AkaSci 📡 Profile picture
Space-time: the final frontier Writing mainly about space missions and astronomy. @AkaSci@fosstodon.org https://t.co/REZl0u77U0
Chris Profile picture 1 added to My Authors
Jun 8 14 tweets 6 min read
Around May 24, JWST sustained a dust-sized micrometeroid impact to its primary mirror segment C3. Initial assessment shows that the telescope's performance remains above all mission requirements although there is a marginally detectable effect in its data.
1/ The size of the micrometeroid and the physical nature of the damage are not clear from the report. JWST does not have cameras to observe such damage. The impact of the micrometeroid is judged based on its effect on image quality.
2/
Jun 8 8 tweets 3 min read
While #MarsHelicopter Ingenuity is learning how to fly with a broken Inclinometer, Mars Rover Perseverance has been been busy roaming the "bacon strip" area near the Delta region, looking for interesting rocks. Hopefully, it will find one worthy of a rock core collection soon.
1/ This is the current location of Perseverance, right on top of the "bacon strip". Percy is probably hesitant to climb up the delta until Ingenuity moves to a better location, since Ingenuity needs Percy to communicate with earth.
2/
Jun 6 7 tweets 3 min read
Update on #MarsHelicopter Ingenuity. As the heaters and electronics have been shut off at night to conserve power, one of the navigation sensors, called the inclinometer, has stopped functioning. But the team will still be able to fly it soon using some spare accelerometers.
1/ The inclinometer's two accelerometers measure gravity prior to spin-up and takeoff; the direction of the sensed gravity is used to determine Ingenuity's orientation. NASA scientists had created a backup method to generate this data before Perseverance landed on Mars!
2/
Jun 6 13 tweets 7 min read
The Artemis @NASA_SLS rocket left the Vehicle Assembly Building around 12:01am ET earlier today and completed its four-mile trek to Launch Complex 39B around 8:20 a.m. EDT.
Let’s take a look at the unique NASA crawler-transporter vehicle used for this purpose.
1/ Image A pair of crawlers (nicknamed “Hans” and “Franz”) were built in 1965 to move the massive Saturn V rocket from Kennedy’s Vehicle Assembly Building to Launch Complex 39. After the Moon landing and Skylab programs ended, the crawlers were used to transport the space shuttles.
2/ Image
May 5 4 tweets 2 min read
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/ 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/
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 🙁

1/
Earlier in the day, a hydraulic leak on the @ulalaunch transport vehicle caused some delays.

2/
May 2 19 tweets 7 min read
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/
Jan 25 4 tweets 2 min read
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.
1/ 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/
Jan 24 9 tweets 4 min read
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/
Jan 23 9 tweets 4 min read
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/
Jan 22 15 tweets 5 min read
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
Jan 11 22 tweets 7 min read
While we wait 6 months for #JWST to get ready, let's explore what sorts of images and data we can expect from JWST.
We are all used to seeing Hubble's dazzling images of galaxies and nebulae. Will JWST's images look like these?
1/ Hubble primarily observes in the UV and visible light wavelengths from 0.1-0.8 μm but it can also see parts of the infrared (IR) spectrum from 0.6-2.5 μm.
Visible light images can produce the colorful ghostly images of nebulae but IR can reveal more distant stars and galaxies.
2/
Jan 9 5 tweets 4 min read
Where does #JWST reside on the spectrum of telescopes? The EM spectrum ranges for various space-based telescopes and a few ground telescopes are shown below. JWST observes in the 0.6–28.3 μm wavelength range (orange to mid-infrared). Hubble ST observes in the 0.1–1.0 μm range. The Herschel Space Observatory, active from 2009 to 2013, observed in the far IR 55-672 µm range, from its perch at L2 (same as #JWST!). Its 3.5 m mirror was made of sintered silicon carbide. Detectors were kept at temps below 2 deg K, using 2,300 litres of liquid helium at 1.4 K
Jan 8 8 tweets 2 min read
Here is a simple approximate method to compute the distance of the Lagrange L2 point from Earth.
An object at L2 is orbiting around the Sun at the same period as earth, i.e., 365.25 days. Let’s assume a circular orbit, centered at the Sun. Image At L2, the centrifugal force on the object due its orbital motion must balance out the gravitational forces of earth and the Sun on the object.
i.e., Fsun + Fearth = Fc
Using the notations from the diagram, we have
Fsun = G * Ms * m / (R + r)^2 (Newton’s equation)
Jan 7 24 tweets 10 min read
Let’s take a look at JWST mirrors.
Besides the familiar large primary mirror, JWST contains 3 other mirrors – a secondary mirror mounted at the end of the tripod struct, a tertiary mirror and a fine steering mirror. The figure below shows the path of IR light across the mirrors. Image We all know that the JWST primary mirror is composed of 18 hexagonal mirror segments.
Each mirror segment is 1.3 meters from side-to-side, 2 inches thick and weighs 40 kg. Image