The James Webb Space Telescope

[lpetrich]

NASA Webb Telescope on Twitter: "NASA's Kepler & TESS missions paved the way. Now it’s time for the next step…with #NASAWebb!

In @NASAAstrobio’s new series, Dr. Giada Arney explains how Webb will revolutionize exoplanet science by studying the atmospheres of Earth-size planets. Watch the series intro (vid link)" / Twitter
noting
NASA Astrobiology: Exploring Life in the Universe (@NASAAstrobio) / Twitter - "Studying the origin and evolution of life on Earth to inform the search for life elsewhere in the Universe. @NASA’s official account for Astrobiology."

NASA Webb Telescope on Twitter: "When 2 interstellar interlopers recently whizzed through our solar system, scientists had few ways to study them. But now #NASAWebb may give researchers an up-close-and-personal view of an object trespassing on our cosmic turf: (link)

Image: Artist conception (pic link)" / Twitter
noting
Studying the Next Interstellar Interloper with Webb | NASA
With JWST's infrared-spectroscopy capabilities.

But JWST can only safely observe something that is in approximate quadrature with the Sun (90d from it), so that will limit what it will be able to observe.

 

[lpetrich]

Webb’s Fine Guidance Sensor Is Guiding! – James Webb Space Telescope

To make more progress, the team needs to use another instrument, the Fine Guidance Sensor, to lock onto a guide star and keep the telescope pointed to high accuracy.

...
To ensure Webb stays locked on its celestial targets, the FGS measures the exact position of a guide star in its field of view 16 times per second and sends adjustments to the telescope’s fine steering mirror about three times per second. In addition to its speed, the FGS also needs to be incredibly precise. The degree of precision with which it can detect changes in the pointing to a celestial object is the equivalent of a person in New York City being able to see the eye motion of someone blinking at the Canadian border 500 kilometers (311 miles) away!

NASA Webb Telescope on Twitter: "Meet Webb’s guide to #UnfoldTheUniverse

The Fine Guidance Sensor (FGS) instrument, one of @CSA_ASC's contributions, helps keep Webb pointed to high accuracy & locked on a target star. It has successfully performed its 1st guiding operation! More: (links)" / Twitter
then
NASA Webb Telescope on Twitter: "Fun fact: FGS’s degree of precision would be the equivalent of a person in New York City being able to see someone blinking at the Canadian border 311 miles (500 km) away! " / Twitter

 

[lpetrich]

Webb Team Brings 18 Dots of Starlight Into Hexagonal Formation – James Webb Space Telescope
Once they identified each segment's image, they moved the segments so that their images are in a hexagonal pattern that matches the pattern of the segments themselves.

NASA Webb Telescope on Twitter: "He(X)agon marks the spots ..." / Twitter

He(X)agon marks the spots

Last week, 18 spots helped confirm that each of Webb's mirror segments can see starlight. Now we've arranged those dots into our primary mirror shape, completing the first of Webb's mirror alignment phases: (link) #UnfoldTheUniverse (pic link)

We don't just have a soft spot for hexagons: As explained by @SpaceTelescope's Matthew Lallo, we steer the segment dots into this array so they have the same relative locations as the physical mirrors. This arrangement will make it easy for us to visualize any adjustments needed.

Here is each spot of starlight labeled with the mirror segment that captured it.

Next: spot checks! Our team will adjust the mirror segments & update the alignment of our secondary mirror, focusing each dot. The dots will then be stacked on top of each other. #UnfoldTheUniverse (pic link)

 

[Elixir]

The farthest thing that we can observe is the

Cosmic microwave background, something nearly 14 billion years old, at a Universe age of 400 thousand years.

A question I keep forgetting to ask is, what is a “year”? What elapsed over the course of “universe year #400,001”? There were no cesium atoms… is it about the frequency of a hydrogen atom, and is that constant?

 

[lpetrich]

 Astronomical system of units - an Earth year. The "year" is the Julian year, 365.25 days. In turn, the "day" is 86,400 seconds, a close approximation of the Earth's mean solar day.

 Astronomical constant has more.

 

[Elixir]

How long is a day or a year when there’s no earth or sun? How long is a second in a universe composed of only hydrogen and helium?

 

[bilby]

How long is a day or a year when there’s no earth or sun? How long is a second in a universe composed of only hydrogen and helium?

How fast is a car with no speedometer? The ability (or inability) to measure a fundamental property isn't a requirement for that property to exist. Taking the speedometer out of your car won't stop you from getting a ticket.

 

[Elixir]

You only get a ticket because there’s an observer with a measuring device that emits a signal and times its return.
That analogy doesn’t feed the donkey.

 

[bilby]

You only get a ticket because there’s an observer with a measuring device that emits a signal and times its return.
That analogy doesn’t feed the donkey.

Do you accept the existence of length, in the early universe?

If so, you can derive time via the constant velocity of propagation of em radiation.

 

[Elixir]

You only get a ticket because there’s an observer with a measuring device that emits a signal and times its return.
That analogy doesn’t feed the donkey.

Do you accept the existence of length, in the early universe?

If so, you can derive time via the constant velocity of propagation of em radiation.

Yeah, the answer to my question actually lies in space expanding faster than light, allowing for 14b light year distances to be directly observed and more than 40b light year distances to be inferred, which as you say, enables an expression of time in current units to be applied to the early universe.

 

[lpetrich]

NASA Webb Telescope on Twitter: "In its first year of science, #NASAWebb will examine the TRAPPIST-1 star system, revealed #OnThisDay 5 years ago. What makes the 7 Earth-size worlds of TRAPPIST-1 a “natural laboratory” for studying planet habitability? Watch @NASAAstrobio's latest video
#UnfoldTheUniverse (vid link)" / Twitter

Looking for atmospheres by observing transits and seeing if those planets are different-sized at different wavelengths. That's what one expects to happen, but will the JWST be able to observe that effect?

NASA Webb Telescope on Twitter: "The discovery of the TRAPPIST-1 system — an extraordinary collection of 7 Earth-size worlds — made us wonder: are any of these worlds suitable for life? #NASAWebb will look for signs of atmospheres around these planets to help find out: (link) #UnfoldTheUniverse (pic link)" / Twitter
noting
Day of Discovery: 7 Earth-Size Planets – Exoplanet Exploration: Planets Beyond our Solar System

NASA Webb Telescope on Twitter: "On the 5th anniversary of @NASA’s TRAPPIST-1 system announcement, these 7 worlds are still largely a mystery. Tune into our @TwitterSpaces — happening in ONE HOUR — to learn how #NASAWebb will be a game changer. Ask questions LIVE or use #AskNASA! (link)" / Twitter
Then some podcast I'll have to catch up with later.

 

[lpetrich]

To Find the First Galaxies, Webb Pays Attention to Detail and Theory – James Webb Space Telescope

This week, as the Webb team continues to make progress in aligning the telescope, other successful activities include the calibration of the NIRISS filter wheel and pupil wheel tuning for NIRCam. There are hundreds of activities like these planned during the commissioning process, and each is as important as the next to ensure that Webb can achieve its ambitious science goals. One such goal – detecting the earliest galaxies – also requires a lot of planning and theory to prepare for the observations.

Then describing simulations of the early Universe and what it will look like to the JWST.

NASA Webb Telescope on Twitter: "How do we prepare #NASAWebb to see galaxies in the distant universe? One way is to create realistic simulations of what we may see to help us interpret what Webb captures. Take a technical look at how the science will work on our blog: (link) #UnfoldTheUniverse (pic link)" / Twitter

 

[lpetrich]

Webb Mirror Alignment Continues Successfully – James Webb Space Telescope

NASA Webb Telescope on Twitter: "#NASAWebb has completed 2 more phases of its 3-month mirror alignment process: First, the team made adjustments to its mirror segments & updated the alignment of its secondary mirror, refining each of the 18 dots of starlight from its 18 mirror segments. #UnfoldTheUniverse (pic link)" / Twitter
showing an animated GIF of the segment images each being focused.

NASA Webb Telescope on Twitter: "Then, each of those 18 dots was stacked to produce one unified image. Up next: fine-tuning this single dot of starlight to make it progressively sharper. Read more on our blog: (link) #UnfoldTheUniverse (pic link)" / Twitter
showing a single image: the 18 segments' images coinciding.


NASA Exoplanets on Twitter: "So far, the only place we know of with life is the planet you're on right now. But we're looking! How do we search and what might the process be? @NASAWebb can look for signs of biosignatures in exoplanet atmospheres, but that is just the beginning. (links)" / Twitter
noting
Can We Find Life? | The Search For Life – Exoplanet Exploration: Planets Beyond our Solar System

The James Webb Space Telescope, launched in 2021, could get the first glimpses: the mix of gases in the atmospheres of Earth-sized exoplanets. Webb, or a similar spacecraft in the future, could pick up signs of an atmosphere like our own – oxygen, carbon dioxide, methane. A strong indication of possible life. Future telescopes might even pick up signs of photosynthesis – the transformation of light into chemical energy by plants – or even gases or molecules suggesting the presence of animal life. Intelligent, technological life might create atmospheric pollution, as it does on our planet, also detectable from afar. Of course, the best we might be able to manage is an estimate of probability. Still, an exoplanet with, say, a 95 percent probability of life would be a game changer of historic proportions.

By seeing if some exoplanet is apparently larger at these gases' spectral lines.

 

[lpetrich]

Checking Out the Mechanisms in Webb’s NIRSpec Instrument – James Webb Space Telescope

This week, the Webb team has been working on the fourth stage of mirror alignment, called Coarse Phasing, which measures and corrects smaller height differences between the mirror segments.

In the meantime this past week, Webb’s Near-Infrared Spectrograph (NIRSpec) team successfully finished the check-out and initial characterization of three crucial onboard mechanisms.

A description of that spectrograph:

To work properly as a spectrograph, NIRSpec has three mechanisms: a Filter Wheel Assembly (FWA), a Grating Wheel Assembly (GWA), and a Refocus Mechanism Assembly (RMA). The gratings in the GWA spread the incoming light over its colors or wavelengths to make a spectrum. The filters in the FWA block the wavelengths that are outside the range of interest to prevent contamination between different optical paths, or ‘orders.’ The RMA adjusts the instrument focu

NASA Webb Telescope on Twitter: "What are some ways we can tell that distant planets are orbiting a star, and how can we #UnfoldTheUniverse by peeking at their atmospheres?

Space scientist Dr. Giada Arney talks about the techniques #NASAWebb will use to study other worlds in this @NASAAstrobio video (vid link)" / Twitter
She explained not only transit spectroscopy but also the "phase-curve technique" - directly observing a planet near its star, something that has been done with some close Jovian planets.

 

[lpetrich]

Webb Will Use Spectroscopy to Study Composition of Distant Galaxies – James Webb Space Telescope

NASA Webb Telescope on Twitter: "Out of the darkness of the early universe, stars began to form. We believe these first stars were made of hydrogen, helium — and not much else, as heavier elements weren't created yet! #NASAWebb will study a distant galaxy to learn more: (link) #UnfoldTheUniverse (pic link)" / Twitter


NASA Webb Telescope on Twitter: "Small adjustments, major progress! ..." / Twitter

Small adjustments, major progress!

Having completed 2 more mirror alignment steps, #NASAWebb’s optical performance will be able to meet or exceed its science goals. Now that’s good optics! (link) #UnfoldTheUniverse

Curious about this image? Thread (pic link)

While the purpose of Webb’s latest image was to focus on a bright star and evaluate the alignment progress, Webb’s optics are so sensitive that galaxies and other stars can be seen in the background. Watch this video for an in-depth explanation of how the image was created! (vid link)

an of a photo filter? @NASAHubble & Webb actually record light in black and white. They use filters that allow only a specific color of light through. The filtered images are then individually colored by scientists and image processors, then combined: (link)

Colors in space telescope images sometimes recreate the way our eyes see; other times they’re selected to highlight interesting features of an object, such as different elements in a nebula. Here, the red color palette of Webb’s image was chosen to optimize visual contrast.

Look how far we've come: We started with 18 scattered dots — 18 reflections of the same star, one from each of Webb’s primary mirror segments. These dots were then re-arranged, stacked, and fine-tuned, setting the stage for our first science images this summer! #UnfoldTheUniverse (pic link)

The Meaning of Light and Color - on how astronomical-image colors are sometimes fake, in order to bring out details that are not very apparent in typical RGB imaging, or else turning UV and IR into colors.

 

[lpetrich]

NASA’s Webb Reaches Alignment Milestone, Optics Working Successfully | NASA

Following the completion of critical mirror alignment steps, NASA’s James Webb Space Telescope team expects that Webb’s optical performance will be able to meet or exceed the science goals the observatory was built to achieve.

On March 11, the Webb team completed the stage of alignment known as “fine phasing.” At this key stage in the commissioning of Webb’s Optical Telescope Element, every optical parameter that has been checked and tested is performing at, or above, expectations. The team also found no critical issues and no measurable contamination or blockages to Webb’s optical path. The observatory is able to successfully gather light from distant objects and deliver it to its instruments without issue.

NASA Webb Telescope on Twitter: "Looking sharp, Webb! A special lens inside the NIRCam instrument took a "selfie" of Webb's mirror segments, verifying their alignment with NIRCam. The segments are bright as they are all collecting light from the same star in unison. (link) #UnfoldTheUniverse (pic link)" / Twitter
Showing a picture of all JWST's mirror segments looking well-illuminated, from their being well-aligned to bounce the light of a star into the instruments.

Nancy Grace Roman Space Telescope on Twitter: "Congrats on completing two more mirror alignment milestones, @NASAWebb! We love your focus. (links)" / Twitter
then
NASA Webb Telescope on Twitter: "Thanks for cheering us on during our “eye exam,” @NASARoman! We’re reflecting on our progress now that the universe is almost within our sights. Can’t wait to share it all with you and everyone back on Earth!" / Twitter

 

[lpetrich]

NASA Adds Giant New Dish to Communicate With Deep Space Missions | NASA

Managed by NASA’s Jet Propulsion Laboratory in Southern California for SCaN, the DSN allows missions to track, send commands to, and receive scientific data from faraway spacecraft. Now with 14 operational antennas, the network supports about 40 missions and is expected to support another 40 that will launch in the coming years.

With so many missions to support currently and in the future, NASA began a project to expand the DSN more than a decade ago. DSS-53 is the fourth among six new beam waveguide antennas that the agency is adding to the network. When the project is complete, each ground station – Madrid, along with one in Canberra, Australia, and the Goldstone facility near Barstow, California – will have a total of four such antennas. The DSN’s three ground stations are spaced almost evenly around the globe so the network never loses sight of missions as Earth turns.

...
DSS-53 will act as a “workhorse” antenna capable of communicating on the frequencies most commonly used by NASA spacecraft. Its construction began in 2016. A complicated two-year commissioning period included a weekslong process when engineers and technicians adjusted each of the dish’s some 300 reflector panels, often as little as a quarter-turn of a screw, to optimize performance.

The new antenna follows DSS-56 coming online in Spain in early 2021, making the Madrid facility the first to have completed its build-out as part of NASA’s antenna-enhancement effort. The fifth new antenna in the effort, DSS-23, is expected to go online at Goldstone in 2025. The sixth antenna will be at the Canberra facility.

The  NASA Deep Space Network (started in October 1, 1958) includes  Goldstone Deep Space Communications Complex (started in 1958) and  Madrid Deep Space Communications Complex (started in 1961) and  Canberra Deep Space Communication Complex (started on 19 March 1965)

NASA Webb Telescope on Twitter: ".@NASA’s Deep Space Network allows scientists and engineers to “talk” with spacecraft in deep space, including Webb. Now it's even easier — @NASASCaN just welcomed its newest Deep Space Network antenna, DSS-53, in Madrid! More: (links)" / Twitter
With a time-lapse video of the new antenna's dish being put into place.

 

[lpetrich]

 History of the Deep Space Network
Oldest antennas:

• Goldstone CA US: 1958
• Woomera AU: 1961
• Johannesburg ZA: 1961
• Canberra AU: 1965
• Madrid ES: 1965

The article also mentions the telescope mounts:

• Polar - Equatorial - celestial north-south
• Az-El (Azimuth-Elevation) - Altazimuth (Altitude-Azimuth) - vertical
• X-Y - horizontal - Features of X-band X/Y Type Pedestal Ground Station

With each kind of mount, I have given an alternate name, if any, and the orientation of the primary rotation axis. All of these also have a secondary rotation axis for approximately complete sky coverage, and that axis is always perpendicular to the primary one.

The earliest of DSN's telescopes are equatorial-mount ones, like many astronomical telescopes until the last half-century. That is because this design makes tracking simpler: constant rotation rate.

But the more recent ones are altazimuth or X-Y. Altazimuth designs require less structural strength, and tracking can easily be done by computer. X-Y avoids a problem with alt-az telescopes: difficulty of tracking near the zenith. That is because the primary axis is horizontal and not vertical, getting rid of that problem.

 

[lpetrich]

Webb Begins Multi-Instrument Alignment – James Webb Space Telescope

After meeting the major milestone of aligning the telescope to NIRCam, the Webb team is starting to extend the telescope alignment to the guider (the Fine Guidance Sensor, or FGS) and the other three science instruments. This six-week-long process is called multi-instrument multi-field (MIMF) alignment.

JWST's four instruments look through the telescope optics simultaneously, but they look in different directions, over roughly a 16' * 8' field of view (1/2 * 1/4 times the angular size of the Sun and the Moon). So it's possible to use all four of them at the same time.

NASA Webb Telescope on Twitter: "What's lined up for #NASAWebb?

So far, Webb's mirrors are only aligned with its NIRCam instrument. In the next 6 weeks, the telescope will undergo multi-instrument alignment to be well-aligned across all of its science instruments: (link) #UnfoldTheUniverse (pic link)" / Twitter

 

[Loren Pechtel]

How long is a day or a year when there’s no earth or sun? How long is a second in a universe composed of only hydrogen and helium?

How fast is a car with no speedometer? The ability (or inability) to measure a fundamental property isn't a requirement for that property to exist. Taking the speedometer out of your car won't stop you from getting a ticket.

This isn't a case of no speedometer, but the lack of the concept. A year is the time it takes to go around the primary--if there's no primary there is no duration spent going around it.