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@sonhouse saidI have to admit the mathematics are too much for me, House Man, but it sure is cool to contemplate!
@Liljo
That was a biggie, getting the shield up, without that NOTHING else works, might as well throw up a Walmart 100 dollar telescope....
I wish I had enough bucks to launch my own telescope, say only half the size of Hubble, even that would give some 1/10 arc second res and I would be the one doing the looking🙂
Hub clocks in at about 1/20th arc second res, 1 arc ...[text shortened]... round a circle which means it would spot stuff 600 times smaller than a scope with 1 arc second res.
Found this NASA site for more of the basic facts on Webb. Reading through it now:
https://webb.nasa.gov/content/about/faqs/faqLite.html
@Liljo
Well, it is not going as fast as I thought, but I guess speed isn't needed.
It is going about 2400 MPH, 3800 Km/hr. 300K miles to go, about 125 hours at that velocity. One good thing, not going very fast means less fuel to slow down to zero at L2. Once there, L2 will make a kind of fake gravity well that will tend to keep Webb in place.
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@sonhouse saidYes I read that the less fuel it has to use for orbital placement, the longer the mission will last.
@Liljo
Well, it is not going as fast as I thought, but I guess speed isn't needed.
It is going about 2400 MPH, 3800 Km/hr. 300K miles to go, about 125 hours at that velocity. One good thing, not going very fast means less fuel to slow down to zero at L2. Once there, L2 will make a kind of fake gravity well that will tend to keep Webb in place.
According to NASA’s site, it is currently going .2915mps. I have that at 1049.4mph.
I multiplied the speed per second times 60 for the speed per minute, then by 60 for the speed per hour.
At this posting it is now 603,240 miles out and doing outstanding!
@Liljo
In that case they have about 300 hours left to get to L2. Less than 2 weeks.
But even when it gets there and mirrors deployed perfectly and data coming and going also perfectly, the mirrors still have to slowly cool down to its operating point, about 400 degrees below zero F.
THEN we get new science.
Funny, I was thinking how huge it is, but with the mirror at 14 feet in diameter that equals a single reflector scope of 168 inches. Smaller than the Palomar observatory scope, 200 inches, near 17 feet in diameter. I used to go to Palomar College and lived on the road to the big scope.
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@sonhouse saidI think this thing has a mirror of over 21 feet!
@Liljo
In that case they have about 300 hours left to get to L2. Less than 2 weeks.
But even when it gets there and mirrors deployed perfectly and data coming and going also perfectly, the mirrors still have to slowly cool down to its operating point, about 400 degrees below zero F.
THEN we get new science.
Funny, I was thinking how huge it is, but with the mirror a ...[text shortened]... , near 17 feet in diameter. I used to go to Palomar College and lived on the road to the big scope.
Yes, when I was a kid and really got into astronomy for awhile ('cause I dated a Really Cute Girl whose father worked for NASA), I used to read with wonder about the Palomar observatory.
Also, this thing (the Webb) is engineered to see infrared light much better, so it will be able to gather light that has S-T-R-E-T-C-H-E-D out over time, thus go MUCH further back in the universe's history and perhaps see things that happened when the universe was only 100 million-250 million years old!
Yes, it will be at least 6 months after it settles in at L2 before we get any pics, but this is just so fascinating. I'm thankful to have lived to see this day. Sure hope I'm still around in 6-8 months!
Peace to ya.
PS: Fun fact! The Webb sunshields would cover an entire tennis court! And yes, -400F is the required temp for the mirror. A NASA analyst says its like SPF 1000,000 to block that much of the sun's heat! LOL! I don't think she meant that literally, but still, -400F is Pretty F'n Cold! ! ! !
@Liljo
I may be wrong but I think you can make ice cream at that temp🙂
I saw 14 feet on some site or other but I see now it is a 6.5 meter dish equivalent
which clocks in at 268 inches or 21 feet.
So that means my bits were off. Still it should have some 3 times the res of Hubble with special optics and sensors for sniffing out fine details in IR and the ability to stay on target for a year if they wanted, much easier than losing the image every 90 minutes like Hubble so it wins a 2 to 1 advantage in light gathering power per day if both Hubble and Web were pointed at the same object, Hubble loses sight so besides the resolution being worse it only gets half the time on target per day so it loses on many fronts. All of course assuming come June or so, we start seeing early universe stuff, as opposed to having a problem even triple redundancy didn't cover.
All we can do is wait. I wish I was back at Goddard right now.....
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@sonhouse saidAnother successful step completed: The "Aft Deployed Instrument Radiator"
@Liljo
I may be wrong but I think you can make ice cream at that temp🙂
I saw 14 feet on some site or other but I see now it is a 6.5 meter dish equivalent
which clocks in at 268 inches or 21 feet.
So that means my bits were off. Still it should have some 3 times the res of Hubble with special optics and sensors for sniffing out fine details in IR and the ability to s ...[text shortened]... riple redundancy didn't cover.
All we can do is wait. I wish I was back at Goddard right now.....
As the name suggests, this device is responsible for helping cool the Earth/Sun facing side of the telescope, where the bus and info-gathering technology is located.
620,550 miles gone.
278,000 miles to go.
All is well!
@Liljo
So at L2 it is still in Earth orbit which means it is getting full power from the sun, about 1 kw/square meter. The shield is ~20 meters square so it is deflecting about 400 kilowatts of direct solar energy, looks like a series of such reflectors, each one limiting further the influx of solar energy to where the final shield cuts that 400 kw to about 20 milliwatts. Not bad for a device with no moving parts.
Some 270 hours left, at 1000 mph, 1600Km/hr.
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@sonhouse saidI think you are correct.
@Liljo
I wonder what is causing it to slow down? It must be gravitational attraction to Earth even at a half million miles away.
I don't think they are firing a retro rocket.
The math involved in all of this must be staggering. But yes, they want the scope to slow to practically 0mph before using just a little fuel for orbital placement at L2. And the less fuel they use for that step, the longer the mission lasts.
No doubt the calculations of Earth's gravitational pull were taken into account.