NASA's latest orbiter to visit the Red Planet is well into its main phase of aerobraking. Mars Reconnaissance Orbiter has cut about 10 hours off of its initial orbit by strategically dipping in and out of Mars' thin atmosphere. Now at a 25 hour-orbit, the spacecraft is circling the planet roughly once per martian sol (day), which is 24 hours, 39 minutes. The periapsis altitude (the closest the spacecraft comes to the planet) of its orbit is at 106 kilometers (66 miles). Periapsis is near 75 degrees south latitude in the South Pole region of Mars. "The spacecraft will perform a small maneuver tonight (May 10, 2006) that will lower periapsis altitude to 104 kilometers (65 miles)," said Deputy Mission Manager Dan Johnston. "This will allow us to maintain our desired aerobraking orbit period reduction rate. The spacecraft continues to perform very well as we skim through the martian atmosphere.