How to register a VGOS radio telescope at ITU and why it is important

VGOS radio telescopes enable observations in the range of 2-14 GHz and are much more receptive for unwanted radio frequency interference. Some space-borne transmitters may cause detrimental radiation to VGOS receivers. The registration of new VGOS sites at ITU is important to obtain administrative protection. This may help to avoid direct illumination by strong radars, as well as provide protection in the dedicated RAS bands from lower-level interference that degrades system sensitivity. This article introduces the risk of damage and explains the registration procedur

Differences Between S/X and VLBI2010 Operation

The intended VLBI2010 operation has some significant differences to the current S/X operation. The presentation focuses on the problem of extending the operation of a global VLBI network to continuous operation within the frame of the same given amount of human resources. Remote control operation is a suitable solution to minimize operational expenses. The implementation of remote control operation requires more site specific information. A concept of a distributed-centralized remote control of the operation and its implications is presented

Status of the TIGO VLBI Station in Concepcion

The main activities at the TIGO VLBI station during 2012 have been 120 successful VLBI sessions and the investigation of an alternate site for TIGO for future operation

Short Report of IVS Working Group 5 (WG5) on Space Science Applications - An IVS Perspective

No abstract availabl

E-Control: First Public Release of Remote Control Software for VLBI Telescopes

Automating and remotely controlling observations are important for future operations in a Global Geodetic Observing System (GGOS). At the Geodetic Observatory Wettzell, in cooperation with the Max-Planck-Institute for Radio Astronomy in Bonn, a software extension to the existing NASA Field System has been developed for remote control. It uses the principle of a remotely accessible, autonomous process cell as a server extension for the Field System. The communication is realized for low transfer rates using Remote Procedure Calls (RPC). It uses generative programming with the interface software generator idl2rpc.pl developed at Wettzell. The user interacts with this system over a modern graphical user interface created with wxWidgets. For security reasons the communication is automatically tunneled through a Secure Shell (SSH) session to the telescope. There are already successful test observations with the telescopes at O Higgins, Concepcion, and Wettzell. At Wettzell the software is already used routinely for weekend observations. Therefore the first public release of the software is now available, which will also be useful for other telescopes

Fermi Large Area Telescope View of the Core of the Radio Galaxy Centaurus A

We present gamma-ray observations with the LAT on board the Fermi Gamma-Ray Telescope of the nearby radio galaxy Centaurus~A. The previous EGRET detection is confirmed, and the localization is improved using data from the first 10 months of Fermi science operation. In previous work, we presented the detection of the lobes by the LAT; in this work, we concentrate on the gamma-ray core of Cen~A. Flux levels as seen by the LAT are not significantly different from that found by EGRET, nor is the extremely soft LAT spectrum (\G=2.67\pm0.10_{stat}\pm0.08_{sys} where the photon flux is \Phi\propto E^{-\G}). The LAT core spectrum, extrapolated to higher energies, is marginally consistent with the non-simultaneous HESS spectrum of the source. The LAT observations are complemented by simultaneous observations from Suzaku, the Swift Burst Alert Telescope and X-ray Telescope, and radio observations with the Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry (TANAMI) program, along with a variety of non-simultaneous archival data from a variety of instruments and wavelengths to produce a spectral energy distribution (SED). We fit this broadband data set with a single-zone synchrotron/synchrotron self-Compton model, which describes the radio through GeV emission well, but fails to account for the non-simultaneous higher energy TeV emission observed by HESS from 2004-2008. The fit requires a low Doppler factor, in contrast to BL Lacs which generally require larger values to fit their broadband SEDs. This indicates the \g-ray emission originates from a slower region than that from BL Lacs, consistent with previous modeling results from Cen~A. This slower region could be a slower moving layer around a fast spine, or a slower region farther out from the black hole in a decelerating flow.Comment: Accepted by ApJ. 32 pages, 5 figures, 2 tables. J. Finke and Y. Fukazawa corresponding author

VGOS wideband reception and emerging competitor occupations of VLBI spectrum

The VGOS wideband receivers cover a spectrum from 2 to 14 GHz. In this range, many frequencies are allocated to other services. VGOS provides up to four 1 GHz wide sub-bands, which can be tuned to frequencies where detrimental radio frequency interference is absent. The increasing demand of commercial users of radio spectrum and related on-going telecommunication projects are threatening the VGOS observation plans. The examples of a compatibility study for 5G concerning the GermanWettzell site and the global availability of Starlink/OneWeb illustrate the impact on VGOS and the need of regulation by spectrum authorities. This article contains a brief introduction how spectrum management is organized and what needs to be done on the national level to achieve protection for VGOS sites

The compatibility of DORIS with VGOS

<p>The most precise global geodetic reference frame, the International Terrestrial Reference Frame (ITRF), is based on four space geodesy techniques: Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS) and the Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) System. All four techniques complement each other with their observations for the terrestrial reference frames, because of the individual advantage: VLBI is unique for the Earth orientation parameters and the tie of ITRF to the International Celestial Reference Frame (ICRF), SLR is strong in the determination of the centre of mass of the planet Earth and of the scale in the ITRF, GNSS is good for densification of global networks and of orientation and DORIS technique is unique in the most homogeneous global network of reference sites. In order to combine these advantages in a synergetic way, a co-location of these techniques in geodetic observatories is an objective for progress in global geodesy.</p><p>The question of how the desired co-location of DORIS at a VLBI site (or vice-versa) can be achieved is under permanent discussion. The VLBI systems are designed to receive extremely faint cosmic signals down to -110 dBm, whereas the DORIS beacon emits signals at a frequency of 2,036 MHz with 40 dBm output power. There is a potential for coupling between DORIS emissions and the VLBI receiving chain generating spurious signals. A risk of overloading or even damaging the VLBI low noise amplifiers (LNA) is possible. Even if in VLBI the same frequency is not being observed, in the worst case the LNA of the VLBI receiver could be saturated by DORIS transmission leading to useless VLBI observations.</p><p>Meanwhile, several geodetic observatories collected measurements, made studies, and even co-located active DORIS beacons. The CRAF-VGOS group presents a compatibility study in pycraf with simulations of exclusion zones for DORIS with respect to VGOS radio telescopes. It collates site-specific experiences and may be helpful for future decisions on how to co-locate both techniques at new sites.</p&gt