One revamp from the JWST is the usage of hexagonal mirrors. In the JWST, 18 sturdy and lightweight hexagonal segments are attached together to form its primary mirror. The benefit of using hexagonal mirrors is their high filling factor and six-fold symmetry (NASA, n.d-a). Since hexagonal shapes are symmetrical in nature, they are able to fit perfectly within the frame without any gaps. Removing any gaps would maximize the collecting area of the mirror. The primary mirror is folded on its side to fit within the rocket during launch (Clark, 2022). This allowed NASA to send a primary mirror of 6.5 diameters in width to space, a significantly larger diameter than that of the HST’s 2.4 diameter mirror (NASA, n,d-b). Furthermore, each hexagonal segment is composed of beryllium and plated in gold, giving the mirror its lustrous and gold appearance (Gohd, 2021). Beryllium has a high durability-to-weight ratio, making it a great choice for the mirror to be both sturdy and light.
Another change brought to the space telescope in the JWST is the use of 3 supporting struts. Struts are what hold the secondary mirror in place. For the JWST, the struts “are hollow composite tubes” that are made to be durable and light. Each strut measures up to 25 feet with a thickness of 1 millimeter. They are able to tolerate extreme conditions in space (Garner, 2017). HST uses 4 struts, giving the captured image the only 4 diffraction spikes. When the JWST unfolds, the struts adopt a tripod-like structure with an angle of 120 degrees between each strut. The struts are aligned in a way where the little light is blocked from the mirrors, allowing 8 diffraction spikes to form on the captured image (Siegel, 2022). This ensures that the images are crisp and clear.
A completely new addition to the JWST is the NIRCam. The NIRCam comes equipped with 2 instrument modules, enabling it to simultaneously observe both short and long wavelengths (Arizona.edu, n,d). What this means is that most temperatures of light from the stars are captured, allowing the image produced to be highly accurate. Moreover, the NIRCam is able to focus the camera on distant and dimmer objects which was not possible on the HST. This is achieved with a coronagraph which obstructs light from the brighter light source (NASA, n.d-c). Most of the light captured by the camera comes from the smaller and dimmer stars in the background. The NIRCam is used to capture images, but it also doubles as an Optical Telescope Element wavefront sensor, it has imaging correction (NASA, n.d-c). The camera obtains wavefront sensing data essential for periodic “alignment and phasing of the segments of JWST's primary mirror” (STScI, n.d). Unlike its predecessor, the JWST is able to obtain images of greater detail and clarity due to its NIRCam.
To summarise, the JWST is a major leap in development from the HST. It has been further refined to capture images that are clearer and scientifically accurate. The primary mirror has been modified to capture more light. The strut position has also been designed to create more diffraction spikes, improving the image quality. Lastly, the NIRCam is capable of filtering what light would be needed for specific situations. Thus, to say that the JWST is the gold standard for future the construction of future space telescopes would be accurate.
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