100000 Orbits
Published on Aug 11, 2008 at 9:30 am.
1 Comment.
Filed under space telescopes.
As I start to write this, the orbit counter on Hubble Space Telescope’s HubbleSite reads 100001. That means that the Hubble has traveled 2.72 billion miles in the last 18 years that its been in orbit. Of course, it didn’t really go very far. It is only a few hundred kilometers above Earth’s surface at all times. From going around giving public talks and from talking with my students, I realize that a lot of people are quite uninformed about how Hubble gets its fantastic images. I find that a lot of people seem to think that it flies around to different planets, nebulae, galaxies, etc, and photographs them. That would be nice, but that isn’t what it does. In fact, its 2.72 billion miles traveled wouldn’t even get it to Neptune. Rather, the amazing images come from the fact that the Hubble doesn’t have to look through Earth’s atmosphere. Looking through the atmosphere both blurs the image, and attenuates certain wavelengths of light. Outside of Earth’s atmosphere, certain wavelengths of light can be observed that are difficult or impossible to observe on the ground. In fact, Hubble can see a wide range of wavelengths of light well in excess of what humans can see. Of course, astronomers want to be able to study objects in these kinds of light, so what we often do is to display those wavelengths as certain colors in an image. Naturally, if the object already has light of those colors, then you’d want to display those colors as some other color, and so forth. The end result is an image that has far more detail and color than the original object would appear if you could see it in visual light, no matter how good of a telescope that you were using. The Hubble team uses a color palette that is not commonly used by other astronomers. The end result is an image that has a lot of scientific information (what astronomers want) and looks beautiful (what the public generally wants). An example of such an image is the star forming region in star cluster NCG 2074 seen below. This image was taken yesterday and released as part of the announcement of Hubble’s completion of 100000 orbits around Earth.
The Hubble telescope is alive, but not doing well right now. It is getting old, and many components are past their useful lives. Also, the telescope was designed to be serviced every 3 years during a Space Shuttle mission. The last servicing mission was in March, 2002, over six years ago. Several instruments have failed, along with some of the gyroscopes that keep the telescope pointed where it needs to point. Also, it is gradually spiraling back to Earth. Without another Space Shuttle mission to boost it to higher orbit, it will reenter the Earth’s atmosphere on its own sometime after about 2010. However, NASA has plans for one final servicing mission, STS-125, due to launch in a couple of months. They have a lot to do. It won’t be possible for them to replace everything on Hubble that really ought to be replaced. That would take two servicing missions. But, they’ll get most of it, and they’ll boost Hubble to as high of an orbit as they can. That will give us some time until the final goodbye to this instrument that has become one of NASA’s best success stories. Pretty much everyone has heard of the Hubble Space Telescope and knows of at least some of what it has done. I would image that it is by far NASA’s most popular mission right now among the general public. And, during its 18 years on the job, it has become one of astronomers’ most useful tools.
-Astroprof
Images courtesy NASA, STScI
sea_dot on August 12, 2008 at 11:48 am: 1
God bless the HST! The images it has taken have been my biggest art influences (and also my evidence that even real-life can be visually “abstract”).