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So, I have a few questions. 1. Can the telescope be pointed in any direction? (of course, orthogonal to the suns rays, I understand the need to cool it down).

So, I have a few questions. 1. Can the telescope be pointed in any direction? (of course, orthogonal to the suns rays, I understand the need to cool it down). 2. If it can be pointed, I am assuming some boosters would be used to pivot it. How long do these last? 3. Is there any info on the orbit? Can the orbit degrade? 4. All the fluid / gas required to correct / point, can it be refilled?

Bjartr 4y ago
For 2, JWST uses reaction wheels to manage it's orientation. These are just heavy wheels it spins faster or slower to change it's own angular momentum. https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-momentum-management https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-m...
Laremere 4y ago
1. It can be pointed at any direction, just not at any time. It actually can't look directly away from the sun either, just to the sides. See https://jwst-docs.stsci.edu/jwst-observatory-characteristics/jwst-observatory-coordinate-system-and-field-of-regard/jwst-target-viewing-constraints https://jwst-docs.stsci.edu/jwst-observatory-characteristics... 2. Basically any satellite in use today uses spinning masses which it can speed up or down to change the direction it's looking. Angular momentum is conserved, but direction pointing isn't. Eventually due to uneven forces (eg, from the sun), these reaction wheels become "saturated" and some propellant is used slow the wheels down. Current estimates put the fuel running out in more than a decade. 3. It's an orbit in L2, past the Earth from the Sun's view. This orbit is unstable, and some of the fuel will also be used to maintain this orbit. 4. There is no refilling mechanism built in. It's likely once the propellant is out the mission will be done. There is the possibility of another spacecraft grabbing onto James Webb and pushing it for station keeping, but it wouldn't be able to refill it. One major innovation with the James Webb though is that it's refrigerator is closed loop, as otherwise running out of coolant would be the mission limiting factor.

Bjartr 4y ago

For 2, JWST uses reaction wheels to manage it's orientation. These are just heavy wheels it spins faster or slower to change it's own angular momentum. https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-momentum-management https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-m...

Laremere 4y ago

1. It can be pointed at any direction, just not at any time. It actually can't look directly away from the sun either, just to the sides. See https://jwst-docs.stsci.edu/jwst-observatory-characteristics/jwst-observatory-coordinate-system-and-field-of-regard/jwst-target-viewing-constraints https://jwst-docs.stsci.edu/jwst-observatory-characteristics... 2. Basically any satellite in use today uses spinning masses which it can speed up or down to change the direction it's looking. Angular momentum is conserved, but direction pointing isn't. Eventually due to uneven forces (eg, from the sun), these reaction wheels become "saturated" and some propellant is used slow the wheels down. Current estimates put the fuel running out in more than a decade. 3. It's an orbit in L2, past the Earth from the Sun's view. This orbit is unstable, and some of the fuel will also be used to maintain this orbit. 4. There is no refilling mechanism built in. It's likely once the propellant is out the mission will be done. There is the possibility of another spacecraft grabbing onto James Webb and pushing it for station keeping, but it wouldn't be able to refill it. One major innovation with the James Webb though is that it's refrigerator is closed loop, as otherwise running out of coolant would be the mission limiting factor.