By Paul Rincon
The science editor is on the website.
Steve Gribben is the image source.
One day, a dangerous asteroid may be tipped off by a test of technology that is set to launch.
A proposal to neutralise a large space rock headed for Earth will be evaluated by the Dart mission.
The object called Dimorphos will be crashed into to see how much it can be altered.
If a chunk of debris measuring a few hundred metres across were to hit our planet, it could cause a lot of damage.
It's the first attempt to divert an asteroid to learn how to protect Earth.
DART will only be changing the period of the Dimorphos' flight by a small amount. Kelly Fast, from the planetary defense coordination office, said that all that's needed is for an asteroid to be discovered.
On Wednesday, a Falcon 9 rocket will blast off from the Space Force Base in California.
Most asteroids pose no threat to our planet and are left over building blocks of the Solar System. A collision may occur when a space rock's path crosses that of Earth so that the two objects intersect at the same time.
A pair of asteroids that are close to each other will be targeted by the Dart mission. The larger of the two objects, Didymos, is around 780m across, while the smaller object, Dimorphos, is 160m wide.
A typical nuclear bomb has the same energy as a Dimorphos object and could cause tens of thousands of casualties. Asteroids with a diameter of 300m and larger could cause a lot of destruction, while those with a diameter of 1 km could have a lot of effects.
After it launches, it will follow its own path around the Sun. The intercept will take place in September of 2022.
The Dimorphos will be hit at a speed of around 15,000mph. The object's speed should be changed by a fraction of a millimetre per second. It could be enough to knock an object off a collision course.
Tom Statler, the mission's program scientist, said that the most likely asteroid threat would be from an asteroid around this size.
Congress directed Nasa to find and track 90 percent of near-Earth asteroids larger than 140m. 40% of the asteroids in this category have actually been found, but no known asteroids pose an immediate threat to Earth.
The camera called Draco is in Dart and will help the craft point itself in the correct direction to collide with Dimorphos.
A small Italian-built satellite will be deployed by the American spaceship about 10 days before the target is hit. The smaller craft will send back images of the impact, as well as the debris that kicked up.
The tiny change in Dimorphos' path around Didymos will be measured by telescopes. Tom Statler asked if we really diverted the asteroid and how efficient we were.
The perfect natural laboratory for such a test is a binary. The impact should change Dimorphos' position around Didymos by 1%, which can be detected by ground telescopes in weeks or months.
The image is from NASA and Ed Whitman.
The image caption is.
The team inspected the solar array in August.
It would take a long time to measure the change in Dart's orbital period if it were to slam into an asteroid.
To the most powerful telescopes, it appears as a single point of light. Dimorphos blocks some of Didymos' reflected light as it passes in front, while the smaller object moves behind its bigger companion.
Andy Rivkin said that they can measure the dimmings' frequencies and that they know that Dimorphos goes around Didymos for 11 hours.
Astronomers will take those measurements again after the impact. Dr Rivkin, who is based in Maryland, said that they will happen a little bit more frequently.
He said there was a degree of uncertainty over how Dimorphos would respond to the impact because it wasn't known how the interior structure would look. If Dimorphos is relatively solid inside, it could produce a lot of debris, which would give the object an extra push.
The method of dealing with a hazardous asteroid is known as the kinetic impactor technique. There are other options, such as detonating a nuclear bomb and moving the asteroid more slowly.
The company that does it is called SpaceX.
It's Nasa.
There is space.
Space exploration.
Asteroids.
