How to defend Earth against an asteroid
1 Find the asteroid
Ground and spacebased telescopes are used to identify nearEarth objects (NEOs) that could pose a threat when entering Earth’s neighbourhood.
2 Track the asteroid
When an NEO is detected, scientists map its orbit and make repeated observations to assess whether it’s on a collision course with Earth.
3 Characterise the asteroid
Scientists then characterise the asteroid to determine orbit trajectory, size, shape, mass and composition to better understand how to deflect it.
4 Deflect the asteroid
There are three main techniques to deflect an asteroid: use gravity to pull the asteroid off course, smash a spacecraft into the asteroid or use lasers to vaporise the asteroid.
5 Global coordination
An impact would affect the world, and needs a cohesive worldwide response effort. Planetary defence requires advanced coordination and education of NEO threats.
DART is a simple spacecraft. The box-shaped main vehicle measures roughly 1.2 by 1.3 by 1.3 metres (3.9 by 4.3 by 4.3 feet) – about the size of a refrigerator. Each of the two large solar arrays is 8.5 metres (27.9 feet) long when fully deployed.
The DART spacecraft contains just one instrument, the Didymos Reconnaissance and Asteroid Camera for Optical Navigation (DRACO). It turns out that if your primary goal is to smash into an asteroid, you don’t need to take a lot with you.
Once DART launches on its SpaceX Falcon 9, it will deploy its Roll Out Solar Arrays (ROSA) to power itself for the journey to Didymos. Scientists tested the ROSA arrays on board the International Space Station in June 2017, and they were deemed suitable to provide the power required to support DART’s electric propulsion system. In fact, NASA is adding larger versions of the ROSA arrays to the space station’s own power grid. The DART spacecraft will use the next-generation, fuel
efficient NASA Evolutionary Xenon Thruster – Commercial (NEXT-C) solar-electric propulsion system as part of its in-space propulsion.
DART will be guided to its target Dimorphos by sophisticated autonomous navigation software.
It’s no easy feat to locate a target that’s 160 metres (525 feet) in diameter and 11 million kilometres (6.8 million miles) from Earth. The navigation software is designed to identify both Didymos and Dimorphos and distinguish between the two so that DART can be directed to the smaller body, Dimorphos, for its impactful mission.
As the spacecraft approaches its target, DRACO, the onboard high-resolution camera, will help navigate the DART spacecraft and take measurements of the target asteroid, including the size and shape of Dimorphos.
But the DART spacecraft won’t be making its journey to the near-Earth asteroid binary alone. The spacecraft will be joined by LICIACube, or the Light Italian Cubesat for Imaging Asteroids. LICIACube is a CubeSat contributed by the Italian Space Agency and built by Italian aerospace engineering company Argotec. The LICIACube weighs just 14 kilograms and measures roughly the length of an adult’s hand and forearm. The little CubeSat has a very important job, and will be deployed by DART around ten days before the spacecraft will impact Dimorphos. LICIACube will then hang back and witness the impact, capturing images of the collision to help researchers verify the efficacy of the impact.
“DART WILL BE GUIDED TO ITS TARGET DIMORPHOS BY SOPHISTICATED AUTONOMOUS NAVIGATION SOFTWARE”