This week, the Space Shuttle Atlantis will return to the Hubble Space Telescope for a fifth and final time. The mission will bring the telescope new instruments, batteries, and gyroscopes that will extend its lifetime for hopefully several years or more.
This year marks the 10th anniversary that the Shuttle launched and deployed Chandra . There haven't been any visits since and none will ever take place. That's because Chandra was designed to be different than Hubble -- in more ways than just the type of radiation it detects.
Although early plans for AXAF (Chandra's old name before launch) called for servicing trips to the telescopes ala Hubble, a redesign and restructuring of the program in the early 1990s changed that. Instead, Chandra was given a highly elliptical orbit that takes it almost a third of the way to the Moon. Even at its closest approach to Earth, Chandra is still nearly 10,000 miles away and far beyond the reach of the Shuttle. (By contrast, the astronauts going to Hubble are only about 350 miles above the planet's surface.)
So, while there are probably times that we'd like to go up and visit Chandra, we're very happy with our path through space. After all, our wide-swinging trajectory gives us up to 55 hours of uninterrupted observations as we avoid the Van Allen belts about 85% of the time. This means we get more observations than if we were in a low-Earth orbit like Hubble.
But for those astronauts and everyone else involved with this Hubble Shuttle mission, we wish you the best of luck. We look forward to getting Hubble back up to full health so we can continue to explore the Universe together.
-Megan Watzke, CXC