James Webb Space Telescope: launch date, equipment

With each additional centimeter of the aperture, each additional second of observation time and each additional atom of atmospheric noise removed from the telescope's field of view, it is better, deeper and more intelligible to see the universe.

25 years old "Hubble"

When the Hubble telescope began operating in 1990, he opened a new era in space astronomy. It was no longer necessary to fight the atmosphere, worry about clouds or electromagnetic flicker. All that was required was to deploy the satellite to the target, stabilize it and collect photons. For 25 years, space telescopes began to cover the entire electromagnetic spectrum, which allowed us to consider the universe for the first time at each wavelength of light.

But as our knowledge has increased, our understanding of the unknown has also grown. The further we look into the Universe, the deeper past we see: the finite amount of time since the Big Bang combined with the finite speed of light provides the limit of what we can observe. Moreover, the expansion of the space itself works against us, stretching the wavelength of the light of the stars while it travels the universe to our eyes. Even the Hubble Space Telescope, which gives us the deepest, most exciting image of the universe that we have ever discovered, is limited in this respect.

Disadvantages of the Hubble

The Hubble is an amazing telescope, but it has a number of fundamental limitations:

• Only 2.4 m in diameter, which limits its resolution.
• Despite the coating with reflective materials, it is constantly exposed to direct sunlight, which heats up. This means that, due to thermal effects, it can not observe the wavelength of light more than 1.6 μm.
• The combination of limited light and wavelengths, to which it is sensitive, means that the telescope can see galaxies not older than 500 million years old.

These galaxies are beautiful, far off and existed when the universe was only about 4% of its present age. But it is known that stars and galaxies existed even earlier.

To see this, the telescope must have a higher sensitivity. This means a transition to longer wavelengths and lower temperatures than the Hubble. That's why the James Webb Space Telescope is being created.

Prospects for Science

James Webb Space Telescope (JWST) is designed to overcome these limitations: with a diameter of 6.5 m, the telescope allows you to collect 7 times more light than the Hubble. It opens the possibility of ultra-high resolution spectroscopy from 600 nm to 6 μm (4 times longer than the wavelength that Hubble can see), to perform observations in the middle infrared region of the spectrum with a higher sensitivity than ever before. JWST uses passive cooling to the surface temperature of Pluto and is able to actively cool mid-infrared devices up to 7 K. The James Webb telescope will give the opportunity to do science in ways that no one has done before.

It will allow:

• Observe the earliest galaxies ever formed;
• See through the neutral gas and probe the first stars and the reionization of the universe;
• Conduct a spectroscopic analysis of the very first stars (population III) formed after the Big Bang;
• Get amazing surprises, like the discovery of the earliest supermassive black holes and quasars in the universe.

The level of scientific research of JWST is not similar to 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 telescope of James Webb is a real work of art. The project went a long way: there were budget overruns, backlogs and the danger of canceling the project. After the intervention of the new leadership, everything changed. The project suddenly worked like a clock, funds were allocated, errors, failures and problems were taken into account, and the JWST team began to fit into all terms, schedules and budget frameworks. The launch is scheduled for October 2018 on the Ariane-5 rocket. The team not only follows the timetable, it has nine months in reserve to take into account all unforeseen situations, so that everything is collected and ready for this date.

The James Webb telescope consists of 4 main parts.

Optical block

Includes all mirrors, of which the most effective eighteen primary segmented gold plated mirrors. They will be used to collect distant stellar light and focus it on instruments for analysis. All these mirrors are now ready and impeccable, made exactly on schedule. Upon completion of the assembly, they will be stacked in a compact design to be launched over a distance of 1 million km from the Earth to the Lagrangian point L2, and then automatically turn around to form a honeycomb structure that will accumulate ultra-long light for many years. This is really a beautiful thing and a successful result of the titanic efforts of many specialists.

Near-infrared camera

Webb is equipped with four scientific tools, which are already 100% ready. The main camera of the telescope is a camera of the near-IR range: from visible orange light to deep infrared. It will provide unprecedented images of the earliest stars, youngest galaxies still in the process of formation, 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 main camera used by most observers.

Near Infrared Spectrograph

This tool not only divides the light into separate wavelengths, but is able to do this for more than 100 separate objects at the same time! This device will be a universal spectrograph "Webba", which is capable of working in 3 different modes of spectroscopy. It was built by the European Space Agency, but many components, including detectors and a multi-shutter battery, are provided by the Space Flight Center. Goddard (NASA). This device has been tested and is ready for installation.

Medium-infrared instrument

The device will be used for broadband visualization, that is, with its help the most impressive images from all Webb tools will be obtained. Scientifically, it will be most useful when measuring protoplanetary disks around young stars, measuring and visualizing with unprecedented accuracy the objects of the Kuiper belt and dust heated by the light of stars. It will be the only instrument with cryogenic cooling down to 7 K. Compared with the Spitzer space telescope, this will improve the results 100 times.

Neutral IR spectrograph (NIRISS)

The device will produce:

• Wide-angle spectroscopy in the near infrared wavelength range (1.0 - 2.5 μm);
• Grim-spectroscopy of one object in the visible and infrared range (0.6 - 3.0 μm);
• Aperture-masking interferometry at wavelengths of 3.8-4.8 μm (where the first stars and galaxies are expected);
• Wide-range survey of the entire field of view.

This tool was created by the Canadian Space Agency. After passing the cryogenic test, it will also be ready for integration into the instrument compartment of the telescope.

Sunshield

Space telescopes have not yet been equipped with them. One of the most frightening aspects of each launch is the use of a completely new material. Instead of cooling the entire spacecraft actively using a disposable expendable refrigerant, the James Webb telescope uses a completely new technology - a 5-layer sunscreen that will be deployed to reflect solar radiation from the telescope. Five 25-meter sheets will be connected by titanium rods and installed after the deployment of the telescope. Protection was tested in 2008 and 2009. The full-scale models that participated in the laboratory tests did everything they had to do here on Earth. This is a beautiful innovation.

In addition, it is also an incredible concept: do not just block the light from the Sun and place the telescope in the shade, but do it in such a way that all the heat is radiated in the direction opposite to the orientation of the telescope. Each of the five layers in the vacuum of the cosmos will become cold as it moves away from the outer, which will be slightly warmer than the surface temperature of the Earth - 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 unfavorable environment of deep space. One of the things to worry about here is tiny pebbles the size of pebbles, grains of sand, dust particles and even less, flying through interplanetary space at a speed of tens or even hundreds of thousands of miles per hour. These micrometeorites are capable of making tiny, microscopic holes in everything they encounter: space vehicles, cosmonaut suits, telescope mirrors and much more. If the mirrors receive only dents or holes, which will slightly reduce the amount of available "good light", the solar shield can tear from edge to edge, which will make the entire layer useless. A brilliant idea was used to combat this phenomenon.

The whole solar shield was divided into sections in such a way that if there is a small gap in one, two or even three of them, the layer will not break further, like a crack in the windshield of the car. Sectioning will preserve the entire structure of the whole, which is important for preventing degradation.

Spacecraft: assembly and control systems

This is the most common component, as there are all space telescopes and scientific missions. At JWST it is unique, but also completely ready. All that remains to be done by the general contractor of the Northrop Grumman project is to finish the shield, assemble the telescope and test it. The device will be ready to start in 2 years.

10 years of discoveries

If everything goes right, humanity will be on the verge of big scientific discoveries. The veil of neutral gas, which has hitherto obscured a review of the earliest stars and galaxies, will be eliminated by the infrared capabilities of "Webba" and its tremendous aperture. It will be the largest, most sensitive telescope with a huge wavelength range from 0.6 to 28 microns (the human eye sees from 0.4 to 0.7 microns) from ever built. It is expected that it will provide a decade of observations.

According to NASA, the term of the "Webba" mission will be from 5.5 to 10 years. It is limited by the amount of fuel that is needed to maintain the orbit, and the lifetime of electronics and equipment in the harsh conditions of space. The James Webb's orbital telescope will carry a fuel reserve 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 can go wrong?

The main limiting factor is the amount of fuel on board. When it is over, the satellite will drift away from the Lagrange point L2, coming out into a chaotic orbit in the immediate vicinity of the Earth.

Coma of this, there may be other troubles:

• Degradation of mirrors, which will affect the amount of light collected and create artifacts of the image, but will not damage 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 a very near infrared (2-3 μm);
• Breakdown of the cooling system of the middle IR-range instrument, which will make it unusable, but will not affect other instruments (from 0.6 to 6 microns).

The most difficult test that the James Webb's telescope expects is launching and launching into a given orbit. It was these situations that were tested and successfully passed.

Revolution in Science

If the James Webb telescope works in its normal state, there will be enough fuel to ensure its operation from 2018 to 2028. In addition, there is the potential for refueling, which could increase the lifespan of the telescope for another decade. Just as the Hubble was exploited for 25 years, JWST could provide a generation of revolutionary science. In October 2018, the Ariane-5 launch vehicle will put into orbit the future of astronomy, which after more than 10 years of hard work is ready to begin to bear fruit. The future of space telescopes has almost come.