Cassini-Huygens Periapsis Raising Manoeuvre

The Cassini-Huygens spacecraft has successfully performed its scheduled Periapsis Raising Manoeuvre (PRM). A 51 minute burn of the primary engine corrected the spacecraft trajectory to place it on a course to encounter Saturn’s largest moon, Titan, in October. The manoeuvre also raised the periapsis (point of closest approach to Saturn) by over 400 000 km.

If left in this orbit the spacecraft would not encounter Titan with the correct velocity to make further orbital changes for the successful deployment of the Huygens probe, and would return to a periapsis point 20 000 km above Saturn’s cloud tops and also a second ring plane crossing.

The PRM was performed when Cassini-Huygens was near the outer point in its orbit at about 9 million kilometers from Saturn. Here the orbital velocity had reduced to a mere 325 ms-1 compared to the 30 000 ms-1 after the SOI engine burn on 30 June.

The new periapsis is located in the safe, tenuous outer regions of Saturn’s E-ring instead of only 20 000 km above Saturn’s cloud tops.

This periapsis is of little significance because the Titan encounter on 26 October, at an altitude of only 1200 km, will change the orbital parameters again.

Titan Encounters