6 research outputs found
First observations with a GNSS antenna to radio telescope interferometer
We describe the design of a radio interferometer composed of a Global
Navigation Satellite Systems (GNSS) antenna and a Very Long Baseline
Interferometry (VLBI) radio telescope. Our eventual goal is to use this
interferometer for geodetic applications including local tie measurements. The
GNSS element of the interferometer uses a unique software-defined receiving
system and modified commercial geodetic-quality GNSS antenna. We ran three
observing sessions in 2022 between a 25 m radio telescope in Fort Davis, Texas
(FD-VLBA), a transportable GNSS antenna placed within 100 meters, and a GNSS
antenna placed at a distance of about 9 km. We have detected a strong
interferometric response with a Signal-to-Noise Ratio (SNR) of over 1000 from
Global Positioning System (GPS) and Galileo satellites. We also observed
natural radio sources including Galactic supernova remnants and Active Galactic
Nuclei (AGN) located as far as one gigaparsec, thus extending the range of
sources that can be referenced to a GNSS antenna by 18 orders of magnitude.
These detections represent the first observations made with a GNSS antenna to
radio telescope interferometer. We have developed a novel technique based on a
Precise Point Positioning (PPP) solution of the recorded GNSS signal that
allows us to extend integration time at 1.5 GHz to at least 20 minutes without
any noticeable SNR degradation when a rubidium frequency standard is used.Comment: 33 pages, 19 figure
Recommended from our members
Multiple personality integrated circuits and the cost of programmability
textThis dissertation explores the cost of programmability in computing devices as measured relative to fixed-function devices implementing the same functionality using the same physical fabrication technology. The central claim elevates programmability to an explicit design parameter that (1) can be rigorously defined, (2) has measurable costs amenable to high-level modeling, (3) yields a design-space with distinct regions and properties, and (4) can be usefully manipulated using computer-aided design tools. The first portion of the the work is devoted to laying a rigorous logical foundation to support both this and future work on the subject. The second portion supports the thesis within this established logical foundation, using a specific engineering problem as a narrative vehicle. The engineering problem explored is that of mechanically adding a useful degree of programmability into preexisting fixed-function logic while minimizing the added overhead. Varying criteria for usefulness are proposed and the relative costs estimated both analytically and through case-study using standard-cell logic synthesis. In the case study, a methodology for the automatic generation of reconfigurable logic highly optimized for a specific set of computing applications is demonstrated. The approach stands in contrast to traditional reconfigurable computing techniques which focus on providing general purpose functionality at the expense of substantial overheads relative to fixed-purpose implementations.Electrical and Computer Engineerin