The JWST will not orbit Earth. It will be located near the second Lagrange point (L2) over 1,500,000 km away (The Moon is just 405,000 km from the Earth).
Space Shuttle could not have reached it.
Space Shuttle could not have reached it.
I think more accurately it will go around the sun once per year. The earth will provide the extra gravitational pull (toward the sun) needed to orbit the sun at a larger radius than the earth in the same amount of time as the earth.
Normally, objects with smaller orbits take less time to make a circuit. But this is placed where the earth's gravity pulls it back, just enough to make it take one (earth) year to finish its smaller orbit. So gravity from the earth and the sun are involved.
Maybe "co-orbits the Sun with the Earth using Earth's gravity"
Does use of the thrusters impact the sensors that the telescope uses?
> One kind is called "Secondary Combustion Augmented Thrusters" (SCAT), and they are used for orbit correction (like applied changes in velocity for each maneuver the spacecraft makes and also for orbit station-keeping). The SCATs are bi-propellant thrusters, using hydrazine (N2H4) and dinitrogen tetroxide (N2O4) as fuel and oxidizer, respectively.
> The other kind of thruster on Webb is called a MRE-1, or mono-propellant rocket engine, since it only uses hydrazine. There are eight MRE-1s on Webb, and they are used for attitude control and momentum unloading of the reaction wheels
Ref: https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-s...
The point of sitting in a lagrange point is that you can stay there without moving due to two gravitational forces. That's not perfectly accurate, but I don't think it needs constant thrust, just occasional taps.
It does have thrusters - a ring of 16 hydrazine "burning" units that can produce thrust on 3 axis.
The fact that the L2 point is unstable and that thrusters are required puts a lifetime on the telescope - I think NASA plans for a minimum of 5 1/2 years and are hoping to get up to 10. That's entirely reliant on the fuel supply.
The use of thrusters does impact the sensors the telescope uses. NASA et al schedule usable telescope time around burns, and general attitude shifts/correction. The telescope uses a bunch of gyroscopes/flywheels to point itself in the proper direction, during maneuvers like that the sensors aren't operable.
So when the fuel is exhausted the orbit decays and the unshielded telescope disintegrates on re-entry into Earth's atmosphere?
Or drifts off into its own orbit around the Sun, but essentially yes.