Cassini sends back first photos taken from ring-grazing orbit
NASA’s Cassini spacecraft has returned the first photographs of Saturn and its rings taken from its new, nine-month ring-grazing orbit phase. The new images (shown above and below right) were acquired high above Saturn’s northern hemisphere, which show the planet’s enigmatic hexagon-shaped jet stream.
Begun on November 30, 2016, this phase involves a daring flight over Saturn’s rings and moons that will conclude with a mission-ending plunge into the giant planet’s atmosphere on September 15, 2017.
Taken on December 2 and 3, the latest pictures include breathtaking close-ups of the hexagonal jet stream above Saturn’s north pole as well as the planet’s northern hemisphere and rings captured using four separate spectral filters.
The hexagon surrounds a circular storm located at its center, directly over Saturn’s north pole. Each of the storm’s six individual sides is about the diameter of Earth.
Cassini photographed the giant jet stream with its wide-angle camera from a distance of approximately 240,000 miles (390,000 kilometers) at a scale of 14 miles (23 kilometers) per pixel.
The mysterious hexagon was photographed about a day-and-a-half before Cassini made its first close flyby of the ring system’s outer edges.
Four separate images of the same region were taken, one each with filters sensitive to violet (420 nanometers), red (648 nanometers), near-infrared (728 nanometers), and infrared light (939 nanometers).
Taken from a distance of 400,000 miles (640,000 kilometers), these images have a scale of 95 miles (153 kilometers) per pixel.
Like many photos taken by Cassini, the latter four were compressed to smaller sizes as a means of allowing the capturing and storage of more photos than would ordinarily be possible on the spacecraft.
Although they initially had a resolution of 256 pixels by 256 pixels, the mission team enlarged the photos by a factor of two before releasing them.
Using a gravity assist from Saturn’s largest moon, Titan, Cassini began the first of 20 ring-grazing orbits on November 30 and first crossed the ring plane December 4. It is currently in an elliptical orbit with about a 60-degree inclination to the ring plane.
The second ring plane crossing occurred on December 11.
Each ring-grazing orbit will last a week and will start with the spacecraft at its most distant position from Saturn. Crossing of the ring plane in every orbit will occur when Cassini is closest to Saturn.
On April 22, 2017, Cassini will fly by Titan for the final time, using its gravity to make the first of 22 dives between the innermost ring and Saturn itself – a gap of about 1,500 miles (2,400 kilometers) – four days later.
These 22 plunges will culminate in the September 15 dive into Saturn’s atmosphere. Data on the atmosphere’s composition will be returned until the last moment possible.
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.