Introducing DART: an exciting space mission starting this week.

Just a little while, and then the long-awaited Double Asteroid Redirection Test (DART) mission started. And it promises to be an exciting mission. The spacecraft will head for the asteroid Didymos to attempt to alter its orbit. Because in the future that may be an effective way to protect the earth from dangerous near-Earth objects.

The DART Mission

If all goes according to plan, the DART mission will launch on November 24. DART will be launched aboard a SpaceX Falcon 9 rocket from the military spaceport Vandenberg Air Force Base, located in the US state of California. DART will then arrive at asteroid Didymos in just under a year. Didymos (Greek for twins) is a binary system that consists of two parts. Didymos A has a diameter of 780 meters. Around Didymos A, a smaller celestial body of about 160 meters orbits. “This moon, called Dimorphos, completes one orbit every 11 hours and 55 minutes,” said planetary scientist Nancy Chabot, involved in the DART mission. And this moon, along with the DART spacecraft itself, faces a meaningful but doomed fate.

Speed

The intention is for the DART spacecraft to deliberately smash itself against the small moon. And at about 6 km/sec (about nine times faster than a bullet). As a result, the researchers hope to change Dimorphos’ orbit. Because the spacecraft is about 100 times smaller than Dimorphos, it is necessary for DART to head towards the moon at some speed.

Instruments
DART is a very simple spacecraft. There is therefore only one instrument on board, namely the DRACO instrument (short for Didymos Reconnaissance and Asteroid Camera for Op-nav). This instrument is an imaging camera derived from the Long Range Reconnaissance Imager on NASA’s New Horizons spacecraft. DRACO will image both parts of the Didymos system (so both the asteroid and its moon). In addition, this also includes the autonomous navigation system.

The DART mission will use the so-called kinetic impact technique. This involves gently tapping a space rock, forcing a small change in orbital velocity. DART will demonstrate the technique and from Earth observatories will determine the change in the moon’s orbit. This will give scientists around the world the opportunity to learn more about kinetic impact and whether this is a working strategy for asteroid deflection.

little push

Incidentally, it is not the intention that Dimorphos is completely blown up, Chabot assures us. “It’s just a little push,” she emphasizes. By means of the impact, the researchers only hope to slightly adjust the moon’s orbit. And because Dimorphos is part of a binary system, it’s relatively easy to calculate the custom trajectory after DART hits it. “We think its orbital time could be shortened by ten minutes,” Chabot says. “It would mean that the telescopes would measure 11 hours and 45 minutes after the collision with DART. However, we don’t know for sure yet. These measurements will therefore become one of the main goals of the DART mission.”

Threat to the Earth

We can also reassure you: Didymos currently poses no threat to Earth. The mission is therefore only a demonstration mission to see whether such a technique, in which the direction of a space rock is deflected by means of an impact, works. Although we may not want to think too much about it, it could just be that in the future a space rock will be on a collision course with Earth. And then of course we need to know how to deal with such dangerous near-Earth objects that could potentially damage our planet.

Injury

What damage could a Dimorphos-sized asteroid cause if it hit Earth? “At 160 meters, Dimorphos is a space rock that we are really concerned about,” said Chabot. “A planetoid a kilometer or more in size could even herald global mass extinctions.” It means that a moon like Dimorphos, when it crashes on Earth, can already cause major regional devastation. And that’s why missions like DART’s are so important. We may be able to protect Earth from imminent dangers in the future thanks to the DART mission. The DART mission is therefore a kind of experiment in the context of what NASA calls ‘planetary defense’. Should a potentially dangerous asteroid ever head towards Earth (see box), we may be able to prevent an impact thanks to the knowledge and skills we gain during the DART mission.

More about Potentially Dangerous Asteroids
Astronomers call it a Potentially Hazardous Asteroid if it comes close (in the future) to Earth and is large enough to cause significant regional damage if it hits Earth. Meanwhile, the Minor Planet Center has amassed a huge laundry list of dangerous asteroids. Fairly well-known asteroids on this list include Ryugu (currently visiting spacecraft Hayabusa2) and Bennu (currently orbiting spacecraft OSIRIS-REx). To date, researchers have discovered more than 18,000 near-Earth objects. The largest specimens are of course the easiest to find; it is estimated that astronomers have already detected about 90% of all near-Earth objects larger than a kilometer. However, the big challenge now is to map as many smaller asteroids (up to a size of about 140 metres) as possible. New instruments are currently being built for this, such as the Large Synoptic Survey Telescope, which will become operational in 2022. And in the future – with new technologies and techniques – the hunt for space rocks smaller than 140 meters will also be opened. It is estimated that millions of asteroids in the latter category are still waiting to be discovered.

Didymos is expected to pass through Earth next fall. And researchers have devised it in such a way that DART will ram the moon Dimorphos at exactly that moment. Because this happens relatively close to Earth, scientists can study the fatal impact of DART and its immediate aftermath, with telescopes from the ground and in space. “The distance between the earth and Didymos is then at its smallest,” says Chabot. “That won’t happen again for the next 40 years.”

spectacle

Incidentally, interested parties who gaze at the night sky will unfortunately not be able to witness the spectacle. However, the researchers hope to collect important data with the help of the Hubble Space Telescope and the James Webb Telescope. And, of course, DART itself will also take pictures of his fatal crash. “We receive one photo per second,” says Chabot. “The surface will quickly get closer, until the images stop.” If the scientists don’t receive any more photos, it means that DART successfully rammed Dimorphos. “The final images will therefore be quite spectacular,” said Chabot.

Aftermath

The aftermath of the bombing will then be mapped by the Italian CubeSat called LICIACube. LICIACube is traveling with DART and will separate from the spacecraft about ten days before the crash. “LICIACube will flyby about three minutes after the collision of DART and produce some spectacular images,” said Chabot. CubeSat HERA will then also be launched in 2024, which will further investigate the aftermath of the bombing. The satellite will approach the moon’s surface as far as 200 meters. This allows Hera to produce high-resolution images – 2 cm per pixel. In particular, the researchers want to obtain sharp images of the crater that DART will leave behind on the moon.

All in all, it promises to be a groundbreaking mission, where a space probe will attempt to change the orbit of an asteroid for the first time. And the mission will help us better understand how to protect our precious planet from potentially dangerous future nearers.