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February 27, 2008

Nasa selects 19 studies for the next space observatories


Physics professor Jacqueline Hewitt, director of MIT's Kavli Institute for Astrophysics and Space Science, stands behind a prototype of a radio telescope array.

NASA has selected a proposal by an MIT-led team to develop plans for an array of radio telescopes on the far side of the moon that would probe the earliest formation of the basic structures of the universe. The agency announced the selection and 18 others related to future observatories on Friday, Feb.15. The present plan is for a one-year study to develop a detailed plan for the telescope array, whose construction would probably not begin until sometime after the year 2025, and is expected to cost more than $1 billion.

Proposals by the 19 teams selected by NASA Feb. 15 will help guide decisions made during the Astronomy and Astrophysics Decadal Survey in 2010, led by the National Academy of Sciences to identify the most promising space observatory proposals. The 2008 NASA awards for the next-generation of astronomy missions ranged from $250,000 to $1 million each.

The New Worlds Observer got $1 million for its study. The estimated cost to design and build the New Worlds Observer mission would be roughly $3.3 billion. It is estimated that within a 2-year period the starshade could help astronomers to get a better look at upwards of 75 different planetary systems.

The Lunar Array for Radio Cosmology (LARC) project is headed by Jacqueline Hewitt, a professor of physics and director of MIT's Kavli Institute for Astrophysics and Space Science. LARC includes nine other MIT scientists as well as several from other institutions. It is planned as a huge array of hundreds of telescope modules designed to pick up very-low-frequency radio emissions. The array will cover an area of up to two square kilometers; the modules would be moved into place on the lunar surface by automated vehicles.


Observations of the cosmic Dark Ages are impossible to make from Earth, Hewitt explains, because of two major sources of interference that obscure these faint low-frequency radio emissions. One is the Earth's ionosphere, a high-altitude layer of electrically charged gas. The other is all of Earth's radio and television transmissions, which produce background interference everywhere on the Earth's surface.

The only place that is totally shielded from both kinds of interference is the far side of the moon, which always faces away from the Earth and therefore is never exposed to terrestrial radio transmissions.

Besides being the top priority scientifically for a telescope on the moon, this low-frequency radio telescope array will also be one of the easiest to build, Hewitt says. That's because the long wavelengths of the radio waves it will detect don't require particularly accurate placement and alignment of the individual components. In addition, it doesn't matter if a few of the hundreds of antennas fail, and their performance would not be affected by the ever-present lunar dust.

The new lunar telescopes would add greatly to the capabilities of a low-frequency radio telescope array now under construction in Western Australia, one of the most radio-quiet areas on Earth. This array, which also involves MIT researchers, will be limited to the upper reaches of the low-frequency radio spectrum, and thus will only be able to penetrate into a portion of the cosmic Dark Ages.

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