Metal in the Meadow

Despite the beautiful landscape and the shining dishes of the millimeter-wave radio telescope at Hat Creek, the scene is rather unremarkable – a drilling rig in a sage-covered field. It could be drilling a new water-well for the local rancher or an exploratory oil well for a transnational company. In fact, the rig’s rhythmic pounding and the rising plume of dust signify the first moments of construction of the Allen Telescope Array.

Arecibo Telescope
Arecibo. World’s largest dish, radio telescope. Puerto Rico.

The Allen Telescope Array will consist of 350 individual 20-foot antennas linked to form the equivalent of a single large antenna. When fully operational in 2005, the Allen Telescope Array will have more collecting area than the newly completed Green Bank Telescope in West Virginia, and better resolution than the venerable Arecibo dish in Puerto Rico that has been so important to the SETI Institute.

This innovative new telescope – a joint project between the SETI Institute and the University of California Berkeley’s Radio Astronomy Lab (RAL) – is funded through prototype construction by visionary philanthropists Paul G. Allen and Nathan P. Myhrvold.

The Allen Telescope Array will be the "new kid in town" at the Hat Creek Radio Observatory in northern California, where the University of California currently operates an array called BIMA (Berkeley-Illinois-Maryland Array) that observes at millimeter-wavelengths. Because BIMA will perform better at a higher elevation site, it will migrate south in the next few years to mate with an array operated by Caltech, leaving the Allen Telescope Array alone in the lava and sage-covered valley just north of Mount Lassen National Park.

Allen Telescope Array
Allen Telescope Array (ATA)

The development of the Allen Telescope Array is marked by many innovations crafted with the express purpose of building a world-class state-of-the-art astronomical facility at a fraction of the price of existing radio telescopes.

Some examples of these innovations are:


  • the gangly offset Gregorian optics;
  • the ultra-precise 20-foot primary antenna surface, made by a novel process that rapidly forms a single flat piece of aluminum into the required shape;
  • an intriguing wide-band microwave "feed" and receiver, that collects all of the energy transported via radio waves from the far reaches of the universe so they may be amplified and examined by scientists;
  • miniature refrigerators (housed inside the feed itself) that use sound waves to chill down the amplifiers to -315 °F, preventing the thermal rattling of the electrons in the wires from adding its local roar to the quiet whisper of the received distant signal;
  • analog fiber-optic links that allow us to cheaply bring back the entire band of frequencies at which we can operate for processing, allowing different astronomers to examine the universe at separate frequencies simultaneously.


    The doppler effect
    Earth as seen by the departing Voyager spacecraft: a tiny, pale blue dot.
    Credit: NASA

    Although the physical structure of the Allen Telescope Array is dominated by the "metal in the meadow" described above, what truly makes it distinctive is that it will be one of the first digital radio telescopes to allow astronomers to look at completely different frequencies at the same time, and to observe completely different parts of the sky concurrently. This means that the Allen Telescope Array is not just one instrument, but in effect, many.

    The capability allowed by this flexibility makes the partnership between the SETI Institute and the Radio Astronomy Lab particularly beneficial; while the RAL embarks on its ambitious observing programs of astronomical sources, the SETI Institute will concurrently use the full extent of the array to search our galactic neighborhood for that quiet tone with its thunderous implications.

    The Allen Telescope Array allows everyone to not only get their cake and eat it too, but also to pick out their favorite flavors and toppings as well. In fact, each person gets the whole cake and not just a small, unsatisfying sliver. And finding the distant whine from a galactic neighbor would certainly be a very nice cherry on top.

    Related Web Pages

    Hipparcos Catalog
    Allen Telescope Array Capabilities
    The Astrophysical Journal (March 2003, v. 145,pp. 181-198): "Target Selection for SETI: I. A Catalog of Nearby Habitable Stellar Systems" (PDF)
    SETI Institute
    How To Find An Extrasolar Planet
    SIM (NASA’s Space Interferometry Mission
    GAIA – The Galactic Census Project
    FAME: Full-sky Astrometric Mapping Explorer
    Extrasolar Giant Planet Detection with Next Generation Instruments (M. Turnbull, et al)
    SETI Institute