Cassini reaches the 1-bar level of Saturn, September 15, 2017

Instant (UTC)

September 15, 2017, 10:45:33 UTC

Distance from the centre of Saturn

60,253 km

Latitude (planetocentric)

2.7°

Saturn has no solid surface: the level where the pressure is 1 bar is the reference of its radius. This is the second at which the trajectory of Cassini passes below that level, on the ellipsoid of the radii the International Astronomical Union publishes, oriented by the pole it publishes for Saturn at that date.

Its speed relative to the rotating planet is then 0.58 km/s. At 10:34:00 UTC, 666 km higher, it was 31.18 km/s: the trajectory has slowed down in the atmosphere, it is not a free fall crossing a sphere.

Horizons continues this trajectory below the 1-bar level, through the planet; Galaxy stops drawing the spacecraft just before it.

Open Cassini one minute before this instant, at true scale

Pages of the spacecraft and of the body:

• Cassini
• Saturn

The position and velocity of the spacecraft relative to the planet are read from Horizons every minute in the hours before the 1-bar level, then every second. The level is the ellipsoid of the equatorial and polar radii of the IAU rotation model that NASA NAIF distributes; the speed relative to the planet subtracts the rotation of a rigid body at the period of that model.

NASA/JPL Solar System Dynamics, Horizons System. Read on October 23, 2026.

Trajectory solution cited by Horizons: cassini_merge

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