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8 Common Questions About Our James Webb Space Telescope

You might have heard the basics about our James Webb Space Telescope, or Webb, and still have lots more questions! Here are more advanced questions we are frequently asked. (If you want to know the basics, read this Tumblr first!)

Webb is our upcoming infrared space observatory, which will launch in 2021. It will spy the first luminous objects that formed in the universe and shed light on how galaxies evolve, how stars and planetary systems are born, and how life could form on other planets.

1. Why is the mirror segmented? 

The James Webb Space Telescope has a 6.5-meter (21.3-foot) diameter mirror, made from 18 individual segments. Webb needs to have an unfolding mirror because the mirror is so large that it otherwise cannot fit in the launch shroud of currently available rockets.

The mirror has to be large in order to see the faint light from the first star-forming regions and to see very small details at infrared wavelengths. 

Designing, building, and operating a mirror that unfolds is one of the major technological developments of Webb. Unfolding mirrors will be necessary for future missions requiring even larger mirrors, and will find application in other scientific, civil, and military space missions.

2. Why are the mirrors hexagonal?

In short, the hexagonal shape allows a segmented mirror to be constructed with very small gaps, so the segments combine to form a roughly circular shape and need only three variations in prescription. If we had circular segments, there would be gaps between them.

Finally, we want a roughly circular overall mirror shape because that focuses the light into the most symmetric and compact region on the detectors. 

An oval mirror, for example, would give images that are elongated in one direction. A square mirror would send a lot of the light out of the central region.

3. Is there a danger from micrometeoroids?

A micrometeoroid is a particle smaller than a grain of sand. Most never reach Earth's surface because they are vaporized by the intense heat generated by the friction of passing through the atmosphere. In space, no blanket of atmosphere protects a spacecraft or a spacewalker.

Webb will be a million miles away from the Earth orbiting what we call the second Lagrange point (L2). Unlike in low Earth orbit, there is not much space debris out there that could damage the exposed mirror. 

But we do expect Webb to get impacted by these very tiny micrometeoroids for the duration of the mission, and Webb is designed to accommodate for them.

All of Webb's systems are designed to survive micrometeoroid impacts.

4. Why does the sunshield have five layers?

Webb has a giant, tennis-court sized sunshield, made of five, very thin layers of an insulating film called Kapton.  

Why five? One big, thick sunshield would conduct the heat from the bottom to the top more than would a shield with five layers separated by vacuum. With five layers to the sunshield, each successive one is cooler than the one below. 

The heat radiates out from between the layers, and the vacuum between the layers is a very good insulator. From studies done early in the mission development five layers were found to provide sufficient cooling. More layers would provide additional cooling, but would also mean more mass and complexity. We settled on five because it gives us enough cooling with some “margin” or a safety factor, and six or more wouldn’t return any additional benefits.

Fun fact: You could nearly boil water on the hot side of the sunshield, and it is frigid enough on the cold side to freeze nitrogen!

5. What kind of telescope is Webb?

Webb is a reflecting telescope that uses three curved mirrors. Technically, it’s called a three-mirror anastigmat.

6. What happens after launch? How long until there will be data?

We’ll give a short overview here, but check out our full FAQ for a more in-depth look.

In the first hour: About 30 minutes after liftoff, Webb will separate from the Ariane 5 launch vehicle. Shortly after this, we will talk with Webb from the ground to make sure everything is okay after its trip to space.

In the first day: After 24 hours, Webb will be nearly halfway to the Moon! About 2.5 days after launch, it will pass the Moon’s orbit, nearly a quarter of the way to Lagrange Point 1 (L2).

In the first week: We begin the major deployment of Webb. This includes unfolding the sunshield and tensioning the individual membranes, deploying the secondary mirror, and deploying the primary mirror.

In the first month: Deployment of the secondary mirror and the primary mirror occur. As the telescope cools in the shade of the sunshield, we turn on the warm electronics and initialize the flight software. As the telescope cools to near its operating temperature, parts of it are warmed with electronic heaters. This prevents condensation as residual water trapped within some of the materials making up the observatory escapes into space.

In the second month: We will turn on and operate Webb’s Fine Guidance Sensor, NIRCam, and NIRSpec instruments. 

The first NIRCam image, which will be an out-of-focus image of a single bright star, will be used to identify each mirror segment with its image of a star in the camera. We will also focus the secondary mirror.

In the third month: We will align the primary mirror segments so that they can work together as a single optical surface. We will also turn on and operate Webb’s mid-infrared instrument (MIRI), a camera and spectrograph that views a wide spectrum of infrared light. By this time, Webb will complete its journey to its L2 orbit position.

In the fourth through the sixth month: We will complete the optimization of the telescope. We will test and calibrate all of the science instruments.

After six months: The first scientific images will be released, and Webb will begin its science mission and start to conduct routine science operations.

7. Why not assemble it in orbit?

Various scenarios were studied, and assembling in orbit was determined to be unfeasible.

We examined the possibility of in-orbit assembly for Webb. The International Space Station does not have the capability to assemble precision optical structures. Additionally, space debris that resides around the space station could have damaged or contaminated Webb’s optics. Webb’s deployment happens far above low Earth orbit and the debris that is found there.

Finally, if the space station were used as a stopping point for the observatory, we would have needed a second rocket to launch it to its final destination at L2. The observatory would have to be designed with much more mass to withstand this “second launch,” leaving less mass for the mirrors and science instruments.

8. Who is James Webb?

This telescope is named after James E. Webb (1906–1992), our second administrator. Webb is best known for leading Apollo, a series of lunar exploration programs that landed the first humans on the Moon. 

However, he also initiated a vigorous space science program that was responsible for more than 75 launches during his tenure, including America's first interplanetary explorers.

Looking for some more in-depth FAQs? You can find them HERE.

Learn more about the James Webb Space Telescope HERE, or follow the mission on Facebook, Twitter and Instagram.

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Jack Hathaway

Jack Hathaway, a distinguished naval aviator, was born and raised in South Windsor, Connecticut. An Eagle Scout, Hathaway volunteers as an assistant scoutmaster for the Boy Scouts. https://go.nasa.gov/4bU8QbI

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What Does Two Decades of Rain and Snow Show Us?

You are seeing the culmination of almost twenty years of rain and snow, all at once.

For the first time, we have combined and remastered the satellite measurements from two of our precipitation spacecraft to create our most detailed picture of our planet’s rain and snowfall. This new record will help scientists better understand normal and extreme rain and snowfall around the world and how these weather events may change in a warming climate. 

The Most Extreme Places on Earth

Using this new two-decade record, we can see the most extreme places on Earth. 

The wettest places on our planet occur over oceans. These extremely wet locations tend to be very concentrated and over small regions.

A region off the coast of Indonesia receives on average 279 inches of rain per year.

An area off the coast of Colombia sees on average 360 inches of rain per year.

The driest places on Earth are more widespread. Two of the driest places on Earth are also next to cold ocean waters. In these parts of the ocean, it rains as little as it does in the desert -- they’re also known as ocean deserts! 

Just two thousand miles to the south of Colombia is one of the driest areas, the Atacama Desert in Chile that receives on average 0.64 inches of rain per year.

Across the Atlantic Ocean, Namibia experiences on average 0.49 inches of rain a year and Egypt gets on average 0.04 inches of rain per year.

Global Patterns

As we move from January to December, we can see the seasons shift across the world.

During the summer in the Northern Hemisphere, massive monsoons move over India and Southeast Asia.

We can also see dynamic swirling patterns in the Southern Ocean, which scientists consider one of our planet’s last great unknowns.

Close-up Patterns

This new record also reveals typical patterns of rain and snow at different times of the day -- a pattern known as the diurnal cycle. 

As the Sun heats up Earth’s surface during the day, rainfall occurs over land. In Florida, sea breezes from the Gulf of Mexico and Atlantic Ocean feed the storms causing them to peak in the afternoon. At night, storms move over the ocean.

In the winter months in the U.S. west coast, the coastal regions generally receive similar amounts of rain and snow throughout the day. Here, precipitation is driven less from the daily heating of the Sun and more from the Pacific Ocean bringing in atmospheric rivers -- corridors of intense water vapor in the atmosphere.

This new record marks a major milestone in the effort to generate a long-term record of rain and snow. Not only does this long record improve our understanding of rain and snow as our planet changes, but it is a vital tool for other agencies and researchers to understand and predict floods, landslides, disease outbreaks and agricultural production.

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What dose it feel like being inside a space suit?

The suit weighs about 300 pounds. We are made neutrally buoyant in the pool, but over time we can become negatively buoyant. The suit can feel heavy, even the bearings can become stiff, so it can be difficult to operate in the suit. With practice and the help of a great spacewalk team, we can make a spacewalk look seamless.

Planets: As Seen by Voyager

The Voyager 1 and 2 spacecraft explored Jupiter, Saturn, Uranus and Neptune before starting their journey toward interstellar space. Here you’ll find some of those images, including “The Pale Blue Dot” – famously described by Carl Sagan – and what are still the only up-close images of Uranus and Neptune.

These twin spacecraft took some of the very first close-up images of these planets and paved the way for future planetary missions to return, like the Juno spacecraft at Jupiter, Cassini at Saturn and New Horizons at Pluto.

Jupiter

Photography of Jupiter began in January 1979, when images of the brightly banded planet already exceeded the best taken from Earth. They took more than 33,000 pictures of Jupiter and its five major satellites. 

Findings:

Erupting volcanoes on Jupiter's moon Io, which has 100 times the volcanic activity of Earth. 

Better understanding of important physical, geological, and atmospheric processes happening in the planet, its satellites and magnetosphere.

Jupiter's turbulent atmosphere with dozens of interacting hurricane-like storm systems.

Saturn

The Saturn encounters occurred nine months apart, in November 1980 and August 1981. The two encounters increased our knowledge and altered our understanding of Saturn. The extended, close-range observations provided high-resolution data far different from the picture assembled during centuries of Earth-based studies.

Findings:

Saturn’s atmosphere is almost entirely hydrogen and helium.

Subdued contrasts and color differences on Saturn could be a result of more horizontal mixing or less production of localized colors than in Jupiter’s atmosphere.

An indication of an ocean beneath the cracked, icy crust of Jupiter's moon Europa. 

Winds blow at high speeds in Saturn. Near the equator, the Voyagers measured winds about 1,100 miles an hour.

Uranus

The Voyager 2 spacecraft flew closely past distant Uranus, the seventh planet from the Sun. At its closest, the spacecraft came within 50,600 miles of Uranus’s cloud tops on Jan. 24, 1986. Voyager 2 radioed thousands of images and voluminous amounts of other scientific data on the planet, its moons, rings, atmosphere, interior and the magnetic environment surrounding Uranus.

Findings:

Revealed complex surfaces indicative of varying geologic pasts.

Detected 11 previously unseen moons.

Uncovered the fine detail of the previously known rings and two newly detected rings.

Showed that the planet’s rate of rotation is 17 hours, 14 minutes.

Found that the planet’s magnetic field is both large and unusual.

Determined that the temperature of the equatorial region, which receives less sunlight over a Uranian year, is nevertheless about the same as that at the poles.

Neptune

Voyager 2 became the first spacecraft to observe the planet Neptune in the summer of 1989. Passing about 3,000 miles above Neptune’s north pole, Voyager 2 made its closest approach to any planet since leaving Earth 12 years ago. Five hours later, Voyager 2 passed about 25,000 miles from Neptune’s largest moon, Triton, the last solid body the spacecraft had the opportunity to study.

Findings: 

Discovered Neptune’s Great Dark Spot

Found that the planet has strong winds, around 1,000 miles per hour

Saw geysers erupting from the polar cap on Neptune’s moon Triton at -390 degrees Fahrenheit

Solar System Portrait

This narrow-angle color image of the Earth, dubbed ‘Pale Blue Dot’, is a part of the first ever ‘portrait’ of the solar system taken by Voyager 1. 

The spacecraft acquired a total of 60 frames for a mosaic of the solar system from a distance of more than 4 billion miles from Earth and about 32 degrees above the ecliptic.

From Voyager’s great distance, Earth is a mere point of light, less than the size of a picture element even in the narrow-angle camera.

“Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives.” - Carl Sagan

Both spacecraft will continue to study ultraviolet sources among the stars, and their fields and particles detectors will continue to search for the boundary between the Sun's influence and interstellar space. The radioisotope power systems will likely provide enough power for science to continue through 2025, and possibly support engineering data return through the mid-2030s. After that, the two Voyagers will continue to orbit the center of the Milky Way.

Learn more about the Voyager spacecraft HERE.

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The Artemis Story: Where We Are Now and Where We’re Going

Using a sustainable architecture and sophisticated hardware unlike any other, the first woman and the next man will set foot on the surface of the Moon by 2024. Artemis I, the first mission of our powerful Space Launch System (SLS) rocket and Orion spacecraft, is an important step in reaching that goal.

As we close out 2019 and look forward to 2020, here’s where we stand in the Artemis story — and what to expect in 2020. 

Cranking Up The Heat on Orion

The Artemis I Orion spacecraft arrived at our Plum Brook Station in Sandusky, Ohio, on Tuesday, Nov. 26 for in-space environmental testing in preparation for Artemis I.

This four-month test campaign will subject the spacecraft, consisting of its crew module and European-built service module, to the vacuum, extreme temperatures (ranging from -250° to 300° F) and electromagnetic environment it will experience during the three-week journey around the Moon and back. The goal of testing is to confirm the spacecraft’s components and systems work properly under in-space conditions, while gathering data to ensure the spacecraft is fit for all subsequent Artemis missions to the Moon and beyond. This is the final critical step before the spacecraft is ready to be joined with the Space Launch System rocket for this first test flight in 2020!

Bringing Everyone Together

On Dec. 9, we welcomed members of the public to our Michoud Assembly Facility in New Orleans for #Artemis Day and to get an up-close look at the hardware that will help power our Artemis missions. The 43-acre facility has more than enough room for guests and the Artemis I, II, and III rocket hardware! NASA Administrator Jim Bridenstine formally unveiled the fully assembled core stage of our SLS rocket for the first Artemis mission to the Moon, then guests toured of the facility to see flight hardware for Artemis II and III. The full-day event — complete with two panel discussions and an exhibit hall — marked a milestone moment as we prepare for an exciting next phase in 2020.

Rolling On and Moving Out

Once engineers and technicians at Michoud complete functional testing on the Artemis I core stage, it will be rolled out of the Michoud factory and loaded onto our Pegasus barge for a very special delivery indeed. About this time last year, our Pegasus barge crew was delivering a test version of the liquid hydrogen tank from Michoud to NASA’s Marshall Space Flight Center in Huntsville for structural testing. This season, the Pegasus team will be transporting a much larger piece of hardware — the entire core stage — on a slightly shorter journey to the agency’s nearby Stennis Space Center near Bay St. Louis, Mississippi.

Special Delivery

Why Stennis, you ask? The giant core stage will be locked and loaded into the B2 Test Stand there for the landmark Green Run test series. During the test series, the entire stage, including its extensive avionics and flight software systems, will be tested in full. The series will culminate with a hot fire of all four RS-25 engines and will certify the complex stage “go for launch.” The next time the core stage and its four engines fire as one will be on the launchpad at NASA’s Kennedy Space Center in Florida.

Already Working on Artemis II

As Orion and SLS make progress toward the pad for Artemis I, employees at NASA centers and large and small companies across America are hard at work assembling and manufacturing flight hardware for Artemis II and beyond.  The second mission of SLS and Orion will be a test flight with astronauts aboard that will go around the Moon before returning home. Our work today will pave the way for a new generation of moonwalkers and Artemis explorers.

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NASA Spotlight: Brandon Rodriguez, Jet Propulsion Laboratory Education Specialist 

Brandon Rodriguez is an education specialist at our Jet Propulsion Laboratory (JPL) in Pasadena, California where he provides resources and training to K-12 schools across the Southwest. Working with a team at JPL, he develops content for classroom teachers, visits schools and speaks with students and trains future teachers to bring NASA into their classroom. When he’s not in the classroom, Brandon’s job takes him on research expeditions all around the world, studying our planet’s extreme environments.  

Fun fact: Brandon wakes up every morning to teach an 8 a.m. physics class at a charter school before heading to JPL and clocking in at his full time job. When asked why? He shared, “The truth is that I really feel so much better about my role knowing that we’re not ‘telling’ teachers what to do from our ivory tower. Instead, I can “share” with teachers what I know works not just in theory, but because I’m still there in the classroom doing it myself.” - Brandon Rodriguez

Brandon took time from exciting the next generation of explorers to answer some questions about his life and his career: 

What inspired you to work in the educational department at NASA?

I was over the moon when I got a call from NASA Education. I began my career as a research scientist, doing alternative energy work as a chemist. After seven years in the field, I began to feel as if I had a moral responsibility to bring access to science to a the next generation. To do so, I quit my job in science and became a high school science teacher. When NASA called, they asked me if I wanted a way to be both a scientist and an educator- how could I resist?

You were born in Venezuela and came to the U.S. when you were 12 years old. Can you tell us the story of why and how you came to America?

I haven't been back to Venezuela since I was very young, which has been very difficult for me. Being an immigrant in the USA sometimes feels like you're an outsider of both sides: I'm not truly Latin, nor am I an American. When I was young, I struggled with this in ways I couldn't articulate, which manifested in a lot of anger and got me in quite a bit of trouble. Coming to California and working in schools that are not only primarily Latinx students, but also first generation Latinx has really helped me process that feeling, because it's something I can share with those kids. What was once an alienating force has become a very effective tool for my teaching practice.

Does your job take you on any adventures outside of the classroom and if so, what have been your favorite endeavors?

I'm so fortunate that my role takes me all over the world and into environments that allow to me to continue to develop while still sharing my strengths with the education community. I visit schools all over California and the Southwest of the USA to bring professional development to teachers passionate about science. But this year, I was also able to join the Ocean Exploration Trust aboard the EV Nautilus as we explored the Pacific Remote Island National Marine Monument. We were at sea for 23 days, sailing from American Samoa to Hawaii, using submersible remotely operated vehicles to explore the ocean floor. 

Image Credit: Nautilus Live 

We collected coral and rock samples from places no one has ever explored before, and observed some amazing species of marine creatures along the way.

Image Credit: Nautilus Live 

What keeps you motivated to go to work every day?

There's no greater motivation than seeing the product of your hard work, and I get that everyday through students. I get to bring them NASA research that is "hot off the press" in ways that their textbooks never can. They see pictures not online or on worksheets, but from earlier that day as I walked through JPL. It is clearly that much more real and tangible to them when they can access it through their teacher and their community.

Do you have any tips for people struggling with their science and math classes? 

As someone who struggled- especially in college- I want people to know that what they struggle with isn't science, it's science classes. The world of research doesn't have exams; it doesn't have blanks to be filled in or facts to be memorized. Science is exploring the unknown. Yes, of course we need the tools to properly explore, and that usually means building a strong academic foundation. But it helped me to differentiate the end goal from the process: I was bad at science tests, but I wanted to someday be very good at science. I could persevere through the former if it got me to the latter.

If you could safely visit any planet, star, or solar system, where would you visit and what would you want to learn?

Europa, without a doubt. Imagine if we found even simple life once more in our solar system- and outside of the habitable zone, no less. What would this mean for finding life outside of our solar system as a result? We would surely need to conclude that our sky is filled with alien worlds looking back at us.

Is there a moment or project that you feel defined (or significantly impacted) your career up to today?

While I never worked closely with the mission, Insight was a really important project for me. It's the first time while at JPL I was able to see the construction, launch and landing of a mission.

If you could name a spaceship, what would you name it?

For as long as I can remember, I've been watching and reading science fiction, and I continue to be amazed at how fiction informs reality. How long ago was it that in Star Trek, the crew would be handing around these futuristic computer tablets that decades later would become common iPads?  In their honor, I would be delighted if we named a ship Enterprise.

Thanks so much Brandon! 

Additional Image Credit: MLParker Media

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HBCU Students Make Moves with NASA Tech

In September 2023, students at HBCUs participated in a hackathon at the National HBCU Week Conference, where they used NASA’s technologies to create solutions to problems that affect Black communities. The winning team, Team Airtek, proposed a nano-sensor array for medical diagnoses that would give students on HBCU campuses a non-invasive, non-intensive way to test themselves for precursors for diseases and illnesses like diabetes and COVID.

The hackathon they participated in is a modified version of the full NASA Minority University Research and Education Project Innovation and Tech Transfer Idea Competition (MITTIC) that takes place each fall and spring semester at NASA’s Johnson Space Center in Houston.

No matter what you’re studying, you can join the MITTIC competition and come up with new and innovative tech to help your community and the world.

MITTIC could be the beginning of your career pathway: Teams can go on exclusive NASA tours and network with industry experts. Show off your entrepreneurial skills and your team could earn money—and bragging rights.

Don’t wait too long to apply or to share with someone who should apply! The deadline for proposals is Oct. 16, 2023. Apply here: https://microgravityuniversity.jsc.nasa.gov/nasamittic.

After 20 years in space, the Cassini spacecraft is running out of fuel. In 2010, Cassini began a seven-year mission extension in which the plan was to expend all of the spacecraft’s propellant exploring Saturn and its moons. This led to the Grand Finale and ends with a plunge into the planet’s atmosphere at 6:32 a.m. EDT on Friday, Sept. 15.

The spacecraft will ram through Saturn’s atmosphere at four times the speed of a re-entry vehicle entering Earth’s atmosphere, and Cassini has no heat shield. So temperatures around the spacecraft will increase by 30-to-100 times per minute, and every component of the spacecraft will disintegrate over the next couple of minutes…

Cassini’s gold-colored multi-layer insulation blankets will char and break apart, and then the spacecraft's carbon fiber epoxy structures, such as the 11-foot (3-meter) wide high-gain antenna and the 30-foot (11-meter) long magnetometer boom, will weaken and break apart. Components mounted on the outside of the central body of the spacecraft will then break apart, followed by the leading face of the spacecraft itself.

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TESS: The Planet Hunter

So you’re thinking...who’s TESS? But, it’s more like: WHAT is TESS? 

The Transiting Exoplanet Survey Satellite (TESS) is an explorer-class planet finder that is scheduled to launch in April 2018. This mission will search the entire sky for exoplanets — planets outside our solar system that orbit sun-like stars.

In the first-ever space borne all-sky transit survey, TESS will identify planets ranging from Earth-sized to gas giants, orbiting a wide range of stellar types and orbital distances.

The main goal of this mission is to detect small planets with bright host stars in the solar neighborhood, so that we can better understand these planets and their atmospheres.

TESS will have a full time job monitoring the brightness of more than 200,000 stars during a two year mission. It will search for temporary drops in brightness caused by planetary transits. These transits occur when a planet’s orbit carries it directly in front of its parent star as viewed from Earth (cool GIF below).

TESS will provide prime targets for further, more detailed studies with the James Webb Space Telescope (JWST), as well as other large ground-based and space-based telescopes of the future.

What is the difference between TESS and our Kepler spacecraft?

TESS and Kepler address different questions: Kepler answers "how common are Earth-like planets?" while TESS answers “where are the nearest transiting rocky planets?”

What do we hope will come out of the TESS mission?

The main goal is to find rocky exoplanets with solid surfaces at the right distance from their stars for liquid water to be present on the surface. These could be the best candidates for follow-up observations, as they fall within the “habitable zone” and be at the right temperatures for liquid water on their surface.

TESS will use four cameras to study sections of the sky’s north and south hemispheres, looking for exoplanets. The cameras would cover about 90 percent of the sky by the end of the mission. This makes TESS an ideal follow-up to the Kepler mission, which searches for exoplanets in a fixed area of the sky. Because the TESS mission surveys the entire sky, TESS is expected to find exoplanets much closer to Earth, making them easier for further study.

Stay updated on this planet-hunting mission HERE.

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