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Posts Tagged ‘GPS

Can GPS find variations in Planck’s constant?

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Read more: physicsworld.com/cws/article/news/49135

Artist's impression of a GPS satellite (Courtesy: NASA).

Global Positioning System Test of the Local Position Invariance of Planck’s Constant
J. Kentosh and M. Mohageg
Phys. Rev. Lett. 108, 110801 (2012)
Published March 15, 2012

Pinpointing Planck’s Constant with GPS
GPS is helping drivers find their way and parents track their kids and pets. But now a pair of researchers—reporting in Physical Review Letters—has used the same technology to put new limits on variations in Planck’s constant.

Certain theories allow physical constants, such as the speed of light or the gravitational constant, to vary, and some astronomical observations have been interpreted as suggesting the electromagnetic coupling was different in the past. Testing these hypotheses often requires sophisticated instruments. But James Kentosh and Makan Mohageg of California State University, Northridge, have found a way to use the ubiquitous global positioning system, or GPS, to evaluate the constancy of Planck’s constant, h.

GPS relies on atomic clocks, which are sensitive to Planck’s constant through their ticking frequency, f=E/h, where E is the energy of a specific atomic transition. For a clock orbiting in one of the 32 GPS satellites, this frequency can shift with respect to ground-based clocks because of well-known relativistic effects. The GPS system keeps track of this frequency drift and broadcasts a clock correction with its signal.

Kentosh and Mohageg looked through a year’s worth of GPS data and found that the corrections depended in an unexpected way on a satellite’s distance above the Earth. This small discrepancy could be due to atmospheric effects or random errors, but it could also arise from a position-dependent Planck’s constant. Assuming the latter, the authors derive an upper limit on Planck variation. –

Michael Schirber – physics.aps.org/synopsis

Written by physicsgg

March 28, 2012 at 12:46 pm

NORAD and Satellite Technology Help Santa Deliver

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NORAD Tracks Santa. Credit: NORAD

According to the U.S. Department of Commerce Census Bureau, the world’s population is approximately 7 billion (6,979,978,073+) people. Santa Claus has had to adapt over the years to having less and less time to deliver gifts to more people. To better assure prompt deliveries and safe flights, higher technology systems are increasingly being used by the United States Northern Command at Peterson Air Force Base, Colo., to support the North American Aerospace Defense Command (NORAD).

NORAD is a joint United States and Canadian organization which provides aerospace warning and control. The United States Air Force (USAF) uses ground based radars, National Oceanic and Atmospheric Administration (NOAA) operational satellites provided by NASA Goddard Space Flight Center, as well as Santa Cams, Google maps, and jet fighter aircraft.

Global Positioning System (GPS) satellite information and carefully timed gravity assists from the sun, moon, and/or Earth are used to speed Santa’s sleigh faster and more precisely than ever before.

Multi-variable numerical modeling improvements in the solar wind, auroras, geomagnetic force fields, and space/Earth weather predictions are also being credited for important improved sleigh routing efficiencies. Rudolph (the red-nosed lead reindeer) provides a great infrared (warm) signature for the satellite instruments to focus on. The satellite data indicates where fog is and Rudolph can take over the reins from Santa as they use microwave data to know where the rain, snow, and ice are for those precise landing adjustments.

From 22,300 miles in space, NORAD will use for the first time the GOES-15 (covers the U.S. west coast and Pacific Ocean areas) significantly improved Earth location accuracy and heat detection infrared equipment from various satellites. Rudolph’s nose gives off an infrared signature similar to a small missile launch and satellites can detect Rudolph’s bright red nose very precisely.

Artist's concept of GOES-15 in orbit being used to help track Santa. Image Credit: NASA/Honeywell Tech Solutions, C. Meaney

NOAA, NASA, and the USAF have satellites expertly positioned and additional volunteers are supporting the improved Santa tracking beginning after sundown on Christmas Eve December 24. Near “real time” public updates of progress should be available from the web site http://www.noradsanta.org/ NORAD Santa and thanks to worldwide corporate and international support updates will be provided in eight languages.

NASA is in the process of checking out the new NPOESS Preparatory Project (NPP) satellite, launched in October. NPP will provide even more precise and more timely updates of weather information in the years ahead so Santa and his reindeer team can safely deliver more and more presents in all weather conditions in one night!

To track Santa using NORAD, visit: http://www.noradsanta.org
www.nasa.gov

Written by physicsgg

December 24, 2011 at 8:37 am

Posted in SPACE

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