Tuesday, 30 December 2014

Looking to Hubble's Future and to Hubble's Successor

Artist's conception of the James Webb Space Telescope. Space Telescope Science Institute

On my recent trip to the Washington D.C. area to begin work on the history of the Hubble Space Telescope, I spent most of my time at the Goddard Space Flight Center in the Maryland suburbs of the American capital.

The control centre for Hubble is located at Goddard, and much of the development work for the space telescope was done there. Although my work is of necessity focused on Hubble's past, the engineers and scientists  at Goddard and at the Space Telescope Science Institute in Baltimore are, not surprisingly, looking to the future.

Hubble is nearing its twenty-fifth anniversary on orbit, and it has been nearly six years since the final space shuttle servicing mission upgraded its systems. Nonetheless, there is a great deal that can be done to keep Hubble operating, including changing operating procedures to minimize wear and tear on the spacecraft. The hope is to keep HST operating through the year 2020.

When Goddard staff draw up procedures designed to prolong Hubble's lifetime, they can test them on equipment that faithfully reproduces Hubble's systems. Because of Hubble's advanced age, some computer systems in these simulators resemble computers from the early days of personal computers in the 1980s.

At present, Hubble is still going strong, and with its relatively new instruments, it is delivering the best science of its career on orbit. When its systems age and force an end to its working life, a new space telescope should already be in operation.

That new instrument is the James Webb Space Telescope (JWST), which will be much larger than Hubble and operate at a much greater distance from Earth. The Webb Telescope will reside about a million miles from Earth at a point where the gravity of the Earth and the Sun balance each other out, and its mirror, which will be seven times the size of Hubble's, will operate at very low temperatures behind a gigantic sunshade.

JWST will be most sensitive to light in the infrared portion of the spectrum, which is not visible to human eyes. By concentrating on this light, the Webb Telescope will be able to peer even deeper into the history of the universe than Hubble.

The Canadian Space Agency, which was not involved in the creation of Hubble, is joining HST partners NASA and the European Space Agency in JWST. Canada is contributing a Fine Guidance Sensor that will help aim the telescope, and the Near-InfraRed Imager and Slitless Spectrograph (NIRISS), an instrument that will help Webb search for distant objects in the universe and for planets orbiting other stars. 

JWST is scheduled to be launched in 2018, and scientists hope that Hubble will still be operating at that time so that both instruments can obtain data from the same objects that can be compared, which will increase the value of the Hubble data.

The Webb Telescope is now being assembled at Goddard, and one of the highlights of my recent visit was to have a look at JWST inside its cleanroom in Building 29. Once JWST is assembled, it will undergo rigorous testing at Goddard and at the Johnson Space Center to make sure that it will be able to withstand the rigours of launch and the vacuum of space. 

JWST can be seen behind the railing along the upper centre of the photo, taken December 11 at the NASA Goddard Space Center. The silver object at left is an instrument for JWST near the end of the black booms that will hold telescope's secondary mirror. One of the golden mirror segments for the main mirror can be seen at right. Chris Gainor photo

Thursday, 18 December 2014

Visiting Two Pieces of the Hubble Space Telescope

The Hubble Space Telescope's Wide Field and Planetary Camera 2,  on display at the National Air and Space Museum. The holes in its radiator mark impact craters that were removed for study. Chris Gainor photos

My work on the history of the Hubble Space Telescope's operations in space began last week with a visit to NASA's Goddard Space Flight Center in Greenbelt, Maryland, where Hubble is controlled, NASA Headquarters in Washington, D.C., and the Space Telescope Science Institute at Johns Hopkins University in Baltimore, Maryland. There I met some of the talented people who keep HST operating who I will call on to help me tell the story of Hubble's nearly 25 years on orbit.

I also made another stop in Washington at the Smithsonian National Air and Space Museum. In my last blog entry, I included a photo from a previous visit to that museum where I stood in front of the Structural Dynamic Test Vehicle that was used as a stand-in for Hubble. Last week I returned to that spot to see two instruments that were part of the space telescope for fifteen years. 

At the heart of Hubble's history is the fact that its instruments could be changed out by astronauts who flew to the telescope aboard the space shuttle and serviced it. After those two instruments were returned to Earth, the Smithsonian put them on display next to the Hubble test article.

Both were placed on board HST in the historic first servicing mission in December 1993 that restored Hubble's eyesight after it was discovered that Hubble's main 2.4-meter mirror was defective. 

One instrument is known as COSTAR (for Corrective Optics Space Telescope Axial Replacement), which acted much like a pair of glasses in that it changed the path of light going to Hubble's instruments to correct for the main mirror's defect. Instead of lenses, COSTAR used a set of ten sophisticated mirrors to do the job. Not only did the mirrors, each of which are about the size of a dental mirror, have to be ground to the correct shape, COSTAR had to move each mirror to the right place to direct light to the correct path for each instrument.

Close-up of the pick-off mirrors from HST's COSTAR instrument, now on display at the National Air and Space Museum.

The other instrument is the Wide Field and Planetary Camera 2 or WFPC2. It too was installed on Hubble in December 1993, and this instrument took many of Hubble's most famous images of the heavens, including the Hubble Deep Field image which when released in 1996 gave us our deepest view of the universe, which took us 12 billion years back in time. 

Both COSTAR and WFPC2 were removed from Hubble and returned to Earth on the final shuttle HST servicing mission in May 2009. By then, all new instruments on Hubble carried their own corrective optics, which meant that COSTAR was no longer needed, and the spaces occupied by COSTAR and WFPC 2 were taken by more advanced and up-to-date instruments. 

On show at the Smithsonian, COSTAR looks unremarkable, rather like a metal box the size of a phone booth. COSTAR's most interesting exterior feature is found on one corner, where  one can see those small and sophisticated mirrors on mechanical arms that extended to allow the mirrors to "pick off" the light from HST's main mirror. 

WFPC2 is a different story. Shaped something like a baby grand piano, the camera includes a radiator on one side that was exposed to space throughout WFPC2's 15 years on Hubble. Today that radiator is full of holes. When the instrument was returned to Earth, its radiator was pocked with scores of craters from micrometeoroids and small pieces of space debris. Each crater area was removed from the radiator for study of the growing problem of impacts on orbiting space vehicles. 

Both these instruments have stories to tell about the Hubble Space Telescope, its development, and the environment where HST still flies. 

Hubble is supposed to be directed to a destructive re-entry over an isolated part of the Earth once its work is done. More than five years after the last shuttle servicing mission, Hubble is still going strong, so the question of how much longer it will be able to operate remains a matter of speculation. Even though much of this historic telescope will be lost after HST ends its operational career, instruments such as the two I visited at the Smithsonian will remain on display for people to see and consider.

Monday, 8 December 2014

Pursuing the History of the Hubble Space Telescope

Visiting the full-scale test article for the Hubble Space Telescope in 2006. Randy Attwood photo

In the coming spring, astronomers and many other people will be marking the twenty-fifth anniversary of the launch of the Hubble Space Telescope. 

In that quarter century, our view of the universe has been revolutionized, thanks to a large part - but not entirely - to the Hubble Telescope. Today we know that the universe is expanding at an increasing rate, much to the surprise of astronomers and physicists. These scientists are now trying to understand the reasons for that accelerating growth, suggesting that a mysterious "dark energy" is the reason.

Hubble has allowed us to measure the age of the universe more accurately than ever. Today it is believed to be 13.7 billion years old, give or take a few hundred million years. Hubble's famous Deep Field and Ultra Deep Field photos have looked back in time and picked out galaxies from the early years of the universe.

While planets orbiting other stars were first discovered in the 1990s using Earthbound telescopes, Hubble and more specialized space telescopes have provided more information about these planets, with Hubble taking the first visible light photo of such an object.

But what most non-scientists remember are Hubble's amazing photos that go from nearby planets to stellar nurseries and from exploding novae to mysterious nebulae and evolving galaxies.

In addition to these and many other discoveries, Hubble has caused major changes to NASA and more importantly, to the way astronomy is done, both by professional astronomers and even rank amateurs like me.

Hubble is revealing the stories of our universe, but the space telescope's quarter century of operations have generated their own stories. And finding and telling those stories and looking for their meaning will be my job for the next few years.

Under a contract with NASA, I will head a group producing this history and a database of documents and interviews on the history of the HST. My colleague and mentor Dr. Robert W. Smith, now at the University of Alberta, wrote the definitive history of how Hubble was conceived and built in his 1989 book, The Space Telescope: A study of NASA, science, technology and politics

My book will pick up the story on April 24, 1990, when the shuttle Discovery carried HST into orbit. Soon horrified scientists discovered that the telescope's main mirror was misshapen, but in late 1993 the first shuttle mission dedicated to repairing and updating Hubble installed equipment that corrected the defective mirror and allowed the Hubble Telescope to live up to its original promise and exceed it. 

Since then, four more teams of astronauts have visited HST and performed needed repairs. When the administrator of NASA in 2004 decided to cancel the last repair mission due to safety concerns in the wake of the 2003 Columbia shuttle disaster, an aroused public caused NASA reverse itself and fly that mission in 2009. Five years on, Hubble is still operating well, but  the end of the shuttle program in 2011 means that Hubble is now nearing the end of its own mission, since further repairs will not be possible.

Collecting and writing all that history is going to be a big challenge. The photo above showing me standing in front of the full-scale Structural Dynamic Test Vehicle for HST on display at the National Air and Space Museum in Washington, D.C., represents what I see as the dimensions of the task ahead. 

Watch this space for my adventures as I chase the history of Hubble. And, yes, I'll continue to keep an eye on other developments outside of Earth's atmosphere.

An article I wrote in 2010 on Hubble can be found here:  http://www.canadianspace.ca/2013/11/the-hubble-space-telescope-and.html