NASA isn’t just wasting expensive and sophisticated spacecraft for entertainment. Agencies do the job.
In 2005, Congress mandated NASA to discover, by 2020, 90% of the near-Earth asteroids large enough to destroy a city (with a diameter of 140 meters or more). But Congress has never provided NASA with significant funding to carry out that task, so more than half remain unfinished, and about 15,000 more asteroids still need to be discovered.
While the agency searches the skies for deadly space rocks, it also develops methods to respond to threats as they emerge.
DART missions are different from movies ArmageddonBlowing up asteroids is generally not a good idea. Rather, the mission is a proof-of-principle that striking an approaching asteroid with a projectile can propel it into a different orbit.
For dangerous approaching asteroids, that nudge could be enough to change the trajectory from a direct hit to a near miss.
What happens during a collision?
The mission’s target is Dimorphus, a small asteroid about 500 feet (152 meters) in diameter, orbiting a 1-kilometer-wide asteroid called Didymos. Dimorphus makes one lap around Didymus every 11 hours and 55 minutes.
DART is essentially a self-driving suicide spacecraft, and most of the people in the Mission Operations Center at the Johns Hopkins Applied Physics Laboratory in Maryland are bystanders, leading themselves to its demise.
DART Mission Systems Engineer Elena Adams said: “And at that point, you can’t really send commands. So the system has to be very precise in how it controls the spacecraft.”
DART’s camera does not recognize Dimorphos as a separate dot from Didymos until about an hour before the crash. It then adjusts its flight path and ends in a spectacular collision.
“It’s really hard to hit very small objects in space, but we’re trying to do it,” Adams said.
What happens if the mission is successful?
If DART and Dimorphos connect as planned, the orbit of the small asteroid will approach the big Didymo. The magnitude of the change depends on the structure and composition of the dimorphos.
If Dimorphus is solid and DART only carves small craters, the transformation follows the basics of physics 101 problem. That is, two objects collide and stick together. Because DART is moving in the opposite direction to Dimorphos, it absorbs some of the asteroid’s angular momentum, bringing it closer to Didymos and speeding it up.
But if Dimorphus resembles a pile of debris held together by gravity, then the collision would form a deep crater, sending a shower of debris flying into space. That rock cascade is like the thrust of a rocket engine pushing an asteroid. In that case, the orbit of Dimorphus is even closer to Didymus.
This article was originally new york times.
How to watch NASA’s asteroid interception attempt
Source link How to watch NASA’s asteroid interception attempt