VLBI Global Observing System (VGOS)

VGOS at NASA's GGAO
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To improve VLBI data to meet increasingly demanding requirements, an end-to-end redesign called the VLBI Global Observing System (VGOS, formerly VLBI2010) is in progress. The key concepts are a broadband signal acquisition chain (2-14 GHz) with digital electronics and fast, small antennas. By placing up to four carefully chosen RF bands in the 2–14 GHz range, Radio Frequency Interference (RFI) should be ameliorated and the requisite observation precision achieved. Fast antennas will provide many more observations. More observations support higher temporal and spatial resolution in estimating the effect of the troposphere at each station. Simulations show tropospheric effects as the largest noise source. High recording bandwidths are required to achieve the necessary sensitivity.

VGOS is being developed to be minimally staffed, remotely controllable, broadband, RFI avoiding, fully digital, fast slewing, and capable of producing VLBI delays with precision of 4 picoseconds (in 4 picoseconds light travels 1 millimeter.) The system is designed to observe continuously.

Two complete signal acquisition chains are needed for testing and validation. Proof-of-concept systems were successfully tested using the MV-3 antenna at Goddard Geophysical and Astronomical Observatory (GGAO) and the Westford antenna at the Haystack Observatory in Massachusetts. After the construction of a 12-m Patriot antenna at GGAO, prototype cryogenic broadband receivers, flexible RF selection, digital signal processing and high data rate recorders were developed and tested. Regularly scheduled broadband observations on the GGAO-Westford baseline began in 2014. The signal chain design at GGAO was used extensively in the development of the 12-m systems for Kokee Park Geophysical Observatory in Hawaii and McDonald Observatory in Texas.

The International VLBI Service for Geodesy and Astrometry (IVS) anticipates a gradual introduction of VGOS systems into the new broadband network as they become available. The provisional roll-out plan includes broadband test observations in 2015, mainly on the GGAO-Westford baseline. The goal in 2016 is to have one 24-hr VGOS session every week complementing the current weekly sessions and in 2017 to have several 1-hr sessions for Earth Orientation Parameters (EOP) each day. The pilot project for 2018 would be the combination of the 2016 and 2017 observing scenarios using more than ten VGOS stations.


Kokee Park Geophysical Observatory (KPGO) blog

The Space Geodesy Project is pleased to announce a new blog. This blog follows the implementation of the Space Geodesy Project’s new 12-meter broadband Very Long Baseline Interferometry (VLBI) station at NASA’s Kōkeʻe Park Geophysical Observatory (KPGO) on Kauai, Hawaii. The new station is a joint effort by NASA Goddard Space Flight Center and the United States Naval Observatory, and will become part of the VLBI2010 Global Observing System (VGOS). The station design is based on the successful prototype VLBI2010 station at NASA’s Goddard's Geophysical and Astronomical Observatory (GGAO) in Greenbelt, MD. The new KPGO antenna was developed by Intertronics Solutions, Inc. (ISI), and the MIT Haystack Observatory is responsible for the development of the broadband signal chain.