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I knew little about Larange points[0] or the James Webb[1] before reading your comment and spending 10 minutes on Wikipedia. The L2 is a stable orbit with the E
by mamurphy 10y ago
I knew little about Larange points[0] or the James Webb[1] before reading your comment and spending 10 minutes on Wikipedia. The L2 is a stable orbit with the Earth between the L2 point and the sun; the Webb is a telescope that seems twice as large as the Hubble scheduled for launch in 2018. Fascinating stuff!
As noted in the Webb article:
>The JWST will operate near the Earth-Sun L2 (Lagrange) point, approximately 1,500,000 km (930,000 mi) beyond the Earth. Objects near this point can orbit the Sun in synchrony with the Earth, allowing the telescope to remain at a roughly constant distance and use a single sunshield to block heat and light from the Sun and Earth. This will keep the temperature of the spacecraft below 50 K (−220 °C; −370 °F), necessary for infrared observations.
There's a great picture[2] on Wikipedia comparing sizes of major telescopes.
[0]https://en.wikipedia.org/wiki/Lagrangian_point https://en.wikipedia.org/wiki/Lagrangian_point
[1]https://en.wikipedia.org/wiki/James_Webb_Space_Telescope https://en.wikipedia.org/wiki/James_Webb_Space_Telescope
[2]https://en.wikipedia.org/wiki/File:Comparison_optical_telescope_primary_mirrors.svg https://en.wikipedia.org/wiki/File:Comparison_optical_telesc...
- sliverstorm 10y agoIdle speculation, but I wonder if the distance will impair service, repair and upgrades, all of which I believe Hubble has benefited from
- Aeolos 10y agoIt makes servicing impossible. The telescope will eventually run out of fuel and stop working. Still, the quality of the images it expected to be so much better than Hubble that the limited lifespan will be a worthwhile trade-off.
- deleted 10y ago[deleted]
- XorNot 10y agoYes. No human has ever been out that far into space. Though I suspect by the time it launches it is conceivable SpaceX and NASA could actually put a mission together to do that since at SpaceX prices repairs might be cost effective.
- nitrogen 10y agoOn that note, is it possible for the mission operators to put the telescope in earth orbit first, make sure everything is working, then repair if needed before sending it out to L2?
- lmm 10y agoNo. It would be too warm to take good observations. And the mirror unfolds in sections, and isn't AFAIK equipped to fold back down again for the journey to L2. And repairing in LEO would still be tremendously expensive in any case.
- brianpgordon 10y agoUnmanned satellites aren't generally serviced, even ones in low Earth orbit. The Hubble is an extremely rare exception.
- InclinedPlane 10y agoYup, it's a one shot deal, mostly. That said, as the parent post mentioned, the cost of all those servicing missions was very high. It actually would have been cheaper, overall, to just launch a new one, or several. However, because of the weirdness of the Shuttle program, most of the actual cost of the Shuttle missions to service the Hubble weren't charged against Hubble's budget (substantially because the Shuttle program was looking for reasons it was useful). At nearly the full cost of building the Hubble itself per servicing mission (about $1.2 billion plus extras per flight) it really didn't make any financial sense. And now that the Shuttle program is over, it wouldn't be a factor anyway. Putting the JWST in low Earth orbit wouldn't make it any easier to be serviced, since there are no vehicles capable of servicing. But it would make it impossible for it to do it's primary mission. Moreover, we've gotten a lot better at building spacecraft and space telescopes since Hubble was constructed, most likely JWST will do just fine.
- ajnin 10y agoThe L2 orbit is not a stable one, it is an unstable equilibrium point in the gravitation field of Earth and the Sun, so objects at this point or in orbit around it will slowly drift away and will need small active trajectory corrections to stay around.