Graham writes …
This blog post is a very brief heads-up about the upcoming impact event, which is the centre piece of NASA’s DART (Double Asteroid Redirection Test) mission. This will occur, as planned, on 26 September. For more detail about the mission, please refer to the December 2021 blog post, which includes a video discussion between John and myself.
Essentially, this is the first spacecraft mission devoted to planetary defense science. In particular, the objective is to study the effectiveness of the kinetic impactor technique in changing the orbit of an asteroid to prevent a future, devastating asteroid collision with our home planet. Although such collisions with a large asteroid (greater than, say, 1 kilometre in diameter) are very rare, nevertheless we know that such events are inevitable in the long term. For this test, the target asteroid is a 160 metre diameter object called Dimorphos, which itself is in orbit around a larger asteroid (780 metres across) called Didymos. It’s worth pointing out that neither object poses an impact threat to the Earth! The idea is that the spacecraft will impact Dimorphos, causing a tiny change in its orbital speed. Although this change is very difficult to measure directly, the magnitude of the change can be calibrated very precisely by observing long-term changes in Dimorphos’s orbit around Didymos. In particular, the resulting cumulative change in its orbit period over many orbit revolutions can be observed subsequently using Earth-based telescopes.
Watch out for media coverage of this historic event in the coming days, and for information about what DART tells us about planetary defense in slower time.
John Bryant and Graham Swinerd comment on biology, physics and faith.