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May 4 • 4 tweets • 2 min read
The Boeing Orbital Flight Test-2 #Starliner began its journey to @ulalaunch's Space Launch Complex-41. By the end of the day, Starliner wil be mated to the #AtlasV rocket. Launch is scheduled for May 19.
But it had a rather jarring glitch on the way 🙁

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Earlier in the day, a hydraulic leak on the @ulalaunch transport vehicle caused some delays.

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And then Starliner got moving. Looks like the wish below came true, with that sudden wind force that dislodged that window cover?

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We send our best wishes to Starliner for a successful trip - on the road and into space.

4/

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More from @akaschs

AkaSci 📡 Profile picture
May 5
Where is Mars Rover Perseverance and where is it headed next?
The map below shows its path over the past few days, as it traveled west and then doubled back.
Mars Helicopter Ingenuity is parked about 1 km east after its Flight 28 on Apr 29.
1/ Image
It appears that Perseverance is going to try the alternate route through an area called Hawksbill Gap to climb up the Jezero crater delta region. The diagram below includes some guesses for the new route.
2/ Image
During its journey through the region called the Enchanted Lake, no samples were collected in anticipation of more geologically interesting rocks along Perseverance's long journey.
mars.nasa.gov/mars2020/missi…
3/
Read 4 tweets
AkaSci 📡 Profile picture
May 2
Here is an insightful thread by JWST experts, prompted by a question about expectations of JWST optical performance and how well it is meeting or exceeding them so far.
@markmccaughrean @MartynEdin @cathirame @marshallperrin @pontoppi @fox_ori @AndrasGaspar @leefeinberg1
1/ Image
The tweets have been arranged in a single thread here. The originals had a few branches.
2/
JWST optical performance expectations and uncertainties.
3/
Read 19 tweets
AkaSci 📡 Profile picture
Jan 25
Guess whose birthday falls #OTD? Pioneering mathematician and astronomer Joseph-Louis Lagrange (25 Jan 1736 – 10 Apr 1813) who has now become a household name, thanks to JWST and its new home around the Sun-Earth Lagrange L2 point.
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Lagrange made significant contributions to the fields of analysis, number theory, and classical and celestial mechanics.
His study of the 3-body problem and Lagrange points is described in this famous 1772 paper “Essai sur le Problème des Trois Corps.”
gallica.bnf.fr/ark:/12148/bpt…
2/
His seminal work Mécanique analytique (1788–89) reduced the theory and the art of solving mechanics problems to general formulae, providing all the equations necessary for the solution of each problem.
en.wikipedia.org/wiki/M%C3%A9ca…
3/
Read 4 tweets
AkaSci 📡 Profile picture
Jan 24
Around 2 p.m. ET today, JWST will enter the L2 halo orbit, with a 4m 58s MCC-2 thruster burn using 2.3 kg fuel, dV = 1.5 m/s.
Here is my guess of JWST's trajectory before and after the burn.
1/
 @fox_ori @markmccaughrean @TM_Eubanks
JWST is in an elliptical orbit around earth, nearing it farthest point and has slowed down to 0.2020 km/s. JWST is high above the ecliptic plane to the right as seen from earth. The MCC-2 burn will steer it a bit towards the L2 point on its way down and back as shown above.
2/
Note that the halo orbit is ellipse-like, 1.6mil km wide and 0.8mil km tall, tilted so that the bottom is closer to earth. The center of the ellipse lies above the ecliptic and closer to earth than L2.
The above trajectory is based on this diagram at jwst-docs.stsci.edu/jwst-observato…
3/
Read 9 tweets
AkaSci 📡 Profile picture
Jan 23
The JWST team is testing the Ka-band (K-band really) HGA/link at the full rate of 28 Mbps today 👏😇
@markmccaughrean @nascom1 @NASAWebb @giopagliari Image
Link to the DSN site - eyes.nasa.gov/dsn/dsn.html
The JWST K-band downlink supports 3 data rates - 7, 14 and 28 Mbit/s. Data rate is selected based on the signal quality, which is affected by earth's atmosphere and weather.
2/
There is no K-band uplink; commands and data are sent to JWST via the S-band uplink at 2 to 16 kbps.
The S-band downlink rate is 40 kbps. The S-band signal, at a lower frequency than K-band, is less affected by earth's atmosphere and weather.
3/
Read 9 tweets
AkaSci 📡 Profile picture
Jan 22
Here is an attempt to understand why a spacecraft like JWST can orbit around the L2 Lagrange point. Instead of qualitative explanations based on gravity wells, we will use some simple physics and calculations.
1/ Image
Figure 1 shows the forces on an object at the Lagrange point L2. The distance L2d is such that the combined gravitational forces of the Sun (Fs) and Earth (Fe) equals the centrifugal force (Fc) of the body revolving around the sun in sync with earth.
2/ Image
In Fig 2, we move the object up by a distance r. Fs and Fc change little, but Fe is now smaller and has two components Fex and Fey. Fc > Fs + Fex, so the object drifts outwards and also down towards L2. As it drifts out, Fex gets weaker speeding up the drift.
3/ Image
Read 15 tweets

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