NASA confirms orbit of DART's target asteroid; collision to take place on September 27

NASA has confirmed the orbit of the asteroid moonlet Dimorphos which is a target of the DART spacecraft launched on November 24, last year. This confirmation was made following a six-night observation campaign using ground-based telescopes and now the agency knows where the asteroid would be when DART collides with it.

Short for Double Asteroid Redirection Test, the DART mission is NASA’s first attempt to artificially deflect an asteroid to churn out planetary defence ideas for the future. Recently, NASA even shared visuals of the asteroid moving across the night sky.

Where would Dimorphous be at the time of impact?

The observations have confirmed that the asteroid will be approximately 10.8 million kilometres when it makes its closest approach to Earth in late September to early October. According to NASA, the DART spacecraft is scheduled to ram into the space rock at 4:44 am IST on September 27 (7:14 EDT on Sept 26). Notably, the Dimorphos is not an independent asteroid but is part of a binary system, meaning it orbits a bigger asteroid named Didymos. While Dimorphos has a diameter of 160 metres, its parent asteroid measures 780 metres across. 

"The measurements the team made in early 2021 were critical for making sure that DART arrived at the right place and the right time for its kinetic impact into Dimorphos,” Andy Rivkin, the DART investigation team co-lead said in a statement. "Confirming those measurements with new observations shows us that we don’t need any course changes and we’re already right on target". 

NASA says that besides confirming Dimorphos’ orbital period and expected location, the teams also refined the process they will use to determine whether DART successfully changed Dimorphos’s orbit post-impact. If the spacecraft is successful in altering the asteroid's path, it is expected to move closer to Didymos which would reduce its orbital period. However, scientists are eying careful measurements to confirm that nothing other than the spacecraft had a role in affecting the asteroid's orbit. The other unwanted factor of concern is radiation recoil from the asteroid’s Sun-warmed surface, which could also play a role in changing the orbit. 

Following the impact, mission teams will again take measurements using the ground-based telescopes in October to calculate Dimorphos' new orbit. Scientists hope that the time it takes the moonlet to orbit Didymos would be reduced by several minutes.