What is the James Webb Space Telescope?
|The panels of the JWST being assembled|
For the first time in history, a mission has been named after a human, James Webb. James Webb ran NASA from 1961 to 1968 and is more closely associated with the Apollo program than he is science development, but his support of space science may have made him the most inspiring government official of the time. His ability to balance trying to get the first humans to the moon and the improvement of aerospace industries and space science in general made him a legendary NASA figure. His vision went beyond the one-shot beat-the-soviets ideal by striving to create the basis for longstanding success in the aerospace industry. The naming of the Hubble's successor is apt because under Webb, humans had the first into the landscape of outer space and the first view of how science could be used to further human curiosity.
Now, moving on to the more modern aspects of the JWST. The Webb will be launched by an Ariane 5 rocket,
which is part of the ESA's contribution to the mission. It will be launched from Arianespace's launch complex located near Kourou, French Guiana. Unlike the Hubble, the Webb will not orbit the earth. Instead, it will orbit the sun from point L2, which is around 1 million miles away from the earth. L2 is past earth, 1 million miles farther from the sun than the earth. Part of the reasoning for the position of L2 is the accessibility to communication. Earth will communicate to the Webb via the Deep Space Network, allowing the telescope to downlink data to the earth at least twice a day. The Webb will take 30 days to reach L2 where it will begin its orbit. Here is a timeline of events after the launch:
|Ariane 5 rocket on the ESA launchpad|
- In the first hour: The ariane rocket will provide thrust for about 8 minutes after which the Webb will separate from the launch vehicle 30 minutes after launch.
- In the first day: Two hours after launch the high gain antenna will deployed. After 10 and a half hours, the Webb will pass the moon's orbit, being nearly a quarter of the way to L2. 12 hours after the launch, small trajectory correction will be made by onboard rocket engines.
- In the first week: A second trajectory correction will be made 2.5 days after launch. The sequence of major deployments of the craft will be started after that, beginning with the sunshield pallets followed by the secondary and primary mirrors.
The Webb has 4 main science based themes: first light and reionization, assembly of galaxies, birth of stars and protoplanetary systems, and planets and the origins of life.
|Timeline of events since the big bang|
|Two combining galaxies|
|Rings of heat around a star signifying planetary development|
4. Planets and Origins of Life. One of the main uses of the Webb will be to study exoplanets that we have found. Their atmospheres are of interest to us because if one of these planets has a similar atmosphere to us it could house life. But since the infrared wavelengths of the Webb are not made directly for studying planets, we will have to use other methods, such as the transit method. The transit method means looking for a dimming of the light from a star, which could signify a planet passing between the telescope and the star. Collaboration with ground-based telescopes can help us measure the mass of the planets via the radial velocity technique. This technique involves measuring the stellar wobble produced by the gravitational tug of a planet to find the mass of the planet. The Webb will then do spectroscopy on the atmosphere of that planet. The Webb will also carry coronagraphs to allow direct imaging of exoplanets near bright stars, which are needed because of the light pollution that the star would cause. The questions that the Webb will try to answer include How are the building blocks of planets assembled, How do planets reach their ultimate orbits, How do large planets effect smaller ones, How did life develop on earth and many more planetary questions. The JWST will try to answer some of these by observing life first on our own planet and then looking beyond to the rest of our solar system and exoplanets to try to deduce which planets could have life.
Now let's get into the instruments that will be used to give us all the data to answer all those detailed, heavy scientific questions. The instruments of the JWST are housed in the ISIM, or Integrated Science Instrument Module, which is one of the three major elements that make up the JWST Observatory flight system. The ISIM is considered the main payload and carries many important objects, such as the NIRCam, NIRSpec, MIRI, and FGS. I'll go more into depth later on these, but for right now let's stick to the ISIM. The ISIM is divided into 3 regions. Region 1 is the cryogenic instrument module which cools the heat detectors of the craft down to 39 Kelvin. This region is necessary so that the spacecraft's own heat doesn't interfere with the infrared light detected from whatever is being imaged. Region 2 is the electrics compartment which provides the mounting surfaces and ambient thermally controlled environment for instrument control electronics. Region 3 is the command and data handling subsystem. It also contains flight software as well as the cryocooler of the MIRI and its control electronics.
|The NIRCam being assembled|
The James Webb Space Telescope is an extremely exciting amalgamation of new technologies that will facilitate the research of astronomers and scientists worldwide. It will pay homage to its predecessor, the Hubble Space Telescope. This telescope represents the most cutting edge technology couple with the imagination and determination of the human spirit. Exciting stuff.
Thank you for reading this post!