April 24 1990 – The Hubble Space Telescope is Launched

April 24 1990 – The Hubble Space Telescope is Launched
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*Image Credit: Wikimedia Commons

Some 44 years after the idea was first proposed by Princeton University astronomer and theoretical physicist Lyman Spitzer, the Hubble Space Telescope (HST) was lifted into orbit aboard the Space Shuttle Discovery on April 24, 1990. Coming in at more than six times the projected cost by the time it was launched, the HST has provided researchers unparalleled views of the universe for more than two decades.

The foundation for placing a large telescope in orbit was laid in the early 1920s, when physicists Hermann Oberth and Robert Goddard made advances in rocket technology that would allow massive payloads to escape Earth’s gravity. By the end of World War II, after German scientist Werner von Braun’s team invented the V-2 rocket — a ballistic missile capable of reaching an altitude of 128 miles — it seemed likely man would one day be able to explore well beyond the upper atmosphere.

Writing in 1946, Spitzer felt there would be enormous advantages to launching an observatory beyond the atmosphere. Unlike terrestrial telescopes, he postulated, the lack of distortion created by weather systems and winds would allow for clearer views of deep space phenomena — minor distances between far-off stars could be observed with precision. On top of that, objects outside the visible spectrum of light would show up, allowing more complex objects to be identified.

What followed were a series of experiments that proved the existence of the ultraviolet spectrum, as well as X- and gamma-rays put off by the Sun. This was followed by an appointment in 1965 to a committee charged by the United States National Academy of Sciences with creating a series of goals a large space telescope should achieve. In the meantime, NASA sent the Orbiting Astronomical Observatory up the following year to gather information about the ultraviolet signatures of other stars and galaxies. The first attempt failed due to a faulty battery, but the second — launched in 1968 — lasted well beyond its intended mission.

By the 1970s, the benefit of a large telescope was clear. In order to keep such a complex piece of equipment online, NASA engineers required assurances that technicians could make repairs in orbit, a possibility fit within the mission profile of a spacecraft in development at the time, the Space Shuttle. However, with severe cuts to the budget put forth by the US Congress in 1974, funding for the project dried up. At the end a four-year fight in the Senate, plus concessions with respect to the size of the instruments and a promise of funding from the European Space Agency, a $36 million outlay — half the original amount — was guaranteed in 1978.

Given a target of 1983, NASA divided the work among a host of departments. With the wide parameters created for observation, particularly the wide range of wavelengths the telescope would have to measure, the design and manufacturing process proved incredibly challenging. The two mirrors necessary, for example, had to be shaped to pick up deviations of just 10 nanometers — a human hair is approximately 5,000 times thicker. (Construction of the delicately-polished glass slabs would take almost three years.)

As the months passed, the HST program — named after astronomer Edwin Hubble early in 1983 — ran into delay after delay. Production of the mirrors and instruments took longer than expected, as did the assembly of the housing itself. The harsh conditions in orbit required dense insulation to protect the various pieces of the telescope, leading to further cost overruns — the project was three years late and nearing a billion-dollar price tag by the end of 1985 with a possible launch date of March 1986.

Then, disaster struck: the Space Shuttle Challenger exploded over the Atlantic Ocean on January 28, 1986. The launch vehicles were grounded indefinitely, leaving the HST without a transport just as it seemed like the project was nearing a conclusion. (Engineers finally felt confident the fully-assembled telescope would be complete by that fall.) Stored in a sealed room at a cost of $72 million per year, there hardly seemed to be a bright side to the postponement.

Forced to wait for another four years before a final launch date was approved, NASA scientists were hard at work on the computer software to control the massive telescope. Technology able to handle the vast amount of information generated by the HST was only just catching up by 1990. With the launch scheduled for April 10th of that year, programmers refined the code necessary to distinguish transmissions from the five instruments on board and guide the HST’s placement in orbit.

Two weeks after the planned launch of NASA mission STS-31, the Space Shuttle Discovery took off just after 8:30am on April 24, 1990 bound for an altitude of 370 miles, the highest-ever orbit for a manned flight at the time. With a final funding total of more than $2.5 billion for the HST, the original $400 million estimate looked like small change.

Almost immediately, NASA noticed a problem: the quality of the images was less than expected — and degrading rapidly. In a matter of weeks, the photos were hardly better than those produced by observatories on Earth. An investigation revealed the mirrors were off by 2,200 nanometers, a defect ignored in final measurements by the manufacturer. Government oversight placed the blame squarely at NASA’s feet, embarrassing the agency publicly.

Finally, in 1993, the first servicing mission scheduled for the HST came up and provided NASA an opportunity to fix the issue. In a brilliant bit of problem solving, engineers created a set of compensatory lenses for the astronauts of STS-61 to install, not unlike how a person with vision problems would put on a pair of glasses. The resulting images were markedly sharper, revealing details researchers hoped for during the planning stages.

Over the course of three additional maintenance missions, the components of the telescope were continuously upgraded, allowing for better power usage and improved data collection. Far more than simply providing breathtaking photos of stars and galaxies from birth to death, the HST has allowed astrophysicists to understand the rate at which the universe is expanding and refine estimates of its age.

Following the last scheduled service mission in 2009, NASA officials believe “the Hubble” will continue in service until at least 2014. Set to be replaced by the James Webb Space Telescope in 2018, the HST will re-enter the atmosphere between 2019 and 2032.

Also On This Day:

1184 BCE – The fall of Troy, according to tradition

1800 – President John Adams authorizes a law appropriating $5,000 to establish the United States Library of Congress, now the largest library in the world.

1898 – The Spanish-American War begins with the US declaring war.

1918 – Three British Mark IVs and three German A7Vs comprise the world’s first tank-to-tank battle at Villers-Bretonneux, France.

1967 – Cosmonaut Vladimir Komorov becomes the first human casualty of a mission to space when the parachute on Soyuz 1 fails to open.

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