Daily Image
14-09-2007Explaining the SMART-1 diffraction patterns
| Submitter: | Sergei Pogrebenko |
| Description: | From the 14th century (first mentioned in Chinese chronicles) untill mid 18th century (before accurate clocks became available) Lunar occultations of Sun, stars and planets were used by sailors to pinpoint their ship’s position on the Geoid with LORAN-C or near-GPS accuracy: a few hundred meters in both latitude and longitude, with some luck and due to the fact that the occultation event is a distinctive marker in both time and space dimensions. Lunar occultation of a spacecraft orbiting the Moon allows (in principle) locking its orbital position with respect to the “Lunoid” with an accuracy of several meters. Work toward developing a relativistic model of the S/C signal diffraction on the 3D topography of the Moon is in progress as a cooperative effort of JIVE and Shanghai Radio Astronomical Observatory scientists. The picture on the left illustrates Fresnel rings distribution over the Moon’s limb, wile plots on the right show the comparison of modeled diffraction patterns of power, phase and Doppler shift with those observed during SMART-1 observations in May 2006. The modeled and observed results agree qualitatively, which is encouraging. |
| Copyright: | Pogrebenko |
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