Cassini’s Grand Finale shown live on Sept. 15, 2017

After two decades in space, NASA’s Cassini spacecraft is nearing the end of its remarkable journey of exploration. Having expended almost every bit of the rocket propellant it carried to Saturn, operators are deliberately plunging Cassini into the planet to ensure Saturn’s moons will remain pristine for future exploration. Over the course of numerous orbits, NASA adjusted the spacecraft’s orbit to first pass the edge of the main rings, and then pass between the planet and the rings’ inner edge, before entering Saturn’s atmosphere tomorrow. To this end, INNOVIM staff at NASA’s Goddard institute for Space Studies (GISS), performing under a joint venture, developed and tested algorithmic improvements tailored to exploit the unique ultra-close, high-resolution images of Saturn’s clouds that the “Grand Finale” has yielded.

CASSINI spacecraft (Photo:
NASA’s Cassini spacecraft is shown during its Sept. 15, 2017, plunge into Saturn’s atmosphere. (Photo: NASA/JPL-Caltech)

In the grandest tradition of exploration, NASA’s Cassini spacecraft has once again blazed a trail, showing us new wonders and demonstrating where our curiosity can take us if we dare,” said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington.

As stated by NASA, Cassini is ending its 13-year tour of the Saturn system with an intentional plunge into the planet to ensure Saturn’s moons – in particular Enceladus, with its subsurface ocean and signs of hydrothermal activity – remain pristine for future exploration. The spacecraft’s fateful dive is the final beat in the mission’s Grand Finale, 22 weekly dives, which began in late April, through the gap between Saturn and its rings. No spacecraft has ever ventured so close to the planet before.

The mission’s final calculations predict loss of contact with the Cassini spacecraft will take place on Sept. 15 at 7:55 a.m. EDT (4:55 a.m. PDT). Cassini will enter Saturn’s atmosphere approximately one minute earlier, at an altitude of about 1,190 miles (1,915 kilometers) above the planet’s estimated cloud tops (the altitude where the air pressure is 1-bar, equivalent to sea level on Earth). During its dive into the atmosphere, the spacecraft’s speed will be approximately 70,000 miles (113,000 kilometers) per hour. The final plunge will take place on the day side of Saturn, near local noon, with the spacecraft entering the atmosphere around 10 degrees north latitude.

When Cassini first begins to encounter Saturn’s atmosphere, the spacecraft’s attitude control thrusters will begin firing in short bursts to work against the thin gas and keep Cassini’s saucer-shaped high-gain antenna pointed at Earth to relay the mission’s precious final data. As the atmosphere thickens, the thrusters will be forced to ramp up their activity, going from 10 percent of their capacity to 100 percent in the span of about a minute. Once they are firing at full capacity, the thrusters can do no more to keep Cassini stably pointed, and the spacecraft will begin to tumble.

Watch live coverage of Cassini’s end of mission on NASA TV beginning at 7 a.m. EDT on Friday, Sept. 15.

  • 7 to 8:30 a.m. EDT — Live commentary on NASA TV and online. In addition, an uninterrupted, clean feed of cameras from JPL Mission Control, with mission audio only, will be available during the commentary on the NASA TV Media Channel and on Ustream.
  • About 8 a.m. EDT — Expected time of last signal and science data from Cassini
  • 9:30 a.m. EDT — Post-mission news conference at JPL (on NASA TV and online). Participants include: ◦Thomas Zurbuchen, associate administrator for the Science Mission Directorate, NASA Headquarters, Washington
    • Mike Watkins, center director, JPL
    • Earl Maize, Cassini project manager, JPL
    • Linda Spilker, Cassini project scientist, JPL
    • Julie Webster, spacecraft operations chief, JPL