Telescopes have only been around for about 400 years. Since then, they have evolved quickly and helped astronomers make remarkable discoveries. Ground based telescopes were the first, but we needed a way to observe the cosmos in the vacuum of space, without the light pollution and atmosphere of earth. The Hubble Space Telescope (HST) was the tool that helped propel astronomy to the next level. It has helped us understand the universe in new ways, but Hubble’s journey has been difficult and it has required many service missions to remain operational.
Without those repairs and replacements, Hubble would not have helped make the discoveries it has, from confirming black holes to helping determine the age of the universe, Hubble has been instrumental to our current understanding of the universe. With this said, is Hubble the most important telescope to have ever been built and used? Yes it is, and Hubble will continue to make progress in the field of astronomy throughout its remaining years. To help understand why it is the most important telescope in history, we must first look at why and how it was developed. Ground based telescopes posed many problems for astronomers.
Earth’s cloud cover, atmosphere, and light pollution all create obstacles for ground-based telescopes. There are some techniques astronomers can use to compensate for these things, but there are still many problems with ground-based telescopes. The turbulence of the air in the atmosphere distorts distant objects and the light pollution makes it difficult to see faint objects. Also, the inability of some forms of radiation to penetrate the atmosphere makes it so some objects in space cannot reach earth’s surface, particularly infrared and ultraviolet. X rays and gamma rays are also distorted when they reach earth’s surface. The need for a long-term space-based observatory was evident as early as the 1920’s when Herman Oberth, the German pioneer of space flight, put forth the idea.
2 A telescope that could capture images from above earth’s atmosphere where there was less light and distortion would give us valuable research data which could lead to scientific breakthroughs. 1 As Lyman Spitzer, an American astronomer who proposed a large space based telescope in 1946 said, Hubble “would not be to augment our current ideas about the universe we live in, but to discover new questions which nobody can yet imagine. 2 Astronomers wanted a large space telescope to see deeper into the cosmos than ever before. In 1972, the Marshall Space Flight Center, under the direction of NASA, led the project for a large space telescope. 2 Hubble was designed to make a large range of observations, from comets and asteroids in our own solar system, to distant galaxies light years away. The vision for Hubble was ambitious and it ran into many budget constraints, which slowed the project down considerably. NASA decided to team up with the European Space Agency (ESA) to help fund and develop the project. The HST is 13. meters long and weighs 25,500 pounds. 3 At the time of its launch, it contained the most technically advanced instruments ever.
The Wide Field Planetary Camera, the Faint Object Camera, the Faint Object Spectrograph, the Fine Guidance Sensors, the Goddard High Resolution Spectrograph, and the High Speed Photometer are the main instruments of the HST. These instruments are responsible for the pictures Hubble produce, keeping the telescope pointed in the right direction, intensifying faint objects, detecting a wide range of frequencies, and determining how light from a source changes with time. Hubble was scheduled to launch in 1986, but then, the Space Shuttle Challenger exploded. Everything was suspended, but within a few years everything went back to normal and the launch was scheduled for sometime in 1990. Finally, on April 24 1990, 18 years after it had been approved, the Hubble Space Telescope was launched from Cape Canaveral Florida on the Space Shuttle Discovery. 1 The HST was released at an altitude of between 613 and 615 Km. 2 It remains in a LEO 600km above earth where it makes 1 revolution around the earth every 97 minutes.
It could do things that no other telescope on earth could, but it has needed a lot of repairs throughout its 20 years. On 20 May, when it pointed its mirror towards the star cluster NGC 3532, problems began to surface. The images were not in focus, the two solar panels were causing the telescope to jitter when they expanded and contracted from the heat and cold, and the FGS were not working properly. They fixed the FGS with new software coding, but the other two problems were much more severe. After investigation, it was determined that the mirror was flawed (it was made too flat).
The manufacturer, Perkin-Elmer, had not completed the proper testing. 2 The next few years for the Hubble were bumpy ones. Some wanted to bring the telescope back down after learning of the mirror fault so they could repair it. 3 Others wanted to abandon it all together and build another one. Still, others wanted to repair it in orbit. There were several methods of repair being discussed, such as reshaping the mirror, depositing a new mirror coating, or mounting huge corrective lenses or mirrors. The best idea was the corrective optics space telescope axial replacement (COSTAR). It was presented to NASA on October 26, 1990 and accepted. 3 COSTAR would correct and refocus the light. The wide field and planetary camera would also have to be replaced during HST’s first servicing mission. Servicing mission 1 (SM-1) was the first of 5 servicing missions. These service missions had been anticipated as necessary maintenance throughout Hubble’s lifetime, but this first mission to restore its vision was extremely crucial.
Space Shuttle Endeavor lifted off on Dec 2, 1993. 2 The two solar panels and the Wide Field Planetary Camera replacements went perfectly. On the sixth day, COSTAR was installed without any major problems. 2 The 11-day mission was a complete success. 4 On January 13th, 1994, it was confirmed that the Hubble had been fixed and was now working properly during a press conference. In February of 1997, a second service mission was being planned so that the Hubble Space Telescope could see in infrared. Its objective was to improve the telescopes visual acuity and range. The Goddard High Resolution Spectrograph and Faint Object Spectrograph were replaced with space telescope imaging spectrograph (STIS) and the NICMOS (near infrared camera and multi object spectrometer). The NICMOS had the ability to see the universe in infrared, while the STIS could take detailed pictures and hunt for black holes. An FGS, data recorder, and reaction wheel assembly were also replaced and some thermal insulation was repaired. 5 On November 17 1999, the fourth of six gyroscopes failed and Hubble had to be shut down. Without these gyroscopes, the instrument could not position itself.
Its other attitude maintaining gyroscopes previously started to fail in 1997 and more kept going out up until the 4th one finally went out in 1999. 5 On December 19, 1999 the gyroscopes were replaced on an emergency visit, service mission 3A. A new computer, one of the three Fine Guidance Sensors, and a transmitter were also installed along with some battery improvements. 5 Servicing missions 3B took place on March 1, 2002. The Advanced Camera for Surveys (ACS), Solar Array Panels, Infrared, and steering were the mission’s priorities. 5 The ACS, which was he latest and greatest in digital, replaced the Faint Object Camera of the 1980s. It would give Hubble a bigger, sharper view. A new neon crycooler also had to be replaced to support the NICMOS. 5 The fifth and final servicing mission was servicingmission 4. 6 This mission almost never happened because of the risks involved and the recent Space Shuttle accident. New instruments were to be installed, others replaced, and finally some repairs needed to be accomplished. This was a very difficult undertaking that needed extremely complex tools and a perfect time line.
The mission launched on May 11, 2009 aboard Space Shuttle Atlantis. The new instruments were the Wide Field Camera 3 and the Cosmic Origins Spectrograph. The WFC3 has much better resolution than the previous camera, WFPC2. The COS replaced the COSTAR and improved Hubble’s ultraviolet light sensitivity between 10 – 70 times, depending on what it is viewing. The most amazing thing about servicing mission 4 was the repair mission. The ACS and STIS both needed on site repairs because they had stopped working.
It was a long and difficult task, but the astronauts got it done. 6 Without these missions, the Hubble Space Telescope would not have been able to make some of its incredible discoveries. 6 One of the biggest questions mankind has pondered has been, how big and how old is the universe? Before Hubble, we were not able to look more than 7 billion light years into the universe, but with the Hubble, we can see to when the universe was just a few hundred million years old, something no other telescope can do. One of the main goals of the HST was to determine how old the universe was by more accurately defining the Hubble constant, since the two are related. The Hubble constant is a number used to determine the current rate of expansion of the universe.
To find it, Hubble would measure the distances to pulsating stars in distant galaxies, Cepheid variable stars, and ground based telescopes would determine the redshift. 2 With this and the measurements of the cosmic background, it was determined that the universe is around 13. 7 billion years old. This discovery alone makes it the most important telescope ever used, but there are many more. The reinforcement from Hubble that the universe is in fact expanding added more questions about the universe. Why was its expansion now accelerating? Gravity should have been stopping the acceleration. Scientists concluded that it was a mysterious substance pushing along the expansion of the universe called dark energy. For a long time, there has been debate on whether or not there is enough gravity to slow down and stop the expansion of the universe.
Dark energy is kind of a counterbalancing force that keeps the universe from imploding. Before Hubble, scientists knew of black holes, but only confirmed that they existed in stellar binary systems. In 1997, when the STIS became operational, it was pointed towards the M87 galaxy in Virgo. The galaxy had a telltale jet of material ejected from the core at high speeds, indicating black hole qualities. Ultimately it confirmed a black hole. 27 more nearby galaxies all had black holes as well and now astronomers conclude that just about every galaxy has a black hole in its center.
Hubble has also helped us understand how galaxies are formed. The Hubble Deep Field Survey shows galaxies billions of years ago when they were in their early years, just forming. The galaxies were smaller and more irregular in shape and size, showing that galaxies evolved from smaller structures. Before Hubble was launched, we were not sure if planets existed outside of our solar system. Ground based telescopes discovered that there were other planets out there by the way they would tug on a star and make it wobble.
Only the size, ellipticity of its orbit, and the lower limit on its mass is known from ground-based observations. Hubble focused on these planets that were previously discovered. Hubble made the first measurements of the atmosphere of an exoplanet and determined their chemical make up. 8 In Hubble’s coming years, many more studies will be conducted by studying other planets in the galaxy and new discoveries will be made. The Hubble Space Telescope is nearing the end of its service life. No more service missions are planned. The Hubble relies on batteries to power itself, so they have a limited life.
Aside from the batteries, it is easy to conclude from all of the equipment failures and maintenance required that the Hubble will not last for a very long time without something going wrong. Additionally, Hubble’s orbit is not very high (600Km), which creates friction with the upper atmosphere. This means that the HST is slowly falling towards the earth. Eventually its orbit will cause it to fall into the earth’s surface. Its successor, the James Webb Space Telescope, will be the telescope of the future and will continue with space-based observations. It is scheduled to launch in 2014. The infrared observatory will be able to see deeper into space, meaning further back in time to the very beginning of when the first galaxies were forming and hopefully even further. It will help us to determine how galaxies are formed, the birth of stars and planetary systems, and the origins of life. Its mirror will be much larger than Hubble, at 6. 5 meters in diameter. It will orbit around the sun, beyond the earths orbit to protect it from the suns heat. 9 The Hubble Space Telescope is an incredible instrument and it has been a great research tool for mankind.
It is the most important telescope mankind has ever used since it has led us to confirming fascinating discoveries. It has had 5 servicing missions, with everything from replacing equipment and repairing malfunctioning equipment to upgrading instruments with new technology. Without these servicing missions, the HST wouldn’t have helped us discover that there is dark energy throughout the universe causing expansion, the approximate age of the universe, and that there are black holes. These are just a couple of the telescopes discoveries and there will be more in the remaining years of the Hubble.