NASA DART crash highlights: Crash into asteroid successful, here’s what happens next

Here is a recap of the last few seconds before DART crashed into Dimorphos

After NASA’s DART mission, the European Space Agency (ESA) plans to launch the Hera mission in October 2024. Hera is another planetary defence test that is currently under development. It will investigate the Didymos binary asteroid system and measure the outcome of the DART mission in great detail. 

The Hera spacecraft will first rendezvous with the target and then it will begin characterising it in detail. It will measure the internal properties of Dimorphos and the crater made by DART to measure the efficiency of the momentum transfer. Hera will also deploy two Cubesats, Milani and Juventas. These CubeSats will operate in the vicinity of the asteroid for a few months to provide scientific measurements. 

The Didymos system is within 11 million kilometres of Earth and currently, scientists are using dozens of telescopes stationed around the world and in space to observe the asteroid system. In the coming weeks, they will precisely measure the orbital change that happened to Dimorphos to understand how effectively DART deflected the asteroid. These results will help validate the effectiveness of this technique as a reliable method for asteroid deflection. 

ATLAS or Asteroid Terrestrial-impact Last Alert System is an asteroid detection system funded by NASA. It uses three telescopes—one each in Haleakal? and Maunaloa in Hawai’i, and two more in South Africa and Chile—to scan the entire sky every 24 hours to detect near-Earth objects that pose a threat to our planet. Below is ATLAS’ observation of the DART spacecraft impacting the Dimorphos system.

At 8.51 AM IST on September 27, the Artemis 1 mission’s Space Launch System (SLS) rocket and Orion spacecraft left launch pad 39 B and began its 6.4-kilometre journey to the Vehicle Assembly Building at the Kennedy Space Centre. NASA decided to roll back the Artemis 1 stack because of the threat posed by Hurricane Ian.

The kinetic impactor method is not the only trick up scientists’ sleeves. If an asteroid approaching Earth was to be detected early enough, it might be possible to use a method called “gravity tractor,” which involves the use of a spacecraft’s gravity to divert the asteroid.

In this method, instead of crashing into an asteroid, a gravity tractor device would fly along with the asteroid for a long period of time that could last anywhere between years to decades, deviating the path of the asteroid with its own gravitatipnal pull. This technique could potentially work on asteroids of any shape or composition, even if the asteroid in question is just a pile of rubble. 

This method offers great control and could even be used to divert approaching asteroids to a separate location where scientists can use them for research or commercial purposes. But the technique is still untested and it could be decades before we can build, launch and carry out a mitigation mission that uses this technique. 

As Amitabh Sinha explains one of the reasons scientists chose to target Dimorphos was because of its relatively shorter orbit around Didymos. The two asteroids together orbit the sun. In his explained piece, he notes that "a deviation in this orbit was likely to be more noticeable, and thus easier to measure, than say, if Didymos itself was targeted and an attempt was made to measure the change in its orbit around the Sun." Read our full explained on the NASA Dart mission. 

According to NASA's press statement, its investigation team will now observe the asteroid with relying on ground-based telescopes to confirm and determine just how much DART altered the asteroid's orbit around Didymos. Didymos is a much bigger asteroid and one classified as being a potential threat to Earth, according to the space agency. 

NASA notes in its press statement that "researchers expect the impact to shorten Dimorphos’ orbit by about 1%, or roughly 10 minutes; precisely measuring how much the asteroid was deflected is one of the primary purposes of the full-scale test." 

“At its core, DART represents an unprecedented success for planetary defense, but it is also a mission of unity with a real benefit for all humanity,” said NASA Administrator Bill Nelson in a press statement. “As NASA studies the cosmos and our home planet, we’re also working to protect that home, and this international collaboration turned science fiction into science fact, demonstrating one way to protect Earth.”

If you search for NASA Dart on Google, you might be in for a surprise. The search results will also show the spacecraft crashing into the page. Check out NASA's tweet on this below: 

The DART spacecraft has successfully crashed into the asteroid Dimorphos in what is humanity’s first attempt to test a planetary defence mechanism.

The SMART Nav system has stopped manoeuvring and the DART spacecraft is coasting to its impact with the asteroid Dimorphos. The window for sending any commands to the spacecraft is over.

SMART Nav has precision locked onto Dimorphos and it is no longer tracking Didymos at all. With this, the DART mission has completed its last milestone before impact.

NASA has completed the last Status Poll for the mission ahead of the impact. With all systems working as expected, the mission is on the right track. 

The LICIACube, A CubeSat built by the Italian Space Agency, will try to take images of DART's impact with Dimorphos.

Less than 50 minutes before the collision, the DART spacecraft’s SMART Nav is target locked onto Dimorphos.

“We can see Dimorphos and we are on our way. So SMART Nav is looking for bright parts of the image. As Dimorphos gets closer, brighter and bigger, SMART Nav will target it as opposed to Didymos,” said Angela Stickle, planetary geologist and DART Investigation team lead during the NASA livestream.

The DART spacecraft has reached an important milestone as the DRACO instrument is able to detect the asteroid Dimorphos. Until now, DRACO has only been able to detect Didymos, the much larger asteroid. The next milestone is for the SMART Nav system to be locked on to Dimorphos.

Here is an image from October 4, 2021, where technicians are preparing to move NASA’s Double Asteroid Redirection Test (DART) spacecraft from a shipping container onto a work stand at the Astrotech Space Operations Facility at Vandenberg Space Force Base in California. The spacecraft was later launched aboard SpaceX’s Falcon 9 rocket from Vandenberg on November 23, 2021.

NASA's DART spacecraft is scheduled to collide with the asteroid Dimorphos in just two hours

NASA’s DART spacecraft will use a “kinetic impactor” method for deflecting the asteroid Dimorphos. The space agency is using this method because it is the simplest and most technologically mature method available to defend our planet against asteroids. In case an actual asteroid poses a threat to the Earth, we only need to either delay or hasten its intersection with Earth’s orbit by seven minutes. This is because the Earth takes about seven minutes to travel the distance of its diameter. So if an asteroid arrives seven minutes late or early, it will miss our planet completely.

Scientists don’t yet know the exact mass of Dimorphos but it is estimated to be around five billion kilograms. Meanwhile, the DART spacecraft will weigh about 570 kilograms when it crashes into the asteroid. Nancy Chabot, DART coordination lead at NASA compared the collision to a “golf cart crashing into the great pyramid,” during a press conference on September 12. 

The crash is intended to be a “small nudge” that will change the position of the asteroid ever so slightly. In the event of an asteroid that actually poses a threat to Earth, this collision will have to happen years ahead of time. Over the years, the small change in position will add up to a large deviation.

There is no known asteroid that presents a significant risk of impact on Earth in the next 100 years. But there is a 1 in 714 chance that an asteroid called 2009 FD will impact the Earth in 2185. This means that the chance of impact is close to 0.2 per cent. NASA’s Jet Propulsion Laboratory’s Center for NEO (near-Earth object) maintains a Sentry Impact Risk Table, which is updated continuously as new asteroids are discovered and known asteroids are better observed.

ATLAS (Asteroid Terrestrial-impact Last Alert System) is a NASA-funded asteroid detection system operated by the Institute for Astronomy at the University of Hawai’i. It is capable of searching the entire sky every 24 hours for near-Earth objects that pose a potential threat to the planet. It consists of four telescopes—one each in Haleakal? and Maunaloa in Hawai’i, and two more in South Africa and Chile. 

In a single exposure, each of the four ATLAS telescopes can image a part of the sky that is 100 times larger than the full moon. When it is daytime in Hawai’i, the two telescopes located at Sutherland Observing Station in South Africa and El Sauce Observatory in Chile will allow ATLAS to observe the night sky.

The DART spacecraft is not alone on its journey. On September 11, LICIACube, a CubeSat built by the Italian Space agency, separated from the spacecraft. LICIACube is programmed to document the effects of DART’s impact while also capturing images of the asteroid surface and images of the debris ejected due to the collision. 

LICIACube has two optical cameras—LUKE (LICIACube Unit Key Explorer) and LEIA (LICIACube Explorer Imaging for Asteroid). Three minutes after DART’s collision, LICIACube will fly past Dimorphos to confirm the spacecraft impact, observe the evolution of the ejected plume and potentially even capture images of the newly-formed impact crater. 

During the last four hours before the crash, the DART spacecraft will go into the terminal phase where it will operate completely autonomously. It will target Didymos till around 50 minutes before impact. Then, it will manoeuvre by a quarter of a degree in terms of field of view to put itself on course for collision with Dimorphos. 

“That is a very ‘sweaty’ time for us. The spacecraft is so far away that it takes 38 seconds for one-way communication. It will be travelling at a speed of 6 kilometres per second. It is going at a speed that will cover the distance between DC and Philadelphia in about 40 seconds,” explained Evan Smith, deputy mission systems engineer for DART, during a NASA press conference on September 12.

The rapid spin of Didymos suggests that Dimorphos may have formed because of a process known as rotational fission, where material is shed from an asteroid due to fast rotation. Scientists think that Didymos started spinning fast and fast because infrared light was emitted unevenly from its Sun-warmed surface, which would have resulted in a twisting force.

This process could have gained enough momentum over millions of years to release material from the surface. This material could have then gathered to become Dimorphos. While this is a sound theory, other possibilities of formation have not been conclusively ruled out.

While the DART spacecraft was on its way to the planned encounter with the Didymos system, its DRACO instrument captured thousands of images of stars and other cosmic objects, including the image of Jupiter below. 

To test the spacecraft’s SMART Nav system, the DART mission team pointed the DRACO imager at Jupiter. DRACO detected and targeted Jupiter’s moon Europa, similar to how it is expected to visually separate Dimorphos from the larger Didymos. Until that test, all SMART Nav systems tests were done via simulations performed on the ground. 

“We are not aware of a single object right now threatening the earth in the next 100 years. But I guarantee you that there will eventually be one. We can deduce that from the geological records of our planet and even data from the Moon. We want to test the technology now so that it is ready in case we ever need it,” said Thomas Zurbuchen, the associate administrator for the Science Mission Directorate at NASA, during a press conference on September 12. 

The DART spacecraft lifted off from Space Launch Complex 4E at the Vandenberg Space Force Base in California atop a SpaceX Falcon 9 rocket at 1.21 AM ET (10.51 AM IST) on November 24, 2021. Image credit: NASA/Bill Ingalls

The asteroid Didymos and the small moonlet Dimorphos make up a binary asteroid system. Didymos is about 780 metres in diameter while Dimorphos is about 160 metres in diameter. Didymos is shaped like a spinning top and has a raised ridge running along its equator, which is a common shape among binary asteroids. But not much is known about Dimorphos except that it appears to be somewhat elongated. 

The binary asteroid system poses no threat to Earth but it occasionally approaches relatively close to our planet. According to NASA, it passed only 0.0487 astronomical units away from our planet in 2003. One astronomical is the distance between the Sun and the Earth.

The DART spacecraft has only one instrument on board—DRACO or the Didymos Reconnaissance and Asteroid Camera for Optical navigation. Not only will this high-resolution camera capture images of Didymos and Dimorphos, but it will also be supporting DART’s autonomous guidance system that will take over about one hour before the planned collision.