ESA troubleshooting JUICE radar antenna

A radar antenna on a European mission to Jupiter has yet to fully deploy after launch, although project officials say they still have plenty of options to fix the problem. The European Space Agency said April 28 that the radar instrument on the Jupiter Icy Moons Explorer (JUICE) spacecraft had not fully deployed its 16-meter antenna as expected in the week after its April 13 launch. The antenna, extending from either side of the spacecraft, was only about a third of its intended length. Engineers suspect that a pin in the antenna is stuck, keeping the antenna stowed. “In this case, it is thought that just a matter of millimeters could make the difference to set the rest of the radar free,” the agency said in a statement. ESA is considering other measures to deploy the antenna. An upcoming engine burn will shake the spacecraft, potentially freeing the pin. The spacecraft will also rotate so that the antenna, currently in shadow, will move into sunlight and warm up. The radar instrument, called Radar for Icy Moons Exploration (RIME), is one of 10 instruments on JUICE. It is designed to probe into the icy surfaces of Jupiter’s moons Europa, Ganymede and Callisto to a depth of nine kilometers. Development of RIME was led by the University of Trento in Italy, with NASA’s Jet Propulsion Laboratory contributing components for the instrument. RIME is based on radar instruments flown on two Mars missions, ESA’s Mars Express and NASA’s Mars Reconnaissance Orbiter. Many of the RIME team members worked on those two missions.

The antenna for JUICE's RIME instrument in its stowed configuration shortly after launch. The antenna, 16 meters long, had not fully deployed two weeks after launch. Credit: ESA

The problem with RIME is the only major issue reported during the commissioning phase of JUICE, which is set to last two months. Other many systems, including the deployment of a 10.6-meter magnetometer boom, have taken place without incident.

JUICE, which will arrive in the Jupiter system in 2031, is one of ESA’s flagship science missions. “It is really a fantastic mission. It is ESA’s most complex mission this decade in terms of space science missions,” Josef Aschbacher, director general of ESA, said in an interview during the 38th Space Symposium, days after the launch of JUICE.

Ariane 5 ready to launch ESA’s JUICE mission to Jupiter

Europe’s first mission to Jupiter is ready to launch on the next to last flight of the Ariane 5 on April 13. The Ariane 5 rocket, carrying the European Space Agency’s Jupiter Icy Moons Explorer, or JUICE, spacecraft rolled out to the pad at Kourou, French Guiana, on April 11. Liftoff is scheduled for 8:15 a.m. Eastern April 13 in an instantaneous launch window. The launch will start a long journey for the six-ton spacecraft. It will perform several gravity-assist flybys of the Earth and Venus between August 2024 and January 2029 before arriving at Jupiter in mid-2031. Once at Jupiter, it will conduct 35 flybys of the large moons Europa, Ganymede and Callisto before going into orbit around Ganymede, the solar system’s largest moon. “The main goal is to understand whether there are habitable environments among those icy moons,” said Olivier Witasse, JUICE project scientist at ESA, in an April 6 briefing. “We will characterize in particular the liquid water oceans which are inside the icy moons.” JUICE will carry out those observations with a suite of 10 science instruments of which one, an ultraviolet imaging spectrograph, is provided by NASA. Several other instruments include contributions from NASA, the Japanese space agency JAXA and the Israel Space Agency. JUICE will be joined by NASA’s Europa Clipper mission, scheduled to launch in October 2024 and arrive at Jupiter in 2030. That spacecraft will conduct dozens of flybys of Europa to study the potential for life on that icy moon.

The Ariane 5 launching ESA's JUICE mission rolled out to the launch pad April 11. Credit: ESA/CNES/Arianespace/Optique vidéo du CSG/P.Baudon

It will be “very fantastic” to have both Europa Clipper and JUICE operating at the same time in the Jovian system, Witasse said. “The two missions are very complementary,” with the potential of joint observations. One example is planned flybys of Europa by the two spacecraft just four hours apart.

JUICE will focus more on Ganymede, entering orbit around the moon in late 2034 and remaining there through the end of the mission, currently planned for September 2035. That orbit will be at an altitude of 500 kilometers, but if there is sufficient fuel left on the spacecraft, he said the spacecraft could lower its orbit to 200 kilometers.

JUICE ultimately will crash onto the surface of Ganymede. “With the current knowledge of Ganymede, we can crash on the surface” without violating planetary protection guidelines to prevent harmful contamination. “We have shown that we cannot contaminate any subsurface ocean even if we crash on the surface.”

The launch is the sixth flight of the Ariane 5 to carry ESA science missions. The rocket has previously launched the XMM-Newton X-ray observatory, Rosetta comet mission, Herschel and Planck observatories, the BepiColombo mission to Mercury and, most recently, the James Webb Space Telescope, a NASA-led mission with European contributions.

Preparations for the JUICE launch have been similar to Ariane 5 missions with the exception of enhanced cleanliness requirements, according to Veronique Loisel, JUICE project director at Arianespace. That is similar to launches of imaging satellites, she said, but with additional contamination monitoring also used for the launch of JWST.

The launch is also the penultimate flight for the Ariane 5. The vehicle is scheduled to make its final launch in late June, carrying the Syracuse 4B military communications satellite for France and the Heinrich Hertz communications satellite for the German government.

“Is it routine? Never. Is it of special significance? Yes,” said Ruedeger Albat, head of the Ariane 5 program at ESA, of the final launches of the rocket. For those final launches there is a reinforced qualification monitoring and verification program, he said, but otherwise operations are kept as close to normal as possible.

He compared those final launches to an airline pilot’s final flight before retirement. “He will fly with much attention but stick as much as possible to nominal operations.”