Hera Mission Launches to Witness Asteroid-Crash Aftermath

Two years ago, NASA’s Double Asteroid Redirect Test (DART) mission intentionally ran into the asteroid moonlet Dimorphos at 15,000 mph (6.6 km/s). Now, a new mission is headed to the scene of the collision to show us a detailed view of the aftermath.

A SpaceX Falcon 9 rocket lifted off from Cape Canaveral Space Force Station in Florida on October 7th at 16:52 UT / 10:52 a.m. EDT with the European Space Agency’s Hera Mission. The launch marks one of the first collaborations of NASA, ESA, and SpaceX. (SpaceX also launched ESA's Euclid space telescope last year.)

Lift-off and ascent were nominal. Hera successfully deployed from the Falcon 9 upper stage booster 1 hour and 53 minutes after launch, and ESA’s Estrack ground stations picked up signals from Hera three minutes later. Solar panels have also successfully deployed.

ESA aims to use Hera to better understand DART's experimental collision and, ultimately, turn it into a technique for planetary defense.

Now, Hera will head to asteroid 65803 Didymos and its tiny moon Dimorphos. On its way there, the spacecraft will fly by Mars in March 2025, using the opportunity to test its instruments out on the tiny Martian moon Deimos.

Hera will arrive at Didymos on December 14, 2026, entering orbit around the binary pair and examining the impact crater on Dimorphos created by the DART impact. The Hubble Space Telescope saw the debris tail generated by the DART impact, which gives us only some indication of the immense changes that took place on the moonlet's surface. The Hera mission will also aim to understand changes in the asteroids' mutual orbit, refining measurements made from the ground and from Earth orbit.

Both the DART and Hera missions were born as proposals for a program named Asteroid Impact and Deflection Assessment, a joint U.S.-European effort that started more than a decade ago. Once approved, Hera went from design and development to completion for launch in just four years. Hera carries a suite of instruments, including two cameras, a hyperspectral imager, an infrared imager provided by Japan's space agency JAXA, and an altimeter. The spacecraft also includes an X-Band radio science experiment, which will use radio waves to measure the asteroids' rotation rate and slight gravitational pull.

Two CubeSats are also hitching a ride on Hera, named Juventas and Milani. These will deploy after Hera reaches the system, carrying out observations to complement those of the spacecraft. If all goes as planned, Juventas and Milani will eventually soft-land on the moonlet Dimorphos; Hera will end its days on the surface of larger Didymos.

This event was the 23rd and final launch for the Falcon 9 first stage B1061. Falcon 9 needed all of its fuel to send Hera into orbit and on its way to Didymos, so there was no fuel remaining for a recovery landing and reuse.

Problems with a Falcon 9 second stage in September had planners worrying that the launches of Hera as well as of Europa Clipper (launching on a Falcon Heavy) might slip. But since this launch didn't have a second-stage reentry planned, the Federal Aviation Authority gave the Falcon 9 the go-ahead.

Meanwhile, Europa Clipper's lift-off has slipped to no earlier than October 12th as Hurricane Milton will take aim at central Florida and the Kennedy Space Center this week. Thankfully, Hera was able to leave Earth before the hurricane started impacting the Space Coast region.

The mission's ambition to study asteroid impacts is a worthy ambition, should we ever have to move an Earthbound asteroid out of the way. DART and Hera together represent an excellent example of international cooperation in the name of planetary defense.

Editorial note (Oct. 9, 2024): The text was edited to note that the Federal Aviation Authority approved this Falcon 9 launch because there was no second-stage reentry planned.