Fwd: NASA Spacecraft to Hunt for Elusive Gravity Ripples
It's always nice to see that, in a world where Feng Shui asian geomancy is treated like
a legitimate form of consultation, there is still real science happening. Gravity waves!
How cool is that?
--- JPLNews@jpl.nasa.gov wrote:
> Date: Tue, 20 Nov 2001 14:16:35 -0800 (PST)
> From: JPLNews@jpl.nasa.gov
> Subject: NASA Spacecraft to Hunt for Elusive Gravity Ripples
> Reply-to: news-owner@www.jpl.nasa.gov
> To: undisclosed-recipients:;
>
> MEDIA RELATIONS OFFICE
> JET PROPULSION LABORATORY
> CALIFORNIA INSTITUTE OF TECHNOLOGY
> NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
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> http://www.jpl.nasa.gov
>
> Contact: Guy Webster (818) 354-6278
>
> FOR IMMEDIATE RELEASE November 20,
> 2001
>
> NASA SPACECRAFT TO HUNT FOR ELUSIVE GRAVITY RIPPLES
>
> Barely perceptible fluctuations in the speed of a distant
> NASA spacecraft coasting away from Earth could provide
> science's first direct detection of gravitational waves, a
> basic feature of how the universe behaves.
>
> A 40-day search beginning Nov. 26 will use the Cassini
> spacecraft and specially upgraded ground facilities of NASA's
> Deep Space Network. "We've tried this before with other
> spacecraft, but this time we have new instrumentation on the
> spacecraft and on the ground that gives us 10 times the
> sensitivity," said astronomer Dr. John Armstrong of NASA's Jet
> Propulsion Laboratory, Pasadena, Calif. "We're able to measure
> the relative velocity between Earth and Cassini with exquisite
> accuracy."
>
> Cassini's speed relative to Earth will vary during the 40
> days, but will typically be about what it would take to zip
> from New York to Chicago in five minutes. In contrast, this
> experiment could detect any change in speed so small it would
> lengthen or shorten that trip by a mere fraction of a second.
>
> Gravitational waves are ripples in the fabric of space
> and time that are set off by accelerations of massive bodies,
> such as black holes or supernovas. Albert Einstein theorized
> they exist, and indirect evidence confirmed his prediction in
> the 1970s.
>
> "Gravitational waves are at the frontier of astrophysics.
> There's no question they exist, but they have not yet been
> detected directly," said Armstrong, leader of an international
> team that has been preparing for years to conduct this search.
>
> "Gravity waves can give us another window into the
> universe, the way Galileo's telescope did in the 17th century
> and radio telescopes did in the 1940s," said JPL's Randy
> Herrera, lead operations engineer. The ability to detect
> gravitational waves could lead to their use as a way to study
> black holes and other massive phenomena, he added.
>
> Cassini is in a quiet cruise phase of its mission, 11
> months past Jupiter but still more than 30 months from its
> destination at Saturn. The researchers will use radio
> transmissions between Cassini and Earth to search for
> gravitational waves measurably warping space between the two.
> The transmissions reveal velocity changes by the Doppler
> effect, the same phenomenon that raises the pitch of an
> approaching train's whistle or lengthens the light waves from
> a receding galaxy. If gravitational waves within a particular
> range of long wavelengths are passing through our solar
> system, they will alternately stretch and compact space in a
> way that would rhythmically affect the Earth-to-Cassini
> distance.
>
> Italian scientists Dr. Bruno Bertotti of the University
> of Pavia and Dr. Luciano Iess of the University of Rome are
> co-leaders of the experiment. Italy's national space agency,
> Agenzia Spaziale Italiana, provided crucial equipment aboard
> Cassini enabling the gravitational-wave experiment to use
> higher-frequency radio transmissions than have been used in
> earlier gravitational-wave searches with Galileo, Mars
> Observer, Ulysses and Mars Global Surveyor spacecraft. The
> higher frequency suppresses noise from the solar wind,
> allowing more precise measurements of velocity changes.
>
> JPL engineers have carefully instrumented a large dish
> antenna at the Deep Space Network's Goldstone complex near
> Barstow, Calif., to send and receive the higher frequencies
> with unprecedented Doppler sensitivity. The upgrade includes
> refined pointing capability needed to exploit the higher
> frequencies, said Sami Asmar, supervisor of JPL's Radio
> Science Group. Other new equipment at Goldstone will allow
> researchers to correct for the atmosphere's distortion of
> radio transmissions and improve performance of the search.
>
> The experiment will use links at lower radio frequencies
> between Cassini and Deep Space Network antennas near Madrid,
> Spain, and Canberra, Australia. This will enable around-the-
> clock observations. Taking data with independent equipment at
> three sites will help discriminate subtle instrumental effects
> from signals that might be gravitational waves.
>
> The scientific importance of detecting gravitational
> waves has also prompted ground-based projects, most notably
> the highly sensitive Laser Interferometer Gravitational Wave
> Observatory, coordinated by the California Institute of
> Technology, Pasadena, and Massachusetts Institute of
> Technology, Cambridge. The two approaches complement each
> other because the Cassini experiment is sensitive to million-
> fold longer wavelengths of gravitational waves than the
> ground-based laser interferometers are, Armstrong said.
>
> The Cassini experiment is timed so that Earth is on a
> line between the Sun and the spacecraft, minimizing noises on
> the radio link. Measurements taken during the 40 days will
> take several months to analyze. The experiment will be
> repeated twice more in the next two years when the
> spacecraft's position will make the measurements sensitive to
> gravitational waves from different directions in the sky.
>
> Information about the Cassini-Huygens mission is
> available online at http://www.jpl.nasa.gov/cassini .
> Cassini, launched in 1997, will begin orbiting Saturn on July
> 1, 2004, and drop its piggybacked Huygens probe onto the haze-
> wrapped moon Titan about six months later. The mission is a
> collaboration of NASA, the European Space Agency and the
> Agenzia Spaziale Italiana. JPL, a division of Caltech,
> manages the Cassini program for NASA's Office of Space
> Science, Washington, D.C.
>
> # # # # #
>
> NOTE TO BROADCASTERS: A video file with a new animation
> portraying gravitational waves will air on Nov. 20 and 21 at
> noon, 3 p.m., 6 p.m., 9 p.m. EST. NASA Television is
> available at GE-2, Transponder 9C at 85 degrees West
> longitude, with vertical polarization. Frequency is on 3880.0
> megahertz with audio on 6.8 megahertz.
>
> 11/20/01 GW
> #2001-227
>
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=====
Mark Morgan: mark_morgan@yahoo.com
http://www.VoicesOfUnreason.com "obeisances before the written word"
CS Lewis: "We read to know we're not alone."
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