Each orbit will expose Juno’s instruments to a radiation dose equivalent to 100 million dental X-rays.
Mission scientists at NASA working with the probe Juno, which entered into orbit around Jupiter on July 4 this year, are gearing up for an exciting weekend. At 5.51 am PST (6.21 pm IST) on Saturday, Juno made its closest approach to the gas giant, coming as close as 4,200 km to its tumultuous atmosphere while flying at a speed of 208,000 km/hr. As it swung by the top of the clouds, its suite of scientific instruments switched on for an hour for the first time since orbital insertion. And so, the Juno mission officially commenced.
Juno reached Jupiter after a five year journey from Earth. Its first task had been to perform two extremely elliptical 53-day orbits around the planet before it could settle into more perfect, more circular orbit on October 19. The first of the elliptical orbits was completed on Saturday, and the titanium-vault of a craft has started its second.
To protect against Jupiter massive and abrasive radiation belts, the probe’s instruments have all been encased in a titanium structure at its centre. The three solar panels are splayed out from the side of this structure, the whole probe spinning around like a ceiling fan in its orbit. To further reduce risk, the instruments had been switched off while Juno had been in transit.
This is the closest any probe has ever been to Jupiter, and as a result will be able to take the best high-res picture of the planet yet. Juno also represents the first chance scientists will have of observing Jupiter’s poles, which we have never seen clearly before. “This is our first opportunity to really take a close-up look at the king of our solar system and begin to figure out how he works,” Scott Bolton, a physicist at the Southwest Research Institute, San Antonio, and the principal investigator, said in a statement. Juno’s photographs and other observations will be beamed back to Earth over the next few months. Given how far Jupiter is, signals from Juno take 45 minutes to reach ground control.
Juno’s official mission objectives are determining if Jupiter hosts a solid core; studying the magnetic field of this behemoth; following up on clues about how the planet could’ve formed; mapping its gravitational field; and study its atmosphere and auroras. To perform the various attendant tests, Juno carries eight instruments. There’s also JunoCam, a camera to took images that NASA will press in the service of Juno’s public outreach programme. The first high resolution photos from today’s flyby are expected to be released later next week.
The probe will orbit Jupiter 37 times over the next 20 months. Unlike with most other missions, scientists don’t really expect the Juno mission to live longer than its designated duration because its instruments will already have started to get cooked by the radiation belts. Consider: each orbit will expose the instruments to a radiation dose equivalent to 100 million dental X-rays.
Sandhya Ramesh is a science writer focusing on astronomy and earth science.