NASA’s Cassini orbiter has beamed back its first photos of the gas giant Saturn and the planet’s major moons since beginning the so-called ‘ring-grazing’ phase, the latest phase of its mission.
This view from Cassini was obtained about half a day before its first close pass by the outer edges of Saturn’s main rings during its penultimate mission phase. The view shows part of the giant, hexagon-shaped jet stream around the planet’s north pole. Each side of the hexagon is about as wide as Earth. A circular storm lies at the center, at the pole. The image was taken with Cassini’s wide-angle camera on Dec. 3, 2016, at a distance of about 240,000 miles (390,000 km) from Saturn. Image credit: NASA / JPL-Caltech / Space Science Institute.
“This is it, the beginning of the end of our historic exploration of Saturn,” said Cassini imaging team leader Dr. Carolyn Porco, from the Space Science Institute.
Cassini began its new mission phase, called ring-grazing orbits (or F-ring orbits), on Nov. 30, 2016.
Each of these weekly orbits (a series of 20) carries the spacecraft high above Saturn’s northern hemisphere before sending it skimming past the outer edges of the gas giant’s main rings.
This collage of images shows Saturn’s northern hemisphere and rings as viewed with four different spectral filters. Each filter is sensitive to different wavelengths of light and reveals clouds and hazes at different altitudes. Clockwise from top left, the filters used are sensitive to violet (420 nm), red (648 nm), near-infrared (728 nm) and infrared (939 nm) light. The image was taken with Cassini’s wide-angle camera on Dec. 2, 2016, at a distance of about 400,000 miles (640,000 km) from Saturn. Image credit: NASA / JPL-Caltech / Space Science Institute.
Cassini’s imaging cameras acquired these latest views on Dec. 2 – 5.
Future passes will include images from near closest approach, including some of the closest-ever views of the outer rings and tiny moons that orbit there.
“Let these images — and those to come — remind you that we’ve lived a bold and daring adventure around the Solar System’s most magnificent planet,” Dr. Porco said.
The next pass by the rings’ outer edges is planned for Dec. 11. Cassini will cross Saturn’s ring plane within 6,867 miles (11,051 km) of F ring.
This image of Saturn’s rings was taken with Cassini’s narrow angle camera on Dec. 5, 2016, and received on Earth on Dec. 7. The camera was pointing toward Saturn, and the image was taken using two filters. Image credit: NASA / JPL-Caltech / Space Science Institute.
To calibrate Cassini’s magnetometer for later, the spacecraft will roll for part of its second ring-grazing orbit.
The Sun will be between Earth and Saturn in what’s called a conjunction, during which the solar wind interferes with normal radio communications and radio science experiments.
Cassini will take advantage of the alignment by using its radio science instrument to study that interference for the benefit of future missions.
This image of Saturn’s moon Tethys was taken with Cassini’s narrow angle camera on Dec. 4, 2016, and received on Earth on Dec. 6. The camera was pointing toward Tethys, and the image was taken using two filters. Image credit: NASA / JPL-Caltech / Space Science Institute.
The orbiter will also practice for its Grand Finale Orbits, in which the spacecraft passes in the unexplored narrow space between the planet and its rings.
Inward and outward from Saturn’s dense, visible rings, a less-dense population of hard-to-see particles reside in the ring plane and can pose a hazard to the spacecraft. To minimize the hazard from ring particles, the spacecraft will orient its high-gain antenna toward the direction the spacecraft is traveling like a snow plow.
Only a few of Cassini’s instruments extend beyond the diameter of the spacecraft’s high-gain antenna. So during the first Grand Finale Orbit, the dish will serve as a shield when Cassini punctures Saturn’s ring plane at thousands of miles per hour. As a result, most instruments should be relatively safe from ring particles.
This image of Saturn’s moon Enceladus was taken with Cassini’s narrow angle camera on Dec. 4, 2016, and received on Earth on Dec. 6. The camera was pointing toward Enceladus, and the image was taken using two filters. Image credit: NASA / JPL-Caltech / Space Science Institute.
The ring-grazing orbits will continue until April 22, 2017, when the last close flyby of Saturn’s moon Titan will once again reshape Cassini’s flight path.
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This article is based on a press-release issued by NASA.
