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2 2013

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Spectral analysis of Borowiec SLR data for spin determination of geodetic satellite EGP

Kucharski D., Schillak S., Lim H. C., Otsubo T.

Artificial Satellites : Journal of Planetary Geodesy

2013

Vol. 48, No. 1

15--23

Borowiec 10 Hz Satellite Laser Ranging (SLR) station is capable to measure spin of the Japanese Experimental Geodetic Satellite (EGP). Spectral analysis of 391 passes measured from March 10, 1994 to November 27, 2009 gives frequency signal representing the 3rd and the 6th harmonics of the satellite spin rate. Analysis of this signal, corrected for the apparent effects, indicates en exponential slowing down of the satellite: the spin rate decreases according to the equation f = 671.115907 exp(-4.08324 x 10-5 D) [mHz], where D is a day after launch. More than 15 years of the SLR measurements allowed investigating the initial spin rate of the satellite fini = 671.116, RMS = 0.203 [mHz] (initial spin period Tini = 1.49006, RMS = 0.0007 [s]).

Seismicity and reservoir induced crustal motion study around the Tehri Dam, India

Choudhury S., Gautam P., Paul A.

Acta Geophysica

2013

Vol. 61, no. 4

923--934

The Tehri Dam is located in a seismotectonically active region in the Indian Himalayan belt. This 260.5 m high dam has a live water storage of 2615 × 106 m3 and is capable of generating crustal deformation corresponding to water fluctuation. Filling of the reservoir started in October 2005. Seismic data around the dam between 2000 and 2010 shows that seismicity is corresponding to drawdown levels of the reservoir rather than to higher water levels. GPS data at twelve local benchmarks were collected from 2006 to 2008 during filling and drawdown reservoir levels. The velocity vectors show ground motion to be between ~0.69-1.50 mm in the different filling-drawdown cycles with reference to the permanent station at Ghuttu. The motion appears to be inwards into the reservoir when the reservoir is filled and outwards when the reservoir is drained. This ground motion corresponds to elastic deformation and rebound due to effect of the oscillating water levels.