GPS Time Disruptions on 26-Jan-2016

On Tuesday, January 26th 2016 Aalto University Metsähovi Radio Observatory discovered that three out of its four GPS receivers on-site (used for monitoring the performance of four on-site hydrogen (H) maser atomic clocks) performed abrupt 13.0 microsecond time jumps in their "1pps" (one pulse per second) time synchronization outputs. The disruptions lasted for approximately 12 hours during which different GPS receiver units outputted erroneous time signal at different times, preventing their use for microsecond-level time synchronization. The event was later acknowledged by the 2nd Space Operations Squadron at the 50th Space Wing, Schriever Air Force Base, Colorado, USA, as an erroneous time correction parameter upload to GPS satellites

Metsähovi Radio Observatory - Annual report 2010

Metsahovi Radio Observatory, a research institute at Aalto University (formerly: Helsinki University of Technology, TKK), operates a 14 – m -diameter radio telescope at Metsahovi, the village of Kylmala in Kirkkonummi, about 35 km west from the Otaniemi university campus. Metsahovi is active in the following fields: radio astronomical research, multifrequency astronomy and space research, development of instruments and methods for radio astronomy, and (radio) astronomical education. Geodetic VLBI observations are also done in Metsahovi in collaboration with the Finnish Geodetic Institute. In 2010 twenty-four scientists, engineers, research assistants and support personnel worked at the institute. In 2010 the total expenditure of Metsahovi Radio Observatory was 1 177 941 euros including salaries and the rent of the office and laboratory space. This was funded by Aalto University, Academy of Finland, European Union, and other outside sources. The past few years have been full of organisational changes in our university. In the introduction of the previous Annual Report I wrote: "These years of reformation have been full of increased administrative load. We are looking forward to the new university taking its form and becoming fully operational, when we will hopefully once again have time to concentrate on scientific research!" Unfortunately I was overly optimistic. Year 2011 was even worse than the ones before that, which is also the reason why our Annual Report 2010 was delayed so much (published in spring 2012). The faculty of Electronics, Communications and Automation that was established in 2008 (and where Metsahovi was merged) ceased to exist in 2011, and now we are part of the Aalto University School of Electrical Engineering (ELEC)

The use of the Long Baseline Array in Australia for precise geodesy and absolute astrometry

We report the results of a successful 12 hour 22 GHz VLBI experiment using a heterogeneous network that includes radio telescopes of the Long Baseline Array (LBA) in Australia and several VLBI stations that regularly observe in geodetic VLBI campaigns. We have determined positions of three VLBI stations, ATCA-104, CEDUNA and MOPRA, with an accuracy of 4-30mm using a novel technique of data analysis. These stations have never before participated in geodetic experiments. We observed 105 radio sources, and amongst them 5 objects which have not previously been observed with VLBI. We have determined positions of these new sources with the accuracy of 2-5 mas. We make conclusion that the LBA network is capable of conducting absolute astrometry VLBI surveys with accuracy better than 5 mas.Comment: Published in Publications of the Astronomical Society of Australia. 10 pages, 3 figures, 5 tables. Table 5 in a machine readable form is accessible in the source of this submissio

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 Titan's atmosphere. The Probe radio signal was successfully acquired by a network of terrestrial telescopes, recovering a vertical profile of wind speed in Titan's atmosphere from 140 km altitude down to the surface. Ground-based observations brought new information on atmosphere and surface properties of the largest Satumian 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 imnortance for the interpretatinn of results from the Huygens mission

Calibration of CALLISTO data

The CALLISTO spectrometer is a programmable low-cost heterodyne receiver that can be used, for example, for radio-frequency solar monitoring. Together, various CALLISTO instruments around the world form the e-Callisto network, with each station having the same CALLISTO spectrometer installed in various antenna configurations. Only a few of the stations in the e-Callisto network currently provided calibrated CALLISTO observations, however, limiting the usability of the measurements in, for ex-ample, exact solar flux density estimations. This document describes the essence of how CALLISTO data can be calibrated by using measured power of the cold sky level and an external noise source, using the technical implementation of the calibration sys-tem at Aalto University Metsähovi Radio Observatory, Finland

First Result from the Alpha Magnetic Spectrometer on the International Space Station: Precision Measurement of the Positron Fraction in Primary Cosmic Rays of 0.5350 GeV

Peer reviewe

Solar polarization observations at 3 and 13 mm

The first solar radio polarization observations at 3 mm (86 GHz) and 13 mm (22 GHz) were made at Aalto University Metsähovi Radio Observatory in Finland in spring 2019. This was the first time that 3 mm (86 GHz) and 13 mm (1.3 cm) solar polarization observations were made with the same radio telescope. In this paper we describe the observing system and data analysis, and present the first results. We also compare our data with polarization observations made with the Nobeyama Radioheliograph and find that the results are consistent. Additionally, we determine the quiet Sun level brightness temperature at 3 mm (86 GHz) using the New Moon for refererence, and obtain a mean value of 6310 K.Peer reviewe

Ultra-Rapid DUT1-Observations with E-VLBI

We give a short overview about the achievements of the Fennoscandian- Japanese ultra-rapid dUT1-project that was initiated in early 2007. The combination of real-time data transfer, near real-time data conversion and correlation, together with near-real time data analysis allows to determine dUT1 with a very low latency of less than 5 minutes after the end of a VLBI-session. The accuracy of these ultra-rapid dUT1-results is on the same order than the results of the standard rapid-service of the International Earth Rotation and Reference Frame Service (IERS). The ultra-rapid approach is currently extended to 24 hour sessions and is expected to become an important contribution for the future next generation VLBI system called VLBI2010