Mars Global Surveyor
After the 1992 failure of NASA's "Mars Observer" orbiter, NASA retooled and launched "Mars Global Surveyor" (MGS). "Mars Global Surveyor" launched on November 7, 1996, and entered orbit on September 12, 1997. After a year and a half trimming its orbit from a looping ellipse to a circular track around the planet, the spacecraft began its primary mapping mission in March 1999. It observed the planet from a low-altitude, nearly polar orbit over the course of one complete Martian year, the equivalent of nearly two Earth years. "Mars Global Surveyor" completed its primary mission on January 31, 2001, and completed several extended mission phases.