Cormac Reynolds

Overview of the coordinated ground-based observations of Titan during the Huygens mission

Coordinated ground-based observations of Titan were performed around or during the Huygens atmospheric probe mission at Titan on 14 January 2005, connecting the momentary in situ observations by the probe with the synoptic coverage provided by continuing ground-based programs. These observations consisted of three different categories: (1) radio telescope tracking of the Huygens signal at 2040 MHz, (2) observations of the atmosphere and surface of Titan, and (3) attempts to observe radiation emitted during the Huygens Probe entry into Titans atmosphere. The Probe radio signal was successfully acquired by a network of terrestrial telescopes, recovering a vertical profile of wind speed in Titans atmosphere from 140 km altitude down to the surface. Ground-based observations brought new information on atmosphere and surface properties of the largest Saturnian moon. No positive detection of phenomena associated with the Probe entry was reported. This paper reviews all these measurements and highlights the achieved results. The ground-based observations, both radio and optical, are of fundamental importance for the interpretation of results from the Huygens mission.

European VLBI network observations of fourteen GHz-peaked-spectrum radio sources at 5 GHz

We present the results of EVN polarization observations of fourteen GHz-Peaked-Spectrum (GPS) radio sources at 5 GHz. These sources were selected from bright GPS source samples and we aimed at finding Compact Symmetric Objects (CSOs). We have obtained full polarization 5 GHz VLBI observations of 14 sources providing information on their source structure and spectral indices. The results show that two core-jet sources 1433−040 and DA193, out of 14 GPS sources, exhibit integrated fractional polarizations of 3.6% and 1.0% respectively. The other 12 sources have no clear detection of pc-scale polarization. The results confirm that the GPS sources generally have very low polarization at 5 GHz. The sources 1133+432, 1824+271 and 2121−014 are confirmed as CSOs. Three new CSOs 0914+114, 1518+046 and 2322−040 (tentative) have been classified on the basis of 5 GHz images and spectral indices. The sources 1333+589, 1751+278 and 2323+790 can be classified either as compact doubles, and then they are likely CSO candidates or core-jet sources; further observations are needed for an appropriate classification; 0554−026, 1433−040 and 1509+054 are core-jet sources. In addition, we estimate that a component in the jet of quasar DA193 has superluminal motion of 3.3 ± 0.6h −1 c in 5.5 years.

VLBI in transition

European VLBI is undergoing a rapid development. On one hand electronic or e-VLBI is changing the very nature of the European VLBI Network (EVN), on the other hand a dramatically increased time resolution will enable the EVN to image vast areas of sky at unprecedented resolution. The resulting increase of data volumes will require new calibration tools and new ways of computing, storing and distributing data products.

eEVN: a Pan-European radio telescope

Technological advances are changing the nature of VLBI. Disk based recording has already led to sustantial increases in sensitivity and with the advent of new telescopes and data acquisition systems VLBI will start penetrating the micro-Jansky sky. With the employment of fibre based communication networks as the basis for production, real-time VLBI networks will become a reality. This changes the way VLBI is done and removes bottlenecks in operation and scientific exploration. At the output side, fantastic new correlator output data rates and the ability to deal with these via powerful PC clusters promises to expand the typical VLBI field-of-view to scales previously reserved for connected, short baseline interferometers. These developments require new algorithms for user processing, as well as new interfaces to present the product to the users.