NASA's Asteroid Deflection mission, DART, was a huge success. Not only did the impact alter the asteroid's orbit, but the mission also surpassed its minimum benchmark by more than 25 times.
An analysis of NASA’s Double Asteroid Redirection Test (DART) data shows the mission was very successful. Data analysis over the past two weeks shows the DART spacecraft’s kinetic impact successfully altered the asteroid’s orbit. It is the first time humanity has purposefully changed a celestial object’s motion. It is also the first time asteroid deflection technology has been demonstrated on full-scale.
Before its collision with DART, Dimorphos took 11 hours and 55 minutes to orbit Didymos, its larger parent asteroid. Using telescopes on Earth, astronomers measured the change of orbit since DART intentionally collided with Dimorphos. Dimorphos’ orbit around Didymos has been altered by 32 minutes as a result of the spacecraft’s impact. This results in an 11-hour and 23-minute orbit instead of the usual 11 hours and 55-minute orbit. Approximately 2 minutes are within the margin of error for this measurement. A successful change in Dimorphos’ orbital period was defined by NASA as 73 seconds or more before DART impacted it. As you can see from the early data, DART surpassed this minimum benchmark by more than 25 times.
Understanding how to deflect asteroids
“This result is an imperative step towards understanding the full effects of DART’s collision with its target asteroid,” said Lori Glaze, director of NASA’s Planetary Science Division. As more data are collected, astronomers can determine whether a mission like DART might be beneficial in the future to protect Earth from an asteroid collision. In addition to ground-based observatories worldwide, the investigation team is also using radar facilities at NASA’s Goldstone planetary radar in California. Experts will also use the Green Bank Observatory in West Virginia, operated by the National Science Foundation. The period measurement is being updated with frequent observations to improve its precision.
Now, the focus is on measuring how well momentum is transferred from DART’s collision with its target at 14,000 miles per hour (22,530 kilometers per hour). Among the findings is further analysis of the “ejecta” – the loads of asteroidal rock that were displaced by the impact and launched into space. Like jets of air shooting out of a balloon, this blast of debris significantly enhanced DART’s push against Dimorphos. However, we need more information about the asteroid’s physical properties, such as its characteristics and strength, to understand how the recoil from the ejecta affects the asteroid. There is still a lot of investigation to be done on these issues.
Future study
According to Nancy Chabot, the DART coordination lead at Johns Hopkins Applied Physics Laboratory (APL), “DART has given us some fascinating data about both asteroid properties and kinetic impactor effectiveness as planetary defense technologies.” This first test of asteroid deflection for planetary defense continues to be studied by the DART team. To estimate Dimorphos’ size and mass, astronomers will examine images of the asteroid taken by DART’s terminal approach cam. Data from the Italian Space Agency’s Light Italian CubeSat for Imaging of Asteroids (LICIACube) will also be used. The Hera project of the ESA will also conduct detailed surveys of both Dimorphos and Didymos in four years. It will focus on the crater left by DART’s collision and measure Dimorphos’ mass precisely. There has never been a hazard from Dimorphos or Didymos to Earth before or after DART’s controlled collision with Dimorphos.
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