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MISSION ENDING

A busy schedule for Cassini

The spacecraft's final week will be crammed with 'appointments'. Its 'Grand Finale' is coming nearer

Cassini spacecraft is 17 days from its mission-ending dive into the atmosphere of Saturn. Its fateful plunge on Sept. 15 is a foregone conclusion -- an April 22 gravitational kick from Saturn's moon Titan placed the two-and-a-half ton vehicle on its path for impending destruction. 

The spacecraft is expected to lose radio contact with Earth within about one to two minutes after beginning its descent into Saturn's upper atmosphere. But on the way down, before contact is lost, eight of Cassini's 12 science instruments will be operating. In particular, the spacecraft‘s ion and neutral mass spectrometer (INMS), which will be directly sampling the atmosphere's composition, potentially returning insights into the giant planet's formation and evolution. On the day before the plunge, other Cassini instruments will make detailed, high-resolution observations of Saturn's auroras, temperature, and the vortices at the planet's poles. 

In its final week, Cassini will pass several milestones en route to its science-rich Saturn plunge. (Times below are predicted and may change slightly; see https://go.nasa.gov/2wbaCBT for updated times.)  

-- Sept. 9 -- Cassini will make the last of 22 passes between Saturn itself and its rings

-- Sept. 11 -- Cassini will make a distant flyby of Saturn's largest moon, Titan. Even though the spacecraft will be at 119.049 kilometers away, the gravitational influence of the moon will slow down the spacecraft slightly as it speeds past. A few days later, instead of passing through the outermost fringes of Saturn's atmosphere, Cassini will dive in too deep to survive the friction and heating.   

-- Sept. 14 -- Cassini's imaging cameras take their last look around the Saturn system, sending back pictures of moons Titan and Enceladus, the hexagon-shaped jet stream around the planet's north pole, and features in the rings.  

-- Sept. 14 (5:45 p.m. EDT / 2:45 p.m. PDT) -- Cassini turns its antenna to point at Earth, begins a communications link that will continue until end of mission, and sends back its final images and other data collected along the way.  

 

Saturn - Credits: Nasa

-- Sept. 15 (4:37 a.m. EDT / 1:37 a.m. PDT) -- The "final plunge" begins. The spacecraft starts a 5-minute roll to position INMS for optimal sampling of the atmosphere, transmitting data in near real time from now to end of mission. 

-- Sept. 15 (7:53 a.m. EDT / 4:53 a.m. PDT) -- Cassini enters Saturn's atmosphere. Its thrusters fire at 10 percent of their capacity to maintain directional stability, enabling the spacecraft's high-gain antenna to remain pointed at Earth and allowing continued transmission of data.

-- Sept. 15 (7:54 a.m. EDT / 4:54 a.m. PDT) -- Cassini's thrusters are at 100 percent of capacity. Atmospheric forces overwhelm the thrusters' capacity to maintain control of the spacecraft's orientation, and the high-gain antenna loses its lock on Earth. At this moment, expected to occur about 1510 kilometers above Saturn's cloud tops, communication from the spacecraft will cease, and Cassini's mission of exploration will have concluded. The spacecraft will break up like a meteor moments later. 

As Cassini completes its 13-year tour of Saturn, its Grand Finale and final plunge are just the last beat. Following a four-year primary mission and a two-year extension, NASA approved an ambitious plan to extend Cassini's service by an additional seven years. Called the Cassini Solstice Mission, the extension saw Cassini perform dozens more flybys of Saturn's moons as the spacecraft observed seasonal changes in the atmospheres of Saturn and Titan. From the outset, the planned endgame for the Solstice Mission was to expend all of Cassini's maneuvering propellant exploring, then eventually arriving in the ultra-close Grand Finale orbits, ending with safe disposal of the spacecraft in Saturn's atmosphere.

The Cassini mission is a cooperative project of NASAESA and the Italian Space Agency

ASI is one of the partners of the Cassini mission: on the basis of a cooperation agreement with NASA it has developed for Cassini the high gain antenna with the incorporation of a low-gain antenna (that ensure telecommunications with the Earth for the entire duration of the mission), the VIMS spectrometer, the radio-science subsystem (RSIS) and the radar which also uses the high-gain antenna. 

ASI has also developed for the Huygens spacecraft the HASI instrument which measured the physical properties of the atmosphere and Titan's surface.