Daniel Pope

Space Shuttle Atlantis is scheduled to launch on May 11 for the final repair and upgrade mission to the Hubble Space Telescope (HST).

From 1609 when Galileo first turned his telescope to the night sky, a major problem for telescopes has been Earth’s atmosphere. The uneven temperatures and the moving air are what cause stars to appear to twinkle. It is pretty to the naked eye but is a problem for astronomers trying to learn more about what they are seeing. In April 1990 the Space Shuttle Discovery placed the Hubble Space Telescope in an orbit about 350 miles above our Earth. The original plan called for a life expectancy of 15 years with repair and upgrade missions about every 3 years.

The first images that came from the HST were fuzzy and not in the sharp focus that had been expected and anticipated. After some testing they came to the conclusion that the main mirror in the telescope did not have the exact correct shape. Needless to say this caused a lot of turmoil. The engineers designed a hardware fix that was delivered by Space Shuttle Endeavour in 1993. It was a spectacular success.

Stars of a class known as Cepheid variables have been used by ground based telescopes since the 1920s to estimate distances to other galaxies and across our Universe. Astronomers used these distances to estimate the size and age of our Universe and how fast it was expanding. The problem was they knew their measurements of the Cepheid variable stars contained significant errors. For a long time the best they could estimate the age of our Universe was between 10 and 20 billion years. The HST was able to determine a much more accurate measure of the distances to the Cepheid variable stars and arrived at an estimate of 13.7 billion years for the age of our Universe. Since the 1920s it had been assumed that while our Universe was expanding, its rate of expansion was slowing down due to gravity. Data from the HST cast doubt on that assumption and led to the discovery that the rate of expansion has increased in the recent past. The HST provided the first evidence of the existence of planets around stars in the Orion Nebula. HST was a major contributor to confirming the existence of Black Holes at the centers of nearby galaxies. HST gave us very useful data, not to mention spectacular pictures, when Comet Shoemaker-Levy 9 crashed into Jupiter in 1994. Thousands of scientific papers have been published based on HST’s data and those papers have been cited extensively in subsequent papers by others. Some say the HST is the most productive scientific instrument of all time.

The Space Shuttle Columbia was scheduled to make the last repair and upgrade mission to HST in February 2005. In the aftermath of the tragic lost of the Columbia and her crew in 2003, the mission to HST was cancelled. Due to differences in altitudes and orbits a Space Shuttle cannot reach both the HST and the International Space in the same mission. It was this concern for the safety of the crew that led to the cancellation of the HST mission. It was not surprising that astronomers and scientists voiced their opinions and expressed their need for a way to be found to repair the HST. What was somewhat surprising was that the public voiced their desire for the Hubble to be repaired so that it could continue its mission. Members of the public emailed, wrote letters, held forums, etc. A robotic mission was proposed but after a study it was deemed unfeasible. Given the reactions and expectations of scientists, citizens, and the government, NASA made a commitment to find a way to keep Hubble running. To address the safety concerns, it was decided to have a second shuttle in position to launch to affect a rescue if needed. Space Shuttle Endeavour will be in that role on May 11.

Clear skies.