#TITLE_ALTERNATIVE#

• Main Author: HAFIEDUDDIN (NIM : 10313021), MOHAMMAD
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/29011
• Institution: Institut Teknologi Bandung

In the start of its development, application of astronomical observation in the radio regime is constrained by its bad angular resolution. Interferometry technique then becomes a solution from this problem. With the advancement of recording technology, the limitation of how far inferometer elements can be placed has vanished. This advance becomes a key for the development of very long baseline interferometer. The technique of observation using very long baseline interferometer is called Very Long Baseline Interferometry (VLBI). The development of VLBI brings new application in astrometry and geodynamics. One of them is measurement of Earth Orientation Parameters (EOP). Earth orientation is parametrized by its polar motion, length-of-day variation, and its precession-nutation. Precession-nutation and polar motion is conventionally defined using an intermediate pole called celestial intermediate pole (CIP). Despite constant improvement in modelling, there is still some difference between results obtained from model and those obtained from observations. The difference of CIP position in two of them is called celestial pole offset (CPO). The offset and some geophysical phenomena that caused them would be analyzed in this writing. The data that is being used is International VLBI Service for Geodesy and Astrometry (IVS) data in the range of 1993 to 2016. Analysis method used in this writing is periodogram analysis. We found that the dominant spectral component in CPO is related with resonant frequency of Free Core Nutation (FCN). The period corresponding with this frequency is around 430 days in retrogade sense. Further analysis from the data using 8 years time window shows there is a variation in FCN period. The periods we found are periode -434,87 days, -449,90 days, dan -417,85 days. This change may be caused by atmospheric excitation, Earth flattening, ocean loading, and electromagnetic torque in Core-Mantle Boundary (CMB).