DART is the name of NASA’s Emergency Emergency Planning On-The-Fly mission, that was officially launched on Friday, May 25, 2020. DART will launch a 1,100kg small impactor spacecraft to the edge of the atmosphere on a trajectory that will have it crash into a space rock of 10 metres-large, thus triggering a reaction-sensing system that will provide comprehensive clues to the impact hazard to Earth. (Asteroids are often in orbits very similar to those used for Earth’s transit. So during observations, it may appear that the asteroid is anywhere from 1.8 to 6km in diameter.)
It will be an absolutely critical mission. The fact that DART is the first to be launched under the Integrated Emergency Planning On-The-Fly concept (you can read more about how it works here), indicates an urgent need to respond in an emergency. The DART launch time is chosen to coincide with the annual COSMIC or Total Lunar eclipse, an event which has the unique ability to cause the sun to shine in a way that causes ultraviolet radiation to burn up any remaining surface out to 100cm. This could be a critical time for an asteroid, one that could be flying over the earth, and last 100 seconds. If an asteroid was on a collision course with the earth, the last thing an observatory would want to see is solar-radiation reflecting back. However, if the moon is blocking the sun, the vehicle’s visual visibility may be very good.
After the spacecraft goes through re-entry and is vaporised, ground-based observations will reveal the actual mass (astronomical unit, M0) of the impact, allowing officials to more accurately plan for the problem of impact in future. The reliability of a swift, detailed response to any asteroid, comet or other celestial object that could endanger the Earth is arguably the most pressing issue that the scientific community faces today.
NASA is responsible for keeping a close eye on nearly 14,000 objects (including asteroids, comets, comets near-Earth objects, comets and asteroids in orbits that closely resemble Earth’s) that are flying near the earth. Of those objects, around 55 are on track to impact the earth within the next 100 years. So just two things to think about when you see DART: Are there going to be opportunities to see it? And will it be on the top of your list to watch when it returns? [NASA]