4 research outputs found
Correction due to finite speed of light in absolute gravimeters
Correction due to finite speed of light is among the most inconsistent ones
in absolute gravimetry. Formulas reported by different authors yield
corrections scattered up to 8 Gal with no obvious reasons. The problem,
though noted before, has never been studied, and nowadays the correction is
rather postulated than rigorously proven. In this paper we make an attempt to
revise the subject. Like other authors, we use physical models based on signal
delays and the Doppler effect, however, in implementing the models we
additionally introduce two scales of time associated with moving and resting
reflectors, derive a set of rules to switch between the scales, and establish
the equivalence of trajectory distortions as obtained from either time delay or
distance progression. The obtained results enabled us to produce accurate
correction formulas for different types of instruments, and to explain the
differences in the results obtained by other authors. We found that the
correction derived from the Doppler effect is accountable only for of
the total correction due to finite speed of light, if no signal delays are
considered. Another major source of inconsistency was found in the tacit use of
simplified trajectory models
Search for geodynamic signals in time series of astrometric observations
Since 1963 astronomical observations are conducted at Borowa Gora Geodetic-Geophysical Observatory of the Institute of Geodesy and Cartography with the use of transit instrument. Instrumental, technological and methodical improvements in acquiring and pre-processing of rotational time observations make the time series inconsistent over the whole period of operation of the instrument. The rotational time determined was initially referred to the FK5 catalogue system; starting from the data of 1986 it is also referred to the Hipparcos catalogue system. Data series from last almost 25 years is particularly valuable for the analysis. Complex spectral analysis of a long-standing rotational time data series from 1986.0-2010.6 was performed. A number of periodic terms were separated from the series investigated and the numerical model of the series has been formed.
The effects of beat observed in the numerical model were discussed. The existence of a distinguished weekly term in the data investigated has been observed. The results obtained were compared with the spectra of EOP from the analysis of IERS data