With every additional centimeter of aperture, every additional second of observation time, and every additional atmospheric noise atom removed from the telescope's field of view, the Universe can be seen better, deeper, and more clearly.
25 years of Hubble
When the Hubble Telescope began operating in 1990, it ushered in a new era in astronomy - space. There was no need to fight the atmosphere anymore, worry about clouds or electromagnetic flickering. All that was required was to turn the satellite to the target, stabilize it and collect photons. In 25 years, space telescopes began to cover the entire electromagnetic spectrum, allowing for the first time to see the universe at every wavelength of light.
But as our knowledge has increased, so has our understanding of the unknown. The further we look into the universe, the deeper the past we see: a finite amount of time since the Big Bang, combined with the finite speed of light, provides a limit to what we can observe. Moreover, the expansion of space itself works against us, stretching the stars as it travels through the universe towards our eyes. Even the Hubble Space Telescope, which gives us the deepest, most breathtaking view of the universe we have ever discovered, is limited in this regard.
Disadvantages of "Hubble"
Hubble is an amazing telescope, but it has a number of fundamental limitations:
- Only 2.4m in diameter, which limits it
- Despite being coated with reflective materials, it is constantly exposed to direct sunlight, which heats it up. This means that due to thermal effects, it cannot observe light wavelengths greater than 1.6 microns.
- The combination of its limited luminosity and the wavelengths to which it is sensitive means the telescope can see galaxies no older than 500 million years.
These galaxies are beautiful, distant, and existed when the universe was only about 4% of its current age. But it is known that stars and galaxies existed even earlier.
To see it must have a higher sensitivity. This means a shift to longer wavelengths and lower temperatures than the Hubble. That is why the James Webb Space Telescope is being created.
Perspectives for science
The James Webb Space Telescope (JWST) is designed to overcome precisely these limitations: with a diameter of 6.5 meters, the telescope can collect 7 times more light than the Hubble. It opens up the possibility of high-resolution ultra-spectroscopy from 600 nm to 6 microns (4 times the wavelength that Hubble can see), to carry out observations in the mid-infrared region of the spectrum with higher sensitivity than ever before. JWST uses passive cooling to the temperature of Pluto's surface and is capable of actively cooling mid-infrared instruments down to 7 K. The James Webb Telescope will provide an opportunity to do science in a way that no one has done before.
It will allow:
- observe the earliest galaxies ever formed;
- see through neutral gas and probe the first stars and the reionization of the universe;
- carry out spectroscopic analysis of the very first stars (population III) formed after the Big Bang;
- get amazing surprises like the discovery of the earliest and quasars in the universe.
The JWST level of scientific research is unlike anything in the past, and therefore the telescope was chosen as the flagship mission of NASA in the 2010s.
Scientific masterpiece
From a technical point of view, the new James Webb Telescope is a true work of art. The project has come a long way with budget overruns, schedule delays and the danger of project cancellation. After the intervention of the new leadership, everything changed. The project suddenly started working like clockwork, funds were allocated, errors, failures and problems were taken into account, and the JWST team began to fit into all the timelines, schedules and budgetary limits. The launch of the device is scheduled for October 2018 on the Ariane-5 rocket. The team not only follows the schedule, they have nine months in reserve to deal with all the contingencies, so that everything is assembled and ready for that date.
The James Webb Telescope has 4 main parts.
Optical unit
Includes all mirrors, of which eighteen primary segmented gold plated mirrors are the most effective. They will be used to collect distant starlight and focus it on analysis instruments. All of these mirrors are currently ready and flawless, made right on schedule. Once assembled, they will be folded into a compact structure in order to be launched more than 1 million km from Earth to the L2 Lagrange point, and then automatically unfold to form a honeycomb structure that will collect ultra-long-range light for many years. This is a truly beautiful thing and a successful result of the titanic efforts of many specialists.
Near infrared camera
The Webb is equipped with four scientific instruments that are 100% complete. The main camera of the telescope is a near-infrared camera: from visible orange light to deep infrared. It will provide unprecedented images of the earliest stars, the youngest galaxies still in the process of forming, the young stars of the Milky Way and nearby galaxies, hundreds of new objects in the Kuiper belt. It is optimized for direct imaging of planets around other stars. This will be the primary camera used by most observers.
Near infrared spectrograph
This tool not only splits light into separate wavelengths, but is capable of doing so for over 100 separate objects at the same time! This device will be a versatile Webb spectrograph capable of operating in 3 different spectroscopy modes. It was built but many of the components, including detectors and a multi-shutter battery, were provided by the Space Flight Center. Goddard (NASA). This device has been tested and is ready to be installed.
Mid-infrared instrument
The instrument will be used for broadband imaging, which means it will produce the most impressive images from all Webb instruments. Scientifically, it will be most useful in measuring protoplanetary disks around young stars, measuring and visualizing Kuiper belt objects and dust heated by starlight with unprecedented accuracy. It will be the only instrument with cryogenic cooling down to 7 K. Compared to the Spitzer space telescope, this will improve results by a factor of 100.
Slitless Near Infrared Spectrograph (NIRISS)
The device will make it possible to produce:
- wide-angle spectroscopy in the near infrared region of wavelengths (1.0 - 2.5 microns);
- grism spectroscopy of one object in the visible and infrared range (0.6 - 3.0 microns);
- aperture cloaking interferometry at wavelengths of 3.8 - 4.8 microns (where the first stars and galaxies are expected);
- wide-range shooting of the entire field of view.
This instrument was created by the Canadian Space Agency. After passing cryogenic testing, it will also be ready for integration into the instrument compartment of the telescope.
Sun protection device
Space telescopes have not yet been equipped with them. One of the most daunting aspects of every launch is the use of a completely new material. Rather than actively cooling the entire spacecraft with a disposable, consumable refrigerant, the James Webb Telescope uses a completely new technology - a 5-layer sunscreen that will be deployed to reflect solar radiation off the telescope. Five 25-meter sheets will be connected by titanium rods and installed after the telescope is deployed. Protection was tested in 2008 and 2009. The full-scale models that took part in laboratory tests did everything they had to do here on Earth. This is a beautiful innovation.
It's also an incredible concept: don't just block the light from the sun and place the telescope in the shadows, but do it in such a way that all the heat is radiated in the opposite direction of the telescope's orientation. Each of the five layers in the vacuum of space will become cold with distance from the outer one, which will be slightly warmer than the temperature of the Earth's surface - about 350-360 K. The temperature of the last layer should drop to 37-40 K, which is colder than at night on the surface Pluto.
In addition, significant precautions have been taken to protect against the harsh environment of deep space. One of the things to worry about here are tiny pebbles the size of pebbles, grains of sand, specks of dust, and even less, flying through interplanetary space at tens or even hundreds of thousands of km / h. These micrometeorites are capable of making tiny, microscopic holes in everything they encounter: spacecraft, astronaut suits, telescope mirrors, and more. If the mirrors only get dents or holes, which slightly reduces the amount of "good light" available, then the sun shield could tear from edge to edge, rendering the entire layer useless. A brilliant idea was used to combat this phenomenon.
The entire solar shield was divided into sections in such a way that if there was a small break in one, two, or even three of them, the layer would not break further, like a crack in a car windshield. Partitioning will keep the entire structure intact, which is important to prevent degradation.
Spacecraft: assembly and control systems
This is the most common component, as all space telescopes and scientific missions have. JWST has it unique, but also completely ready. All that remains for the general contractor of the Northrop Grumman project is to finish the shield, assemble the telescope, and test it. The device will be ready for launch in 2 years.
10 years of discovery
If everything goes right, humanity will be on the cusp of great scientific discoveries. The blanket of neutral gas that has so far obscured the view of the earliest stars and galaxies will be removed by Webb's infrared capabilities and enormous aperture ratio. It will be the largest, most sensitive telescope with a huge wavelength range of 0.6 to 28 microns (the human eye sees from 0.4 to 0.7 microns) ever built. It is expected to provide a decade of observations.
According to NASA, the Webb mission will last from 5.5 to 10 years. It is limited by the amount of fuel needed to maintain an orbit and the lifespan of electronics and equipment in the harsh environment of space. The James Webb Orbital Telescope will carry a fuel supply for the entire 10-year period, and 6 months after launch, flight support testing will be carried out, which guarantees 5 years of scientific work.
What could go wrong?
The main limiting factor is the amount of fuel on board. When it ends, the satellite will drift away from L2, entering a chaotic orbit in close proximity to the Earth.
Coma of this, other troubles can occur:
- degradation of mirrors, which will affect the amount of collected light and create image artifacts, but will not harm the further operation of the telescope;
- failure of part or all of the solar screen, which will lead to an increase in the temperature of the spacecraft and narrow the used wavelength range to the very near infrared region (2-3 microns);
- breakage of the mid-infrared instrument cooling system, making it unusable, but not affecting other instruments (0.6 to 6 microns).
The most difficult test that awaits the James Webb Telescope is launch and placement into a given orbit. These situations were tested and passed successfully.
A revolution in science
If the Webb telescope works normally, there will be enough fuel to keep it running from 2018 to 2028. In addition, there is the potential for refueling that could extend the telescope's lifespan by another decade. Just as the Hubble has been in operation for 25 years, the JWST could provide a generation of revolutionary science. In October 2018, the Ariane 5 launch vehicle will launch the future of astronomy into orbit, which, after more than 10 years of hard work, is ready to start bearing fruit. The future of space telescopes is almost here.
The idea of \u200b\u200bbuilding a new powerful space telescope arose almost 20 years ago, in 1996, when American astronomers released the report HST and Beyond, which discussed the question of where astronomy should go next. Not long before that, in 1995, the first exoplanet was discovered next to a star similar to our Sun. This excited the scientific community - after all, there was a chance that somewhere there could be a world resembling the Earth - so the researchers asked NASA to build a telescope that would be suitable, among other things, for searching and studying exoplanets. This is where the story of "James Webb" begins. The launch of this telescope has been continually delayed (originally planned to send it into space back in 2011), but now it appears to be on the home stretch. Editorial staff N + 1 tried to figure out what astronomers expect to learn from Webb, and spoke with those who create this instrument.
The name "James Webb" was given to the telescope in 2002, before that it was called the Next Generation Space Telescope ("Space telescope of a new generation"), or NGST for short, because the new instrument should continue the research begun by Hubble. If "" explores the Universe mainly in the optical range, capturing only the near infrared and ultraviolet ranges, which border on visible radiation, then James Webb will concentrate on the infrared part of the spectrum, where older and colder objects are visible. In addition, the expression "next generation" refers to the advanced technology and engineering that will be used in the telescope.
Telescope mirror making process
Fragment of telescope mirror
Telescope mirror making process
Fragment of telescope mirror
Fragment of telescope mirror
Fragment of telescope mirror
Perhaps the most non-standard and complex of them is the main mirror of "James Webb" with a diameter of 6.5 meters. Scientists did not create an enlarged version of the Hubble mirror, because it would weigh too much, and came up with an elegant way out of the situation: they decided to assemble a mirror from 18 separate segments. For them, a light and durable metal beryllium was used, on which a thin layer of gold was applied. As a result, the mirror weighs 705 kilograms, while its area is 25 square meters. The Hubble mirror weighs 828 kilograms with an area of \u200b\u200b4.5 square meters.
Another important component of the telescope that has been causing a lot of trouble for engineers lately is the deployable heat shield, which is necessary to protect the James Webb instruments from overheating. In near-earth orbit, objects in direct sunlight can heat up to 121 degrees Celsius. James Webb's devices are designed to operate in conditions of fairly low temperatures, so a heat shield was needed to shield them from the sun.
It is comparable in size to a tennis court, 21 x 14 meters, so it is impossible to send it to the L2 Lagrange point (this is where the telescope will work) in an expanded form. This is where the main difficulties begin - how to deliver the shield to its destination so that it is not damaged? The most logical decision was to fold it down for the duration of the flight, and then deploy it when the James Webb is at its operating point.
The outer side of the shield, where the antenna, on-board computer, gyroscopes and solar panel are located, will heat up, as scientists expect, to 85 degrees Celsius. But on the "night" side, where the main scientific instruments are located, it will be frosty: about 233 degrees below zero. Thermal insulation will be provided by five layers of the shield - each colder than the previous one.
"James Webb" deployable shield
What scientific instruments are required to be so carefully hidden from the Sun? There are four of them: the NIRCam near-infrared camera, the MIRI device for working in the mid-infrared range, the NIRSpec near-infrared spectrograph and the FGS / NIRISS system. In the picture below you can clearly see in what "light" they will see the Universe:
The image shows the range that the telescope instruments will capture.
With the help of scientific instruments, scientists hope to answer many fundamental questions. First of all, they concern exoplanets.
Despite the fact that the Kepler telescope has discovered more than 2,500 exoplanets to date, density estimates exist for only a few hundred. Meanwhile, these estimates allow us to understand what type the planet belongs to. If it has a low density, it is obviously a gas giant. If a celestial body has a high density, then most likely it is a rocky planet, reminiscent of Earth or Mars. Astronomers hope that James Webb will help collect more data on the masses and diameters of planets, which will help calculate their density and determine their type.
NASA / Goddard Space Flight Center and the Advanced Visualization Laboratory at the National Center for Supercomputing Applications
Another important question concerns the atmospheres of exoplanets. Hubble and Spitzer have collected data on the gas envelopes of about a hundred planets. James Webb's tools will increase this number by at least three times. Thanks to scientific instruments and different observation modes, astronomers will be able to determine the presence of a huge number of substances, including water, methane and carbon dioxide - not only on large planets, but also on terrestrial planets. One of the observational targets will be where seven earth-like planets are located at once.
Most of the results are expected for young, newly formed Jupiters who are still emitting in the infrared. In particular, in the solar system, as the mass of gas giants decreases, the content of metals (elements heavier than hydrogen and helium) in them increases. "Hubble" at one time showed that not all planetary systems obey this law, but there is still no statistically reliable sample - it will be received by "James Webb". In addition, the telescope is also expected to study sub-Neptuns and super-Earths.
Ancient galaxies will be another important target for the telescope. Today we already know a lot about the surrounding galaxies, but still very little about those that appeared in a very young universe. Hubble can see the Universe as it was 400 million years after the Big Bang, and the Planck Observatory observed cosmic microwave radiation that appeared 400 thousand years after the Big Bang. James Webb will fill the gap between them and figure out what galaxies looked like in the first 3 percent of space history.
Now astronomers observe a direct relationship between the size of a galaxy and its age - the older the Universe, the more small galaxies it contains. However, this trend is unlikely to continue, and scientists hope to determine some "turning point", to find a lower limit on the size of galaxies. Thus, astronomers want to answer the question of when the first galaxies appeared.
A separate point is the study of molecular clouds and protoplanetary disks. In the past, Spitzer could only look into the immediate vicinity of the solar system. Webb is much more sensitive and will actually be able to see the other end of the Milky Way, as well as its center.
Also, "James Webb" will be looking for hypothetical population III stars - these are very heavy objects, in which there are almost no elements heavier than helium, hydrogen and lithium. It is assumed that stars of this type should make up after the Big Bang.
A pair of interacting galaxies called "Antennas"
Today, the launch of James Webb is slated for June 2019. Initially, the telescope was supposed to be sent into space in early spring, but the mission was postponed for several months due to technical problems. Christine Pulliam, Deputy Project Academic Supervisor, answered questions N + 1about the telescope itself and the difficulties in its construction.
I'll probably ask an obvious question, but what makes James Webb so unique?
Webb will allow us to see the universe as we have never seen it before. It will conduct observations in the infrared range, that is, at other wavelengths than the Hubble, it will be able to look further than the Spitzer, and in other areas than the Herschel. It will fill in the gaps and help create a holistic picture of the universe. Extensive infrared observations will help us see nascent stars and planets. The first galaxies will finally be revealed to us, and this will help put together the entire cosmological history. Some people like to say that telescopes are time machines, which is a very good expression. When we look into space, we see the past because it takes time for light to reach Earth. We will see the Universe when it was extremely young - and this will help us understand how we came to be and how the Universe works. If we talk about something closer to humanity, then we will see how stars arose, how exoplanets were formed, and we can even characterize their atmospheres.
Yes, the question of the atmospheres of distant planets worries very many. What results do you expect to get?
We had missions like Kepler looking for candidates. Thanks to them, today we know of thousands of exoplanets. Now "James Webb" will look at already known objects and explore their atmospheres. In particular, this applies to giant planets - celestial bodies in size located between Neptune and super-Jupiters. It is extremely important for us to understand how such objects are formed, how they evolve, and what the systems they are part of are like. For example, if we see a system of several planets, it is important for us to determine whether there may be water there and where to look for it.
Actually define the habitable zone?
Exactly. It will be different for different stars. James Webb will help us characterize distant planets and understand how unique our home is.
The telescope's mission is expected to last about ten years. However, what are the real predictions? We all remember Voyagers, which are still in working order and send data to Earth, although no one planned this.
The nominal service life of the tool is five years, and we hope that it will be able to work that much. If we give more daring estimates, then it is ten years. We are limited to a supply of coolant to keep the telescope systems in good working order. I don't think James Webb can, like Hubble, last 29 years.
Yes, James Webb will be too far from Earth, at the second Lagrange point. Do you think technology will allow us in the future to reach the telescope and repair it in the event of a breakdown?
This possibility is not excluded. For this case, the telescope has a mount for a robotic arm that can be mounted on the Webb. However, the telescope was not intended to be serviced from the outset, so it should not be hoped for too much. Taking into account the fact that the instrument will work for only 5-10 years, we are unlikely to have time to step that far forward to send a spacecraft to it.
Will James Webb be able to work in tandem with other spacecraft? For example, the University of Colorado Space and Astronomical Center proposes to create an external coronagraph for it. In 2013, they talked about a possible joint work with the telescope - are there such plans in reality?
I would not say that at the moment we are considering such a possibility. If I'm not mistaken, Webb Cash is responsible for this project, but there is another Star Shield project, as well as several other groups that are working on creating similar tools. There are no specific plans for linking James Webb with another instrument today, although hypothetically it could work in conjunction with any space observatory.
How do you plan to distribute the observation time?
Now astronomers from all over the world are sending us their applications, and after they pass the peer review, we will receive a rough plan. There is a “guaranteed observation time” that is assigned to the scientists helping design and build James Webb today, a bit of a thank you for their work. These researchers will study galaxies, exoplanets, for example, planets of the TRAPPIST system. In part, we choose our targets to test the capabilities of James Web. We were just starting to think about exoplanets when creating the telescope, but now this is a very promising area in astronomy, and we must understand how to use James Webb to study planets outside the solar system. This is exactly what the teams that will conduct observations in the first year will do. In the fall it will already be known what we will "see" in the first year.
Hubble Ultra Deep Field
Why are the launch dates shifted again? There are rumors of financial problems and problems with the mirror system.
The fact is that "Webb" is a very difficult telescope, and this is the first time we are solving such a complex problem. There are several main components in the apparatus: mirrors, tools, a huge shield, and cooling mechanisms. All these elements have to be built and tested, combined, tested again - of course, it takes time. You also need to make sure that we did everything correctly, that all the details fit together, that the launch will be successful, and all the elements will unfold correctly. The delays are due to the large number of steps and the need for careful verification.
That is, now you were conducting tests, and realized that you did not fit into the original schedule?
Yes. In fact, we still have a lot of backup time. We initially knew that everything would be all right, but we assumed that the preparation could be delayed for some reason. In addition, when we are ready to launch the vehicle, we will also need to agree on a specific date with the ESA, which owns the Ariane rocket. So we thought - where is the hurry?
Tell us, what tests should the telescope pass and does it pass?
Recently, the OTISS (Optical Telescope and Instrument Assembly) system was tested at the Lyndon Johnson Space Center. It was cooled to extremely low operating temperatures, all the optics and the telescope itself were tested. Scientists recently removed the system from the cooling chamber, reheated it, and now OTISS will travel to California, to the Space Park on Redando Beach, where it will be connected to a sun shield. In addition, work is now underway on the shield itself, experts are conducting numerous checks. When all the elements are attached to the shield, it will be folded and unfolded to make sure it works flawlessly, and then other tests will be carried out, including a vibration test, which the telescope will encounter during the flight on the rocket. Launching into space is a major challenge for the vehicle, so engineers want to be sure that all of its components will survive the flight. The researchers will then prepare the James Webb for launch, load it onto a barge, and send it to the launch site in French Guiana sometime in early 2019.
What about the rest of the tools? As far as I know, you have not mentioned everything. Have they already passed the preliminary checks?
Yes, they have already passed all the tests and are now installed on the telescope. These are separate devices that will carry out numerous scientific studies - a spectrograph that studies the sky in the mid-IR range, a camera. In addition, all tools have different modes, so you need to check if they really work as we intended. This is very important - you need to "shake" the device and make sure that the angle of view remains the same.
When should we expect the first results?
Most likely, the first data will come only at the end of next year or early 2020. Between the launch and the receipt of the first information, about six months will pass. During this time, the telescope will rotate and we will make sure that it is deployed and is working properly. Then the devices will need to cool down, this will take a long time. On Earth, James Webb is at room temperature, but when we launch it into space, we will need to wait until its instruments reach operating temperatures. Then we will put them into operation: a number of "training exercises" are already planned - several planned observations and checks of different modes of operation, which will make sure that everything is functioning as it should. Since we do not have a launch date, and, as a result, we do not know what will fall into the telescope's field of view, a specific object has not been selected for observation. Most likely, we will calibrate the telescope instruments on some distant star. All these are internal processes - first we have to make sure that we can see anything at all.
However, after we make sure that all the tools are working, we will proceed directly to scientific experiments. A team of scientists that specializes in imaging will determine which targets will look truly mesmerizing and will hook the audience. The work will be done by the same artists who worked with the Hubble images - they are people with many years of experience in processing astronomical images. In addition, additional equipment tests will be carried out.
After the first images come out, we will have a little over a year for scientific observations. They include already known programs for the study of very distant galaxies, quasars, exoplanets and Jupiter. In general, astronomers will observe everything that is possible - from regions of active star formation to ice in protoplanetary disks. This research is important to all of us: the rest of the scientific community will be able to see the results of other teams and understand where they should go next.
Christina UlasovichNASA today confirmed plans for the James Webb telescope project. Management said both the current budget and plans to launch the space telescope for 2018 are relevant. It is worth noting that the agency itself views this telescope as the next Hubble model rather than its replacement.
The capabilities of the telescope significantly exceed those of the Hubble. The James Webb will have a 6.5-meter-diameter composite mirror (the Hubble mirror is 2.4 meters) with a collecting surface of 25 m² and a tennis court-sized solar shield. The telescope will be located at the L2 Lagrange point of the Sun - Earth system. 
James Webb will be able to travel into the distant past of the universe - for a time from 100 to 250 million years after the Big Bang. In other words, the new telescope will be able to look much further into the depths of space than Hubble, which can “travel” no further than 800 million - 1 billion years after the Big Bang. In addition, Webb is not "sharpened" for visible light, his specialty is the infrared spectrum. However, James Webb can also detect radiation visible to the human eye.
Simulation of what the James Webb telescope "sees" and what the Hubble sees at the same point in space
Difficulties in project implementation
The main problem with such large projects as James Webb and Hubble is the budget. That the first, that the second project went beyond the budget. But, since a significant part of the budget has already been spent, there is nothing left but to continue to implement the plans.
In the case of Hubble, the situation was further complicated by the fact that the mirror was initially incorrectly installed. This affected the capabilities of the telescope, and it took a long time before the error was corrected with the help of an external expedition, during which corrective lenses were installed.
As for James Webb, the mistake is unforgivable. As mentioned above, the new telescope is planned to be installed at the L2 Lagrange point. If something goes wrong, the project will have to be forgotten. Nevertheless, the chances of a successful project implementation are quite significant.
Webb will peer into the near and mid-infrared spectrum, which will be facilitated by his position at point L2 behind the moon and solar shields, which block the intrusive light of the Sun, Earth and Moon, beneficially affecting the cooling of the apparatus. Scientists hope to see the very first stars in the universe, the formation and collision of young galaxies, the birth of stars in protoplanetary systems - which may contain the chemical components of life.
These first stars may hold the key to understanding the structure of the universe. Theoretically, where and how they form is directly related to the first models of dark matter - an invisible mysterious substance that is detected by gravitational influence - and their cycles of life and death cause feedback that influenced the formation of the first galaxies. And since supermassive stars with a short life span are about 30-300 times heavier than our Sun in mass (and millions of times brighter), these first stars could explode in the form of supernovae, and then collapse and form black holes, which gradually occupied the centers of most massive galaxies.
Seeing all of this is definitely a feat for the tools we've made so far. Thanks to new instruments, as well as spacecraft, we will be able to see even more.
James Webb Space Telescope Tour
Webb looks like a diamond-shaped raft, equipped with a thick, curved mast and sail - if built by giant bees that feed on beryllium. Directed by its lower part towards the Sun, from below the "raft" consists of a shield - layers of kapton, separated by slits. Each layer is separated by a vacuum slot for efficient cooling, and together they protect the main reflector and instruments.
Kapton is a very thin (imagine human hair) DuPont polymer film that is capable of maintaining stable mechanical properties under extreme heat and vibration conditions. If you wish, you can boil water on one side of the shield and keep the nitrogen liquid on the other. It folds up pretty well too, which is important for launch.
A ship's keel consists of a structure that stores a solar shield during launch and solar panels to provide power to the craft. At the center is a box that contains all of the important support functions that Webb is powered by, including power, attitude control, communications, command, data processing, and thermal control. The antenna adorns the appearance of the box and helps to ensure that everything is oriented in the right direction. At one end of the heat shield, perpendicular to it, there is a torque trim that compensates for the pressure exerted by the photons on the apparatus.
On the outer side of the shield is a sail, a giant Webb mirror, a piece of optical equipment, and a box of equipment. The 18 hexagonal beryllium sections will unfold upon launch to become one large primary mirror 6.5 meters across.
Opposite this mirror, held in place by three supports, is a secondary mirror that focuses light from the primary mirror into the aft optical subsystem, a wedge-shaped box protruding from the center of the primary mirror. This structure deflects the scattered light and directs light from the secondary mirror to the instruments located at the rear of the “mast”, which also supports the segmented structure of the primary mirror.
After the unit completes its six-month commissioning period, it will last 5-10 years, maybe more, depending on fuel consumption, but its location will be too far away to be repaired. In fact, Hubble is a kind of exception in this regard. But, like Hubble and other shared observatories, Webb's mission will be to work with competitively selected scientists from around the world. The results will then find their way into the research and data available on the Internet.
Let's take a closer look at the tools that make all this research possible.
Instruments: out of sight
Although he sees something in the visual range (red and gold light), Webb is fundamentally a large infrared telescope.
Its main thermal imager, a near infrared camera NIRCam,sees in the range of 0.6-5.0 microns (near infrared). It will be able to detect the infrared light from the birth of the earliest stars and galaxies, conduct surveys of nearby galaxies and local objects scurrying through the Kuiper belt - expanses of icy bodies orbiting Neptune, which also contain Pluto and other dwarf planets.
NIRCam is also equipped with a coronagraph, which will allow the camera to observe the thin halos surrounding bright stars, blocking out their blinding light - a necessary tool for detecting exoplanets.
The NIR spectrograph operates in the same wavelength range as the NIRCam. Like other spectrographs, it analyzes the physical properties of objects such as stars, dividing the light they emit into spectra, the structure of which changes depending on the temperature, mass and chemical composition of the object.
NIRSpec will study thousands of ancient galaxies with such weak radiation that a single spectrograph will take hundreds of hours to do the job. To simplify this daunting task, the spectrograph is equipped with a remarkable device: a grid of 62,000 individual blinds, each approximately 100 by 200 microns (a few human hairs wide) in size, and each of which can be opened and closed, blocking out the light of brighter stars. With this array, NIRSpec will become the first space-based spectrograph to observe hundreds of different objects simultaneously.
Fine Guidance Sensor and a slitless spectrograph (FGS-NIRISS) are essentially two sensors packed together. NIRISS includes four modes, each of which is associated with a different wavelength. These range from gapless spectroscopy, which creates a spectrum using a prism and grating called a "grism", which together create interference patterns that reveal exoplanetary light against the background of starlight.
FGS is a sensitive and non-blinking camera that takes navigation pictures and feeds them to orientation systems that keep the telescope in the correct direction.
Webb's latest instrument expands its range from near-infrared to mid-infrared, which is useful for observing redshifted objects, as well as planets, comets, asteroids, sun-heated dust and protoplanetary disks. Being a camera and a spectrograph at the same time, this instrument MIRI covers the widest range of wavelengths, 5-28 microns. Its wideband camera will be able to take more kinds of pictures for which we love Hubble.
Also, infrared observations are important for understanding the universe. Dust and gas can block visible light from stars in stellar nurseries, but infrared cannot. Moreover, as the Universe expands and galaxies recede, their light "stretches" and becomes redshift, going into the long-wavelength spectrum of electromagnetic waves like infrared. The further away the galaxy, the faster it moves away and the more important its redshift becomes - this is the value of the Webb telescope.
The infrared spectrum can also provide a wealth of information about the atmospheres of exoplanets and whether they contain molecular components associated with life. On Earth, we call water vapor, methane, and carbon dioxide "greenhouse gases" because they absorb heat. Since this trend is true everywhere, scientists can use Webb to detect familiar substances in the atmospheres of distant worlds, observing patterns of absorption of substances using spectrographs.