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Following the final visit to Hubble…


In just over a week’s time, the space shuttle Atlantis (pictured above, on the launch pad) will blast off from the Kennedy Space Centre at the start of what many space enthusiasts and space commentators believe will be the most important and highest profile shuttle mission for many years – Mission STS125, the fourth, and final, mission to service the famous Hubble Space Telescope.

This is a mission many people thought would never happen. In the afternath of the loss of the shuttle Columbia many voices were raised against another visit to Hubble because it is so risky for the crew. Why is it so risky? Well, post-Columbia the shuttle became essentially a space taxi, ferrying people and payloads up to and back from the space station, and that was deemed “safe” (or “safer”) because if anything went wrong with the shuttle during lift off at least it could dock with the ISS and its crew could stay there until a rescue mission could be organised. But Hubble is way, way away from ISS, much higher, and so any shuttle going up to it is well and truly on its own up there, and has no chance of docking with the “safe haven” space station. It was therefore suggested that Hubble would not be serviced for a fourth time, but be allowed to fail bit by bit and then burn up in the atmosphere at the end of its lifetime, possibly after a special “de-orbiting” braking engine had been fitted by a robot spacecraft.

However, NASA hadn’t counted on Hubble’s popularity with the public and the scientific community. There was a backlash against NASA’s apparent lack of support for the telescope, and eventually NASA was talked around to the idea of visiting it one last time, and gave the go-ahead for STS 125 – as long as another shuttle was on the pad at the same time and ready to go up and retrieve the crew of Atlantis if anything went wrong. That’s why there are two shuttles on the pads at KSC right now – one is on standby to set-off on a rescue mission.

Blast off is now scheduled for May 11th, and Atlantis’ 7 astronaut crew have a tough job ahead of them once they reach the observatory. During a series of daring – and not risk-free – spacewalks, the crew will replace failed instruments, upgrade others and basically give the telescope a new lease of life. If they succeed in all their tasks, Hubble should be in good enough shape to keep working for another 5, maybe even another 10 years.

Hubble is famous, of course, for the magnificent images it has taken, images that have been as popular with the newspaper- and magazine reading and internet-surfing public as they have been with the scientists who work on them for a living. Images like this…


… the “Pillars of Creation”, have been seen by countless millions of people as they have entered popular culture, and have been used in music videos, in sci-fi films and TV series, and even on posters and t-shirts. But Hubble is more than just a fancy camera; it has genuinely revolutionised our view of the universe in many ways. By studying stars and galaxies, black holes and quasars, and many other exotic objects it has peered back in time to the days when the universe was young, and still shaking after the violence and drama of the Big Bang, and it has shown us the future by taking images like this, of stars like our Sun that are further along their lives, and dying…


It’s no exaggeration to say that the eyes of the world will be on this mission. In fact, I think this will be the most closely-followed shuttle mission ever. Public interest in space exploration is, inevitably, growing as the internet grows, and even the slowest modern broadband connections are now good enough to allow people to watch NASA TV without too many interruptions. So although every shuttle launch, spacewalk and landing over the past couple of years have been watched by a dedicated hardcore band of space enthusiasts, this mission will almost certainly be followed on NASA TV by many, many more people than any other. And they’re in for a treat, because this mission is going to be almost breathlessly busy.

What exactly is going to happen up there? Well, rather than clumsily paraphrase what NASA is saying about the mission, here’s the rundown on STS 125’s objectives, straight from NASA’s own website.

The first objective is to extend Hubble’s operational life by at least five years. Over a series of five spacewalks, astronauts will replace all six gyroscopes, install new batteries, and exchange a degraded Fine Guidance Sensor with a new one. They will also install replacement thermal insulation on critical component bays of the telescope, and attach a mechanism that will aid in Hubble’s final de-orbiting.

The second objective is to enhance Hubble’s scientific power. Astronauts will install two new instruments, the Wide Field Camera 3 (WFC3) and the Cosmic Origins Spectrograph (COS). WFC3, which sees in visible, infrared and ultraviolet light, will improve Hubble’s sensitivity 10-30 times because of improvements in technology and design that have occurred since the last instruments were installed.

COS, Hubble’s new spectrograph, will improve Hubble’s sensitivity at least 10 times. Spectrographs are instruments that break light into its component colors, revealing information about the object emitting the light. COS sees ultraviolet light, which is particularly important because most of the ultraviolet light from space is absorbed by the Earth’s atmosphere, making ground-based telescope observations impossible.

The third objective is to repair Hubble’s out-of-commission instruments, the Space Telescope Imaging Spectrograph (STIS) and the Advanced Camera for Surveys (ACS). STIS stopped working in 2004 and ACS failed in 2007.

ACS is Hubble’s most prominent camera. Its wide field of view and ability to see in wavelengths from ultraviolet to visible light allows it to conduct broad surveys of the universe, study the nature and distribution of galaxies, and examine some of the universe’s earliest activity. ACS was responsible for the Hubble Ultra Deep Field Image, NASA’s deepest view of the cosmos.

STIS is a spectrograph. It separates light into its component colors, allowing scientists to examine the object’s temperature, chemical composition, density and motion. STIS can see in ultraviolet, visible and near-infrared and has been used to examine black holes, quasars and planets.

Now, all those activities will be carried out during spacewalks, or “EVAs” to give them their proper title. Each of those spacewalks will be covered live on NASA TV, so we’ll be able to sit here at our computers and see amazing scenes like these on our monitors…


Which will be great to watch, but I’m personally looking forward to the still photographs that will be taken during the spacewalks. On the three previous servicing missions to Hubble, images like these have been sent back for us to drool over…


If you want to follow the mission on NASA TV, here’s a link…


But the images I’m personally looking forward to most of all are the ones taken by the astronauts themselves, with cameras, as they pause during their spacewalks to record what they’re doing, and seeing, so high above the Earth. On previous servicing missions, images like these have been sent back for us to drool over…




But as thrilling and as beautiful as the images taken during this mission will be, the world has moved on, and people are no longer content to just watch a few minutes of NASA TV and read a brief report and see a few pictures on NASA’s website. Now millions of people follow space missions on Facebook and Twitter, devouring every piece of information no matter how small.

Unless you’ve been living on Enceladus for the past year you’ll be aware that Twitter has basically taken over the world, and this mission will be “Twittered” mercilessly, by anyone and everyone involved in the mission: journalists at the space centre, flight controllers in Mission Control, and even one of the shuttle crew will be clickety-clacking away at their keyboards during the mission, making sure everyone out here in the “Tweetverse” is kept fully informed about what’s going on. Here are the Twitter sites I’d recommendyou follow during STS 125…

http://twitter.com/Astro_Mike (Tweets from one of Atlantis’ crew!)

http://twitter.com/sts125 (official mission Twitter site)

http://twitter.com/HubblePAO (Twitters from the Hubble people)

http://twitter.com/SSAtlantis (Tweets “written by” Atlantis herself!)

http://twitter.com/absolutspacegrl (Twitter site of one of the Flight Controllers at JSC)


This has not happened before, so it’ll be interesting to see how it goes. There’s a real danger of “Information Overload” during STS 125! 🙂

NASA itself is making great efforts to increase public awareness of, and participation it, its missions, to the point where they’re now producing special “posters” for each mission. Some people think they’re cheesy and too melodramatic, but of course I love them for those very reasons. Here’s the STS 125 poster…


Anyway… here we are… a week and a bit to go. I’m very excited by this mission, because Hubble is very dear to me. I’ve followed it faithfully from launch, through the “troubles” with and fix of its slightly-the-wrong-shape mirror (when it was cruelly but memorably called “A giant squint for Mankind”… ouch!) and every development since. If this mission fails and the Hubble can’t be serviced for some reason, well, at least they tried instead of just abandoning it, and Hubble will have already done more than enough to justify its cost. But if the mission succeeds, then Hubble will be rejuvenated and revitalised, and when they set it free again the crew of Atlantis will, arguably, be leaving behind a brand new telescope, with capabilities far exceding those of the telescope that was launched in 1990…

All we can do now is wait. But a week isn’t too long to wait, is it..?


Update: Thanks to Cumbrian Sky reader E Davies for pointing out that the main problem with a damaged shuttle reaching the ISS isn’t actually the difference in altitude . He correctly points out:

“The problem with getting to the ISS from the Hubble is not much to do with height but much more a matter of the differences in their orbital planes.  The orbit of the ISS is at quite a steep angle to the equator (about 51°, the latitude of Baikonur) whereas the Hubble’s is only around 22° (IIRC, about the latitude of KSC, I think). 

It takes a lot of energy to change orbital planes: imagine two spacecraft both travelling at about 25 000 km/h passing near each other at one of the points where the planes intersect.  With the angles I gave above they’d be moving on paths at least 29° apart (possibly more depending on the orientations of the orbits) so pretty quickly relative to each other (I make it 12 519 km/h relative velocity).  To change from one orbit to another would mean accelerating by that much.  This is a huge change of speed: about half what was gained in the launch in the first place and way out of the range available to, for example, the Shuttle’s OMS.”

Carnival of Space #101

… is now online over at writer David S.F. Portree’s fascinating “Robot Explorers” blog. So, if you want to catch up on the best of last week’s space blogging, click here  and go take a look…