The Vehicle used to launch a satellite differs with the kind of the satellite. Geostationary satellites are launched with cryogenic rockets or space shuttle. On the other hand, the rockets used to launch polar satellites ( Just another way to say sun-synchronous) are usually smaller and non-cryogenic.

A satellite cannot be put directly into its final orbit. This is because the accuracy needed to place the satellite in the final orbit cannot be achieved by the launching vehicle, which is geared towards producing high thrust. So The satellites are placed in an intermediate orbit called Transfer orbit. The transfer orbit is usually an elliptical one, having the apogee equal to the final height and the perigee quite near to the earth. Then it is put into the final orbit by firing the Apogee Kick Motor ( which is a smaller, but quite accurately controllable rocket).

So now we have the satellite into the orbit, and we are done. Are we? No! because the satellite has to be continually goaded back into orbit as it continually strays away from it. And pray tell me, why does that happen ? Because there are continuously many forces acting on the satellite which tend to change the orbit, its altitude, its inclination and what not. These Perturbing forces are courtesy moon, sun and mother earth's Oblateness. So the satellite has to be continuously monitored and it orbit needs to be continually corrected. We call it Station Keeping.

The satellite dies when we run out of fuel for the rocket motors ( Those used in station keeping) Since we can no longer use the satellites data with any degree of ease and confidence, the satellite's systems are then shut down. Note that other systems of satellite may still be functioning because they draw power from the Solar Panel which is usually a robust structure.

So Folks, That's about the size of it. Now onto the sensors usually used in satellites!