Monday, 11 May 2015

The Hubble Space Telescope at 25

NASA Administrator Charles Bolden - who as an astronaut was on the crew that carried the Hubble Space Telescope into orbit in April 1990 - presides over a NASA awards ceremony honouring the people of HST at the National Air & Space Museum, Washington, on April 24, 2015. Chris Gainor photo

I have been on an extended research trip in the United States gathering information for a book on the history of the Hubble Space Telescope since its launch 25 years ago.

The trip began with the celebrations in April in Washington, D.C., and Baltimore, Maryland, marking the anniversary of Hubble's launch on board the shuttle Discovery. During those celebrations, many good things were said about how Hubble overcame its early problems and delivered a trove of knowledge that has upended our view of the universe we live in. 

There is very little I can add to those statements, except to point out the exceptional nature of Hubble's quarter century of service. A handful of space vehicles have lasted longer than Hubble, most famously the Voyager spacecraft that flew by the outer planets of our solar system in the 1970s and 1980s and now are sending back data from the fringes of the solar system, including the famous image of Earth as a pale blue dot almost lost in the glare of the Sun. Other spacecraft have like Hubble also been serviced by astronauts.

But no spacecraft has come close to Hubble in terms of being so transformed during its lifetime of service. After Hubble was launched in 1990, five teams of shuttle astronauts repaired aging equipment on the space telescope and changed out instruments so that the instruments in use today - some installed during the most recent shuttle servicing mission in 2009 - are vastly more powerful than Hubble's original set of instruments.

Since the end of the anniversary celebrations, I have been searching archives for documents and interviewing the people who have worked on Hubble. 

One perceptive comment that has stood out in my mind from this research trip comes from Frank Cepollina - the Goddard Space Flight Center engineer whose brilliant team created the equipment that the shuttle astronauts used to service Hubble and other satellites. "Hubble isn't great because it's serviceable," Cepollina said. "It's great because you can apply Moore's Law every three or four years."

Moore's Law refers to the spectacular growth in computing power predicted by a founder of the computer chip maker Intel fifty years ago. Hubble instruments use computing power and particularly CCDs, charge-coupled devices that have replaced film for gathering images and other light-generated data. The CCDs on board Hubble today are vastly more powerful than the originals from the late 1980s, thanks the explosive enhancements in the power of transistors and computer chips, including CCDs.

Of course, Cepollina's statement will no longer apply, because no further servicing missions are in prospect for Hubble now that the shuttle has been grounded. But some like Cepollina are still working for the day when the new generation of crewed spacecraft being developed in the U.S. can pick up where the shuttle left off in terms of servicing and repairing satellites.

In the meantime, Hubble continues its work of imaging the universe and analyzing the light that comes from it. Astronomers still have to winnow down the requests for observing time, and new uses for Hubble are still coming from astronomers from around the world.

Much of what was said at the anniversary celebrations were things we have already heard before. Perhaps the most important but least publicized words came at a symposium held that week at the Space Telescope Science Institute in Baltimore. There scientists young and old from many countries discussed what Hubble has taught them and expressed their hopes about the knowledge that could emanate from the space telescope in the coming years. 

As a non-scientist, a lot of what was said was beyond my understanding. But some of the astronomers there assured me that they didn't understand everything either. It will be interesting to see what comes out of that symposium as new ideas to probe the universe turn into new data.

Sadly, these expressions of the brilliance humans are sometimes capable of were overshadowed a few days later when riots and protests took place in Baltimore just a few miles away from the Space Telescope Science Institute, a sharp reminder that humanity still has a great deal to work on in terms of improving life on Earth.