High-resolution imaging of Jupiter and its Great Red Spot by the Subaru Telescope and the Gemini North telescope, both on Hawaii’s Mauna Kea peak, is informing NASA’s Juno mission of compelling events in the gas giant’s atmosphere. On July 10, 2017, Juno will fly directly over the planet’s most famous feature at an altitude of only about 5,600 miles (9,000 km).
Throughout the Juno mission, numerous observations of Jupiter by Earth-based telescopes have been acquired in coordination with the mission, to help Juno investigate the giant planet’s atmosphere.
On May 18, 2017, one day before the Juno mission’s sixth close passage (perijove) of Jupiter, the Gemini North and Subaru telescopes simultaneously examined the planet in very high resolution at different wavelengths.
These latest observations supplement others earlier this year in providing information about atmospheric dynamics at different depths at the Great Red Spot — a swirling storm, centuries old and wider than the diameter of Earth — and other regions of the gas giant.
“Jupiter’s mysterious Great Red Spot is probably the best-known feature of Jupiter. This monumental storm has raged on the Solar System’s biggest planet for centuries,” said Juno principal investigator Dr. Scott Bolton, from the Southwest Research Institute.
“Now, Juno and her cloud-penetrating science instruments will dive in to see how deep the roots of this storm go, and help us understand how this giant storm works and what makes it so special.”
The data collection of the Great Red Spot is part of Juno’s next science flyby over Jupiter’s cloud tops.
Perijove will be on Monday, July 10, at 6:55 p.m. PDT (9:55 p.m. EDT, 1:55 a.m. UTC on July 11). At the time of perijove, Juno will be about 2,200 miles (3,500 km) above the planet’s cloud tops.
Eleven minutes and 33 seconds later, Juno will have covered another 24,713 miles (39,771 km) and will be directly above the coiling crimson cloud tops of Jupiter’s Great Red Spot.
The spacecraft will pass about 5,600 miles (9,000 km) above the Giant Red Spot clouds. All eight of the spacecraft’s instruments as well as its JunoCam will be on during the flyby.
“The success of science collection at Jupiter is a testament to the dedication, creativity and technical abilities of the NASA-Juno team,” said Juno project manager Dr. Rick Nybakken, from NASA’s Jet Propulsion Laboratory.
“Each new orbit brings us closer to the heart of Jupiter’s radiation belt, but so far the spacecraft has weathered the storm of electrons surrounding Jupiter better than we could have ever imagined.”
“Observations with Earth’s most powerful telescopes enhance the spacecraft’s planned observations by providing three types of additional context,” said Dr. Glenn Orton, Juno science team member and coordinator for Earth-based observations supporting the Juno project at NASA’s Jet Propulsion Laboratory.
“We get spatial context from seeing the whole planet. We extend and fill in our temporal context from seeing features over a span of time. And we supplement with wavelengths not available from Juno.”
“The combination of Earth-based and spacecraft observations is a powerful one-two punch in exploring Jupiter.”
Dr. Orton and his colleagues used the Gemini North telescope on May 18 to examine Jupiter through special near-infrared filters.
The filters exploit specific colors of light that can penetrate the upper atmosphere and clouds of Jupiter, revealing mixtures of methane and hydrogen in the planet’s atmosphere.
These observations showed a long, fine-structured wave extending off the eastern side of the Great Red Spot.
“Gemini zoomed in on intriguing features in and around Jupiter’s Great Red Spot: including a swirling structure on the inside of the spot, a curious hook-like cloud feature on its western side and a lengthy, fine-structured wave extending off from its eastern side,” Dr. Orton said.
“Events like this show that there’s still much to learn about Jupiter’s atmosphere — the combination of Earth-based and spacecraft observations is a powerful one-two punch in exploring Jupiter.”
On the same night, the researchers used the Cooled Mid-Infrared Camera and Spectrometer (COMICS) instrument on the Subaru Telescope, with filters sensitive to temperatures at different layers of Jupiter’s atmosphere.
“A wide variety of COMICS’s filters is advantageous in sensing Jupiter’s temperatures in its upper troposphere and in its stratosphere,” said Subaru Telescope staff astronomer Dr. Takuya Fujiyoshi.
“These mid-infrared observations showed that the Great Red Spot, the largest known vortex in the Solar System, had a cold and cloudy interior increasing toward its center, with a periphery that was warmer and clearer,” Dr. Orton added.
“This implied that winds were upwelling more vigorously toward its center and subsiding on the periphery.”
“A region to its northwest was unusually turbulent and chaotic, with bands that were cold and cloudy, alternating with bands that were warm and clear bands.”
“This region is where air heading east toward the Great Red Spot flows around it to the north, where it encounters a stream of air flowing over it from the east.”
“This information will allow us to determine the three-dimensional structure of winds that are otherwise only tracked in two dimensions using cloud features in reflected sunlight,” he said.