With every extra centimeter of aperture, every extra second of observation time, and every extra atom of atmospheric clutter removed from the telescope's field of view, the Universe can be seen better, deeper and clearer.
25 years of Hubble
When the Hubble telescope began operating in 1990, it ushered in a new era in astronomy - space. There was no more fighting with the atmosphere, no more worrying about clouds or electromagnetic flicker. All that was required was to deploy the satellite to the target, stabilize it and collect photons. Within 25 years, space telescopes began to cover the entire electromagnetic spectrum, allowing for the first time to view the universe at every wavelength of light.
But as our knowledge has increased, so has our understanding of the unknown. The farther we look into the universe, the deeper the past we see: the 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 by stretching the wavelengththe light of 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 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, limiting its resolution.
- Despite being covered 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 µm.
- The combination of limited aperture and the wavelengths it is sensitive to 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 this, the telescope must have a higher sensitivity. This means moving to longer wavelengths and lower temperatures than Hubble. That is why the James Webb Space Telescope is being built.
Prospects for Science
James Webb Space Telescope (JWST) is designed to overcome precisely these limitations: with a diameter of 6.5 m, the telescope collects 7 times more light than the Hubble. He openshigh resolution ultra-spectroscopy from 600 nm to 6 µm (4 times the wavelength that Hubble can see), to make observations in the mid-infrared region of the spectrum with higher sensitivity than ever before. JWST uses passive cooling to Pluto's surface temperature and is capable of actively cooling mid-infrared instruments down to 7K.
He will allow:
- observe the earliest galaxies ever formed;
- see through neutral gas and probe the first stars and the reionization of the universe;
- perform 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.
JWST's level of scientific research is unlike anything in the past, which is why the telescope was chosen as NASA's flagship mission for 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: there have been budget overruns, schedule delays, and the danger of the project being cancelled. After the intervention of the new leadership, everything changed. The project suddenly worked like clockwork, funds were allocated, errors, failures and problems were taken into account, and the JWST team began to fit intoall deadlines, schedules and budgetary frameworks. The launch of the device is scheduled for October 2018 on the Ariane-5 rocket. The team not only sticks to the schedule, they have nine months left to account for all contingencies to ensure everything is packed and ready for that date.
The James Webb telescope consists of 4 main parts.
Optical unit
Includes all mirrors, of which the eighteen primary segmented gold-plated mirrors are the most effective. They will be used to collect distant starlight and focus it on instruments for analysis. All these mirrors are now ready and flawless, made right on schedule. Once assembled, they will be folded into a compact structure to be launched more than 1 million km from Earth to the L2 Lagrange point, and then automatically deploy to form a honeycomb structure that will collect ultra-long-range light for years to come. This is a really beautiful thing and the successful result of the titanic efforts of many specialists.
Near infrared camera
Webb is equipped with four scientific instruments that are 100% complete. The main camera of the telescope is a near-IR 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. She isoptimized 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 separates light into separate wavelengths, but is capable of doing this for more than 100 separate objects at the same time! This instrument will be a universal Webba spectrograph capable of operating in 3 different spectroscopy modes. It was built by the European Space Agency, but many components, including detectors and a multi-gate battery, were provided by the Space Flight Center. Goddard (NASA). This appliance has been tested and is ready to install.
Mid-Infrared Instrument
The device will be used for broadband imaging, that is, it will produce the most impressive images from all Webb instruments. From a scientific standpoint, it will be most useful in measuring protoplanetary disks around young stars, measuring and imaging Kuiper belt objects and dust heated by starlight with unprecedented precision. It will be the only instrument to be cryogenically cooled to 7 K. Compared to the Spitzer space telescope, this will improve results by a factor of 100.
Slitless Near-IR Spectrograph (NIRISS)
The device will allow you to produce:
- wide-angle spectroscopy in the near infrared wavelengths (1.0 - 2.5 µm);
- grism spectroscopy of one object invisible and infrared range (0.6 - 3.0 microns);
- aperture-masking interferometry at wavelengths of 3.8 - 4.8 µm (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 undergoing cryogenic testing, it will also be ready for integration into the instrument compartment of the telescope.
Sun shield
Space telescopes have not yet been equipped with them. One of the most intimidating aspects of every launch is the use of completely new material. Instead of actively cooling the entire spacecraft with a one-time consumable coolant, the James Webb Telescope uses an entirely new technology, a 5-layer sunshield that will be deployed to reflect solar radiation from the telescope. Five 25-meter sheets will be connected with titanium rods and installed after the telescope is deployed. Protection was tested in 2008 and 2009. The full-scale models that participated in the laboratory tests did everything they were supposed to do here on Earth. This is a beautiful innovation.
It's also an incredible concept: not just to block the light from the Sun and place the telescope in shadow, but to 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 as it moves away from the outer, which will be slightly warmer than the temperature.the surface 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 of 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 pebble-sized pebbles, grains of sand, specks of dust and even smaller ones flying through interplanetary space at speeds of tens or even hundreds of thousands of kilometers per hour. 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 solar shield can tear from edge to edge, rendering the entire layer useless. A brilliant idea was used to combat this phenomenon.
The entire solar shield has been divided into sections in such a way that if there is a small tear in one, two or even three of them, the layer will not tear 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 science missions have. At JWST, it is unique, but also completely ready. All that was left for the project's general contractor, Northrop Grumman, was to complete the shield, assemble the telescope, and test it. The machine will be ready forlaunch in 2 years.
10 years of discovery
If everything goes right, humanity will be on the threshold of great scientific discoveries. The veil of neutral gas that has so far obscured the view of the earliest stars and galaxies will be eliminated by the infrared capabilities of the Webb and its huge luminosity. It will be the largest, most sensitive telescope ever built, with a huge wavelength range of 0.6 to 28 microns (the human eye sees 0.4 to 0.7 microns). It is expected to provide a decade of observations.
According to NASA, the life of the Webb mission will be from 5.5 to 10 years. It is limited by the amount of propellant needed to maintain orbit and the lifetime of the electronics and equipment in the harsh environment of space. The James Webb Orbital Telescope will carry fuel 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 the L2 Lagrange point, entering a chaotic orbit in the immediate vicinity of the Earth.
Come with this, other troubles can happen:
- degradation of mirrors, which will affect the amount of collected light and create image artifacts, but will not damage the further operation of the telescope;
- failure of part or all of the solar screen, which will lead to an increasespacecraft temperature and narrow the usable wavelength range to the very near infrared (2-3 µm);
- Mid-IR instrument cooling system failure, rendering it unusable but not affecting other instruments (0.6 to 6 µm).
The most difficult test that awaits the James Webb telescope is the launch and insertion into a given orbit. These situations were tested and successfully completed.
Revolution in science
If the James Webb Telescope is operational, there will be enough fuel to power it from 2018 to 2028. In addition, there is the potential for refueling, which could extend the lifetime of the telescope by another decade. Just as Hubble has been in operation for 25 years, JWST could provide a generation of revolutionary science. In October 2018, the Ariane 5 launch vehicle will launch 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 is almost here.
