Early this Wednesday morning, April 26, 2017, The Cassini probe began a set of final maneuvers that took it where no Earth probe has gone before. The Cassini probe flew through the inner gap of Saturn's rings between the rings and the planet. At 5:00 a.m. EST, NASA released a tweet with a gif of what the maneuver looked like.While this maneuver may not sound like much, the small probe had to thread the 1,200-mile gap while cruising along at a blistering speed of 70,000 miles per hour -- all while being controlled by mission specialists here on Earth, over 746 million miles away.
What's Going To Happen?This is the end of a 13-year mission for the small probe, who has spent the past decade and three years gathering data about Saturn and its moons. The probe is running out of fuel, so before its historic mission ends, NASA had one last job for it. During this new mission, which NASA has dubbed, "Grand Finale," Cassini will do 22 flybys in total, zipping by as close as 40,000 miles (64,000 kilometers) from Saturn.
The upcoming milestones that are expected as Cassini completes Grand Finale include multiple transmissions of images back as the probe makes its flybys. The milestones that have been completed and that are immediately expected are as follows.
- 5 p.m. PDT (8 p.m. EDT) on April 25: Cassini is approaching Saturn over the planet's northern hemisphere in advance of its first of 22 planned dives through the gap between the planet and its rings.
- 1:34 a.m. PDT (4:34 a.m. EDT) on April 26: As it passes from north to south over Saturn, Cassini begins a 14-minute turn to point its high-gain antenna into the direction of oncoming ring particles. In this orientation, the antenna acts as a protective shield for Cassini's instruments and engineering systems.
- 2 a.m. PDT (5 a.m. EDT) on April 26: Cassini crosses the ring plane during its dive between the rings and Saturn. The spacecraft's science instruments are collecting data, but Cassini is not in contact with Earth at this time.
- No earlier than around midnight PDT on April 26 (3 a.m. EDT on April 27): Earth has its first opportunity to regain contact with Cassini as the giant, 230-foot (70-meter) Deep Space Network antenna at Goldstone, California, listens for the spacecraft's radio signal.
- Likely no earlier than 12:30 a.m. PDT (3:30 a.m. EDT) on April 27: Images are scheduled to become available from the spacecraft.
What NASA ExpectsNASA wants to find out if the expected models of Saturn's rings are accurate. They aren't precisely sure where the rings end, so on a few of Cassini's trips around Saturn, it will briefly touch where the engineers think it's safe.
Project manager Earl Maize said that the 22 orbits are planned for at least one pass per week until the mission ends in September. At that point, Cassini will go into Saturn's atmosphere and never come out as it vaporizes and plummets to the core.
He anticipates that the material that Cassini will travel through will only be made up of extremely small particles, almost like smoke. These ring particles shouldn't harm Cassini at all. If, however, they are wrong and Cassini is struck by larger particles, then the orbiter will still end up in Saturn.
It was important to NASA that the orbiter not break up or land on or near the moons of Titan or Enceladus. This is because Titan has liquid methane lakes that may harbor life. Enceladus also might contain life in its underground oceans or the ice-encrusted surface. Debris raining down onto either ecosystem would introduce contamination.
Updates will continue to be posted on both NASA's dedicated Cassini site here, and its Twitter feed here.
[Image via NASA/JPL, Cal-Tech]