Very Long Baseline Interferometry (VLBI) is a space-geodetic technique directly connecting the Terrestrial Reference Frame realized by positions of Earth-based stations with the Celestial Reference Frame (CRF) defined by a set of extragalactic radio sources (quasars) well distributed throughout the sky. Due to the rotation of the Solar System Barycentre (SSB) around the centre of Milky Way galaxy, the arising acceleration of the SSB induces an apparent proper motion of the extragalactic objects observed by VLBI, i.e., a change in the apparent source positions over time. The aberration amplitude estimates (5 - 7 microas/year) from geodetic VLBI are close to the independent estimates derived from astrometric measurements of proper motions and parallaxes of masers, and it is not negligible in terms of the upcoming ICRF3 catalogue anymore.
Seminar of PS group (Tuesday, 20 February, 14:00) Christopher Jacobs (NASA JPL, Caltech, USA):VLBI and its application for building reference frames for spacecraft navigation Christopher Jacobs is a senior deep space navigation engineer at NASA’s Jet Propulsion Laboratory (JPL) of the California Institute of Technology. Jacobs holds a degree in Applied Physics from Caltech. He joined JPL in 1983 and has taken on roles of increasing responsibility in the area of deep space tracking specializing in the area of celestial and terrestrial reference frames. He has served as the Reference Frame Calibration task manager for 25 years in which role he has been responsible for delivering the reference frames used to navigate NASA missions such as MSL to planetary targets. In this talk he will give a brief overview of the Very Long Baseline Interferometry (VLBI) technique and show how it is applied to building reference frames for spacecraft navigation.
Alet de Witt (The Hartebeesthoek Radio Astronomy Observatory (HartRAO), RSA): Imaging of extragalactic radio sources at K-band with VLBI Alet de Witt is an operations astronomer at the Hartebeesthoek Radio Astronomy Observatory (HartRAO) in South Africa. She will introduce the K-band imaging project where she is the principal investigator. The VLBI data set at K-band has world-class spatial resolution (few parsecs) coupled with a temporal resolution from a 0.5 to 2 months’ cadence of observation for a given radio source. What can one do with such a data set? Few ideas will be presented such as searching for periodicity as a sign of binary black holes, jet precession, or optical vs. radio offsets. This data set should produce results of interest to the relativistic astrophysics groups theoretical working on black holes and accretions disks and to the relativistic astrophysics group’s studies of spatially resolved AGN which can build a basis for mutual cooperation.