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Hunting Hubble - how to spot the space telescope

David Dickinson, Correspondent
Apr 8, 2015, 0:33 UTC

Sen—The Hubble Space Telescope was launched 25 years ago this month on April 24, 1990, aboard space shuttle Discovery on mission STS-31.

While lots has already been written about the history and the legacy of Hubble, you may not realize that if you live between latitudes 40° north and 40° south—which includes regions from the central U.S. and southern Europe southward—that you can possibly see the Hubble Space Telescope from your backyard tonight. 

The tale of the Hubble Space Telescope is a modern story of astronomical tragedy turned triumph. Plagued with defective optics that were discovered only after the telescope was placed in orbit, the first repair mission to Hubble in 1993 gave it a new vision on the Universe.

Since that time, Hubble has produced some of the most iconic images of the Space Age, which have appeared everywhere in pop culture from Star Trek: Voyager to The Big Bang Theory.

Hubble is the very epitome of modern astronomy, and the research generated by this 2.4 metre Ritchey-Chrétien reflector orbiting the Earth has no less than minted a whole new generation of astronomy PhDs.

Shuttle mission STS-125 was the 5th and final repair mission to Hubble in 2009, and Hubble has exceeded all expectations to become the most well-known space telescope in history.  

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A replica of the Hubble Space Telescope on display at the Kennedy Space Center. Image credit: David Dickinson  

Hubble orbits the Earth once every 95 minutes in a 28.5° inclination orbit, and typically shines at magnitude +1—as bright as the star Spica—when straight overhead. It can also flare in a fashion similar to the Iridium constellation of satellites up to magnitude -2—almost as bright as the International Space Station—when it passes above 70° elevation. This also means that Hubble is visible over a wide swath of the Earth, from Washington D.C. and Madrid Spain, to as far south as Buenos Aires and Sydney, Australia. 

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The region from which the Hubble Space Telescope is observable. Image credit: Orbitron

The Heavens-Above web site gives passage times for the Hubble Space Telescope, and the multitude of satellite tracking applications available today also give passage predictions for Hubble along with the ISS.

To successfully see Hubble—or any satellite—from your backyard, you only need a working set of ‘Mark-1 eyeballs’ and four pieces of information: The satellite’s direction at its highest, its elevation, the key time for the pass, and its brightness. If a satellite is too low (say less than 20°) above the horizon, you’ll be looking through a much denser cross-section of the atmosphere, known as air mass.

All satellites including Hubble shine due to sunlight glinting off of their surface. This means that the pre-dawn and post-dusk hours are key satellite hunting times. Hubble frequents the skies over my home in central Florida, which shares a latitude equal to its orbital inclination. That’s not a coincidence, as Hubble departed the Earth from the Kennedy Space Center located on the Florida Space Coast.

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A pass of the Hubble Space Telescope over central Florida. Image credit: David Dickinson

What’s the history and fate of the Hubble? Well, the end of the shuttle era in 2011 has put the space telescope beyond reach for further repair. There have been ideas for robotic repair missions that would also attach a final de-orbit capability to the Space Telescope. NASA placed its Soft Capture and Rendezvous System on the telescope for just such a contingency during the STS-125 mission, but this concept has thus far never moved past the proposal stage. 

More than likely, Hubble will, like so many missions, survive only as long as its batteries, navigation systems and gyroscopes function. Hopefully, Hubble will operate into the early 2020s.

The James Webb Space Telescope, a primarily infrared telescope which is often touted as ‘the successor to Hubble,’ launches in 2018. But unlike Hubble, the JWST will be placed at the Sun-Earth L2 Lagrange point beyond the orbit of Earth’s Moon. This also means that JWST is out of reach of any possible repair mission, and has to work properly the first time!  

Seeing the Hubble Space Telescope pass overhead is an inspiring sight. Be sure to catch this icon of modern astronomy crossing a sky near you.