In an embarrassing setback to NASA, the Mars Climate Orbiter is believed lost. In the early hours of September 23, the orbiter fired its main engine to go in orbit around Mars and passed behind the planet, losing radio contact as planned. However, due to what was most likely a navigation error, the spacecraft did not resume contact and may have flown too close to the atmosphere and broken apart or burned up. The relatively inexpensive ($125 million) Climate Orbiter was launched in December 1998 to become the first interplanetary weather satellite, studying Martian weather for one Mars year (about two Earth years). It was also to serve as a relay station for five years, relaying information to and from the Mars Polar Lander, due to land on December 3, 1999. NASA, however, insists that the Polar Lander's mission can be accomplished independently and "the science return of that mission won't be affected." The sites listed provide information about Mars Climate Orbiter and its possible loss.