Oscillations, Waves, and Interactions - GWDG

294 Schreiber
∆ Perimeter [*10e12 m]
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
970
0 4 8 12 16
Time [days in 2006]
Figure 14. Time series of the variations of the UG2 ring laser perimeter superimposed
with the atmospheric pressure.
Finally the complete instantaneous geometrical scale factor was computed as a
function of time for the entire period of the measurements. One can see from Fig. 15
that the changes amount to several parts per million for UG2. This certainly can
not be ignored for the analysis of ring laser measurements of Earth rotation. Similar
measurements on the monolithically constructed G ring laser suggest that the scale
factor variations from beamwalk are at least two orders of magnitude smaller and
outside the range of resolution of the available cameras. When the computed corrections
are applied to the UG2 raw data (Fig. 11) the excursions reduce substantially
as shown in Fig. 16. As a result one can see that the amplitude of the departures
from the expected Earth rotation rate have reduced substantially but they have not
completely disappeared. Furthermore there is a strong systematic downwards drift in
the Sagnac frequency contained in the residuals of the corrected measurements. The
∆ K A [ppm]
2
1
0
-1
-2
-3
-4
0 4 8 12 16
Time [days in 2006]
Figure 15. Time dependence of the variation of the ring laser scale factor over the period
of the measurements.
1030
1020
1010
1000
990
980
Atmospheric Pressure [hPa]