Afterward, Surveyor will be used as a communications satellite to relay data to Earth from landers on the surface of Mars. This phase of the mission is scheduled to last until 1 January 2003, or until the spacecraft's maneuvering propellant runs out, whichever comes first. More science collection operations may take place during relay operations if the budget permits.

How long does it take to reach Mars?

Surveyor will take 309 days to reach Mars. In theory, the ideal transit time is 259 days. However, the journey can take anywhere between seven to 10 months depending on type of trajectory chosen and the precise locations of Earth and Mars at the time of launch. How often will Surveyor circle Mars?

Immediately after entering Mars orbit on 12 September 1997, Surveyor will take 48 hours to circle Mars. Over the next four months, the orbit will be gradually trimmed. Surveyor will take only 118 minutes to circle Mars by the time mapping operations begin in March 1998. That's slightly less than two hours. Why does it take so long to get data back from Mars?

The reason is that Mars is far away from the Earth. Depending on the time of year, Mars can be anywhere between 78 million and 377 million kilometers from the Earth. Radio signals that carry the data travel at the speed of light which is about 300,000 kilometers per second. At this speed, the signals can reach Earth in as little as 4 minutes (78 million km), or can take as long as 21 minutes (377 million km). Engineers refer to this length of time as the "one-way light time." Will Surveyor ever return to Earth?

No, Surveyor does not carry enough propellant to return to Earth. The spacecraft will continue to orbit Mars long after its electronics fail or its maneuvering propellant supply is depleted. The orbit that will be used for mapping operations was designed to ensure that Surveyor will not fall out of orbit and crash into the surface for at least 50 years after the conclusion of the mission.