Do You Know the Other "Hubble" Telescopes?
It's a given that most people know what the Hubble Space Telescope (HST) is. The HST is a space telescope that observes visible and near-ultraviolet light for those who don't know. HST was launched in 1990 during STS-31. But did you know that HST is one of four large satellites that are telescopes and is a part of the Great Observatories program?
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| The Four Satellite Telescopes in the Great Observatroies Program |
The Great Observatories program started with the development of HST, which can be traced back to 1946 when astronomer Lyman Spitzer wrote about the advantages of an observatory outside of Earth's atmosphere (The paper was titled Astronomical advantages of an extraterrestrial observatory). From 1966 to 1972, NASA conducted the Orbiting Astronomical Observatory missions to prove that it would be beneficial to have an orbiting telescope. This is because Earth's atmosphere distorts visible light images. In 1978, Congress approved the building of a Large Space Telescope (LST). The LST was later named the HST after Edwin Hubble.
During HST development, NASA also started the gamma-ray program, which examined gamma rays above the atmosphere. In 1977, NASA announced that they had plans to build a space telescope used for gamma-ray astronomy. This led to the construction of the Compton Gamma Ray Observatory (CGRO). CGRO observed space using gamma rays. Late on in its life cycle, it extended into using hard x-rays. It was launched aboard STS-37 in 1991 and was deorbited in 2000 after a gyroscope failed.
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| HST in Orbit |
In 1976, the third telescope that was a part of the Great Observatories program was proposed to NASA. Proposed by Riccardo Giaconni and Harvey Tananbaum, the Chandra X-ray Observatory (CXO) would be an X-ray telescope. It would also be different from CGRO as the CXO would use soft X-rays. Originally, CXO was supposed to be larger, but its scale had to be sized down due to price cuts. CXO was launched in 1999 during STS-93.
The telescope in the Great Observatories program was the Spitzer Space Telescope (SST). Development on SST started in the early 1970s when astronomers considered placing an infrared telescope above Earth's atmosphere. In 1979, their idea finally came into fruition, and NASA developed a Shuttle Infrared Telescope Facility (SIRTF) for Spacelabs. I will go more in-depth about what Spacelabs is in a future blog because it's pretty interesting. After testing the first editions of infrared technologies on Spacelabs, NASA built SST and launched it in 2003 using a Delta II rocket. It was deorbited on January 30, 2020.
Because all of these telescopes were being developed during similar periods, NASA decided to place them under the Great Observatory program. The program had an enormous impact on the astronomy world. Because the telescopes observed space using different wavelengths (HST used VL and UV, CGRO used gamma rays, CXO used x-rays, SST used infrared), the telescopes were able to find many new celestial objects and confirmed old findings. For example, in 2016, the oldest visible galaxy, GN-z11 (I talked about it in a previous blog), was discovered using the HST and SST.
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| Crab Nebula Composite by HST, SST, and CXO |
NASA has also announced the Next Great Observatory Program. This program, which started work in 2016, would have four different telescopes. The telescopes would be the Habitable Exoplanet Imaging Mission (HabEx), the Large UV Optical Infrared Surveyor (LUVOIR), the Origins Space Telescope, and the Lynx X-ray Surveyor. The telescopes' finalization happened in late 2020, and the launch is estimated to be in 2035. Nonetheless, the future is bright, but we can't forget where it all started, the Great Observatories program.
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| Image of Kepler's Supernova Remanent Taked by CXO, HST, and SST |
Sources:
“Great Observatories Program.” Wikipedia, Wikimedia Foundation, 12 Oct. 2020, en.wikipedia.org/wiki/Great_Observatories_program.
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