What is the origin of our universe? When did its constituents, such as vast galaxies, stars, and other matter, evolve? What are some of the cosmological events that unfolded billions of years ago? Are there any habitable exoplanets out there?
We have many unanswered questions. Our thirst for knowledge has always pushed boundaries and helped us better comprehend our boundless universe. James Webb space telescope is one such endeavor. This article gives you a comprehensive explanation of one of the most complicated and expensive missions ever built by us. When proved a success, this mission will significantly change how we view our universe.
James Webb space telescope(JWST) is a space observatory considered the successor to the Hubble space telescope. It is named after the renowned administrator of NASA, James E. Webb, during the Apollo program. It is designed mainly to observe infrared light. In collaboration with European Space Agency(ESA) and Canadian Space Agency(CSA), NASA successfully launched this telescope on December 25th, 2021, on the Ariane 5 rocket.
It is designed to work under unprecedented conditions. For example, it operates under a mindboggling temperature of -233C and a distance of 1.5 million kilometers away from our planet. It will revolve around a location in space called the second Lagrange point(L2) and will take around 30 days to reach this location. A whopping ten billion-dollar venture, it took almost three decades of meticulous planning and effort to complete successfully. It also paves the way for a much clear understanding of the genesis of our universe, the evolution of its constituents such as stars and galaxies.
History of JWST
With the success of the Hubble space telescope(HST), the enthusiasm to design a successor to HST increased manifold. Over the years, HST sent us many marvellous images that helped us understand objects in space better. Since the mid-1990s, one of the main objectives of the scientists at NASA was to create a colder, more sensitive telescope that could probe into infrared light. In the late 1990s, a committee, then a subcommittee, was formed to find answers relating to the evolution of our universe. NASA decided to design a more efficient telescope with an estimated 500 million US dollars and predicted to finish it by 2007.
Northrop Grumman Space Technology was the main contractor for this project and was responsible for developing several critical parts of the telescope. Due to cost overruns, the project got delayed from time to time. Also, the nature of the project itself was non-serviceable because of its highly complex design and underwent detailed reviews during its construction phase. Critical Design Reviews(CDR) was one such review to determine if the mission has successfully met all the stated requirements to finish the mission within estimated cost and risk.
Also, in 2011, due to several budget revisions, the US government decided to cut the project’s funding. But, bowing down to the project’s support from various corners, the US government repealed its decision. When NASA successfully constructed the telescope, it underwent several thorough testing procedures to a great degree. Also, the coronavirus pandemic caused some unnecessary delays in the final stages.
Here is an interesting fact, NASA conducted an independent review to find that there could be as many as 344 single-point failures. Its highly complicated design and the arduous task of putting the telescope in orbit are the potential causes of failure. After planning and developing the project decades ago, NASA, ESA, CSA, several hundreds of companies, government agencies, scientists, and engineers worldwide collaborated to make this project a success.
JWST mainly captures infrared radiation. As light from distant galaxies and stars undergoes redshift, it has a longer wavelength into the infrared spectrum. Thus it can effectively capture images not so clear on the Hubble telescope.
Considering the fact that most of the radiation is blocked by the earth’s atmosphere, NASA has decided to place the telescope in a specific orbit where it is a minimal effect due to gravity. Such points where the gravitational attraction between the sun and the earth balances the centrifugal force between the two are called Lagrange points. James Webb telescope will operate in L2 point, 1.5 million kilometers away from our planet.
Technical details of JWST
Here are the technical details of the JWST telescope
1) Lifetime of the mission: 5 years(10 at most)
2) Operational temperature: under -233C
3) Primary mirror material: gold-coated Beryllium
4) Primary mirror area: 25.4 sq meters
5) Number of segments in the primary mirror: 18 hexagonal mirrors of a combined length of 21 feet.
6) Primary mirror mass: 705 kg
7) Observable wavelength: 0.6 – 28.5 microns
8) Payload mass: 6200 kg
9) Size of the sunshield: 14.162 m × 21.197 m
Internal parts of JWST
Here are the crucial parts of the JSWT
The mirror forms the most crucial element of the telescope. The primary mirror comprises 18 hexagonal mirror segments. These mirror segments are made of highly pure beryllium, have a diameter of 1.32 meters. A sensor is used to determine any imperfection in images formed by these mirror segments.
Beryllium is a rare metal and is very strong and lightweight. It is a good conductor of electricity and non-magnetic in nature. At frigid temperatures, it endures well and remains uniform. Due to these desirable properties, beryllium has a wide range of applications in automobiles, missile systems, fusion reactors, etc.
Beryllium mirrors are thinly coated with gold to improve infrared reflection. The process of coating a very thin layer of gold onto the mirror is called vacuum vapor deposition. Less than 50 grams of gold was used to paint the entire mirror.
The mirror design is a three-mirror anastigmat to reduce the effect of optical aberrations. The secondary and tertiary mirrors are employed to create an aberration-free image.
In order to protect the telescope from various sources of heat and light such as the sun, earth and moon, this system acts as an umbrella to protect internal equipment. This system is comprised of five layers, each with a thickness of human hair and the size of a tennis court, to prevent the heating up of optical instruments. These layers are made up of a material called Kapton and coated with aluminium. The outermost layer is also coated with doped silicon and offers better protection. Each layer has a specific thickness and size and is precisely separated from other layers.
The protection from heat is crucial as the telescope is employed to observe infrared radiation. These extremely low temperatures prevent the tampering of observed infrared light with the radiation released by the equipment itself. These layers are folded during the rocket launch and unfolded in later stages.
Integrated Science Instrument Module(ISIM) has four main parts and is responsible for providing electric power, structural stability, and maintaining optimum temperature.
Mid-Infrared Instrument can measure a wavelength range of 5 to 28 microns. It has a camera and an imaging spectrograph. A unique system(a cryocooler) is deployed to maintain an optimum temperature of 7K.
Near InfraRed Camera(NIRCAM) detects an infrared wavelength range of 0.6 to 5 microns. This instrument acts as a camera and takes pictures of old stars, galaxies etc., that are too dim to observe. Thereby, it helps to observe the evolution of the earliest stars and galaxies after the big bang.
Near InfraRed Spectrograph(NIRSPEC) is designed to perform spectroscopy over the same wavelength. A spectrometer allows us to understand both the physical and chemical properties of matter. This device can observe spectra of around 100 objects simultaneously.
Fine Guidance Sensor(FGS) allows us to obtain high-quality, stable images by orienting the spacecraft in the desired manner. At the same time, Near-Infrared Imager and Slitless Spectrograph(NIRISS) helps in imaging and spectroscopy of light in the wavelength range of 0.8 to 5 microns.
This system has an integrated network of subsystems that assist in several support functions such as communication, power generation, stability, propulsion etc. It is comprised of six subsystems such as
1) Electrical Power Subsystem: This subsystem converts sunlight into electric power necessary to run the entire telescope.
2) Attitude Control Subsystem: This subsystem maintains the telescope in a stable orbit.
3) Communication Subsystem: This subsystem receives and communicates data to the Operations Control Centre.
4) Command And Data Handling System: This system performs functions such as data storage, directing commands from the communication subsystem to other devices.
5) Propulsion System: This system has a fuel tank and rocket thrusters that maintain the observatory’s course in a stable orbit.
6) Thermal Control Subsystem: This system maintains the optimal temperature inside the spacecraft bus.
Several other systems inside the telescope assist in various operations. JWST captures infrared light from distant stars and galaxies billions of years ago to analyse the conditions that existed at that time. JWST is a technological marvel which took a lot of time and resources to complete. Hopefully, we can utilize it to unlock the secrets of this universe.