April 13, 2024

Radar trip to the center of the Hera asteroid with Juventas CubeSat

Space Security

03/27/2024
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A small spacecraft the size of a shoebox delivered to ESA’s Hera mission this week promises to make a giant leap forward in planetary science. Once deployed from the Hera spacecraft into the Didymos binary asteroid system, the Juventas CubeSat will perform the first radar probe inside an asteroid, peering deep into the heart of the Great Pyramid-sized moon Dimorphos.

Juventas CubeSat arrived at ESTEC Test Center

“Today’s asteroids are collisional fragments of the original building blocks of our entire Solar System, so being able to see how an asteroid’s interior is structured will give us valuable insights into the evolution of the Solar System as well as defense. planetary,” explains Michael Kueppers, ESA’s Hera project scientist. “Is this asteroid a solid monolith or a pile of rubble held together by its gravity? The answer has practical consequences for how incoming asteroids might be deflected from Earth in the future.”

Measuring just 37x23x10 cm in size, the Juventas CubeSat was overseen for ESA by Luxembourg company GomSpace, with spacecraft integration taking place at GomSpace’s headquarters in Denmark. The company specializes in CubeSats – small, low-budget satellites assembled from standardized 10cm boxes – although they are generally intended for Earth orbit.

Juventas studies the internal structure of the asteroid

Building for deep space

Jan Persson leads the Juventas project for GomSpace: “This is a very different mission compared to the usual CubeSats we manufacture and fly. Going beyond Earth’s orbit and into deep space is a rare opportunity that requires extremely precise attention to detail. Juventas also needs a navigation system agile enough to fly around an asteroid.”

Hera’s CubeSat deployment process

ESA’s Hera asteroid mission is Europe’s contribution to an international planetary defense experiment. Following the DART mission’s impact with the asteroid Dimorphos, a moon of the larger asteroid Didymos, in 2022 – modifying its orbit around Didymos and sending a cloud of debris thousands of kilometers into space – Hera will return to Dimorphos to perform a close-up survey of the crater left by DART. The mission will also measure the mass and composition of Dimorphos, along with that of Didymos.

Hera is due to launch in October 2024, and on board will be two CubeSats for close-up observations of the asteroid pair: Juventas will be accompanied by the Milani hyperspectral mission. The trio will remain connected around the asteroids through an innovative satellite link system.

Hera, her CubeSats and her rocky destiny

The smallest radar to fly in space

Named after the Roman name of Hera’s daughter, Juventas may be small, but he has a broad technical footprint. Its low-frequency radar instrument – ​​the smallest radar system flown in space – was designed by France’s Institut de Planétologie et d’Astrophysique de Grenoble, the Université Grenoble Alpes and the Technical University Dresden, with electronic components coming from EmTroniX in Luxembourg. Its radar signals will be transmitted from a quartet of 1.5 m long antennas, longer than the Juventas spacecraft itself, which were supplied by Astronika in Poland.

“The Juventas Radar – or JuRa – instrument is unique and will give the scientific community a rare insight into the formation of an asteroid,” explains Jan Persson. “It has been highly miniaturized to fit into the CubeSat envelope. The main challenge has been that the instrument generates a lot of heat inside the spacecraft, something our thermal design team at GomSpace has been working hard to take care of.”

Juventas Orbit

Hera systems engineer Franco Perez Lissi adds: “To fly alone, Juventas also ships a visible light camera, lidar, star trackers for navigation and a cold gas propulsion system, in addition to the inter-satellite radio link for Share your position and data with Hera. ”

In order to perform its radar survey of the smaller asteroid, Juventas will head to a unique ‘Self-stabilized Terminator Orbit’ around Didymos. This involves orbiting in parallel with the asteroid’s day-night terminator line, balancing the asteroid’s weak gravitational pull with the weak but constant pull of sunlight itself – the pressure of solar radiation. In fact, Didymos’ gravity is so low that Juventas will be orbiting at a rate of just centimeters per second, and JuRa will take advantage of this low speed to send the same encoded signal to the asteroid multiple times, increasing the instrument’s overall signal to ratio. noise. The reflected signals will be decoded and converted into a 3D image on Earth.

Juventas lands in Didymos

Arriving to land

Once Juventas completes its radar survey, it will enter orbit around Dimorphos to begin the next phase of its mission: landing on the smaller asteroid. Jan Persson notes: “We are still analyzing the best way to do this, but our speed must be low enough – on the order of centimeters per second – for Juventas to descend without bouncing back into space. Built-in accelerometers and gyroscopes will collect data from this moment to learn more about the surface’s properties. When Juventas finally stops, we want it to be in a stable configuration to operate the spacecraft’s second science payload, the GRASS gravimeter.”

The first instrument to directly measure gravity on the surface of an asteroid, the Gravimeter for Small Solar System Objects, GRASS, was developed by the Royal Observatory of Belgium (ROB) with the Spanish company EMXYS. The plan is to record how gravity levels on Dimorphos change throughout its orbit around Didymos.

Integration of Juventas into GomSpace

Both the Juventas and Milani CubeSats have now joined their Hera mothership for testing at ESA’s ESTEC Test Center in the Netherlands, the largest spacecraft testing facility in Europe. The trio will be placed in the Maxwell electromagnetic compatibility chamber to verify that their inter-satellite links work as planned.

The Amazing Adventures of Hera Mission – Introducing Hera

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