Extract from The Guardian
Test drive of planetary defence system aims to provide data on how to deflect asteroids away from Earth.
A miniaturised satellite will separate from the main spacecraft, enabling images of the impact to be relayed back to Earth.
Our planet is constantly being bombarded with small pieces of debris, but these are usually burned or broken up long before they hit the ground. Once in a while, however, something large enough to do significant damage hits the ground. About 66m years ago, one such collision is thought to have ended the reign of the dinosaurs, ejecting vast amounts of dust and debris into the upper atmosphere, which obscured the sun and caused food chains to collapse. Someday, something similar could call time on humanity’s reign – unless we can find a way to deflect it.
Nasa’s Double Asteroid Redirection Test (Dart) mission is the first attempt to test if such asteroid deflection is a realistic strategy: investigating whether a spacecraft can autonomously navigate to a target asteroid and intentionally collide with it, as well as measuring the amount of deflection.
“This is the first step to actually trial a way of preventing near-Earth object impact,” said Jay Tate, the director of the National Near Earth Objects Information Centre in Knighton in Powys, Wales. “If it works, it would be a big deal, because it would prove that we have the technical capability of protecting ourselves.”
The 610kg Dart spacecraft is scheduled to blast off from the Vandenberg Space Force Base in California onboard a SpaceX Falcon 9 rocket at about 6.21am UK time on Wednesday. Its target is the Didymos system – a harmless pair of asteroids consisting of a 163-metre “moonlet” asteroid called Dimorphos that orbits a larger 780-metre asteroid called Didymos – after the Greek for “twin”).
About 10 days before impact, a miniaturised satellite called the Light Italian CubeSat for Imaging of Asteroids (LICIACube), will separate from the main spacecraft, enabling images of the impact to be relayed back to Earth. Combined with observations from ground-based telescopes, and an onboard camera that will capture the final moments before collision, these recordings should enable scientists to calculate the degree to which the impact has altered Dimorphos’s orbit.
The expectation is that it will change the speed of the smaller asteroid by a fraction of 1% and alter its orbital period around the larger asteroid by several minutes.
Then, in November 2024, the European Space Agency’s Hera spacecraft will visit the Didymos system and conduct a further close-up analysis of the consequences of this celestial snooker game, capturing details such as the precise mass, makeup and internal structure of Dimorphos, and the size and shape of the crater left by Dart. Such details are vital for transforming asteroid deflection into a scalable and repeatable technique, that could be deployed should an apocalyptic asteroid ever be detected heading towards Earth.
Even then, it is unlikely that any single deflection strategy would be enough. “Assuming it works, [this mission] will provide us with real time ground truths on the effects of a small impactor on a small asteroid,” said Tate. “The problem is that no two asteroids or comets are alike, and how you deflect one depends on a huge number of variables: what’s the thing’s made of, how it’s put together, how fast it’s spinning, and of course how much time you’ve got.
“There is no silver bullet in this game. What you need is a whole folder of different deflection methods for different types of target.”
So while this may be one small step towards planetary protection, many more are likely to be necessary to avoid Armageddon.
No comments:
Post a Comment