Ashford Morgan
PHYS 1118
Professor Acquaviva
The Hubble Telescope
    Ever since a human being could look up into the night sky and gaze at bright twinkling stars, we have been curious about what lies beyond our atmosphere. In the past astronomer’s such as the famous Galileo Galilei used a very early version of the telescope to observe the cosmos. However in more recent days we have came upon a spectacular advancement in astrological technology, the Hubble Space Telescope. The Hubble telescope has become something of a professional photographer for most people as we tend to gaze into an image from it as if were the most beautiful thing we had ever seen. Although the entire population might agree with this, the Hubble has also been the most accredited instrument ever built in the discovery of everything from the nearest shooting star to the next planetary system to the closest neighboring galaxy. The Hubble Telescope has changed the way we see a twinkle in the sky and allowed us to map our place in the universe as well as many others.
Astronomer Edwin Powell Hubble essentially proved that our universe in fact was expanding so as gratitude of this we named a telescope after him, that which expands our knowledge of the universe everyday. The National Aeronautics and Space Administration (NASA) constructed its first orbiting telescope called the OAO-2 however decades after, the demand for a larger instrument had risen. NASA requested funding for a 3m telescope but instead only received enough to produce a 2.4m. The funding was fulfilled by the U.S. congress in 1977and was named the Large Space Telescope (LST). Blueprints of what would be the biggest breakthrough in astronomy had been completed in 1979 and four years later given the current name of Edwin P. Hubble Space Telescope (HST). Following the tragic event of the Challenger shuttle takeoff for the Hubble Telescope was delayed until April 24th of 1990.
The Hubble Space Telescope in perspective of a satellite is indeed a very big one. Hubble’s length is about 13m long that match it with a diameter of 4.3m that encompasses a whopping 12.5 tons. Connected to the sides are two solar arrays, composed of solar cells that charge the telescopes batteries with light from our Sun. The most current arrays can support up to five kilowatts of electricity and allows for a more efficient charge. Over and around the telescope are handles and grapple fixtures that make for easy servicing while the Hubble is moving in orbit. The approximate orbit of the Hubble Telescope is about once every ninety-five minutes in an almost circular trajectory. This orbit is performed at just around 350mi or 560km high above Earth and can be reached by our shuttles relatively easily. However since the satellites orbit is so close to us it gradually drops because of very light traces of atmospheric gas. When servicing teams visit the Hubble Telescope they push it into a higher orbit each time to compensate for the problem.
The Hubble Space Telescope is not much different from telescopes that are used right here on the surface of Earth. Being a “reflecting telescope” it gathers light and uses adjustable mirrors to focus it. Essentially there are two mirrors in a reflecting telescope, the primary and secondary. In the Hubble the primary mirror reflects incoming light onto a secondary mirror. The secondary then reflects it back to a hole in the middle of the primary where it goes into focus. This concept may be fairly simple to grasp but there are other parts of this magnificent invention that need to play its part to deliver such amazing images. Along with these two mirrors there is also the High Speed Photometer, the Wide Field and Planetary Camera, the Faint Object Camera and two significant spectrographs. As each of them do expire over time they were each replaced during at least one of the HST’s services.
The Wide Field and Planetary Camera (WF/PC) have the responsibility of recording two kinds of images. In wide-field mode it will observe a vast area such as a star cluster while in planetary mode it will focus on a specific target such as well, a planet. Planetary mode has the ability to produce images with high resolution and greater magnification. The first installation of this camera was replaced by WF/PC-2, which fixed any mistakes caused by the primary mirror. The next type of camera allowed objects that could barely be seen to be enhanced to the best possible image. This Faint Object Camera (FOC) uses an image intensifier that is able to detect the dimmest speck of light. Filters were needed to counteract the production of too much light from this camera. Any astronomical object emitting a magnitude of over 21 can could cause the image to become oversaturated but which on the other hand makes it a very powerful tool for capturing the most that we can.
Since there are is so much traversing light in the universe there are definitely days where you need something just as quick. The High-Speed Photometer is able to measure any type of high-speed light fluctuation that is produced by sources of high energy. A justifying example of this would be a solar prominence or a coronal mass ejection coming out of our Sun. Although because of defects in the primary mirror and vibrations from one of the solar panels the photometer was replaced during the COSTAR mission. The Goddard High Resolution Spectrographs (GHRS) and Faint Object Spectrographs (FOS) both allow us to view spectra of light. While using these spectrographs we are able to better determine elements that a star is composed of. Any shift that a spectrograph records can either tell us if it’s moving away of towards us. Last but not least the Fine Guidance Sensors (FGSs) enable us too view the position of a star with ten times more accuracy than of a determination from Earth. However this sensor can only function properly when the Hubble is completely still.
These cameras and instruments are the backbone of the Hubble Telescope although the Wide-Field and Planetary Cameras are what actually give us images. The images we see are not sent like as photos but rather they have to be put together by combining the product of different color filters. Using a red, green and blue filter the camera is able to capture an image because of the corresponding wavelength. On Earth we then combine these images together to create a realistic image of what was primarily captured in space. Although we see images they are not sent to Earth as such, they are sent as electronic data. However before we can receive this information we have to understand that the Hubble is constantly revolving around the Earth and it can be difficult to transmit anything being that the telescope may come and go in and out of range. Luckily NASA came up with the solution of sending the data to a Tracking and Data Relay Satellite (TDRS), which is in geostationary orbit 22,300mi or 35,900km above Earth. Geostationary means that the satellite is revolving around the Earth at the same speed that the Earth is spinning; the Earth essentially holding the satellites hand as it spins. This satellite then shoots down the data to a facility in New Mexico that is then transferred to the Goddard Space Flight Center in Maryland.
The Hubble Telescope was sent into the space in April of 1990 but did not have its “First Light” until May 20th 1990. The first image captured by the Hubble Telescope was of the star cluster NGC 3532. This image was not very exciting to look at but nonetheless it gave astronomers and scientist’s relief to know that the telescope actually worked. Even though it was fantastic news to have the first image from the Hubble, NASA was actually worried that something was wrong. The image that was received was not in focus and nothing they could do could fix it. When a star is properly seen through a telescope there is a bright sharp spot of light surrounded by faint scattered light. However when the Hubble took a shot there was large ball of light surrounded by spikes of light within a halo-like effect suggesting the Hubble was not performing properly. Newspapers were quick to mock the $1.5 billion investment with headlines such as, “Pix Nixed as Hubble sees double!” (Kerrod 172). NASA figured out that the primary mirror in the telescope was because of spherical aberration. This caused the mirror to have the wrong curvature that resulted in different light rays being focused at the wrong points.
From December 3rd, 1993 to December 9th, 1993 NASA put some of its finest astronauts into space on the space shuttle Endeavor to fix the Hubble’s problems named STS-61. Although in order to fix this problem NASA had to come up with a plan, they created the corrective optics space telescope axial replacement (COSTAR). This remedy for the Hubble Telescope would clarify its vision by simply refocusing light from the defective primary mirror and dispersing it correctly amongst the other instruments within the Hubble. The Hubble’s first Wide Field and Planetary camera had to be replaced in order to correct the defective mirror. However to be able to allow the COSTAR to be apart of the Hubble the High-Speed Photometer had to be taken out. Along with this replacement NASA also had to replace three of the six gyroscopes of the Hubble and two of its memory banks as they had failed.
Dreading the horrible outcome of the Hubble Telescopes first light image NASA wondered if the second trip was worth it. On December 18th of 1993 they saw what they needed to see. They received an image of Melnick 34, which is a star in the Doradus Nebula. The star appeared to be a sharp bright light opposed to the first light where it was blurred and spread out. The Hubble was working the way it should have. By January of 1994 NASA had a number of various images taken by the Hubble were shared with the press assuring the world that the service mission was a success. In February of 1997 the space shuttle Discovery was sent to replace a couple of spectrographs with the Space Telescope Imaging Spectrograph and the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). The spectrograph would improve the overall spectral resolution of the telescope while the spectrometer allowed it to look into closer infrared wavelengths. Between 1997 and 1999 four gyroscopes failed to function properly. Since there were only two gyroscopes left this was not enough to accurately position the telescope and so the Hubble was shut down and put into hibernation mode. The service mission STS-103 shuttled by the Discovery took of December of 1999 to fix the problem.
The space shuttle Columbia shot into space on March 1st of 2002 with the responsibility of service mission STS-109. This trip would replace the Faint Object Camera with the Advanced Camera for Surveys (ACS). The ACS brought along three different but highly beneficial components. First was the ACS’s High-Resolution channel which had the ability to takes detailed shots within galaxies and is able to find extra solar planets. The second was the Solar-Blind channel, which cuts out any visible light therefore enhancing the ultraviolet sensitivity allowing us to observe weather on other planets. Finally the third is the Wide-Field channel that aids in understanding galaxy distribution throughout the universe. This mission also gave the Hubble Telescope a brand new neon cryocooler for the NICMOS that allowed it to be cooled to -200°c for proper use of it in infrared. On May 11th, 2009 service mission 4 (SM4) was launched to install the Wide Field Camera 3 (WFC3) and the Cosmic Origins Spectrograph (COS). The WFC3 is able to view ultraviolet, visible and infrared light while the COS shows us light as information in components of color using ultraviolet light.
The Hubble Space Telescope is in my opinion one of the greatest inventions ever created. We are able not only to see what’s around us but also able to find out so much more. We have the ability to see what stars are composed of, the trajectory of objects, the size and distance of them and accurately paint a picture of our own galaxy as well as our place in the universe. The Hubble is definitely a stepping-stone in what could be a more discoverable future for astronomy. Although the Hubble Telescope was a magnificent invention I thought that a little more concern for certainty should have went into it before it was launched for the first time. The $1.5 billion investment should have been checked rechecked and checked again in my opinion. Also I feel that some of the parts with the exception of technological advances should have been fabricated to last much longer as it seemed that they only lasted roughly a little over year. However the Hubble Space Telescope is nonetheless something that would make Galileo Galilei shed a tear and Johannes Kepler jump up and down with joy.
Works Cited
Peterson, Carolyn Collins and John C. Brandt.  Hubble Vision: Astronomy  with the Hubble Space Telescope.  New York: Press Syndicate of the University of Cambridge, 1995. Print.
Kerrod, Robin.   Hubble: The Mirror on the Universe.   New York: Firefly Books Ltd, 2003. Print.
Devorkin, David and Robert W. Smith.  Hubble: Imaging Space and Time.   Wahington D.C.: National Geographic Society, 2008. Print.
“Team Hubble: Servicing Missions.” HubbleSite. N.p., n.d. Web. 03 Dec. 2012. <http://hubblesite.org/the_telescope/team_hubble/servicing_missions.php>.
