The Past, Present and Future of the Hubble Space Telescope:: 11 Works Cited
Length: 2706 words (7.7 double-spaced pages)
Throughout the ages, humans have been looking for a way to see into the past. In the year 1990, astronomers from NASA made this possible. Sending the Hubble Space Telescope into orbit with the space shuttle Discovery, NASA would make historical discoveries beyond their wildest dreams. Earlier this year they discovered a galaxy approximately 13 billion light years from Earth. Viewing the object at 750 million years after the big bang, scientists have looked into a time shortly after the "Dark Ages," a time before the first galaxies and quasars were formed. This incredible discovery was made with the aid of a cluster of galaxies known as Abell 2218. Being as massive as it is, Abell 2218 bends and amplifies any light that passes through it, working as a natural telescope ("Hubble"). The Hubble Space Telescope has become a great and valuable astronomic tool that NASA says is too costly and dangerous to keep running, a decision that may be premature.
Originally planned to launch in 1986, the Hubble Space Telescope has seen its share of problems. Starting with the explosion of the Challenger space shuttle, the Hubble's birth into space was delayed four years (Raven). On April 24, 1990, NASA put the telescope into orbit, only to discover that its primary mirror had a systematic aberration. To fix the problem, a mission in December 1993 set out on the space shuttle Endeavor.
The astronauts of the Endeavor replaced the High Speed Photometer with the Corrective Optics Space Telescope Axial Replacement (COSTAR). This device was designed to correct the aberration of the primary mirror. Even before the Endeavor mission, the space telescope produced many interesting images and was much more accurate than any Earth telescope. With the lack of atmosphere, the HST can look at objects at an angular distance of only 0.05 arcs second apart. The traditional ground-based telescopes can only resolve images about 0.5 arcs second apart, even under perfect sky conditions. With the new improvements, the HST could perform at the level for which it was designed. It could more accurately calculate the rate at which a galaxy is "receding from the Milky Way as a function of their distance" (qtd. in "Hubble"). For those confused by that statement: the HST would take a picture of a galaxy at one point and three seconds later (or any other given amount of time) take another picture of the galaxy and measure how much farther away it is.
With the new data it could collect, scientists could calculate the age of the universe ("Hubble").
Such missions as the Endeavor are part of NASA's plan (Raven). In the years 1997, 1999, and 2002, service and repair missions were sent to the Hubble Telescope (Barnbaum). The astronauts aboard the space shuttles performed space walks (more scientifically known as Extravehicular Activities or EVAs) to replace and/or repair key instruments in the Hubble Space Telescope. On the second servicing mission SM2 (the first was mentioned earlier), astronauts replaced two old instruments. The Goddard High Resolution Spectrometer and the Faint Object Spectrograph were replaced by the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) respectively. The team will also replace other hardware with upgrades and spares ("STS-82").
The next service mission was split into two separate missions, SM3A and SM3B. The first mission launched in December 1999 and the second in early 2002 (Nelson). The first missions was needed after the fourth of six gyros failed. With only two working gyros, Hubble was unable to function and entered a dormant safe mode. NASA hurried to get SM3A into space. The astronauts of the third service mission not only replaced the six gyroscopes, but also six battery voltage/temperature improvement kits; a faster, more powerful, main computer; a next-generation solid state data recorder; a new transmitter; an enhanced fine guidance sensor; and new insulation ("Servicing").
The Hubble's next visit came in 2002 from the space shuttle Columbia. With three previous HST service missions and a 1984 Solar Maximum repair mission, the SM3B received the advantage of experienced scientists and better-trained astronauts. With the knowledge of the past, NASA created a detailed planning and training sessions for the crewmembers Scott Altman, Duane Carey, Nancy Currie, John Grunsfeld, James Newman, Michael Massimino, and Richard Linnehan (Nelson).
Launching on March 1, 2002, the crew set out to replace, repair and improve. Part of Hubble's design is that it should get better with age. As each new mission services the telescope, the astronauts add new improvements that enhance the Hubble's capabilities. The astronauts of the SM3B installed the Advanced Camera for Surveys (ACS) and a new pair of rigid solar arrays. The ACS works with the current Wide Field and Planetary Camera 2 (WFPC2) surveying a field 2.3 times as large and four times as much spatial area with five times the sensitivity. The solar arrays are much more efficient, producing twenty percent more power than the ones that were on the HST at the time of the mission. These new arrays were also designed to be more resistant to damage and temperature swings caused by the Hubble's orbit. Other minor repairs and replacements were also taken care of during the Servicing Mission 3B (Nelson).
The major components of the HST's configuration are broken down into four basic groups. The Optical Telescope Assembly (OTA) consists of two mirrors and a compilation of other instruments that collect light from celestial bodies. The OTA is what makes the Hubble a telescope. Unlike most telescopes, the HST has no person to look through it. To analyze the light data obtained by the OTA, the HST has a compliment of science instruments and devices that make up the second basic component. Surrounding the OTA and science instruments is the Support Systems Module (SSM), a spacecraft structure that protects the Hubble's innards. The SSM also contains the structures, mechanisms, communications devices, electronics and electrical power systems that are needed for telescope operation. For power, the HST has two large Solar Arrays (SA), two large wings that rotate to face the sun. The solar energy collected by the SAs is converted into electrical power and is used to power the telescope and charge the batteries of the Electrical Power Subsystems (EPS). The power in the batteries is used when the space telescope moves opposite the sun where it receives no solar energy (Nelson).
Throughout the HST's lifetime, it has produced a wealth of scientific images that have led to phenomenal scientific discoveries. Opening the eye of the world, Hubble has been good to some scientists, confirming their theories; challenged others; and completely surprised all with new discoveries for which no theories have been hypothesized (Nelson).
With the Hubble's key characteristics and abilities to see fine detail, produce ultraviolet images and spectra, and observe very faint celestial bodies, its findings are too numerous to name. However, these numerous discoveries can be put into three basic categories: formation and evolution of stars and planets, Earth's solar system, and galaxies and cosmology (Nelson). Some of these discoveries include galaxies billions of years old, massive collisions between galaxies that tear each other apart and evidence that suggests that black holes are at the center of most galaxies (Britt, Barnbaum). On top of that, a discovery of exploding stars. What might seem like an insignificant find, actually proved that the universe is expanding at an accelerated rate, a discovery that disproves decades of thought about our universe ("Achievements").
In the shadow of the Columbia accident in 2003 and new plans for space exploration, NASA boss Sean O'Keefe made the decision on January 16 to cancel the 2006 service mission to Hubble. Many astronomers believe that two of the major reasons for letting Hubble go are probably two of biggest factors in any decision made by NASA: cost and safety. According to the man himself, however, the director of NASA Sean O'Keefe said that his decision was made just for the astronaut's safety (Britt). After the burning destruction of the Columbia and death of the entire crew, another mission to the HST is believed to be too risky (Petit). With this decision, scientists are searching for a way to keep Hubble afloat without sending a manned mission. Steven Beckwith, director of the Space Telescope Science Institute in Baltimore, appointed "tiger teams" to look for ways to keep the HST running as long as possible.
Some of the things the teams were looking at are power-conserving procedures that will extend battery life, ways to keep the telescope functional on only two of the six gyroscopes, and possibly robotic missions to the Hubble Telescope. The robots would launch on unmanned rockets and be controlled from the Earth's surface. The robots would have to perform all the tasks that the astronauts could; such as, replace batteries, gyros, and even install new instruments (Petit).
Some people might ask, "what about sending shuttles into space for the space station?" as NASA wishes to devote the three space shuttles to completing the space station by 2010 (Malakoff). The Columbia Accident Investigation Board, headed by Adm. Hal Gehman, was asked to look into the dangers of shuttle missions to Hubble. The board's August report said that missions to the space station are lower-risk if a shuttle were to be damaged since astronauts could survive on the station. A mission to Hubble could not reach the station without an 8,900 mph velocity change needed to switch to the space station's orbit (Vergano). A velocity change that would be extremely dangerous or even impossible.
There are others in the space world that dispute that a mission to the space station would be a safer flight. Robert Zubrin of the Mars Society, a space advocacy group, says, "If anything, it's the reverse" (qtd. in Vergano). Hubble supporters have pointed out two higher risks for shuttle missions to the space station. A shuttle at the station would dock with its heat shield facing towards incoming debris. The other concern involves a longer rocket firing to reach orbit. The station's orbit is highly inclined and requires more time to reach. With a longer burn, engine failure is more likely (Vergano).
There are, of course, dangers and expenses involved in manned missions to the Hubble Telescope. George Levin, a man who worked on Hubble and Shuttle missions for 36 years and is currently part of the National Academy of Engineering, says that one of the biggest dangers about manned missions are space walks. When astronauts are performing EVAs, they are vulnerable to space debris. Levin also notes a cost issue. For rescue missions, a second very costly shuttle is needed when astronauts perform Hubble service missions. A much cheaper Russian capsule can be used when flying to the space station (Vergano).
Robert Zubrin makes a valuable point that "going to the moon and Mars is going to be more dangerous than Hubble or the International Space Station" (qtd. in Vergano). Space exploration requires safety risks; to accept the risks of traveling to the aforementioned solar bodies, NASA should be willing to take on the risks of furthering our discoveries from the Hubble space telescope.
George Gleghorn, a retired TRW Space and Technology Group engineer, who was part of NASA's aerospace safety advisory panel from 1991 to 2002, says, "every flight is dangerous" (qtd. in Vergano). It would be a huge political risk for NASA to approve a mission that was deemed riskier than a space station mission was, by the investigation board. O'Keefe also felt that manned flights are too dangerous, except for the most important missions, and can Hubble be considered one of the most important missions being fourteen years old? (Vergano).
It is quite possible. Hubble has been getting better with age as each service mission brings new and improved scientific instruments ("Achievements"). "Its greatest achievements... are or should be ahead of it," says Beckwith (qtd. in Petit). With the cancellation of the fourth service mission, approximately $200 million of new instruments and gyroscopes that would enhance the HST will go unused. Beckwith says that along with the loss of the instruments these scientific advancements will be lost with them:
* Better Measures of those distant exploding stars to uncover the "dark energy" behind the universe's runaway expansion.
* Closer Looks at those explosive ancient galaxies, or quasars, to determine how the first star clusters formed after the big bang.
* No planned telescope will, like Hubble, look at visible light from stars, leaving a hole in NASA's Great Observatory program ("Achievements").
These are the sorts of things NASA has to take into consideration when it makes its decision on the famous telescope.
As of now, however, NASA will remain with its decision until proof that the HST is worth keeping around. Plans for removing the spacecraft have already been put in motion. They intend to design a robot that will go into space, attach itself to the telescope and pull it out of orbit to a fiery descent in the Pacific Ocean. This plan may not be possible if the deteriorating batteries fail, says Beckwith. If this were to occur, the HST could spin out of control, and it would be too difficult to attach a robot. Scientists have looked into this problem and are working on ways to keep the Hubble controlled even if the batteries fail. However, NASA engineers are still uncertain exactly what would occur if this were to happen (Britt). This possibility could mean that NASA would have to make a decision final sooner than later, whether it is the destruction of the famous space vessel, or the preservation.
Many of the people of the astronomy world consider Hubble to be "the most spectacular successful science experiment that we've done in astronomy in recent decades," a comment made by John Bahcall of the Institute of Advanced Study at Princeton University. (qtd. in Janega). Bahcall has studied the Hubble on a independent panel with hopes to advise NASA on its decision (Janega). Even if scientists prove the Hubble to be worth the money of our space association, NASA feels that they " cannot delegate [their] ultimate responsibility for decisions related to the safety of human space flight" (qtd. In Vergano). It looks like NASA does not intend to change their minds on the issue unless the safety of the astronauts can be assured.
The loss of this historical telescope would be great. With all the discoveries it has already made, who knows what knew knowledge of our past it will have in store for us in the future. With a lower cost and risk than the planned missions to the moon and Mars, I hope that NASA will come around and realize that the Hubble Space Telescope is worth saving.
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