Estimating dUT1 is one of the major tasks of geodetic VLBI. Within the IVS, dUT1 is measured on a daily base by different observing programs:
– INT1 (MO-FR), 2 stations, 128 Mbps
– INT2 (SA, SO), 2 stations, 256 Mbps
– INT3 (MO), 4-5 stations, 1024 Mbps
All of these observing programs have in common, that they only observe with telescopes located in the Northern Hemisphere (Wz, Kk, Is, Ny, Sh, Wn…).
The Southern Hemisphere Intensive observing program (SI) was initiated to determine dUT1 using VLBI stations located in the Southern Hemisphere, namely in South Africa and Australia. It is a joint collaboration between TU Wien, the HartRAO observatory, and the University of Tasmania. The sessions are observed with three stations: HART15M (South Africa), HOBART12 (Tasmania), YARRA12M (Western Australia). The observations are recorded with a high data rate of 1 Gbps to compensate the reduced sensitivity of the smaller antennas. We slightly adjusted the standard S-band frequencies to avoid local RFI. It is now continuously observed between 2200.99 and 2280.99 MHz. The session start time is either during the IVS-AUA sessions (aligned with the start time of the IVS intensive sessions for comparison reasons) or prior to the IVS-R1 sessions.
There are two key research questions:
– do we see a difference between SI and INT1, INT2, INT3?
– one station HOBART12 is observing using a new VGOS feed, do we see a difference between dUT1 derived from the baseline Ht-Hb and Ht-Yg?
Link to Southern Intensive session master