anorlunda said:This is definitely a case where pictures are far better than words. This video may explain it.
Wow, these are beautiful reasons.anorlunda said:What other place could it be where:
?
- It is not shadowed by Earth or Moon
- The communication antenna always faced toward Earth.
- It stays roughly the same distance away from Earth.
- It scans most of the visible universe without motors to aim it.
- It can always keep one side away from the Sun to make it cold enough.
The L2 orbit can satisfy all of those. If there were other solutions, we would have heard them discussed.
See this related thread in the Classical Physics forum:brajesh said:Why is the Webb placed at L2 (Lagrange point 2)?
The orbit around L2 is large enough that the direct sunlight is never blocked by the Earth or Moon, but small enough that the single sun-shield can shield the telescope from the Sun, Earth, and Moon all at once. So the satellite can always get solar power on the sunny side of the shield but never get heated on the shady side of the shield. It is important to keep the temperatures very stable and to always have power.brajesh said:Why is the Webb placed at L2 (Lagrange point 2)?
I read some articles that said it would be perpetually shaded being on the opposite side of the sun and moon, but that makes no sense when the Webb orbit is so huge?
So why is it at L2?
Flip that over: it's not being illuminated by the Earth and Moon...or heated as much.anorlunda said:What other place could it be where:
- It is not shadowed by Earth or Moon
Hmmm, I never imagined that reflected light from the Earth or moon could make a difference?russ_watters said:Flip that over: it's not being illuminated by the Earth and Moon...or heated as much.
The requirement for the infrared telescope is that there be absolutely minimum energy from outside sources, including the Earth and Moon. Don't forget that full moonlight is bright, now imagine Earth-light. Either would be too much. In fact, a lot of the electronics of the satellite itself are placed on the sunny side of the sun-shield so that it does not mess up the telescope on the other side.brajesh said:Hmmm, I never imagined that reflected light from the Earth or moon could make a difference?
Or would it have made more of a difference if Webb was nearby instead of a million miles away?
It's always on the cooler side of both objects. IR from a 'nearby' warm object will contribute to Noise for an IR sensor on the telescope. They're chasing signals right down in the noise so every little helps.brajesh said:Hmmm, I never imagined that reflected light from the Earth or moon could make a difference?
It needs to be perpetually shaded and it is by the tennis court size sun shade.brajesh said:Why is the Webb placed at L2 (Lagrange point 2)?
I read some articles that said it would be perpetually shaded being on the opposite side of the sun and moon, but that makes no sense when the Webb orbit is so huge?
So why is it at L2?
Clarification. The mirror side needs to be shaded. The solar panels need sunlight to provide power.bland said:It needs to be perpetually shaded and it is by the tennis court size sun shade.
And there's no need to worry about the eclipse situation either. Saves on batteries.anorlunda said:Clarification. The mirror side needs to be shaded. The solar panels need sunlight to provide power.
The Webb Space Telescope was placed at the L2 Lagrange point because it provides a stable orbit with minimal interference from Earth and the Sun. This allows for better observations and reduces the need for constant adjustments.
The L2 Lagrange point is a point in space where the gravitational pull of the Earth and the Sun are balanced, allowing objects to maintain a relatively stable orbit. It is located approximately 1.5 million kilometers from Earth.
Being at L2 allows the Webb Space Telescope to have a constant view of deep space without interference from Earth's atmosphere or the Sun's glare. This allows for more accurate and detailed observations of distant objects.
Yes, there are some challenges with placing the Webb Space Telescope at L2. The distance from Earth makes it difficult to send astronauts for repairs or upgrades, so the telescope must be designed to be self-sufficient. There is also the risk of collisions with space debris at L2, which must be carefully monitored.
Yes, there are other telescopes and satellites at the L2 Lagrange point, including the Herschel Space Observatory and the Planck space observatory. This point is also used for communication satellites and other scientific missions due to its stable orbit.