impact, shows the rocky surface of Dimorphos, including small shadows. These shadows are interesting because they suggest that the camera on board the DART spacecraft was seeing Dimorphos directly, but the Sun was at an angle to the camera. It implies that the DART spacecraft was focused on its trajectory to impact Dimorphos at this time, but it is also possible that the asteroid was spinning slowly relative to the camera.
The final photo, taken a second before impact, only shows the top of an image, but this is incredibly exciting. The fact that NASA received only part of the image implies that the shutter took the photo, but DART, traveling at about 14,000 miles per hour (22,500 kilometers per hour), was unable to transmit the full image before the impact
2. What had to happen?
The purpose of the DART mission was to test whether it is possible to deflect an asteroid with a kinetic impact, by crashing into something. NASA used the analogy of a golf cart hitting the side of an Egyptian pyramid to convey the relative size difference between the tiny DART and Dimorphos, the smaller of the two asteroids. Before the test, Dimorphos orbited Didymos in approximately 16 hours. NASA expects the impact to reduce Dimorphos’ orbit by 1%, or about 10 minutes. Although small, if it occurs far enough from Earth, a glance like this could deflect a future asteroid heading toward Earth enough to avoid an impact.
3. What do we already know?
The last bits of data that came from the DART spacecraft just before the impact show that it was underway. The fact that the images stop transmitting after reaching the target point can only mean that the impact was successful.
While much information is likely to be learned from the images taken by DART, the world will have to wait to find out if the diversion was also a success. Fifteen days before the impact, DART launched a small satellite with a camera designed to document the entire impact. The tiny satellite’s sensors should have taken pictures and gathered information, but since it doesn’t have a large antenna on board, the images will be slowly beamed back to Earth, one by one, over the next few weeks.
4. What does the test mean for planetary defense?
I think this test was a great proof of concept for many technologies that the US government has invested in over the years. And importantly, it shows that it is possible to send a craft to intercept a tiny target millions of miles away from Earth. From this point of view, DART has been a great success.
Over the coming months and years, researchers will learn how much deflection the impact caused and, more importantly, whether this kind of kinetic impact can move a celestial object ever so slightly a distance large enough to avoid a future asteroid. of the threat to Earth.
David Barnhart, professor of astronautics at the University of Southern California
This article is republished from The Conversation under a Creative Commons license. Read the original article.