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Why Four Mirrors?


Why are you going with four small mirrors instead of one larger telescope?

It is much quicker and cheaper to design and build several small optical systems than one large one with the same collecting area. There is also much less technological risk. The downside to using four mirrors is that we need four cameras and a lot more computing power. But the cost of electronic chips and of computers is dropping so rapidly that the multi-system approach is far more economical.

Will the four mirrors always be pointing in the same direction?

Usually, yes. With four images of the same region of sky we can not only collect more light, but can eliminate flaws that occur in a single image due to cosmic rays, bad pixels, and gaps between adjacent CCD chips. However, we also have the option of using different filters in each telescope and measuring four colors simultaneously for certain kinds of studies. Depending on how the mirrors are mounted we may also be able to point them in four different directions, if we need to make a particularly rapid survey.

Will the four mirrors be used as an interferometer?

There are no plans to connect the four optical systems as an interferometer.

Will the four optical systems be built at the same time?

The first telescope, called PS1, has been built as a self-contained prototype instrument. It is used to test hardware and software for the completed instrument, and to set up a grid of astrometric and photometric standards. It is also undertaking an extensive program of scientific observations for the Pan-STARRS Scientific Consortium

Can Pan-STARRS be built with today's technology?

Yes. All of the basic technology is already known. The telescope designs are fairly standard. The CCD focal plane cameras will employ Orthogonal Transfer CCDs (OTCCDs) that have been developed at Lincoln Laboratory and tested at the UH 2.2-meter telescope on Mauna Kea. The computer-processing pipeline is scalable from systems used to analyze data from the current generation of imaging CCD mosaics such as the 12K and MegaCam CCD arrays on the Canada-France-Hawaii telescope. Pan-STARRS will integrate these various components into a finely tuned data gathering, processing, and analysis system.


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