USNO IVS VLBI Analysis Center
The USNO IVS VLBI Analysis Center is an official analysis center of the International VLBI Service for Geodesy and Astrometry (IVS). Here you will find the VLBI analysis products produced by the USNO Radio Optical Reference Frame Division. Very Long Baseline Interferometry (VLBI) is a technique in which the recorded data from multiple radio telescopes hundreds or thousands of kilometers apart is combined interferometrically in order to synthesize the power of a radio telescope hundreds or thousands of kilometers across.
VLBI can be used to produce high-resolution images of distant cosmic radio sources, as well as the precise positions of the individual radio telescopes, the orientation of the Earth at the few mm level, and the precise celestial coordinates of thousands of compact celestial radio sources. The USNO Radio Optical Reference Frame Division uses VLBI to monitor, maintain and update the celestial reference frame, the terrestrial reference frame, daily Earth orientation parameters, and performs the imaging of thousands of radio sources. The analysis center monitors daily variations in UT1-UTC using IVS and VLBA Intensive sessions. We also monitor all 5 Earth Orientation parameters from the weekly R1 and R4 IVS sessions.
The analysis center also regularly monitors and maintains the ICRF3 celestial reference frame using VLBA and IVS sessions. USNO allocates 50% of the observing time for VLBA. This VLBA time is used for projects that support the USNO mission of maintaining, enhancing and expanding the celestial and terrestrial reference frames, the Earth orientation parameters and studying and monitoring the quasar radio sources used for VLBI. In addition to operational VLBI analysis, Analysis Center personnel are actively engaged in research related to enhancements of the reference frames at multiple VLBI frequencies, variations in Earth orientation and quasar source structure. The analysis center also operates the Fundamental Reference Image Data Archive (FRIDA), which contains images of thousands of quasar sources at multiple frequencies and epochs.