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Overview: What is Meant by "Mission Operations"?
The term "mission operations" has different meanings for different types
of robotic space missions. For a "deep space" mission (i.e., to a planet,
asteroid, or comet), mission operations activities begin when the
spacecraft is inserted into what is called a "transfer orbit" around the
Earth. From that orbit, the spacecraft is sent on its trajectory by the
firing of onboard booster rockets. What follows is called the "cruise"
stage of the mission, which may take several years. Once the spacecraft
reaches its destination, the true "operations phase" begins, during which
the spacecraft either flies by, achieves orbit around, or lands on the
celestial body to be observed.
For an Earth-observing mission, the scenario is different. There is no
real cruise stage, because once the spacecraft has achieved orbit around
the Earth and has been checked out to make sure that the spacecraft
subsystems and the science instruments all work properly, it is ready to
begin making scientific observations. After launch, the initial orbit may
need to be "trimmed" a bit to place the spacecraft just where the
engineers and scientists want it to be, but once that is done and the
initial testing or "shakedown" is complete, the operations phase of the
mission begins.
The TOPEX/Poseidon spacecraft had a perfect launch in August 1992 aboard
an Ariane 42B launch vehicle (shown here) from the European Space Agency's
launch site in Kourou, French Guiana. A few weeks later, when the proper
orbit had been achieved and the hardware and software had been checked
out, it began its three-year mission to study the world's oceans. Those
three years went "swimmingly," so to speak, and NASA authorized a two-year
extended mission phase. As of this writing, the satellite is still
operating well and returning excellent science data, due largely to the
efforts of the people in mission operations.
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