Very Long Baseline Interferometry (VLBI), coupled with the transformational ability of SKA-Low and SKA-Mid, is poised to deliver groundbreaking observations with milliarcsecond resolution, surpassing the capabilities of the standard SKAO array.
VLBI, alongside the SKAO, offers the potential to unlock deep insights across a range of astrophysical topics. It is set to transform our...
The SKA-Mid plans to support VLBI observations at frequencies up to 15 GHz in the early phase of AA*. The Qitai 110-m and Jingdong 120-m telescopes in China are also going to become operational over the next five years. Moreover, there are more stations available at Ku band in Oceania, Europe, and China. With 32 Gbps VLBI observations at Ku band, one could easily reach an image sensitivity of...
The SKA-MPIfR telescope (SKAMPI) is a 15-meter prototype antenna for the SKA-Mid located at the SKA site in the Karoo Desert, South Africa. Funded by the Max Planck Institute for Radio Astronomy (MPIfR) and operated togetherwith SARAO (South African Radio Astronomy Observatory). For this telescope, the MPIfR backend development team implemented a novel VLBI backend. In the near future, SKAMPI...
The LOw Frequency ARray (LOFAR) has been operating at the longest radio wavelengths since 2010. It has opened up a wide range of scientific applications, from ionospheric studies to mapping the largest coherent radio structures in our Universe. This was enabled by new technologies such as aperture array antenna systems, and one of the world’s fastest super-computers.
LOFAR consists of two...
With baselines up to 2000 kilometers, the International LOFAR Telescope has a unique high-resolution view on the low-frequency radio sky. Unlike more typical VLBI arrays, however, with its 76 operational stations it forms a sizable network with dense uv coverage across angular scales from approximately a degree down to a few tenths of an arcsecond. Due to its low frequency nature, the ILT's...
Over the past decade, significant efforts has gone into developing calibration and imaging pipelines to automatically process data from the Dutch high-band antennas of the Low Frequency Array (LOFAR), which observe the Universe at about 150 MHz and reach with the Dutch array a 6" resolution (e.g. Shimwell et al. 2017; 2019). Recently, we have extended this work by developing a pipeline to...
Currently, SKA-Low baselines extend only ~70 km, and there are few low-frequency stations in the Southern Hemisphere to enable joint VLBI observations with SKA-Low. On its own, SKA-Low will not deliver the sub-arcsecond angular resolution required to maximise synergy with frontline optical/IR telescopes such as JWST. The planned tied-array mode will add the capability to participate in VLBI,...
A new VLBI Global Observing System (VGOS) radio telescope is currently being constructed at Bosscha Observatory, Indonesia, in partnership with the Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences (CAS). The telescope tower structure, comprising a three-story building that includes the reinforced concrete foundation and the anchor ring assembly for the antenna’s...
The Ghana Radio Astronomy Observatory (GRAO), located at Kutunse near Accra, houses a 32-metre converted telecommunications antenna that is now Africa’s largest fully steerable radio telescope. Since its commissioning, the observatory has advanced steadily towards routine scientific operations, supporting observations of pulsars, methanol masers, and continuum sources. A core focus has been...
We present the usage of radio telescopes for space and environment applications as well as for the science of radio astronomy. In Greece two science projects are taking place involving the conversion of a 2m (called Hellios) and 30m (called THERMOpYlae) dishes into radio telescopes.
The small dish will monitor the solar flux at 10.7cm to study climate change. It is actually a flux monitor....
The Wetterstein Millimeter Telescope (WMT) is a planned radio telescope associated with the Environmental Research Station (UFS) Schneefernerhaus at the Zugspitze in the Bavarian Wetterstein mountains.
The WMT is planned to operate at radio frequencies between 1.2GHz and 120GHz with the goal to extend further towards shorter millimeter wavelengths. It is envisioned as an interdisciplinary...
In this presentation I will talk about the 4-year RADIOBLOCKS project, funded by the EC under the Horizon Europe programme. I will describe its structure, ambition, current status and accomplishments. I will also touch upon its potential for the future of the EVN and European radio astronomy in general.
Within the RADIOBLOCKS EU project, JIVE, in collaboration with partners, is investigating state-of the art accelerator technologies for implementing a (VLBI) correlator. In particular we are developing GPU kernels that implement the same algorithm as the SFXC CPU correlator. This development will provide re-usable VLBI delay and Windowed Overlap (WOLA) filter modules (which we call Radio...
The Australia Telescope Compact Array (ATCA) is a six-element interferometer operated by CSIRO. We are in the process of installing a new digital backend that employs a small cluster of GPU accelerators to process 8 GHz of bandwidth in real time from all six telescopes. In this talk, I will provide a brief overview of the system and discuss some of the technical challenges encountered, along...
In order to construct a submillimeter interferometer in Antarctica, the correlator is a core component that converts the signals received by two antennas into digital signals and performs correlation operations to obtain the visibility function. This talk will introduces a design scheme for the correlator of this project. Firstly, in order to ensure the coherence between the antennas, we will...
The talk gives an overview about current (software) developments for VLBI, which might also be interesting for other VLBI stations.
I will present our newly developed Python module VCAT (VLBI Comprehensive Analysis Tool), which aims at easing data analysis of VLBI data, specifically aimed for studying AGN jets. It allows a comprehensive analysis of the radio signature of AGN jets as obtained from multi-frequency continuum VLBI observations to obtain information about the morphology and polarization of the extended emission.
Very long baseline interferometry (VLBI) requires complex and often manual post-correlation calibration to correct for instrumental, geometric, and propagation-related errors. Unlike connected-element interferometers, VLBI arrays typically provide raw visibilities rather than science-ready data, and existing pipelines are largely semi-automated and reliant on user supervision. This manual...
ASTRON is developing technology for 'large-N, small-D' radio telescopes, i.e. systems having many, small, low-cost antennas. To reduce the receiver cost, we are investigating various technologies, such as non-cryogenic ultra-low noise frontends, simple RF chains with direct sampling receivers and white-rabbit timing.
An L-band technology demonstrator, using one of the Westerbork Synthesis...
Over the last decade JIVE, in collaboration with NRAO, has been working on adding VLBI functionality to CASA. As a result CASA is now a feasible alternative to AIPS. A significant number of EVN and VLBA users use CASA to reduce their VLBI data and the CASA-based rPICARD pipeline is used as one of the two calibration pipelines for the EHT.
However the technology behind CASA is already...
The measurable quantities in radio interferometric observations are visibilities of the target signal at given spatial frequencies. The limiting factor of the visibilities to spatial frequencies and the sampling pattern introduces both spectral and spatial correlated noise in the image. The widespread radio-interferometric image reconstruction algorithms that have been used over the past few...
The high angular resolution and sensitivity of VLBI offers a unique tool to identify and study AGN and star-formation activity over cosmic time. VLBI observations are crucial for identifying young radio sources and unveiling older restarted radio sources. Also, radio imaging over a large range of angular scales is needed to determine the role of black hole feedback and jet-induced star...
The IVS VGOS Technical Committee (IVS VTC) discussed several times on how to maximize the benefits of VGOS for geodesy and astrometry. Unused potential for improvement was identified in (a) increasing the synthesized bandwidth per VGOS observing band from 480 MHz to 1024 MHz, and (b) distributing the four VGOS frequency bands between 3 and 14 GHz instead of only up to 10.6 GHz as is currently...
The Australian VGOS telescopes offer the capability of observing GNSS satellites in L-band, which is not common for traditional VLBI telescopes. Dual-band observations from several GPS satellites were recorded from the three telescopes and graciously shared by the University of Tasmania. Based on the correlation between the recorded samples and locally generated replicas, the signal traveling...
The GENESIS satellite, scheduled for launch in 2028, will contribute to the improvement of the International Terrestrial Reference Frame (ITRF), by combining the four major space geodetic techniques, namely GNSS, DORIS, SLR and VLBI, onboard a single platform at an altitude of 6000 km. The VLBI transmitter (VT) is one of the key instruments, designed to operate in two distinct transmission...
This report presents local-tie experiments using three co-located VLBI stations in China: Tianma and Sheshan in Shanghai, and Urumqi. The VGOS antennas were utilized in mixed-mode observations across the conventional S/X bands, followed by correlation of X-band-only data and subsequent post-correlation analysis. Phase delay analysis was performed to determine the relative coordinates of these...
VLBI tracking and analysis of Earth-orbiting satellites is becoming increasingly important in geodesy and fundamental astronomy, as demonstrated by recent initiatives such as GENESIS. A central requirement for these applications is the accurate modelling of near-field effects, along with realistic treatment of station clocks and atmospheric delays.
To support these scientific goals, we have...
The X-ray emission from resolved knots in the jets of many blazars cannot be explained as a simple extension of the radio synchrotron spectrum. So far no general consensus has been reached on the relative dominant contribution of the different broadband-emission mechanisms at play. In particular, observing the low radio frequencies provides valuable constraints to test different emission...
The European Space Agency (ESA) currently works on the Genesis mission. Genesis is a so-called co-location satellite that should contribute to the improvement of the International Terrestrial Reference Frame (ITRF). The idea is to combine the four space geodetic techniques Very Long Baseline Interferometry (VLBI), Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR) and...
The GENESIS mission will integrate four geodetic techniques onboard a dedicated satellite, including a novel Very Long Baseline Interferometry (VLBI) transmitter. A key requirement for this payload is that the transmitted power flux density (PFD) remains within the operational range of global VLBI radio telescopes. Unlike traditional VLBI observations of distant quasars, where the received...
Source structure introduces a systematic error in VLBI observations on a per-source basis. We have developed a software tool that takes models of the brightness distribution to correct the interferometric phases of the DiFX correlator output. We have tested our method by applying it to observational VGOS data. Here we present our results concerning the effect on imaging the corrected data, the...
Tsukuba Correlator/Analysis Center in GSI are involved in correlation and analysis of intensive sessions INT-2 and VGOS-INT-B/C every weekend. We report on the status and changes in VGOS-INT-B/C sessions’ correlation process which has been updated from last year.
One of the large barriers to full automated correlation is the process of short baseline between ONSA13NE and ONSA13SW. In...
The VLBI Global Observing System (VGOS) has been operational since 2020. To optimize VGOS schedules and derive more accurate geodetic parameters, a SNR-based scheduling approach has recently been introduced. However, many geodetic sources still have poorly known radio flux densities in the operationally used VGOS frequency bands. We have carried out flux monitoring observations at Onsala Space...
Efficient scheduling in the VLBI Global Observing System (VGOS) requires accurate knowledge of source flux densities at 3–11 GHz. However, the lack of such data leads to fixed 30-second scan durations, often resulting in sub-optimal use of observing time and limited scan counts per session. To address this, we present a method to estimate flux density per projected baseline length bin (in 1000...
Since mid-2023, the Onsala Space Observatory has been operating a new modern microwave water vapor radiometer (WVR), Greta, which is a commercial product of type HATPRO-G5. It is co-located with the other microwave radiometer, Konrad, which has been developed and built at Onsala. Konrad has been in operation since 2000 and is usually operated in so-called sky-mapping mode. Usually, the...
The International VLBI Service for Geodesy and Astrometry (IVS) conducts both 24-hour and 1-hour geodetic VLBI sessions. The 24-hour sessions utilize global VLBI networks to estimate all five Earth Orientation Parameters (EOP), but they generate large volumes of data, resulting in product delays of several weeks. In contrast, the 1-hour intensive sessions are designed to provide more timely...
The Square Kilometre Array (SKA) telescope will provide unprecedented sensitivity across a wide frequency range, combined with high resolution and survey speed, offering the astronomical community a state-of-the-art instrument to address ambitious scientific objectives and advance our understanding of the Universe’s history.
During the preconstruction phase of the SKAO project, the Dish...
The transition of VLBI systems towards ultra-wideband receivers represents a decisive step for both radio astronomy and space geodesy, where achieving millimeter-level accuracy critically depends on highly reliable signal conversion and processing chains. Within this context, we present the design, development, and validation of a 4–8 GHz downconverter conceived for cryogenic receivers...
A new Tri-band receiver would advantageously replace Onsala's 20m telescope existing millimeter wave single-pixel receivers within the K,Q and W frequency bands, having next-generation performance, IF bandwidth, and sampling capabilities. The receiver system will support both Astro VLBI observations and single-dish functionality. Moreover, the new receiver aims to enable simultaneous...
Recent geopolitical developments have led to severe disruption for crucial systems that society relies on, even for countries that are not part of any ongoing conflict. This includes intentional sabotage of infrastructure or denial of access to critical support systems. Global Navigation Satellite System is one of those systems that society depends on, both in terms of positioning but also for...
Optical communications have had a remarkable development over the last 50 years thanks to developments in, e.g., fiber optics, laser technology, optical amplifiers and signal processing. Fiber communications form the backbone of there internet, and one can now readily transmit 10-100 Tb/s over transoceanic distances. The presentation will briefly describe these developments, and then discuss...
Over the past decades, ground-based astronomy has advanced through the search for drier sites and the construction of ever-larger telescopes, resulting in facilities such as VLT, ALMA, and soon the SKA and ELT. These observatories deliver unprecedented angular resolution and sensitivity, yet their cost and complexity continue to rise. At the same time, even prime observing sites such as the...
T-REX (Time-Resolving Explorer) is a proposed SmallSat which seeks to time-resolve the accretion disk of Sgr A* through direct radio interferometric imaging utilizing VLBI -- enabling the first constraints on black hole spin. T-REX will operate in Low-Earth Orbit (LEO) at 86 GHz (𝜆 ∼ 3.5𝑚𝑚) with a 𝑑 ∼ 2.5𝑚 antenna. It will co-observe with BHEX (Black Hole Explorer) in MEO and the EHT (Event...
The Chinese Very Long Baseline Interferometry Network (CVN) currently consists of six ground-based radio telescopes, one space-borne experimental telescope, and a data processing center affiliated with the Shanghai Astronomical Observatory. Two newly commissioned 40-meter telescopes are located in Shigatse, Tibet Autonomous Region, and Changbai Mountain, Jilin Province. Shigatse and Changbai...
The ESA NovaMoon proposal includes a Very Long Baseline Interferometry (VLBI) transmitter as part of its longline geodetic payload suit on the surface of the Moon. A stable and consistent lunar reference frame is essential for geodesy, geophysics, and the success of future lunar missions, enabling precise positioning and long-term monitoring of lunar orientation and interior dynamics. To date,...
Big Science Sweden (BiSS) has a government assignment to strengthen the opportunities of Swedish companies, universities and institutes to deliver components and services to thirteen large-scale in- ternational research facilities. The focus of our support is high-tech deliveries that, in addition to the business opportunity, contribute to strengthened research environments in Sweden, that...
The Square Kilometre Array Observatory (SKAO) sets stringent requirements for electromagnetic compatibility (EMC) to ensure minimal radio frequency interference (RFI) from its equipment. This presentation outlines the comprehensive EMC emission testing methodology developed and implemented at RISE using Reverberation Chambers (RCs). Covering a frequency range from 300 MHz to 25.5 GHz, the...
The next-generation very-long-baseline interferometry (VLBI), also known as the VLBI global observing system (VGOS), was designed to observe the frequency band that spans from 2 to 14 GHz.
This range overlaps with numerous licensed radio services, as coordinated by the International Telecommunication Union (ITU).
Essentially, all VGOS frequency bands overlap with other radio services that...
The 5th generation digital backend (DBEv5) is backward compatible for Geodesy work, and adds new features in support of upcoming satellite mission support. Also described are the FPGA personalities in support of legacy S/X systems and some new interesting developments.
Very Long Baseline Interferometry (VLBI) has traditionally been performed by a small group of skilled astronomers who often need to follow a complex and crucially variable process to produce science-quality images and outputs. However, in recent years, radio interferometric arrays have generated a flood of data, and along with this, technical and algorithmic advances have automated much of the...
