Geodesy
Geodesy and geophysics are concerned mostly with what is going on under our feet, so it may seem ironic that these two disciplines are advanced by looking up at the stars! VLBI techniques, which were originally developed for studying radio objects in the universe can, in effect, be turned upside down to do very precise studies of the Earth.
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| Geodetic studies help aid in the use of GPS and other navigational equipment. |
By simultaneously collecting data from a single radio source via a worldwide array of radio telescopes, the relative time-of-arrival of signals from that source to each telescope can be determined to within a few picoseconds (3 picoseconds = 1 mm of light travel time). By observing many radio sources spread widely over the sky over a period of 24 hours, data are collected that allow the ultra-precise measurements of the Earth and its orientation in space. The geodetic VLBI techniques in use at Haystack originated more than three decades ago at the Observatory, which continues to lead the way in new developments and improved accuracy in these important research methods.
Geodetic VLBI in Action
Among the important applications of geodetic VLBI are:
- Measuring tectonic plate motions.
- Measuring "post-glacial" rebound.
- Measuring and monitoring changes in the Earth’s rotation and the wobble of its axis.
- Understanding the interaction between Earth’s mantle and core.
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