Conceptual designs for a "realistic interstellar explorer," or RISE - a highly autonomous craft that would travel far beyond this solar system to collect scientific data - call for a laser-based communications link to Earth that relies in part on a recent NIST invention called a Parallel Cantilever Bi-axial Micro-Positioner.

The prototype NIST device acts as a mechanical filter that generates very straight lines by screening out all other motions. Primarily intended for use in the delicate assembly and alignment of optoelectronic devices and applications in micro- and nano-manufacturing, the micro-positioner in a different application offers a promising means for meeting the demanding range, mass and power requirements for the RISE.

In its interstellar role, the micro-positioner would be used to position a lens that steers a laser beam communication link toward Earth. The beam must be pointed precisely because the distances would be, well, astronomical. The RISE is envisioned as having a range up to 1,000 Astronomical Units (AU) - 1,000 times the distance from the Earth to the sun, or 93 billion miles.

A recent paper by researchers at NIST and Johns Hopkins University Applied Physics Laboratory (which is designing the RISE) concluded that an optical communications downlink spanning 1,000 AU is technically feasible in the next decade if these new technologies can be sufficiently refined. For example, the current range of the NIST micro-positioner would have to be improved by a factor of nearly 10.

NIST Helping Prepare An 'out Of This World' Atomic Clock
Meanwhile, setting the world's clocks from a timepiece far above the Earth someday may be the norm if the National Institute of Standards and Technology (NIST)-led program to put an atomic clock aboard the International Space Station (ISS) proves successful. This effort is part of the NASA-funded Primary Atomic Reference Clock in Space (PARCS) mission, scheduled to fly on the ISS in early 2006.

PARCS will be used to test gravitational theory, study laser-cooled atoms in microgravity and explore ways to improve the accuracy of timekeeping on Earth.

Atoms in microgravity can be slowed to speeds significantly below those used in atomic clocks on Earth, providing a predicted 10-fold improvement in clock accuracy. (The current U.S. standard, the NIST-F1 clock, is accurate to within one second in 30 million years.)

The PARCS space clock will be compared continuously to the hydrogen maser, a fundmentally different clock, to provide a test of an Einstein theory that predicts that two different kinds of clocks in the same environment will keep the same time.

To measure gravitational frequency shift, comparisons will be made between the space clock and a clock on Earth. Signals conveyed to the ground from such space clocks someday might serve as an international time standard available to anyone around the world.

PARCS is a cooperative effort involving NASA's Jet Propulsion Laboratory (JPL), NIST, Harvard-Smithsonian Center for Astrophysics, the University of Colorado at Boulder, and the University of Torino in Italy. JPL is leading the actual development of the space package.

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