With each additional centimeter of the aperture, each additional second of observation time and each additional atom of atmospheric interference removed from the field of view of the telescope, it will be better, deeper and more understandable to see the Universe.
25th Hubble
When the Hubble telescope began operating in 1990, it ushered in a new era in astronomy - the cosmic. There was no need to fight the atmosphere anymore, 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 for the first time to examine the Universe at each wavelength of light.
But as our knowledge increased, so did our understanding of the unknown. The further we look into the Universe, the deeper the past we see: a finite amount of time from the moment of the Big Bang in combination with a finite speed of light provides the limit of what we can observe. Moreover, the expansion of space itself works against us, stretching the wavelength of light from the stars as it travels through the universe to our eyes. Even the Hubble Space Telescope, which gives us the deepest, most breathtaking image of the Universe that we have ever discovered, is limited in this regard.
Hubble Disadvantages
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 being coated with reflective materials, it is constantly exposed to direct sunlight that heats it. This means that due to thermal effects, he cannot observe a wavelength of light greater than 1.6 microns.
- The combination of limited aperture and wavelengths to which it is sensitive means that the telescope can see galaxies no older than 500 million years old.
These galaxies are beautiful, far 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 this, the telescope must have a higher sensitivity. This means switching to longer waves and lower temperatures than Hubble’s. That is why the James Webb Space Telescope is being created.
Prospects for science
The James Webb Space Telescope (JWST) is designed to overcome precisely these limitations: with a diameter of 6.5 m, the telescope allows you to collect 7 times more light than the Hubble. It opens up the possibility of high-resolution ultra-spectroscopy from 600 nm to 6 μm (4 times the wavelength that the Hubble is able to see), to conduct observations in the middle infrared region of the spectrum with higher sensitivity than ever before. JWST uses passive cooling to the surface temperature of Pluto and is able to actively cool mid-infrared instruments up to 7 K. The James Webb telescope will make it possible to engage in science like no one has done before.
He will allow:
- observe the earliest galaxies ever formed;
- see through a neutral gas and probe the first stars and reionization of the Universe;
- conduct spectroscopic analysis of the very first stars (population III) formed after the Big Bang;
- Get amazing surprises like discovering the earliest supermassive black holes and quasars in the universe.
The JWST's research level is unlike anything in the past, and so the telescope was chosen as NASA's flagship mission of the 2010s.
Scientific masterpiece
From a technical point of view, the new James Webb telescope is a real work of art. The project has come a long way: there were budget overruns, lagging behind the schedule 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, mistakes, failures and problems were taken into account, and the JWST team began to fit into all the deadlines, schedules and budget frames. The launch of the device is scheduled for October 2018 on the Arian-5 rocket. The team not only follows the schedule, it has nine months left to take into account all unforeseen situations, so that everything is assembled and ready for this date.
The James Webb telescope consists of 4 main parts.
Optical unit
Includes all mirrors, of which eighteen primary segmented gold-plated mirrors are most effective. They will be used to collect distant starlight and focus it on analysis tools. All these mirrors are now ready and impeccable, made exactly on schedule. At the end of the assembly, they will be folded into a compact design to be launched at a distance of more than 1 million km from the Earth to the Lagrange point L2, and then automatically deploy to form a honeycomb structure that will collect ultra-long light for many years. This is a really beautiful thing and a successful result of the titanic efforts of many specialists.
Near infrared camera
Webb is equipped with four scientific tools that are 100% ready. 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 formation, the young stars of the Milky Way and nearby galaxies, hundreds of new objects in the Kuiper belt. It is optimized for directly receiving images 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 individual wavelengths, but is able to do this for more than 100 individual objects at the same time! This instrument will be a universal Webba spectrograph, which is capable of operating in 3 different spectroscopy modes. It was built by the European Space Agency, but many 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 install.
Mid-infrared instrument
The device will be used for broadband imaging, that is, with its help the most impressive images from all Webb tools will be obtained. From a scientific point of view, 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 to 7 K. Compared with the Spitzer space telescope, this will improve the results by 100 times.
Near Infrared Slit Spectrograph (NIRISS)
The device will allow you to produce:
- wide-field 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-masking 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 tool was created by the Canadian Space Agency. After passing the cryogenic testing, he 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 frightening aspects of each launch is the use of completely new material. Instead of actively cooling the entire spacecraft with a one-time consumable 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 joined by titanium rods and installed after the deployment of the telescope. Protection was tested in 2008 and 2009. The full-scale models involved in the laboratory tests did everything they had to do here on Earth. This is a beautiful innovation.
In addition, this is also an incredible concept: 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 opposite direction to the telescope orientation. Each of the five layers in the vacuum of space will become colder with distance from the outside, 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 adverse 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 smaller ones flying through interplanetary space at a speed of tens or even hundreds of thousands of km / h. These micrometeorites are capable of making tiny, microscopic holes in everything they encounter: spacecraft, cosmonaut suits, telescope mirrors, and much more. If the mirrors get only dents or holes, which slightly reduces the amount of “good light” available, then the sun shield can tear from edge to edge, making the entire layer useless. To combat this phenomenon, a brilliant idea was used.
The entire solar shield was divided into sections in such a way that if a small gap occurs in one, two or even three of them, the layer will not tear further, like a crack in the windshield of a car. Partitioning will keep the whole 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. 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 for launch in 2 years.
10 years of discovery
If everything goes right, humanity will be on the verge of great scientific discoveries. The curtain of neutral gas, which still obscures the overview of the earliest stars and galaxies, will be eliminated by the infrared capabilities of Webb and its huge aperture. It will be the largest, most sensitive telescope with a huge range of wavelengths from 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 the orbit, and the life of the electronics and equipment in harsh space conditions. The James Webb Orbital Telescope will carry fuel for the entire 10-year period, and 6 months after launch, flight support testing will be performed, 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 the Lagrange point L2, entering a chaotic orbit in the immediate vicinity of the Earth.
To whom, other troubles may occur:
- mirror degradation, which will affect the amount of light collected 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 increase the temperature of the spacecraft and narrow the used wavelength range to a very close infrared region (2-3 microns);
- damage to the cooling system of the instrument in the mid-IR range, which will make it unsuitable for use, but will not affect other instruments (from 0.6 to 6 microns).
The most difficult test that awaits the James Webb telescope is the launch and launch into a given orbit. It was these situations that were tested and successfully passed.
Revolution in science
If the James Webb telescope is operating normally, there will be enough fuel to ensure its operation from 2018 to 2028. In addition, there is the potential for refueling, which could extend the life of the telescope by another decade. Just as Hubble has been operating for 25 years, the JWST could provide a generation of revolutionary science. In October 2018, the Arian-5 launch vehicle will launch the future of astronomy into orbit, which, after more than 10 years of hard work, is ready to begin to bear fruit. The future of space telescopes has almost come.