Re:James Webb Space Telescope emerges successfully from fina...
by snowwrestler on Friday May 31, 2019 @02:31PM
(#20063676)
The spacecraft would also keep the same distance from the Earth during the year in Earth orbit, so there has to be another reason they picked L2.
The real reason for L2 is that the sun, moon, and Earth are all the same direction from the telescope when it is at L2, so the sunshield can block them all simultaneously. Yes, the spacecraft will receive insolation at L2 (yay solar power), but it will always be from the same direction and therefore the instrument can be persistently shielded.
EDIT: from the the horse's mouth:
> To have the sunshield be effective protection (it gives the telescope the equivalent of SPF one million sunscreen) against the light and heat of the Sun/Earth/Moon, these bodies all have to be located in the same direction.
> This is why the telescope will be out at the second Lagrange point.
The real reason for L2 is that the sun, moon, and Earth are all the same direction from the telescope when it is at L2, so the sunshield can block them all simultaneously. Yes, the spacecraft will receive insolation at L2 (yay solar power), but it will always be from the same direction and therefore the instrument can be persistently shielded.
EDIT: from the the horse's mouth:
> To have the sunshield be effective protection (it gives the telescope the equivalent of SPF one million sunscreen) against the light and heat of the Sun/Earth/Moon, these bodies all have to be located in the same direction.
> This is why the telescope will be out at the second Lagrange point.
https://jwst.nasa.gov/orbit.html