Cassini spacecraft is beginning its last mission which includes exploring Saturn’s F ring before being sent into the planet to protect its potentially habitable moons. Saturn has seven rings named with alphabet letters in order of discovery. The endgame of the Cassini mission starts November 30 and will officially end in 2017.
NASA engineers have been modifying Cassini’s orbit around Saturn to put the spacecraft closer to the planet’s rings to study their composition and extension for future missions.
Cassini will be orbiting over and under Saturn’s poles through the unexplored regions between F ring and G ring. On November 30 the spacecraft will take advantage of Saturn’s moon Titan gravitational nudge to begin its ring exploration phase. Cassini will circle the planet in an elliptic orbit that will start on November 30 and will end on April 22. The spacecraft will pass Saturn’s poles every seven days in a total of 20 orbits.
Cassini’s instruments will try to collect samples from the rings and elements found near them. The rings cover a vast area but are actually very thin, generally no thicker than the height of a house. The rings are made of small icy particles and the spacecraft mission is to collect samples of those particles and ring molecules.
“We’re calling this phase of the mission Cassini’s Ring-Grazing Orbits, because we’ll be skimming past the outer edge of the rings,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California. “In addition, we have two instruments that can sample particles and gases as we cross the ringplane, so in a sense Cassini is also ‘grazing’ on the rings.”
Once the spacecraft ends its 20 orbits just outside F ring, Cassini will dive between Saturn’s uppermost atmosphere and its innermost ring 22 times, stated NASA. Cassini has performed more missions than intended which have helped to obtained valuable data about Saturn’s gravitational and magnetic fields among other characteristics.
The Cassini Solstice Mission: Almost 20 years out in space studying Saturn and its moons
Cassini ended its initial mission in June 2008, but because the aircraft still had fuel, scientists created an extended mission called Cassini Equinox, which began in September 2010. The second extension is called the Cassini Solstice Mission and will end in 2017. The spacecraft last mission has two phases, and the last one was named the Grand Finale because it will be Cassini’s last exploration in the surroundings of the planet.
Cassini Solstice Mission will determine ring mass, sample the atmosphere and ionosphere, and will also make the last views of Enceladus, one of Saturn’s moon. Cassini ring-grazing orbits will offer a unique opportunity to analyze the menagerie of small moons that orbit near the edges of the rings. Pandora, Atlas, Pan and Daphnis will be closely observed.
Cassini crosses Saturn’s F ring once on each of its 20 Ring-Grazing Orbits, shown here in tan and lasting from late November 2016 to April 2017. Blue represents the extended solstice mission orbits, which precede the ring-grazing phase.
The other highlights of the upcoming Cassini orbits are the grazing of the edges of the rings, which will also allow scientists at NASA to study the outer portions of Saturn’s main rings carefully. Images from the Cassini Solstice Mission will be the most detailed since the spacecraft arrival to the planet’s orbit in 2004.
During the first two orbits close to the F ring, the spacecraft will pass through a significantly faint ring produced by small meteors that regularly strike two small moons: Janus and Epimetheus. Saturn has 53 confirmed moons and Titan, the biggest one, has its own atmosphere.
Cassini will be closely flying around Saturn’s F rings and still will be more than 4,850 miles (7,800 kilometers) away. Regarding dust hazard for the spacecraft, Earl Maize, Cassini’s project manager, stated that the risk is minimum.
The F ring is the fifth farthest ring from the planet and marks the outer boundary of the primary ring system which are rings A, B, C, and D. Cassini has studied the F ring and has discovered that it is always changing. The spacecraft images show different structures on the ring, including bright streamers, wispy filaments, and dark channels that are formed over mere hours, NASA explained.
The F ring is considerably narrow: It is about 500 miles (800 kilometers) wide and its core is a denser region about 30 miles (50 kilometers) wide.
The Grand Finale
Cassini is a cooperative mission between NASA, the European Space Agency (ESA) and the Italian Space Agency. The mission was launched in 1997 and arrived at its intended orbit in 2004. Since then, the spacecraft has discovered significant findings on Saturn’s moons including a global ocean within Enceladus and liquid methane seas on Titan.
After nearly 20 years in space, Cassini is running out of fuel. Thus, people behind the mission designed the spacecraft’s last tasks before sending it into Saturn to monitor the planet’s potentially habitable moons.
The mission will also explore particularly elements in the A ring called “propellers” which are a mystery for space agencies. Cassini will reveal new details about their origins and structure before ending its mission.
Source: NASA