Many of us can probably remember how and when we became interested in the night sky. The feeling of curiosity about the Moon, the Planets, the stars and galaxies seems instinctive to me. People have studied the heavens before the dawn of known history, trying to unravel the many mysteries that exist far, far away from us.
When I was a child, the greatest telescope ever built was the California Institute of Technology’s 200-inch Hale Telescope at the Palomar Observatory near San Diego. Despite the limitations of chemical and light pollution, the Hale Telescope has been instrumental in key astronomical discoveries. Even while astronomers were using the Hale Telescope, the National Academy of Sciences, in 1962, first recommended the placement of a useful telescope into space orbit.
The plan was to have a large, optical telescope away from the distorted, polluted atmosphere of our planet. Engineers needed to design a unit with a primary mirror about half the size of the one in the Hale telescope, yet produce far superior images.
U.S. astronomers gave five main objectives for the orbiting telescope project: 1. explore the Solar System 2. measure the age and size of the Universe 3. search for our cosmic roots 4. chart the evolution of the Universe 5. unlock unforeseen mysteries of outer space. The instrument would need to observe small bodies, like asteroids and comets while also being able to study details of the largest galaxies at the furthest reaches from Earth. All of the requirements had to be met in an instrument small enough to be launched into space atop a rocket that conformed to then, current technology.
The entire satellite/telescope would be packaged within a cylinder about the size of a large school bus. The final result would be 13.2-metres (43-ft) long and weigh 11,110 kilograms (24,490 lbs). The unit would be placed into a lower, non-geosynchronous orbit.
The power supply was to be supplied by a pair of 25 foot long solar panels capable of generating 2,800 watts of power. Some of the power would be needed to recharge the nickel hydrogen batteries to power the craft while it passed through the Earth’s shadow. To protect the sensitive instruments and, most importantly, the main mirror, inside the craft from the fluctuations of temperature between full sunlight and Earth shadow, multiple layers of insulation were needed.
The main optical system was constructed from graphite epoxy and weighed in at only 252 lbs. The main mirror is 94-inches in diameter with a 24-inch hole in the center. Because of changing temperature requirements, Corning Glass Works made the mirror blank out of ultra-low expansion glass in the form of a sandwich structure with a honeycomb shaped core. This allows the glass to contract and expand plus the weight is greatly reduced. The 2,400 pound mirror blank required three months to cool from the 2,146 Fahrenheit to room temperature.
The mirror blank was then sent to Perkins-Elmer optical facilities for finishing. There were many doubts about the company’s competence for a project such as the Hubble Space Telescope. Polishing work slipped behind schedule. NASA postponed work on the back-up mirror and rescheduled the launch date to September 1986. At that time, the total budget had jumped to $1,175,000,000.
Construction of the main space vehicle went more smoothly than the work on the main mirror. However, Lockheed Aerospace reported schedule slippage and cost overruns. The craft was three months behind schedule and 30-percent over budget.
Finally, everything came together.
A launch date of October, 1986 appeared doable. A major delay came with the Space Shuttle Challenger accident. NASA soon grounded the entire Space Shuttle fleet. This postponed the launch of the telescope. The delay bought time for development of the Earth based control software needed to control the satellite telescope.
NASA resumed Space Shuttle excursions in 1988. The revised launch schedule placed the Hubble Space Telescope launch date at April 24, 1990. On that day, Space Shuttle “Discovery” travelled into Space and successfully released the instrument into its planned orbit.
When the first images were transmitted to Earth, experienced astronomers were alarmed to notice that the pictures were the wrong shape and out of focus. It was determined that the mirror was too flat by a few nanometers. After a very embarrassing public relations flap, engineers went about the job of developing corrective optics for the Hubble main mirror.
After a few more years of research, development, and construction, five small mirrors were assembled into a corrective “lens”. Astronauts were then trained how to repair the telescope. In December of 1993, the tools, the “lens”, and the astronauts traveled to the telescope aboard the Space Shuttle “Endeavour”. The fix was completed as designed, with no problems reported.
At last, very early on December 18, 1993, astronomers and officials awaited the first picture from the repaired telescope. The image of a distant star came onto the computer monitor perfectly focused. NASA’s chief astronomer stated that the telescope had been “fixed beyond our wildest expectations.”
The Hubble Space Telescope has become the most talked about telescope ever built. There was the dream, the construction, the launch, the problem, the repair, and, most importantly, the amazing photographs. All of these, together, have kept the telescope in the public eye.
The Blue Jay of Happiness has a favorite Hubble Space Telescope video that he sometimes watches at this link: http://youtu.be/Zmbv4MasPe4 This writer’s favorite musician is featured on the soundtrack.