Images: Observatories at the top of the world

The Smithsonian-Taiwan isn't the only submillimeter observatory at the top of Mauna Kea. The Caltech Submillimeter Observatory is another. Instead of an array of smaller dishes, it uses one 10.4-meter diameter radio dish and has been operating since 1988. In this photograph, you can only see the very bottom curve of the dish because the door to the dome is mostly closed.

Submillimeter dishes observe wavelengths less than one millimeter (approximately 1/25th of an inch) and longer than 100 microns (1/250th of an inch). The Mauna Kea summit is an especially good place to capture that part of the radio spectrum because water vapor, which absorbs submillimeter radiation, is relatively low.