Right now, the Double Asteroid Redirection Test (DART) spacecraft is closing in on its target: a 160-metre-wide mini asteroid called Dimorphos, zipping past Earth tethered in its orbit of its parent asteroid Didymos.
Launched into space by SpaceX’s Falcon Rocket in November, DART is a NASA project run out of John Hopkins University’s Applied Physics Laboratory (APL) to learn whether an asteroid can be moved off-course by a kinetic impact – where motion energy from one object is used to move another.
To determine whether this is possible, the DART spacecraft will be crashed into Dimorphos.
This is a game of millimetres – potentially just a single millimetre – but the smallest adjustment to Dimorphos’ trajectory could shorten its orbital time by around three minutes.
That will be enough to determine success when the DART mission team recalculates Dimorphos’ orbit after the collision. Simply put: shorter orbit equals mission success.
There is new technology and plenty of clever engineering at play on the DART mission too. Here’s a timeline of NASA’s mission to destroy a spaceship on purpose.
The DART Mission: a timeline
April 11 – Joseph Montani, an astronomer at the University of Arizona’s Spacewatch Survey at the Kitt Peak Observatory discovers a 780-metre asteroid orbiting between Earth and Mars. It’s dubbed ‘65803’ or ‘1996 GT’.
November – Astronomers at the Ondrejov Observatory, Czechia, discover 65803 is a binary asteroid system due to the presence of a natural satellite, about 160 metres in diameter, in orbit around the larger asteroid.
July 13 – The International Astronomical Union (IAU) approves Montani’s proposed name for 65803, ‘Didymos’, the Greek word for ‘twin’, due to the asteroid’s binary nature.
June 23 – NASA approves the Double Asteroid Redirection Test (DART) as a world-first mission to test kinetic impact as a means of asteroid deflection for planetary defence.
April 12 – SpaceX is chosen as the launch-service provider for the DART mission for a cost of around US$69 million. A launch schedule of June 2021 for the Falcon 9 rocket to send DART to space is set.
November 15 – NASA confirms a test of its Evolutionary Xenon Thruster – Commercial (NEXT-C) in a vacuum chamber. This electric propulsion system is to undergo its first in-space test in the DART mission.
May 15 – John Hopkins University’s Applied Physics Laboratory (APL) begins final assembly on the DART spacecraft – a vehicle the size of a big refrigerator – for the final fitout of its critical operating systems and its only on-board instrument: the Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO). DRACO is responsible for guiding the ship to its collision point and sending images of the event back to the APL team on Earth.
June 23 – International Astronomical Union redubs the moonlet ‘Dimorphos’ on a suggestion by planetary scientist Kleomenis Tsiganis. Dimorphos is Greek for ‘having two forms’. Tsiganis explains the inspiration as: “[Dimorphos] will be known to us in two very different forms, the one seen by DART before the impact, and the other seen by Hera a few years later.”
January 7-11 – the DART mission team conducts a pre-environmental review presentation to NASA, APL and independent experts. Once the review was signed-off by these experts, the DART team moved to environmental testing.
February 18 – A risk assessment relating to the DART project schedule decides the launch window of 24 November 2021 – 15 February 2022 be adopted for the mission.
August – APL attaches the ROSA (Roll-Out Solar Array) and DRACO to the DART spacecraft ahead of launch. The 10-metre-long ROSA ‘wings’ use solar energy to generate the electricity required to power the spacecraft.
October – The 14-kilogram LICIACube (Light Italian CubeSat for Imaging Asteroids) is inserted into the DART spacecraft ahead of launch. Built by the Italian Space Agency (ASI), LICIACube will be ejected from the spacecraft prior to collision where it will record the collision with Dimorphos and send the images back to the mission team. 60 kilograms of xenon is added to the NEXT-C ion engine.
October 2 – DART arrives at the Vadenberg Space Force Base in preparation for loading onto the SpaceX Falcon 9 rocket.
October 26 – DART is moved into the SpaceX Payload Processing Facility at Vandenberg.
October 28 – DART’s fuel tank is filled with 50 kilograms of hydrazine propellent for spacecraft manoeuvres and altitude control.
November 10 – DART is ‘mated’ to an adaptor atop the Falcon 9 rocket.
November 24 – SpaceX Falcon 9 rocket launches from Vandenberg Space Force Space in California with the DART spacecraft on board at 1:21am (USEDT), with separation from the second stage of the rocket occurring at 2:17am, and the extension of its ROSA solar array taking place at around 4:17am. Interception is scheduled between 26 September and 1 October 2022.
December 7 – DART sends first images of space taken by DRACO to mission control, depicting the constellations Perseus, Aries and Taurus; and Messier 38 (the Starfish Cluster), some 4,800 lightyears from Earth. DART’s collision date is updated to 26 September 2022.
May 27 – DART transmits images of the star Vega – a bright star about 25 light years away – as part of ongoing instrumentation tests.
July 1 (and August 2) – DRACO captures images of Jupiter and its moons Ganymede, Europa, Io and Callisto as part of a test of the Small-body Maneuvering Autonomous Real Time Navigation (SMART Nav) system that will help DART navigate to its impact point.
July 7 – DART’s investigation team completes a six-night observation from the Lowell Discovery Telescope (Arizona) and Magellan Telescope (Chile) to confirm the orbit of Dimorphos around Didymos. Calculating the duration of orbit prior to impact will allow the team to determine whether DART manages to alter the orbit of Dimorphos. A shorter post-crash orbit length would indicate the mission was a success.
July 27 – DRACO captures its first image of Didymos at approximately 32 million miles away.
August 12, 13, 22 – DART returns follow-up DRACO-captured images of Didymos.
September 11 – Mission control transmits signal to DART to release LICIACube at 7:14pm (USEDT). Successful release was confirmed approximately on hour later.
September 26 – Impact is scheduled to occur at 7:14pm USEDT (September 27, 9:14am AEST).