James Webb: A $10bn machine in search of the end of darkness
- Thread starter weltweit
- Start date
Steel Icarus
ersatz maven
Supine
Newt Member
Santa will help push it
2hats
Dust.
That's just how the schedule worked out - next available date where there was a window from which SEM L2 LPO could be achieved given the constraints on the launcher and payload.
Literally the JWST has just been thrown upwards, at immense speed. It's not 'in orbit' as such. It's going to keep climbing, slowing all the time (apart from a brief additional burn in just under 12 hours to add a little extra speed) and then at almost the top of the trajectory, just before it 'turns' to plunge back to Earth, it is going to be nudged towards the L2 point.
Sunray
Its sunny somewhere.
Amazing!!
Truly incredible engineering. How the people that made the telescope must be feeling.
I just looked at where its going to be placed, its way out beyond the moon.
This was what a select few were driving 100 years ago.
This is what a select few were flying 100 years ago
Truly incredible engineering. How the people that made the telescope must be feeling.
I just looked at where its going to be placed, its way out beyond the moon.
This was what a select few were driving 100 years ago.
This is what a select few were flying 100 years ago
2hats
Dust.
So 29 days till arrival at L2. At that point it can start cool down to operational temperature, mirror alignment and guidance tests. First station-keeping burn ~7 weeks after launch. It should reach operational temperature around 4 months after launch (IR remember) and then after two more months of instrument calibration and commissioning, it will finally be ready to collect images, 6 months from now. Currently being tracked by the NASA Canberra DSN.
weltweit
Well-Known Member
The Road to Launch and Beyond for NASA’s James Webb Space Telescope - NASA
Now that NASA’s James Webb Space Telescope has safely arrived at its launch site in French Guiana, on the northeastern coast of South America, technical teams
www.nasa.gov
What happens next ..
A380
How do I change this 'custom title' thing then?
But space isn’t that far away. 100km or 62 miles. I live in Bedford so space is closer than the sea side…
But it's uphill all the way.
2hats
Dust.
Looks like the Ariane 5 ESC-D second stage being passivised en route to trailing heliocentric disposal orbit. The EPC core main stage should have been dumped early on in the E Atlantic off the coast of Côte d'Ivoire, according to the relevant NOTAM.
Apparently seen from India, Thailand and Perth, WA. Likely around 60,000-70,000km altitude at that time. JWST has just passed 100,000km altitude.
Apparently seen from India, Thailand and Perth, WA. Likely around 60,000-70,000km altitude at that time. JWST has just passed 100,000km altitude.
2hats
Dust.
Nice images but (assuming the time and location given are correct) this isn't the JWST but the ESC-D upper stage heliocentric disposal/avoidance burn the best part of an hour after the JWST separated to fly free. The ascent trajectory put the second stage burn with JWST still attached over central Africa much earlier and below the local horizon at that time as seen from (anywhere in) SE Asia.
2hats
Dust.
The first mid-course correction burn, MCC-1a, slightly over 1 hour long, has just been completed. This will have pushed it a little closer towards L2. Ariane 5 was programmed to impart slightly too little energy to reach L2, so JWST fell just short, in order to greatly reduce the chance of an overshoot (which would have lost JWST in interplanetary space since any correction would have led to thermal compromise of the telescope). The shortfall is made up by onboard thrusters with these MCC burns (three in total) to just gently nudge JWST into place, each of them very carefully calculated after measuring the range/range rate to JWST (delta-DOR) prior to that burn.
Meanwhile this fellow is live streaming viewing of JWST from Florida, right now.
Meanwhile this fellow is live streaming viewing of JWST from Florida, right now.
2hats
Dust.
A couple more observations...
JWST and upper stage seen from Scotland overnight; JWST somewhere around mag +12:
And another radio observation. Here the Doppler shift arising from the MCC-1a burn is visible - the frequency change implies a resultant delta V of ~16 m/s (mission planning documentation suggests that burn should have been ~22 m/s, but the difference could reflect better Ariane 5 performance than was budgeted for). The sawtooth feature post-burn - either perhaps the rocking mode to aid thermal stabilisation prior to sun shield deployment or could reflect frequency sweeping as part of the process to gain spacecraft lock - spacecraft downlink follows DSN uplink (unless it is part of delta-DOR operations post-burn to confirm trajectory).
Source.
Though the observer in FL mentioned in the previous post commented at the time that they thought they saw a variation in the light curve post-burn. Here a movie of their frames.
JWST and upper stage seen from Scotland overnight; JWST somewhere around mag +12:
And another radio observation. Here the Doppler shift arising from the MCC-1a burn is visible - the frequency change implies a resultant delta V of ~16 m/s (mission planning documentation suggests that burn should have been ~22 m/s, but the difference could reflect better Ariane 5 performance than was budgeted for). The sawtooth feature post-burn - either perhaps the rocking mode to aid thermal stabilisation prior to sun shield deployment or could reflect frequency sweeping as part of the process to gain spacecraft lock - spacecraft downlink follows DSN uplink (unless it is part of delta-DOR operations post-burn to confirm trajectory).
Source.
Though the observer in FL mentioned in the previous post commented at the time that they thought they saw a variation in the light curve post-burn. Here a movie of their frames.
weltweit
Well-Known Member
BBC Article explaining some of the next steps as the telescope deploys.
James Webb: Hubble telescope successor faces 'two weeks of terror'
Nasa's huge new space observatory must survive a daunting series of deployments if it's to work.
www.bbc.co.uk
a_chap
When the world came apart, where were you?
I bet I'll spend far too much time looking at this over the next 28 days...
Where Is Webb? NASA/Webb
During Webb's launch, deployment and commissioning, 'WhereIsWebb' tracked Webb's 'flight' to L2 orbit, its state and progress during its deployment and commissioning process, and finally the release of its first images. This process is now complete. During this process, the page constantly...
jwst.nasa.gov
2hats
Dust.
Be aware that the distance indicated is that integrated along the orbital path and not the orbital altitude (right now it indicates that JWST is about 290,000km from Earth, but it's actually just under 270,000km in orbital altitude; will pass the Moon's orbit by 2200UTC tomorrow).I bet I'll spend far too much time looking at this over the next 28 days...
Where Is Webb? NASA/Webb
During Webb's launch, deployment and commissioning, 'WhereIsWebb' tracked Webb's 'flight' to L2 orbit, its state and progress during its deployment and commissioning process, and finally the release of its first images. This process is now complete. During this process, the page constantly...jwst.nasa.gov
Interesting to note that several people were surprised by how soon the JWST solar array deployed after payload separation, which serendipitously resulted in video of the event. Indeed some wondered if this was indicative of some erroneous state. But it turns out that the Ariane 5 'tip-off' of JWST (orbital injection) was so precise and gentle that the solar array deployment happened almost immediately (after a ~1 minute safety timeout to gain separation from the upper stage). The pitch/roll/yaw angular rate criteria were already met, so there was no extended waiting around for RCS damping/re-orientation. Obviously this helps conserve propellant for L2 station-keeping.
(Technically not the last view.)
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2hats
Dust.
Arianespace have released their preliminary evaluation of the launcher performance which might suggest orbital insertion will have optimised JWST lifetime (semi-major axis towards the upper end of the targeted mission design range).
| Parameter | Target (range) | Achieved |
| Semi-major axis (km) | 536534 (504836-568232) | 542120 |
| Eccentricity | 0.987527 (0.986801-0.988253) | 0.987655 |
| Inclination (deg) | 4.05 (3.98-4.12) | 4.04 |
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