One of the biggest dangers to humanity is an asteroid impact. At basically anytime, an asteroid could slam into Earth causing widespread destruction. We don't currently have a way to stop an asteroid on a collision course with us, but NASA designed a mission to practice moving a dangerous asteroid away from Earth.
​
Scientists have studied multiple different ways to divert hazardous asteroids. They have considered nuclear bombs, lasers, paint chips, and solar sails. But the simplest option is a kinetic impactor, simply crashing something into an asteroid at the right angle, moving it in a different direction.
DART
The DART mission is managed by John Hopkin University's Applied Physics Laboratory (APL) as a part of the Solar System Exploration Program, which manages miscellaneous planetary science missions.
Credit: NASA/Johns Hopkins APL/Steve Gribben
Goal
The goal of DART was to test out changing the orbit of an asteroid. It did this by crashing into Dimorphos, the moon of 65803 Didymos. It was the first planetary-defense mission to ever launch.
Name
DART is an acronym for Double Asteroid Redirection Test.
Selection
Work on DART began around 2015 in collaboration with the European Space Agency (ESA). Its preliminary design was completed in 2017 and spacecraft construction began in 2018. It is the first mission to be funded by the Planetary Defense Coordination Office, which is responsible for developing ways to defend our planet from asteroids
Difficulties
Impacting a tiny asteroid requires a precisely calculated trajectory and extreme precision. And because of the communication delay the final course corrections had to be done autonomously by the DART spacecraft.
Dimorphos
NASA selected the Didymos system to experiment with moving asteroids. DART collided with Dimorphos, the moon that orbits the larger Dimorphos. After analyzing the dust cloud and brightness of the system, scientists determined that DART had shortened Dimporphos' orbit by 33 minutes, making it the first Solar System object to have its orbit changed by humans. The asteroids were never in a position to cause harm to Earth and were not diverted toward Earth.
Didymos
DART Mission
DART is part of an international collaboration, the Asteroid Impact and Deflection Assessment (AIDA), which is using two spacecraft, 3 CubeSats, and multiple observatories on Earth and in space to demonstrate and study changing an asteroid's orbit. DART, a low-budget spacecraft loaded with technology demonstrators, is the main part of the program, and it launched in November 2021. 15 days before DART destroyed itself for science, it released a small CubeSat: LICIACube. The collision was witnessed by this CubeSat, DART's camera, and a cohort of observatories on and off the Earth.
DART crashed into Dimorphos on September 26th, 2022, shortening its orbit around Didymos from 11 hours and 55-minutes to 11 hours and 23 minutes.
Credit: NASA/John Hopkins APL
Dozens of telescopes observed the Didymos system in the days before and after the collision. The campaign included a large diversity of telescopes from all seven continents. They ranged in size from a 0.3 meter telescope in Qatar, to the four 8.2m telescopes that make up the Very Large Telescope in Chile. Some radio telescopes, Lucy, the Hubble Space Telescope, and JWST, also participated in observations.
Mission Milestones
Didymos and Dimorphos shortly after DART's destructive collision. Taken by LICIACube's LUKE camera. Credit: ASI/NASA
LICIACube
15 days before DART crashed into Dimorphos, a small CubeSat separated from DART. This CubeSat is called LICIACube, and it is a 6U CubeSat built by the Italian company Argotec. LICIACube stands for Light Italian CubeSat for Imaging Asteroids. The name describes the simple purpose: to image asteroids.
It used its two cameras, LUKE, and LEIA to image Dimorphos after DART impacted it.
An engineer from the Italian Space Agency poses next to LICIACube, after it was installed on DART. Credit: NASA/Johns Hopkins APL/Ed Whitman
Hera
Artistic rendering of the Milani CubeSat observing Didymos and Dimorphos. At the end of their missions the two CubeSats will attempt to land on Dimorphos. Credit: ESA
To follow up on the DART mission, the European Space Agency (ESA), is launching the Hera spacecraft in 2024. It will arrive at the Didymos system two years later. It is equipped with a laser altimeter and visible and infrared cameras to answer questions such as: How large is Dimorphos? What is the composition of Dimorphos and Didymos? How big is the crater DART left? Exactly how much did Dimorphos' orbit change? It will deploy two CubeSats, Juventas and Milano which will also perform observations.
Hera, Milani, and Juventas CubeSats will work together to study how DART change the Didymos system. Credit: ESA
A NEXT-C ion thruster prototype undergoing testing. Credit: NASA
The DART spacecraft undergoing final integration before launch. The two ROSAs are the orange cylinders, one is in the process of being attached. The NEXT-C Ion thruster can be seen atop the spacecraft. The RLSA is the white circle in the center of the screen. Credit: NASA/Johns Hopkins APL/Ed Whitman
.png)
An engineer inspects the Transformational Solar Arrays that are installed on DART's Roll Out Solar Arrays. Credit: NASA/John Hopkins APL
DART Spacecraft
Since the DART spacecraft was destroyed as part of the mission, it was simplistic and low budget. During its short mission, it tested out multiple new technologies, including autonomous navigation and Transformational Solar Arrays.
The DART spacecraft used conventional thrusters and an ion thruster for propulsion and steering. The kind of ion thruster that DART used was NASA’s Evolutionary Xenon Thruster-Commercial (NEXT-C). NEXT-C is the successor to the NSTAR Ion engine, which was used on the Dawn spacecraft. It was developed by NASA and is sold commercially by Aerojet Rocketdyne. It is currently the most powerful ion thruster ever created.
DART only carried one science instrument, the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO). It was a small camera based on the LORRI instrument currently on NASA’s New Horizons spacecraft. DRACO helped DART autonomously navigate to Dimorphos and took real-time images as it approached the asteroid.
For power, DART used Roll-Out Solar Arrays (ROSA). These solar cells do not fold out but roll out. This allows them to take up less space and be deployed easily. ROSA solar panels are currently being added to the International Space Station.
NASA is also testing out Transformational Solar Arrays on small sections of the ROSA. These arrays use reflective materials to concentrate solar power onto a few solar cells. These arrays could be more efficient than ordinary solar cells, and could allow solar-powered spacecraft to explore beyond the asteroid belt.
To communicate with Earth, DART used a novel Radial Line Slot Array (RLSA). An RLSA is able to send and receive messages at the same time.
Conclusion
DART was a highly successful and precedent-setting mission. Using data from DART and telescopes, scientists have already discovered that Didymos and Dimorphos have the same density and similar composition. By continuing to study these asteroids, using telescopes, and the upcoming Hera spacecraft, we can check our math and prepare to deflect an actually dangerous asteroid.​
​
DART is NASA's first planetary defense spacecraft. Planetary defense is important. Though the chance of an asteroid hitting Earth and causing widespread damage is minuscule, the effects could set humanity back centuries, or destroy us altogether. This is why NASA opened the Planetary Defense Coordination Office (PDCO) in 2016 to coordinate planetary defense efforts. An infrared telescope known as NEO Surveyor is scheduled to launch in 2028 and will continue to search for and study hazardous asteroids.
​
Using DART, humans moved a celestial object. Decades of work in mathematics, astronomy, and aerospace engineering have led up to this accomplishment. The investment by our governments in space exploration is paying off and could protect our planet from destruction. With DART, advances in solar panel technology, ion propulsion, and automated navigation were made. We cannot predict how these advances will be used by future scientists and engineers. We can only dream.