Against the Odds, Hera Lifts Off on Its Planetary Defense Mission

Against the Odds, Hera Lifts Off on Its Planetary Defense Mission

Despite a grim weather forecast, ESA’s Hera planetary defense spacecraft lifted off on time this morning enroute to the double asteroid Didymos/Dimorphos. Hera will study the after-effects of NASA’s 2022 DART mission that deliberately impacted Dimorphos and changed its orbit — the first time humans affected the course of a planetary object, a useful capability if we ever need to divert an asteroid that threatens Earth.

With Hurricane Milton growing in the Gulf of Mexico, the weather forecast was only 15 percent favorable for today’s 10:52 am ET launch on a Space X Falcon 9 from Cape Canaveral Space Force Station. The launch window was instantaneous, meaning it had to launch at that moment or not until the next day.  SpaceX and the U.S. Space Force’s Space Launch Delta 45 Weather Squadron closely monitored a variety of weather conditions and remained optimistic. Indeed, when 10:52 am ET arrived, a break occurred just long enough for Hera to lift off and it quickly disappeared into the clouds.

Cameras on the rocket provided downward looking views of ascent as well as separation of the first and second stages, setting Hera free on its two-year journey to Didymos/Dimorphos.

SpaceX usually recovers and reuses Falcon 9 first stages, but in this case every drop of fuel was needed to send Hera on its journey. None was left for a boost-back burn, but this first stage had already sent payloads into space 22 times so had more than proved its mettle.

After two second stage firings 45 minutes apart, Hera separated at 12:08 pm ET and ESA’s Space Operations Centre (ESOC) in Darmstadt, Germany anxiously awaited the next critical step, Acquisition of Signal. The applause was loud on ESA’s broadcast when AOS through NASA’s Deep Space Network tracking station in Goldstone, CA was confirmed.

Hera was built in just four years, a comparatively short time for a planetary spacecraft especially taking COVID into account, and cost €363 million ($400 million). Hera project manager Ian Carnelli said at an October 2 ESA briefing that they actually came in under cost, saving about €20 million ($22 million). Part of the savings came from using a SpaceX Falcon 9 instead of Europe’s new Ariane 6 to launch the spacecraft. ESA rarely uses non-European rockets, but delays in Ariane 6’s debut caused them to buy several Falcon 9s for time-critical missions like this one.

ESA Director General Josef Aschbacher watched the launch from ESOC and joined ESA’s broadcast after AOS was confirmed, praising the ESA-industry team. “This has been put together in a very short time, as we all know, and a lot of stress has been on the teams. … This has been an example of newspace at work where we deliver almost 1.1 tons of spacecraft, 20 instruments, and really so sophisticated, but in a really short period of time, so really a big thank you.” He also thanked NASA and Japan’s space agency, JAXA, which provided the Thermal Infrared Imager.

 

Hera is now on its way. At a post-launch briefing today, Hera Project Scientist Michael Kueppers said they expect to get images of the Earth and Moon from Hera on Thursday and Friday and could release them as soon as Saturday. The next big event will be in March when Hera swings by Mars to get a gravity assist and collects data about the planet and its moon Deimos.  Hera will arrive at Didymos/Dimorphos in October 2026.

Didymos/Dimorphos is a double asteroid, with Dimorphos orbiting Didymos. ESA named the spacecraft Hera after the Greek goddess of marriage.  Once there, Hera’s suite of instruments will study the asteroid pair itself and serve as a communications link to two shoebox-sized cubesats, Juventas and Milani, that are also part of the mission. Juventas, named for the daughter of Hera, carries the smallest radar instrument ever flown in space according to ESA. Milani, named for the late Prof. Andrea Milani of Italy’s University of Pisa, will study Didymos and Dimorphos with a hyperspectral scanner, a camera and other instruments. Milani was a key originator of the concept that became Hera.

Hera is a companion to NASA’s Double Asteroid Redirection Test (DART). DART deliberately ran into Dimorphos in 2022 as a planetary defense experiment to determine whether kinetic energy could alter an asteroid’s path. Scientists already know it did — the period of Dimorphos’s orbit changed by 33 minutes — but Hera will do detailed observations of both asteroids and the resulting debris field. The cubesats will end their missions by landing on Dimorphos to get even more data.

On September 28, 2022, the SOAR Telescope in Chile, operated by NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory), imaged the more than 10,000 kilometer-long trail of debris blasted from the surface of Dimorphos by NASA’s DART spacecraft.

Our solar system has 1.3 million asteroids of varying sizes and shapes. A very large asteroid 10 kilometers or more in diameter is thought to have caused the extinction of the dinosaurs 66 million years ago when it impacted Earth, sending clouds of dust and debris into the atmosphere and cooling the climate. The cold-blooded creatures couldn’t survive.

Dimorphos is tiny in comparison, just 160 meters in diameter, but DART and Hera are a step towards understanding what could be done to deflect an incoming asteroid if necessary.

No planet-threatening asteroids are on the horizon, but a smaller asteroid will make a very close pass of Earth in 2029.  Apophis will come as close as 40,000 kilometers, about the same distance as geostationary satellites. Scientists are eager to make detailed observations of Apophis not only with ground-based instruments, but with spacecraft both before and after it passes Earth. Carnelli said the money they saved on Hera will be used for the Rapid Apophis Mission for Space Safety (RAMSES) mission to rendezvous with Apophis before it gets here. NASA’s OSIRIS-APEX will study Apophis after it goes by.

The weather wasn’t the only potential impediment to Hera’s launch today. The second stage of SpaceX’s Falcon 9 that launched NASA’s Crew-9 to the International Space Station on September 28 experienced an anomaly that caused the second stage to reenter and land in the ocean outside the designated area. The FAA oversees public safety of commercial space launches. It is still reviewing SpaceX’s investigation of what happened and how to ensure it doesn’t recur and had to approve this launch. According to a statement from the FAA on Sunday, it approved the Hera launch on Friday. It’s not clear why they didn’t make the decision public at that time. The permission is only for this launch.

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