|Event||Date||Spacecraft Time (UTC)||Local Time (PDT)||Notes|
|Apoapse||Apr 23||3:46 a.m.||8:46 p.m. (Apr 22)||Official start of the Grand Finale orbits.|
|Ring Crossing #1||Apr 26||9:00 a.m.||2:00 a.m.||First pass through the gap between Saturn's atmosphere and innermost ring. High Gain Antenna will be used as a shield to protect from possible ring particle impacts.|
|Downlink||Apr 27||5:52 a.m.||10:52 p.m. (Apr 26)||Estimated Earth Received Time (ERT) is 12:10 a.m. on Apr 27.|
This first Grand Finale orbit begins following a final close flyby of Titan that sends Cassini on its first plunge through the gap between Saturn and its rings.
- Prior to the periapse pass over Saturn, the spacecraft’s Visible and Infrared Mapping Spectrometer (VIMS) captures images to produce a high-resolution movie of Saturn’s north polar region, including the planet’s hexagon jet stream for nearly a full rotation of Saturn.
- The orbit provides Cassini with its best look ever at Saturn’s north pole with both VIMS and the Composite Infrared Spectrometer (CIRS). And the observations should provide the sharpest near-infrared movies to date of the motion in and around the hexagon.
- Before Cassini passes through Saturn’s ring plane for the first time in the region between Saturn and its rings, the spacecraft changes its attitude so that its high-gain antenna faces forward (called “HGA to RAM”) to help shield the spacecraft from ring particles during ring-plane crossing.
- Using its VIMS and Ultraviolet Imaging Spectrograph (UVIS) instruments, Cassini studies Saturn’s smallest ring particles as they pass between the sun and the spacecraft.
- During the hour leading up to closest approach to Saturn, the imaging cameras (ISS) take a strip-like series of images of features in the atmosphere (which the team refers to as "the noodle"). These images are expected to be Cassini's closest views of Saturn thus far, with a resolution up to 10 times higher than before.
- During this orbit, Cassini gets within 1,840 miles (2,950 kilometers) of Saturn’s 1-bar level. Cassini also passes within 2,960 miles (4,760 kilometers) of the inner edge of Saturn’s D ring.
Orbit 1 of 22: Ring Crossing