Stardate 20020225.1209

(On Screen): The Hubble Space Telescope just keeps getting better. After a rocky start, it has turned out to be one of the finest scientific instruments ever created. For the last few years, the star of the show has been the Wide Field and Planetary Camera, version 2 (WFPC2). Images taken with it are recognizable because they look like a top view of a B2 bomber.

It is composed of four 800*800 pixel CCD elements. One of these is lensed differently than the others, so that it has four times the resolution (and therefore a quarter of the area coverage). So when they wanted to look at large objects, they would use the three Wide Field arrays, and when they needed to take a closer look at something small, they could use the Planetary camera. This was a tradeoff which was necessary because at the time no-one could make a CCD bigger than that. So the wide field arrays have a pixel size of 100 milliarcsec, and the planetary camera has a pixel size of 46 milliarcsec.

But the state of the art has improved, and bigger and better CCDs have become available. So right now Columbia is docked with the Hubble, and they are going to install a brand new imaging system called the Advanced Camera for Surveys (ACS). It has several imaging formats. In one format it will use a 4K*4K CCD to view an area of 200*200 arcsec (compared to 150*150 for WFPC2) with a resolution of 50 milliarcsec; the resulting images should be spectacular. In another mode, it will provide imaging resolution of 27 milliarcsec, to permit us to take a look at really small objects in the sky. I can't wait to see the detailed pictures of Supernova 1987A.

They're doing a number of other upgrades such as completely replacing the power system and solar cells and yet another upgrade to the gyros; it's going to be a completely new instrument before they're finished.