Another mouse sized step for the JWST
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Most Recently Completed:
Aft Deployed Instrument Radiator"
Seems something s always going right these days
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As long as we don't spot any Aliens wearing mask when telescope starts operationsWell ,it will be very reassuring when they have covered that last quarter and bivvied up for the night.
Don't think anyone going to jet out there to issue fineDon't think they have planning permission yet.
But only about half way there time wise.According to my calculations now past the ¾ mark at 341+ kilometres
See screenshot
View attachment 4566
Sliding scale at bottom difficult to gauge
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Guess with weight being a critical factor with most launches scientists calculated the minimum speed (as slow as possible) telescope would be and fuel requirements needed to obtain best orientation without wasting fuel slowing the craft downBut only about half way there time wise.
I wonder why.Is there a long deceleration or does docking take a hell of a lot of maneuvering ?
My guess would be that the gravity of the Earth and the Moon is probably slowing it down. Not enough for it to stop in the L2 orbit, though: it will need an orbital insertion burn for that.But only about half way there time wise.
I wonder why.Is there a long deceleration or does docking take a hell of a lot of maneuvering ?
Also, they need to get it into an orbit around L2 perpendicular to the plane of the ecliptic.My guess would be that the gravity of the Earth and the Moon is probably slowing it down. Not enough for it to stop in the L2 orbit, though: it will need an orbital insertion burn for that.
edited to add: actually, I think the insertion burn is probably needed to increase its speed relative to the Sun. Otherwise it would continue on an elliptical orbit and fall back towards the Earth.
Yes, it will be orbiting around L2. I don't think the orbit is perpendicular to the ecliptic, though. (I wonder if it's at the Earth's tilt angle...)Also, they need to get it into an orbit around L2 perpendicular to the plane of the ecliptic.
Neither. It's coasting now, and gravity is still slowing it down. It should arrive at a few hundred MPH, and will require one last firing of its engine to stop it.I wonder why.Is there a long deceleration or does docking take a hell of a lot of maneuvering ?
I thought it had to be perpendicular to take advantage of the gravity well around L2. As I understand it, any motion along the radius of the earth's orbit, i.e. along the extension of the line joining the sun and earth, will be unstable and cause it to move even further in that direction. So it will be metastable if it is perpendicular and even then corrections will be required as it will have a tendency to drift in or out along that radial direction.Yes, it will be orbiting around L2. I don't think the orbit is perpendicular to the ecliptic, though. (I wonder if it's at the Earth's tilt angle...)
A 19 second video clip shows it will orbit ''perpendicular'' to plane of the ecliptic.I thought it had to be perpendicular to take advantage of the gravity well around L2. As I understand it, any motion along the radius of the earth's orbit, i.e. along the extension of the line joining the sun and earth, will be unstable and cause it to move even further in that direction. So it will be metastable if it is perpendicular and even then corrections will be required as it will have a tendency to drift in or out along that radial direction.
But it is interesting and I may have misconstrued what they are going to do. The gravity field around L2 is not that straight forward to understand.
And Webb will orbit around L2, not sit stationary precisely at L2. Webb's orbit is represented in this screenshot from our deployment video (below), roughly to scale; it is actually similar in size to the Moon's orbit around the Earth! This orbit (which takes Webb about 6 months to complete once) keeps the telescope out of the shadows of both the Earth and Moon. Unlike Hubble, which goes in and out of Earth shadow every 90 minutes, Webb will have an unimpeded view that will allow science operations 24/7.
Communicating with Webb
Webb's position out at L2 also makes it easy for us to talk to it. Since it will always be at the same location relative to Earth-in the midnight sky about 1.5 million km away - we can have continuous communications with it as the Earth rotates through the Deep Space Network (DSN), using three large antennas on the ground located in Australia, Spain and California. During routine operations, Webb will uplink command sequences and downlink data up to twice per day, through the DSN. The observatory can perform a sequence of commands (pointing and observations) autonomously. Typically, the Space Telescope Science Institute will upload a full week's worth of commands at a time, and make updates daily as needed.
Yes, that's what I thought. However it doesn't explain the bit about the metastability of an orbit around L2.A 19 second video clip shows it will orbit ''perpendicular'' to plane of the ecliptic.
The NASA article says Webb will orbit around L2 once every six months and that orbit is roughly the same size as the Moon's orbit about the Earth.
See the very short first video on this page:
https://webb.nasa.gov/content/about/orbit.html
Quotes from that page: