The idea of ​​developing a telescope to replace Hubble was proposed between 1989 and 1994. This infrared conceptual telescope with a 4-meter aperture was called Hi-Z and orbited the Sun at a distance of 3 AU (three times the distance of the Earth from the Sun). This circuit was very far away, But it also had advantages. The telescope remained an idea until other designs gave it new life. The scientists gave the initial name of this project NEXUS, which was very innovative at the time; But NASA had a different opinion. In the mid-1990s, the US space agency announced that it would invest in a project that would be done quickly, be the best, and have the lowest cost; So NASA’s top managers focused on building a low-cost space telescope. The result of this decision was the NGST concept telescope with an 8-meter aperture that orbits the Sun in Lagrangian 2 (L2) orbit, But it only cost 500 million dollars.

Early proposed designs for the James Webb Space Telescope.

NASA accepted the project and immediately signed a contract with Goddard Space Flight Center, Bal Aerospace, and TRW to conduct studies on the technical requirements of the project as well as its various costs. In 1999, NASA contracted Lockheed Martin and TRW to build an early version of its concept telescope. In 2002, a conceptual telescope was built and TRW agreed to fully build the NGST, now known as James Webb, and deliver it to NASA by 2010 in exchange for $824.8 million. At the end of 2002, TRW was acquired by Northrop Grumman, and the James Webb project was also assigned to this aerospace company.

NASA later announced in 2005 that there were changes in the program and some of the telescope’s equipment had to be changed, which caused the telescope’s launch to be delayed by 22 months and the launch date was postponed from 2011 to 2013. NASA also announced that it will no longer test systems at wavelengths shorter than 1.7 micrometers to focus on other areas. In 2006, the program had to be revised again; But this time the matter was not only in the technical field, but NASA also had to make a series of changes in the financial field so that the budget it had was distributed correctly.

That same year, NASA estimated that the cost of building and supporting the James Webb Telescope over its life cycle would be about $4.5 billion. Of this amount, $3.5 billion will be spent on design, manufacturing, launch and placement into orbit, and $1 billion will be the cost of supporting the telescope over the decades of the mission. The European Space Agency announced that it will provide 300 million dollars of this funding and will also accept the cost of the launch. On the other hand, the Canadian Space Agency also provided 39 million Canadian dollars from this budget. According to this information, the main cost of the project fell on NASA.

A full-scale model of the James Webb Space Telescope in Battery Park in Manhattan in 2010.

In January 2007, engineers announced that nine of the telescope’s 10 science instruments had successfully passed unshielded tests. In March 2008, the telescope successfully passed the initial design review test. By 2011, the telescope had successfully passed all tests and inspections and entered the final stage of structural design and body design. Since it was not possible to change the design and structure after the project was finalized and the launch time was approaching, the engineers had to use their utmost precision and examine the structure and tools with complete delicacy. From the 90s, when the idea of ​​the telescope was proposed, until 2011, new scientific achievements were achieved that were used in the telescope. For example, in the 1990s, scientists did not know how to design a large telescope with lightweight.

James Edwin Webb (right), former NASA administrator, with former US President Harry Truman in 1961. In 2002, in an unprecedented move, NASA chose the name of a non-scientist for one of its scientific missions.

In 2017, NASA again changed the launch date and postponed it to 2019; Because some instruments needed more testing and the simulation of the placement of the telescope in the rocket had to be done accurately. At the same time, Eric Smith, director of the James Webb project, said:

The biggest challenge in designing space telescopes is their size. A space telescope is launched into space by a rocket; Therefore, the designers had to do the design in such a way that it is possible to assemble and place the James Webb telescope in the upper part of the rocket. Also, this design should be in such a way that it can be opened in the space as easily as possible.

The James Webb Space Telescope is huge. The main mirror of this telescope has a diameter of 6.5 meters, and none of the current launch devices have the ability to accommodate a device with these dimensions. For example, the main mirror of the Hubble Space Telescope has a diameter of 2.5 meters, which made the process of transferring it to space easier. The dimensions proposed for the James Webb telescope made it impossible to transport it into space; But engineers and designers had to think of a solution for this problem. The main mirror of the Hubble telescope, due to its small diameter, was one piece and circular in shape; But since the main mirror of the James Webb telescope has a diameter of 6.5 meters, it could not be designed in one piece.

In this way, the engineers divided the telescope’s main mirror into three parts, which, when opened, are placed next to each other and form a single mirror; But this single mirror could not be any shape because it would cause optical aberration. The task of designing the shape of the mirrors was entrusted to the optical engineers. According to the simulations, the best case for the mirrors was to design them as a set of smaller, hexagonal mirrors. The main mirror of the James Webb telescope is made of a total of 18 smaller hexagonal mirrors that are placed next to each other in a special way, and there is a hole in the center of this mirror.

The James Webb telescope is also of the Casgreen type, and the center of its main mirror is perforated so that the secondary mirror sends the reflected light to the eye placed behind the central hole. Casgrain design has many advantages, including the compactness of telescopes that use this design. In Cassegrain telescopes, the focal length is long and the image distortion is reduced. The Hubble telescope uses this type of design; In fact, many research telescopes have a similar design.

Another challenge faced by the designers was the telescope’s solar shield. The James Webb Telescope can observe infrared and near-infrared lights. In order to receive and observe these thermal signals, the temperature of the telescope must be extremely low. To protect the telescope from light and heat sources (such as the Sun, Earth, Moon and the body of the observatory itself), engineers designed a 5-layer solar shield made of a very thin material called Kapton, which is the size of a tennis court. This solar shield acts like an umbrella or shade to prevent heat and light from reaching the telescope. This shield has a length of 21.197 meters and a width of 14.62 meters, which is large enough to completely cover the telescope. This layer causes the telescope to be placed in an environment with an average temperature of -223 degrees Celsius.

The interesting point in the design of the solar shield is its multi-layered nature. Scientists could produce this shield as a thick layer, But being 5 layers has its advantages. In this solar shield, each layer is cooler than the outer layers. There is a space between these layers that is a very good insulator; Therefore, the heat is spread between the layers and out. If the solar shield was made of a thick layer, the heat would cover the shield from the top to the bottom and it would be difficult to get it out.

The design of the layers of this solar shield could be any shape, But the engineers found that the best case is the kite-shaped design. This particular design as well as the number of solar shield layers play a key role in the telescope. The distance of these kite-shaped layers has also been determined with high precision and delicacy to have the best performance in the field of cooling. The kite-shaped design of the layers causes the heat to be directed to the sides and the remaining part is transferred between the layers until it finally exits between the layers. This unique design ensures that the heat from the satellite bus is instantly transferred by the layers so that it does not reach the optical equipment.

The third area is actually located in the satellite bus. In this area, the command and data processing unit of the telescope is located; Also, integrated flight software and control electronics are located in this area. As it was said, 4 of the scientific instruments of the telescope are placed in this section, which we will introduce and examine in the following.

NIRCAM is a highly accurate and advanced imager developed by the University of Arizona, which is installed on the ISIM module. This very important piece has two main tasks: first, it must image light in the 0.6-5 micron spectrum, and second, it acts as a coordinating sensor to adjust all 18 mirrors so that they can act as a single mirror. Nirkam is an infrared camera that has 10 detector arrays of mercury-cadmium-telluride or HgCdTe (one of the cadmium telluride alloys used in fast and sensitive detectors in the infrared sensor) and each of these arrays has a resolution of 2048×2048. The infrared camera itself also has a field of view of 2.2 x 2.2 arc minutes, which has an angular resolution of 0.07 arc seconds at a wavelength of 2 microns, and for this reason, it is known as the best camera currently.

Next to Nirkam is a chronograph (imager of the star crown) that works seamlessly with it. A chronograph can help gather data on exoplanets, and can image anything near a very luminous body; Because it can completely remove the light of the objects so that the objects around them are defined. The Nirkam camera only works at -236 degrees Celsius.

The Nirkam camera can capture objects with an apparent magnitude of +29 in high resolution during a single exposure of 10,000 seconds (2.8 hours). This camera can view and record at the same time and control the mirrors. All observations of this camera are made between wavelengths of 600 nm to 5000 nm. The precision of the sensors that align the telescope mirrors is so high that they can move the mirrors by less than a human hair. In other words, the movement accuracy of these sensors is at least 93 nm; But during the tests, this accuracy reached 52 and 32 nm, which is very surprising.

Nirkam sensors generally consist of the following parts:

• Separate Hartmann sensor (wavefront meter)
• GRISM (combination of prism and diffraction grating )
• Poor lenses

The Nirkam section is also composed of the following sections:

• The killer of mirrors
• Chronograph
• The first reflective mirror
• collimator lenses
• Dichroic beam splitter
• Long wavelength filter wheels (frequency less than 300 kHz)
• A group of long-wavelength imaging camera lenses
• Long wavelength focal plane
• Short wavelength filter wheels
• A group of short-wavelength imaging camera lenses
• Mirror reflecting short wavelengths
• Pupillary lens
• Short wavelength focal plane

Nirkam camera has two separate and complete optical systems that are used for accuracy in imaging. These two systems, known as sections A and B, can work simultaneously and observe two different paths of the sky. The lenses used in the inner parts of these parts are triple refractive lenses. These lenses are made of lithium fluoride, barium fluoride and zinc selenide respectively. These three lenses are parallel and the largest of them has an aperture of 90 mm.

Nirkam has important tasks that are very valuable for science. By exploring the early universe, this camera will examine how the universe’s first luminous objects formed and evolved to tell the history of the reionization of the universe. This camera can predict what the galaxies and galaxy clusters that we see directly look like in today’s universe; Because the sky we see does not belong to the present, but to the past. For example, if you see a star in the sky that is a thousand light years away from Earth, you are actually seeing an image of the star from a thousand years ago; Not the present time! The Nirkam camera can accurately predict the shape of objects near and far. Another important task of this camera is to examine the physical and chemical structure of objects in the solar system. With this work, James Webb can help scientists in understanding the origin of life on Earth.

Niraspec is a multi-mass spectrometer built by the European Space Agency and installed on ISIM. This advanced spectrometer can simultaneously measure the infrared spectrum of nearly 100 objects (such as galaxies, stars, etc.) with low, medium, and high resolution. The field of view of this spectrometer is 3 arcmin by 3 arcmin and it sees wavelengths between 0.6 µm and 5 µm. This spectrometer has a series of unique apertures that can spectrograph objects individually. It also has an integrated field unit called IFU, which is used for 3D spectroscopy. The European Space Agency has been responsible for installing this part on the ISIM chassis.

Scientists intend to observe the first light of the universe and the period of reionization with the help of Niraspec. Investigating the formation of galaxies and the birth of stars and non-planetary systems is also one of the goals of this piece. Scientists want to use telescopes to examine planetary systems to find signs of the origin of life.

Niraspec spectrometer has four main mechanisms, which are:

• Spectrum filter wheel
• Refocusing mechanism on the subject (RMA) which has two mirrors
• Microshutter (MSA) equipment used for multiple mass spectrometry
• Diffraction grating wheel (GWA) which has 8 positions. Also, 6 diffraction gratings, a prism, and a mirror are also located in this part.

As mentioned, this spectrometer is responsible for observing the first light of the universe after the end of the dark period as well as the reionization period. Near-infrared spectrometry (NIRS) investigates the earliest light sources in the universe (such as stars, galaxies, and active nebulae) at a spectral resolution between 100 and 1000. These lights indicate the beginning of the reionization period of the world. With the help of a multi-mass spectrometer (objects with a redshift between 1 and 7) at a spectral resolution of 1000, observations of a large number of galaxies are made in order to provide scientists with more information about smaller objects in the early universe.

One of Niraspec’s spectrographs takes high-contrast images and can observe objects with a spectral resolution of 100 to several thousand in order to provide scientists with a complete and accurate picture of the formation and evolution of stars and star systems. Another task of this spectrographer is to examine the objects of the solar system in high contrast and medium spectral resolution. Planets, moons, comets, and objects in the Kuiper Asteroid Belt are examined by this spectrograph so that scientists can learn more about the origins of life.

Miri is an advanced spectrometer built by the European Space Agency and NASA’s Jet Propulsion Laboratory. Miri actually consists of a camera and a spectrometer that observes mid-infrared between 5 microns and 28 microns. Miri also has a chronograph, which is specially used for observing exoplanets. Most of the James Webb telescope’s instruments observe the near-infrared spectrum or some wavelengths of visible light; But Miri, through other equipment, can observe longer wavelengths of light. The instrument uses arsenic-doped silicon arrays to observe at long wavelengths. Miri’s imager is designed to have a wide field of view, But Miri’s spectrometer is not like this and has a limited field of view.

As you go, you see longer wavelengths; So it needs to be cooler than other equipment. For this purpose, engineers have considered a special cooling system for this part, which includes a pre-cooling pulse tube and a Joule-Thomson ring as a heat exchanger. This equipment causes the temperature of Miri to drop to 7 degrees Kelvin or -266 degrees Celsius when working in space.

In fact, the spectrograph installed in Miri can observe wavelengths between 4.6 and 28.6 microns and has four separate channels, each with its own diffraction grating and image-cropping tool. The field of view of this spectrograph is 3.5 arc seconds by 3.5 arc seconds. In early 2014, sensors were installed on the ISIM module and their integrity was tested. Miri is mounted by a plastic hexapod structure and carbon fiber mounts on the ISIM and next to the satellite bus; But it is isolated so that it has a certain and constant temperature and is not affected by the temperature of the surrounding environment and the bass, which heats up a lot.

The main parts of Miri are:

• spectroscopic optical equipment (including main spectrographs and prerequisites)
• Arrays of focal planes
• Input light calibration module (including mirrors, imager calibration source and pollution control cover)
• Plastic hexapod and carbon fiber legs
• The main cameraman
• Image cropping tools
• The main page where the equipment is located

Most of Miri’s parts are placed in the main structure of ISIM; But the cooler is located in zone 3, which is near the satellite bass. Miri’s main imager has a special low-resolution spectrograph that can perform cut-free spectroscopy between wavelengths of 5 to 12 microns. The prisms of this spectrometer are made of germanium metal and zinc sulfide to cause more light scattering.

Dysfunction detectors can detect the redshift of distant galaxies, newborn stars, faint comets, and objects in the Kuiper Belt. The spectrometer can also image with medium resolution, which provides scientists with new information about distant objects; Information that Hubble is unable to collect.

FGS/Nyris is another scientific instrument installed on the Canadian Space Agency’s ISIM module. These instruments are actually a combination of a full-conductivity sensor and a near-infrared imager and spectrometer. FGS/Nyris can observe wavelengths between 0.8 and 5 microns. These instruments can perform observations in four different modes. Physically, the FGS and Neris are combined and housed in one enclosure; But the reality is that they do two completely different things. Neris uses the FGS to keep the telescope fixed on the subject and make the observations, which is why it’s called the FGS (Precise Guided Sensor). The near-infrared spectrometer has a special spectroscopic mode that is used only for observing exoplanets. The Neris detector has a mercury-cadmium-telluride or HgCdTe detector array and has a resolution of 2048 x 2048 pixels and a field of view of 2.2 arc minutes by 2.2 arc minutes. The precision guidance sensor helps to keep the telescope fixed on the desired subject; The FGS also sends the necessary data to the position control unit so that the telescope can more easily focus on subjects or rotate around.

In general, Neris is designed to do the following:

• Near infrared imaging
• Wide-field slit-free spectroscopy
• Slitless spectroscopy of a particular object
• Aperture coating interferometry

The aperture cover interferometry mode uses a seven-hole aperture cover plate and can help identify exoplanets orbiting known stars that are in the main light spectra. The FGS unit is designed to focus the telescope on predetermined stars, which makes the targets always worth studying. The action of changing the direction of the telescope is done by other parts, such as the systems in the satellite bus and the telescope mirrors.

The fully assembled James Webb Space Telescope at the Northrop Grumman facility.

The satellite bass along with a series of other important equipment is placed inside a carbon fiber box. Before launch, solar panels are also placed in this box to open in space. The MIRI cooler and some ISIM electronics are also inside this box. As mentioned, in the computer processing part, there is a solid-state memory. The capacity of this memory is 59.9 GB, which is known as SSR. A small satellite dish is also placed under the bass, which is responsible for sending and receiving information. The telescope is designed to be able to communicate with NASA’s deep space communication network. The telescope’s main communications center is located in Maryland, USA.

Installation of 18 parts of the main mirror of the James Webb Space Telescope.

In the first stage, the mirrors had to be polished well through different levels and stages; Because the earth’s gravity causes them to bend and they have different performances at different temperatures. First, a polishing step had to be done, and then the mirrors were sent to the freezer room, stayed there for a while, came out again, and the polishing process was repeated. The surface of the mirrors should remain shiny when exposed to low temperatures in order to have maximum efficiency; Therefore, the mirrors should be polished many times and at different temperatures to achieve an acceptable gloss and to be able to maintain their original state at low temperatures. When the beryllium was completely polished and polished, then the gold coating was added.

The reason for using gold is its high percentage of reflectivity and it can have the maximum reflectivity when the telescope is in infrared light. This gold coating must be thick enough to cover the entire surface of the mirror; But at the same time, it should be thin enough not to damage the original beryllium mirrors. The process of placing the gold coating on the mirrors is known as ” vacuum heater coating “. During this process, the mirrors were placed in a vacuum chamber and then all the air in the chamber was evacuated to create a vacuum. Then, a very small amount of gold was vaporized under certain conditions and injected into the chamber. The back layers of the mirror, which are not going to be covered with gold, are protected by layers so they don’t get damaged. After injecting evaporated gold into the chamber, the gold atoms slowly settled on the shiny surfaces of the beryllium mirrors and this process continued until the thickness of the gold coating layer reached 100 nm.

Gold is very soft and flexible, and a very thin coating of it acts like transparent glass to protect the very delicate beryllium surface and provide a highly reflective surface.

A NASA technician works on the mirrors of the James Webb Telescope at the Marshall Space Flight Center.

As mentioned in the beginning, the launch of the telescope was postponed many times and the final date was finally set for December 25, 2021. As a very sensitive telescope, James Webb had to be launched by a reliable rocket. The European Space Agency announced that it will finance the launch of James Webb and launch it into space on an Ariane 5 rocket. Ariane 5 is one of the most successful and reliable rockets in the world today, and various companies use it to transport their space cargo to Earth orbit. NASA also agreed to launch its new space telescope using this rocket from the French Guiana space base.

Ariane 5, with 108 successful launches out of 113 launches, was considered a suitable and safe option for launching James Webb. The ELA-3 telescope launch pad is located in French Guiana (located in South America) and takes advantage of its proximity to the equator. Near the equator, the rotation of the Earth can create more propulsive force and launch the rocket faster and easier. The rotation speed of the earth at the equator is 1670 km/h. In order for the telescope to fit in the upper part of the rocket, it must be folded. In the picture below, you can see how the telescope is placed in the upper part of the rocket.

After launching and leaving Earth, the telescope began a 30-day journey to reach a distance of 1.5 million kilometers from Earth. This point is known as Lagrangian point 2. Lagrangian points are five points between two masses where the gravitational force between the two masses is neutralized. The Earth and the Sun also have 5 Lagrangian points that place satellites and space telescopes at these points. Lagrangian point 2 has an interesting feature. If any mass is located at this point, it will be in line with the earth and it will go around the sun together with the Earth. James Webb’s placement at this point makes the solar shield able to repel the heat and light of the sun, earth, and moon at the same time.

From the point of view of communication, being at the L2 point has advantages. Since the telescope revolves around the sun at the same time as the earth; Communication with it will be simple and it will never leave the radar point. There are three terrestrial antennas in Australia, California and Spain that communicate with James Webb. The Hubble telescope is not like that and every 90 minutes, it is placed in the shadow of the earth and it is not possible to communicate with it permanently; But the James Webb telescope is always available. The timeline of post-launch events is as follows.

More than a month after launch, the Precision Guidance Sensor, or FGS, was activated, followed by NIRCAM and NIRSPEC. The first image that Nirkam captured was of very bright stars so that scientists could be sure that the light was properly passing through the telescope and reaching the instruments. Since the main mirrors were not yet aligned with each other, this image was out of focus and blurry. The sixth week after the launch, the process of aligning the main mirror began and they tested it by recording an image of a bright star.

As mentioned many times, James Webb is going to replace Hubble; So everything we’ve seen from Hubble so far, plus countless more, we should expect from James Webb. James Webb is a very powerful telescope that can observe the lights of the early universe and help us understand this important period. Scientists have already set goals for James Webb that take precedence over others. These targets include exoplanets, supermassive black holes, protogalaxies (old galaxies that gave birth to newer galaxies), quasars, watery terrestrial planets, the early universe and the reionization period of the universe, Jupiter and its important moons, comets, extragalactic planets. and Kuiper belt objects.

One of the targets that scientists have already begun to observe is the Trappist 1 system. This system has several Earth-like planets, and the James Webb telescope can clearly observe it and provide useful information to scientists. This system is particularly important; Even if none of its planets are habitable, scientists can gain valuable information from them that will help us find other planets.

Investigating the planets of the solar system is also on the agenda of scientists. By studying these planets, scientists can possibly obtain valuable information about the origin of life. James Webb also observes in infrared light; Therefore, we should expect it to discover new exoplanets and extragalactic planets. Due to the high power and the large size of the telescope’s main mirror, in the next few years we will see the release of unique images of galaxies and celestial bodies that we have not seen before.

The Hubble Space Telescope (which is often referred to as HST) is an international collaboration project between NASA and the European Space Agency, which was launched into the near-Earth orbit by the space shuttle Discovery on April 24, 1990 (May 4, 1369) and after 31 Sal continues his mission. Hubble was not the first space telescope to successfully orbit, But it was bigger and better equipped than its fellows, and its amazing discoveries completely changed the human vision of the universe.

Hubble is orbiting about 547 km above the Earth’s surface. Its length is 13.2 meters, which is the size of a big bus, and its weight is 12,200 kilograms, which is the size of two adult elephants. Hubble uses solar energy and moves at about 8 kilometers per second to stay in orbit.

The Hubble telescope takes very high-resolution images of celestial bodies such as planets, stars, and galaxies, and has recorded more than 1.5 million galaxy observations. These observations include detailed images of the birth and death of stars, galaxies billions of light-years away, and remnants of comets that hit planets’ atmospheres.

Hubble was developed as a general-purpose space observatory with the aim of exploring the universe and recording images in visible, ultraviolet, and infrared wavelengths. So far, this telescope has studied more than 40,000 cosmic objects and has provided high-resolution and detailed images to astronomers who could not see them from Earth.

In addition to blocking some wavelengths of light completely, the Earth’s atmosphere contains air currents that are constantly moving and cause the stars to twinkle in the night sky. The constant movement of these air currents blurs the images taken by ground-based telescopes; For this reason, it was necessary to place a telescope in an orbit above the atmosphere to record images free of these effects.

Hubble’s mirror is much smaller than that found in the largest ground-based observatories, But the unique position of this telescope above the Earth’s atmosphere gives extraordinary clarity to the recorded images. As this telescope rotates around the earth, the mirror collects the cosmic lights and transmits them to the earth in the form of images and data. To photograph some of the most distant objects in the sky, the telescope stares at a point in the galaxy for days to capture as much of this very faint glow as possible.

The Hubble Space Telescope takes its name from Edwin Hubble, a famous American astronomer, whose observations showed scientists that there are other galaxies in the universe besides the Milky Way. While working at the Mount Wilson Observatory in 1923, Hubble concluded that Andromeda then considered a nebula, was actually an independent galaxy hundreds of thousands of light-years away from the Milky Way.

Also, in 1929, by discovering that galaxies are moving away from each other at a constant speed, he put a stamp on the “static universe” theory and thus laid the foundation for the Big Bang theory. Edwin Hubble died in 1929, But the telescope that bears his name has since confirmed and modified many of his theories.

Of course, the idea of ​​building a space telescope dates back to 1946; That is, more than 10 years before the establishment of NASA. It was in that year that astrophysicist Lyman Spitzer Jr. wrote an influential paper on the merits of a space-based observatory. In this paper, he argued that an orbiting telescope could observe the sky without encountering the Earth’s atmosphere, which blurs the images and records very high-resolution images.

Spitzer was later instrumental in building the four unmanned Orbiting Astronomical Observatory satellites that NASA launched between 1966 and 1972 and tirelessly petitioned the US government for funding to build a bigger and better space telescope. The huge costs of this project were a big obstacle to its realization, and it was only in 1977 that the American Congress finally agreed to allocate funds for the construction of the telescope, which was named Hubble.

The fledgling Hubble project suffered a major blow in 1986 when the space shuttle Challenger exploded during takeoff, killing seven astronauts. Following this tragic disaster, NASA grounded its space fleet and left Hubble, which needed a shuttle for transportation and repairs, without a vehicle. Of course, scientists made good use of this opportunity and improved the sensitivity of the telescope instruments and improved its ground control software; But these years of delay imposed huge costs on NASA to service and maintain Hubble in a clean and advanced room. When the space shuttle Discovery finally launched Hubble in 1990, the project was seven years behind schedule and over $1 billion over budget.

Unfortunately, this was not the end of Hubble’s problems. That same year, when NASA scientists viewed the first images recorded by Hubble, they discovered that its primary mirror had been polished to the wrong specification. This “spherical deviation” was very small; In fact, less than 1/50 of the width of a human hair; But this slight deviation was enough to blur many Hubble pictures.

Within months, the telescope had become something of a national joke, with one Newsweek magazine even calling it a “$1.5 billion mistake.” NASA had to wait until December 1993 to experience good things; That is when a group of scientists installed a contact lens called COSTAR on Hubble to fix this deviation. Consisting of several small mirrors, Quastar captured the beam emitted by the defective mirror, corrected the defect, and then reflected the corrected beam back to the center of the mirror for analysis.

Hubble’s “space glasses” managed to solve the problem of blurred images, and soon after this telescope began to record amazing images of the universe. Of course, today all the instruments installed in Hubble have internal corrective optics to compensate for mirror defects, and COSTAR is no longer needed.

When the Hubble telescope was launched, it was at a height of 547 km from the earth’s surface; But most of the time it orbits the earth at an altitude of 320 km and sometimes it rises to an altitude of 400 km to visit the International Space Station.

Currently, Hubble’s nearly circular orbit is located at an altitude of 550 km from the Earth’s surface, and each revolution of this telescope takes about 96 minutes. In this way, Hubble goes around the earth 15 times a day; But not everyone can see it in the sky.

Hubble is best seen in regions on Earth between latitudes 28.5 degrees north and 28.5 degrees south. The reason is that Hubble is at an orbital deviation of 28.5 degrees from the equator. This orbital deviation is the same as the latitude of Hubble’s launch site, Cape Canaveral in Florida, and was the easiest and most economical orbit to launch the telescope.

It is not possible to watch the passage of the Hubble telescope from the sky in Iran; But if you want to see where the Hubble telescope is above the earth at this very moment, you can visit the website uphere.space, which provides a real-time image report of Hubble’s movement in orbit. It is also possible to watch the passage of other satellites on this website.

Undoubtedly, the most iconic image captured by Hubble to date is the “Pillars of Creation” taken in 1995. These giant towers consisting of interstellar gases and cosmic particles are located at a distance of 7,000 light years from Earth in the Eagle Nebula.

The reason for choosing the name of the pillars of creation is that a very powerful force of gravity causes these gases and particles to condense and turn them into masses of mass and form a new star system. In fact, the solar system was probably born billions of years ago in the same way. When we look at this picture, it is as if we are looking at the distant past of the earth.

The image above is the same columns of creation recorded with infrared light and as a result, dust and gases can be seen inside. The website space.com has selected the Pillars of Creation as one of the top ten images taken by Hubble.

Hubble’s Deep Field is a stunning image of a section of the Ursa Major constellation that changed the science of astronomy forever. This image, taken in 1995, is as wide as a grain of salt; But it has 3 thousand galaxies in its heart. This image is composed of 342 separate pieces obtained by Hubble’s Deep Wide Astronomical Camera 2 during ten consecutive days.

In this incredibly beautiful image, we are watching the birth of half a million young stars in the middle of a cloud of gas and cosmic particles in the Tarantula Nebula, which is located in the constellation of the Golden Fish at a distance of 160 thousand light years from us; But this nebula is not in the Milky Way galaxy but in the Large Magellanic Cloud galaxy.

The Tarantula Nebula is the brightest non-stellar object ever discovered, and if the Orion Nebula were in the Milky Way, its shadow would fall on Earth.

Saturn has 82 moons, But the passage of the moons over this planet can be seen only when the tilt of Saturn’s rings reaches the point where they look edged, and this event happens once every 14-15 years. This image was captured by Hubble’s Deep Wide Astronomical Camera 2 on February 24, 2009.

The Crab Nebula is located about 6,500 light-years from Earth in the constellation Taurus and is the only survivor of the supernova explosion that Chinese astronomers observed in 1054 AD. This image is obtained in several wavelengths and from the data of three telescopes, the yellow light belongs to Hubble.

The Whirlpool Galaxy or NGC 5194 is an interacting and spiral galaxy located 31 million light-years from Earth in the constellation of the Hounds. This galaxy and its companion, NGC 5195, are easily visible to amateur astronomers and can also be seen with spotting scopes.

The planetary nebula IC 418, known as the Spirograph (due to its apparent resemblance to Euclid’s magic circle), is located about 2,000 light-years from Earth in the constellation Wolf, near the constellation Orion.

The IC 418 nebula was a Sun-like star a few million years ago and became a red giant a few thousand years ago. With the end of the nuclear fuel of this star, its outer shell was ejected and a planetary nebula was formed. In the center of this image, you can see the white dwarf.

Earth comes between Mars and the Sun about once every two years, causing the red planet to glow spectacularly. Hubble recorded this event, called a collision, in 2001.

How does the Hubble telescope work?

The Hubble telescope, 13.2 meters long and currently weighing 12,200 kg, provides its energy with the help of two 7.62 meter panels from the sun and stores it in 6 nickel-hydrogen batteries with a capacity equal to approximately 22 car batteries. saves This telescope is made up of various instruments, each of which is responsible for recording the highest-quality galactic images.

As the telescope orbits the Earth, its Fine Guidance Sensors lock onto the stars. These sensors are part of the pointing control system and guide the Hubble in the right direction. Hubble can lock onto a target a mile away without moving more than the width of a human hair.

After detecting the target, Hubble’s main mirror begins to collect light. This mirror can collect about 40 thousand times more light than the human eye. Light is reflected from the primary mirror to the secondary mirror. The secondary mirror then refocuses the light through a hole in the primary mirror. From there, light shines on Hubble’s scientific instruments.

Hubble has five scientific instruments, including cameras and spectrographs, each with a different way of reading light. Spectroscopy is a tool that divides light into separate wavelengths.

Hubble’s main camera is called Wide Field Camera 3. The camera studies everything in the universe, from the formation of distant galaxies to the planets of the solar system, and can observe three different types of light: near ultraviolet, visible light, and near-infrared. While the human eye can only detect visible light, the Hubble camera can also observe and record near-ultraviolet and near-infrared. Of course, Hubble can only record one type of light at a time.

The Advanced Camera for Surveys takes pictures of large areas in space and has a very high resolution, quantum efficiency, and powerful emulsion filters. This camera increased the resolution of Hubble’s images by 10 times and showed scientists parts of the universe that had never been seen before.

Hubble’s Cosmic Origins Spectrograph reads ultraviolet light. This spectrograph studies the formation and evolution of galaxies, stars, and planets.

Somewhat like a prism, the Space Telescope Imaging Spectrograph breaks down the light that reaches the telescope from celestial objects into its constituent colors, helping scientists determine the temperature, chemical composition, density, and motion of objects in space. determine This spectrograph is also used to detect black holes.

The Near-Infrared Camera and Spectrograph (NICMOS) can sense the heat emitted from distant objects and observe them and spectrograph multiple targets simultaneously. The sensitivity of this camera to infrared waves has made it very efficient for seeing obscure celestial objects such as gases and interstellar dust, as well as for seeing the deepest parts of the universe.

Hubble sends about 150 gigabytes of scientific data to Earth every week. This amount of data is equal to about 45 two-hour movies with HD quality or about 30 thousand mp3 songs. Digital signals are transmitted from Hubble to satellites, then to a ground station, from there to NASA’s Goddard Space Flight Center, and finally to the Space Telescope Science Institute. This institute transforms data into images and information that we can understand.

Hubble’s digital cameras can only take black and white photos; For this reason, astronomers put the recorded image of the object in several exposure modes to record different wavelengths of light using several filters, which are usually red, blue, and green. These images are then superimposed to create a monochrome image. Because Hubble can see in the ultraviolet and infrared ranges, scientists sometimes add extra color to the images to bring out details that are normally invisible to the human eye.

The Hubble telescope is so powerful that it can detect the light of a firefly at a distance of about 11,000 kilometers, and scientists have used this amazing ability to understand many mysteries of the universe. For example, astronomers’ estimates of the age of the universe in the past differed greatly; But Hubble’s observations of old, burned-out stars helped them narrow down the Big Bang to about 13.7 billion years ago.

This telescope was also able to find early signs of supermassive black holes at the center of neighboring galaxies with the help of its high zoom power. The role of this telescope has been very vital in discovering exoplanets that may have suitable conditions for life. Perhaps Hubble’s most important discovery from the study of supernovae was the formation of the theory that a mysterious force known as “dark energy” may be the reason for the acceleration of the universe’s expansion, and this discovery would not have been possible without Hubble’s powerful lenses.

As Hubblesite explains, people often mistakenly think that the power of a telescope depends on its ability to magnify objects; But the fact is that the power of telescopes lies in gathering more light than the human eye can absorb, and the greater the ability of the telescope to gather light, in other words, the larger the surface of the telescope’s mirrors, the greater its power. The Hubble telescope also does this using a technique that was first presented 340 years ago; A technique called Cassegrain reflector, which consists of two convex and concave mirrors. The large, convex primary mirror absorbs light (Hubble’s primary mirror is 2.4 meters in diameter) and reflects it back to a smaller, concave secondary mirror (0.3 meters in diameter on Hubble). The light is then reflected through a hole in the middle of the primary mirror onto the sensors of the Hubble instrument.

Thanks to its large and powerful mirrors, Hubble can look deep into space; But only by looking at the NASA images, you can’t understand the incredible zoom power of this telescope. For this reason, astronomers have published a large number of images recorded by Hubble at different distances in the form of a video that shows off the power of Hubble’s mirrors in the best possible way.

On April 24, 1990, corresponding to May 4, 1369, the space shuttle Discovery took off from the earth with its very valuable cargo, the Hubble telescope. The next day, April 25, a team of astronomers put this telescope into space and Hubble’s exploratory journey began. On that historic day, no one could have predicted the wonders that Hubble was going to observe and record in the next 31 years.

In the same way, April 24th is Hubble’s birthday, and every year on this day, NASA publishes a beautiful and new image recorded by Hubble. Last year, on the occasion of the end of three decades of the Hubble mission in space, NASA published a new and amazing image of two nebulae in the Large Magellanic Cloud, which is a small galaxy at a distance of 163 thousand light years from the Milky Way.

The larger, red nebula is called NGC 2014, and the bright, newly formed stars at its heart are 10 to 20 times the size of the Sun. The blue nebula known as NGC 2020 was formed when a star 200,000 times larger than the Sun ejected a large amount of gas. To the eyes of the researchers, this recorded image resembled a rock or a coral reef; That’s why they named it “Cosmic Reef”.

The Hubble telescope explores the world 24 hours a day, seven days a week. That means the telescope has observed and recorded cosmic wonders every day of the year, including your birthday. To find out what image Hubble recorded on your birthday, you can go to this page on the NASA website and enter your birthday month and day in Gregorian.

Because of its position in space and its advanced lenses, the Hubble telescope can look at the most distant places that are hidden from the view of telescopes based on the Earth. Since it takes a long time for light to travel long distances, Hubble’s amazing capabilities make it a kind of time machine. The light that Hubble observes from distant objects only shows what the object looked like when the light left it, not what it looks like today; So when we look at the Andromeda Galaxy, which is 2.5 million light-years away from Earth, we see it as it was 2.5 million years ago; It is as if we are looking very far into the past.

Therefore, with Hubble, you can observe very distant cosmic objects that would never be visible without this telescope. For example, in 1995, when astronomers pointed the Hubble telescope at a seemingly empty region in the constellation Ursa Major, not expecting the telescope to capture an image of this region, to their disbelief, after 10 days, images of more than 3,000 observed the galaxy. This image was later named “Hubble Deep Field” (Hubble Deep Field), which you saw in the Hubble Telescope Images section.

Some of the galaxies recorded in the Hubble Deep Field were so young that they had not yet begun to form stars in earnest. A little later, other background observations were made in the same area, each time looking deeper into space. The “Hubble Ultra-Deep Field” image, which was released in 2004 and has four times the resolution of the Hubble Deep Field, is the deepest and most distant point in the universe that the human eye has seen. The galaxies recorded in this image are about 13 billion light years away from us; That is when the universe had spent only 5% of its current life.

By observing the early universe, Hubble helped astronomers calculate the time since the Big Bang, thus estimating the age of the universe in the range of 13.7 billion years. This telescope also examines stars separately in different stages of their evolution; From the clouds of cosmic particles that form newborn stars to the remnants of stars that exploded long ago and those that are at the limit of the distance between these two stages. Hubble has been able to look into the Milky Way, neighboring galaxies, the Magellanic Clouds, and the Andromeda Galaxy.

But more challenging than observing stars is observing planets that orbit other suns outside the solar system. However, in 2008, Hubble captured images of Fomalhaut b, the first time an extrasolar planet had been directly imaged in visible light. Most planets are very difficult to photograph. Most recorded images of planets have been obtained by detecting their atmospheres as they pass in front of their sun; In this way, the atmosphere of these planets filters the light of the stars and Hubble records these changes.

Hubble may spend most of its time looking at objects that are light-years away from Earth, But sometimes it also takes pictures of the planets that revolve around our sun. The images recorded by Hubble of Jupiter, Saturn, and even Pluto are of such clarity and detail that only probes orbiting these planets can capture them better. Hubble images allow scientists on Earth to observe changes in the atmosphere and surface of these planets. When Comet Shoemaker-Levy 9 collided with Jupiter in 1994, Hubble recorded the fatal collision. In fact, this event was the first direct observation of an extraterrestrial collision in the solar system and received extensive media coverage. After this collision, a lot of information about the atmosphere of this gas giant was revealed.

Additionally, in 2014 and 2016, Hubble was able to observe geysers erupting from the icy surface of the moon Europa (one of Jupiter’s 69 moons), thus making it one of the important targets in the search for habitable worlds far from Earth.

With more than three decades in orbit, Hubble has provided scientists with a better understanding of planets, galaxies, and the entire universe. Among the most amazing discoveries and research projects of Hubble, the following can be mentioned:

• Creating a 3D map of dark matter
• Discovery of two moons of Pluto named Nix and Hydra
• Help determine the rate of expansion of the universe
• The discovery that almost all massive galaxies are held firmly in place by a black hole
• Help to more accurately calculate the age of the world

Hubble will be 31 years old in 2021. Engineers have designed Hubble so that it can be repaired and upgraded if necessary. Since Hubble’s launch, five space shuttle missions have taken astronauts near the telescope to repair and upgrade it. The last Hubble upgrade mission was in 2009. This telescope will no longer be repaired or upgraded, But it will continue to perform missions in space.

Meanwhile, NASA and its international partners are preparing the $9 billion James Webb Space Telescope. Named in honor of the NASA administrator (1968-1961) who played an important role in the Apollo space program, James Webb, this telescope is an infrared type that is larger than Hubble and capable of seeing inside clouds and particles in space. This telescope will not need repairs during its 6 to 10-year life. Instead of orbiting the Earth, the Webb Telescope will orbit the Sun at a distance of one million miles from the Earth, and therefore will be able to look much deeper into space, and the light that traveled only a few hundred million years after the Big Bang. had started to observe.

Although the launch of the James Webb Telescope has been regularly delayed, it is currently scheduled to launch in November 2021 (Aban 1400). Astronomers hope to have both telescopes in space at the same time before Hubble retires.

Read more: Involvement of the James Webb Space Telescope in a mission beyond its capacity