Today, at 2 p.m. EST, Webb fired its onboard thrusters for nearly five minutes (297 seconds) to complete the final postlaunch course correction to Webb’s trajectory. This mid-course correction burn inserted Webb toward its final orbit around the second Sun-Earth Lagrange point, or L2, nearly 1 million miles away from the Earth.
The final mid-course burn added only about 3.6 miles per hour (1.6 meters per second) – a mere walking pace – to Webb’s speed, which was all that was needed to send it to its preferred “halo” orbit around the L2 point.
“Webb, welcome home!” said NASA Administrator Bill Nelson. “Congratulations to the team for all of their hard work ensuring Webb’s safe arrival at L2 today. We’re one step closer to uncovering the mysteries of the universe. And I can’t wait to see Webb’s first new views of the universe this summer!”
Webb’s orbit will allow it a wide view of the cosmos at any given moment, as well as the opportunity for its telescope optics and scientific instruments to get cold enough to function and perform optimal science. Webb has used as little propellant as possible for course corrections while it travels out to the realm of L2, to leave as much remaining propellant as possible for Webb’s ordinary operations over its lifetime: station-keeping (small adjustments to keep Webb in its desired orbit) and momentum unloading (to counteract the effects of solar radiation pressure on the huge sunshield).
“During the past month, JWST has achieved amazing success and is a tribute to all the folks who spent many years and even decades to ensure mission success,” said Bill Ochs, Webb project manager at NASA’s Goddard Space Flight Center. “We are now on the verge of aligning the mirrors, instrument activation and commissioning, and the start of wondrous and astonishing discoveries.”
Now that Webb’s primary mirror segments and secondary mirror have been deployed from their launch positions, engineers will begin the sophisticated three-month process of aligning the telescope’s optics to nearly nanometer precision.
Watch a special episode of NASA Science Live at 3 p.m. EST today to learn more about what’s next for the James Webb Space Telescope.
Home, home on Lagrange!
Where the rocks and the cosmic dust play.
Where nothing is heard, a discouraging word,
and the skies are not cloudy a day.
Actually, ‘la grange’ means ‘the barn’ in French. :-]
Also the name of the song with one of the best guitars in pop music.
In this case, it refers to 18th-century French mathematician Joseph-Louis Lagrange.
Dang, I kinda liked the imagery of putting the satellite into the barn.
Actually, it was a play on word sounds. “La Grange” vs “the Range”. “Home on the range” is an old American song.
And to further disappoint you, L2 is an unstable gravitational point. It resides at the balanced tug between the sun and earth. A smidge closer and you fall to the sun, a smidge further out and you drift off into space. There are no rocks and cosmic dust sitting here. They keep drifting away. This is an additional benefit of L2, its clean.
As I have described this orbit previously as a track of a 3-dimensional spirograph, it really only appears to be “haloing” about the point. Such orbit are chosen to provide a stable way to hold this location with minimal effort.
Rocketscientist,
I’m trying to get into my head the orbit of the Webb around L2. Is the rotational orbit from a perspective/viewpoint from the sun equal to twice (2) per annual orbit of the earth around the sun? In other words, is the trajectory simply a “wobble” in it’s trajectory/orbit around the sun?
All orbital mechanics are very simple physics and MUST obey mathematical laws which are rather onerous to explain, but perhaps this visualization might help:
As mentioned earlier this path is a mathematical shape called a Lissajous figure. It is not planar. Think of it as the edge of a Pringle’s potato chip, saddle shaped, almost circular, but not quite. The highest point of the elliptical path is just higher than L2 while the lowest if below L2. So the orbit travels around the sun (one of the loci of the elliptical chip) wavering up and down as it follows the edge. Then add to this the chip is also rotating (processing) in a slow progression such that each time the high and low portions of its orbit occur they sort of step ahead of the previous trace. If the traces were to be drawn with a 3-dimensional spirograph they would be braiding an intricate and beautiful ribbon about the sun.
To directly answer your question, Earth/Sun L2 is about .97 times the distance between it and the earth than the earth is from the sun. So L2 is almost as far away from earth as the sun, but not quite. So the path that it travels is almost twice as long (1.97 times the radius). Since it travels that path in the same time as earth (1 year) it is travelling at almost twice earth’s velocity.
Wait, what? The earth is nearly 100 million miles from the sun. JWST is only about a million miles out from earth.
Perhaps your comment isn’t as succinct as you hoped. Or perhaps I’m putting on my dunce hat in public…
Thanks for the reply. What you described is what I reasoned in my primitive way of thinking. But would that wavy trajectory give the impression that the Webb would appear to be in an orbit around the earth if viewed from the sun with a frequency of 2 rotations per year? I’m trying to picture the optical effect that the earth’s elliptical orbit would have.
JWST is in orbit about the sun, but if viewed from the sun it would look like it was orbiting the earth, but far behind it, and very slowly as it seems to circle the earth. It never passes between the earth and sun. It is traveling on the same radial “spoke” as the earth, in that it keeps the earth between it and the sun, sort of.
The “sort of” is the halo orbit that JWST performs about the gravitational point L2. If JWST were in a planar orbit, haloing about L2, it would always be in the shade of the earth (not so good for solar energy collection). So the Halo path is inclined by having the trajectory follow the warped ellipse, so that it can keep its sunny disposition.
Thanks, I reasoned that it would be (optically) slow orbit. Willis and Leif forced me to lose a lot of sleep several years ago! LOL
Going back through the comments I notice that you referred to it as a sinusoidal type trajectory (January 26, 2022 1:49 pm). That is what I had in mind. I should have reread the entire thread again before posting. Thanks again for your replies!
What I find amazing about this is that the James Webb Space Telescope is in orbit about something that isn’t there.
The Sun, Earth, Moon and Jupiter are there, so there is a there there….
The L2 point is there, but it is not a natural orbit. Thrusters need to be fired periodically to keep it close to the critical L2 apex. That is because the L2 is not completely stable, it is a saddle point. So small departures from the critical point will grow, extremely slowly, but eventually the satellite would drift away
Here is the actual measured WMAP, the previous satellite at L2, trajectory. Quite erratic so I wonder will JWST have to compensate for image quality? Animated gif, click to play.
WMAP is in a ‘Lissajous’ orbit, which explains why it looks like an xy scope plot. The Webb scope is in a variant of that called ‘Halo’ which has better features.
Just noticed I used the term ‘scope’ twice, but with two different but valid meanings. First was referring to ‘oscilloscope’ (in x-y mode), the second to ‘telescope’ (JWST). Sorry for any confusion this may have caused.
There are many ways to plot orbital trajectories. All depend on your reference point. As the true orbital path is not planar none but a true 3D computer image that can be manipulated will provide a better comprehension of the trajectory. From a heliocentric view it will look elliptical, from side on, rather sinusoidal as the “halo” is purposefully not in the plane of the ecliptic.
This plot relative to the axis of Earth/Sun is the easiest to picture for the general public
Something else amazing is that that something that isn’t there was discovered to be there by Joseph-Louis Lagrange a couple of hundred years ago! He was a smart cookie! https://www.famousscientists.org/joseph-louis-lagrange/
A couple of hundred year ago means the calculations had to be done by hand, using a quill pen.
Now that’s perseverance.
“I wish to God these calculations had been executed by steam.” Charles Babbage, 1822. (Babbage was complaining about errors in math tables–not Lagrange’s calculations.)
What is going on with the old satellite that got parked somewhere out there?
WMAP was there. Maybe NASA dumps these at L5?
They are moved away into a parking orbit, as JWST will when it expires.
As “orbits” around L2 are unstable, no action needed.
This is just stunning. Meanwhile the wokesters back here are nattering on about making maths and science more wokey for the people who are not smart enough to do stuff like this.
Yes, it’s amazing they’ve actually pulled it off. I must admit I had my doubts the Webb would ever get off the ground. It’ll be fascinating to see just what images it produces in a few months.
10 years late, 10 times over budget. Not sure why… Anyway a lot of physics simply stopped, and must be restarted!
“the wokesters back here are nattering on about making maths and science more wokey”
Oh it’s worse than that; Ouroboros look out…..
“Yes, woke hysteria has now reached such a crescendo that even the 20th century’s most famous warning about tyranny is falling victim to its tyrannous habits. RIP satire, you had a good innings. Orwell’s classic book has been slapped with a trigger warning at the University of Northampton. Students are warned that it contains ‘explicit material’ that they might find ‘offensive and upsetting’. These are adults we’re talking about, by the way. People over the age of majority being told by university officials that a novel about the dangerous, dehumanising consequences of censorship might offend them… we’re only three weeks into 2022 and already we have the most 2022 story we’re likely to get.”
https://www.spiked-online.com/2022/01/24/now-even-1984-comes-with-a-trigger-warning/
Surprised to find that John Cleese actually DID tell a Woke Joke :
https://twitter.com/johncleese/status/1459398678293196800?lang=en
see the triggers….
Really? He’s been kicking off for quite a while about it.
What do you get if you rub your eye after cutting chillies? An orbital insertion burn! Now that is a non-racist joke, unlike most of John Cleese’s radio output.
Here’s a French joke
Where does an Englishman keep his money? Under the soap
Personally, I find it funny. Why? Because there is an element of truth in it.
Try the BBC’s comedy. That is woke beyond belief – and it’s CRT approved.
That brought tears to my eyes, and it isn’t even funny!
Soap will do that
What would happen I anyone wore this around Northampton…
(Check out the DJ on Twitch = nice chilled sets often 10+hrs long – U gotta admire his stamina)
“What would happen”
Probably a woke lynching. (Cancellation etc)
But not a million miles away…
“Student union officials at the University of East Anglia have banned a Mexican restaurant from handing out sombreros to students”
https://www.theguardian.com/world/2015/sep/29/uea-student-union-bans-racist-sombreros
Cultural appropriation of the worst sort.
Does this mean that only French women are allowed to wear bikinis?
Wouldn’t that be only Polynesian women?
Shouldn’t they also object to the food too? If the sombrero is cultural appropriation, so is the food.
Several years ago, many schools banned “Huckleberry Finn”, because the N word was used in it.
Think about it, they are banning a book that strongly argues against slavery and racism, because it used the N word.
I read yesterday that some group is going after “To Kill a Mockingbird”, because it is disrespectful towards blacks.
I tried to find the name of the Country in Africa where the people prefer to be called Negros. Google is not helpful to find it anymore.
… nevermind … I was thinking of Kaffir and the Sri Lankan Kaffirs.
Words are just words.
Here in New Zealand seven Auckland University scientific academics have been pilloried one of whom has resigned after writing an open letter objecting to the inclusion of Maori indigenous knowledge in the school science curriculum. How sad.
Good site to see Webb updates, tho little will be going on for some time.
https://webb.nasa.gov/content/webbLaunch/whereIsWebb.html
What will “be going on for some time” is cool down, and the temperatures are posted there. As is the Cruising Speed, now about 450 MPH, a million miles away around virtually nothing. So interesting!
That NASA site included some very good news, when the announcement was made that L2 insertion had been completed.
Orbital insertion (and indeed, the entire journey,) had been accomplished so precisely, that much less fuel had been used to achieve the goals to date, that the mission’s operating lifetime would be extended.
The Webb telescope will operate at around 40K or -388F. That’s cold! It currently is around -350F so it has a bit to go. It gets harder to cool down the colder it gets since the only way is by radiative cooling and something at -350F isn’t radiating much. A lot of engineering and physics behind controlling the temperature of something in space.
Cryocooler will REALLY cool down the most sensitive receiving instrument.
https://jwst.nasa.gov/content/about/innovations/cryocooler.html
I wonder how they calculate the amount of change in the optics as it cools. With so many disparate mirror panels where they are trying approach nano-meter alignment.
Probably a known star image quality, with numerous actuators per segment to control. Without some kind of AI , manually impossible. Maybe that system took years longer to develop?
Yes, that’s my understanding. (sorry, I wrote my response before seeing that you were essentially saying the same thing.)
Probably through a process somewhat like bracketing artillery.
“A3 is a bit off, Try raising it .004mm, Ned. That’s too far. Drop ‘er back .002mm”.
Look up interferometry.
That’s not really the right way of looking at it. Think about an old-school camera that needs to be focused. Conceptually, if it was focused to room temperature and you cool it down considerably, you could do some calculations to see how things have relatively moved and make adjustments but that’s not what you’re going to do, really got a focus manually or using autofocus option that doesn’t use calculations of temperature. Webb is similar. The going to spend the next few months taking images of stars, where they already know what it should look like, figure out how to do the adjustments of the actuators to make the blurry image come out clear, but that process isn’t going to involve calculations of temperatures and how that would affect the mirrors. In other words, they will focus the telescope but they don’t need to know the temperature.
A spritely God will now strike it with a meteor shower.
Meteor showers occur in Earth’s atmosphere, Webb is about a million miles from the Earth and its atmosphere
He likes His privacy.
I was surprised to read that the telescope had to speed up a bit in order to slip into it’s orbit.
I’m used to reading about satellites having to slow down in order to achieve orbit.
It all depends on how approached L2, the more tangentially it approaches, the more it has to speed up. You are perhaps confusing highly lofted low Earth orbits (LEOs) where satellites are tossed up much higher than their intended orbits and secondary stages are used for circularization burns needed to, round-out the orbital path and match speeds to the orbit desired. In an orbit about the sun, to fly further away from the sun (center of your orbit) you must speed up. If you slow down you sink towards the sun. It seems like everything is speeding up but because you are actually flying a much shorter circumference you are slowing down.
Halo orbits are used for all orbital docking maneuvers. Just as any delivery vehicle approaches the ISS by ‘haloing’ about the ISS until final velocity matching and docking.
I’m thinking of probes sent to the various planets and asteroids, they all had to slow down before being able to go into orbit.
Interesting question, but there’s a good reason why the situation is different. Webb was sent up deliberately a bit too slow. It’s thrusters work in only one direction (a fair question is why not have thrusters in both directions and I do not know the answer). If they were going a little too fast, they’d have to do a 180 to use the thrusters to slow down, and that would mean turning the telescope to face the sun. That would overwhelm the instruments. For that reason, they sent it up going a little bit too slow, and when they got close to L2 and wish to start their halo orbit, they would know exactly how much to speed up to get it into the orbit and not have to turn around.
As others have reported, L2 is not a stable location, and technically Webb is not at L2, it”s orbiting around L2, so we will regularly have to make small thruster adjustments to keep it in its orbit. The sent it up with the plan to have enough fuel to keep it running for 10 years. Happily, they used fuel than planned to get it into orbit, so the expected lifetime exceeds 10 years.
It’s an amazing accomplishment and that’s from a guy who in the 5th grade said why do I need to know fractions.
I’ll bet that you only said that 1/4th of your time there.
An uplifting story about real science that is sure to bring us phenomenal insights into our universe and our place in it.
Now THIS is what I call real science.