Metsähovi Radio Observatory, Finland (vlbi@hut.fi) EVN Station Report, June 2003 Ari Mujunen (Ari.Mujunen@hut.fi) Jouko Ritakari (Jouko.Ritakari@hut.fi) Prisse Könönen (prisse@kurp.hut.fi) Highlights In October 2002 Metsähovi obtained the first intercontinental 1Gbps e-VLBI fringes with Kashima (CRL). CRL's ADS-1000 direct IF VSI sampler was used at both sites. Kashima used its own PC-VSI recorder system and Metsähovi used its own VSIB-based Linux PC recorders. Another successful disk-based 1Gbps Metsähovi--Kashima experiment at 22 GHz was conducted in February 2003. This included both H2O maser and continuum sources, and it was correlated using CRL's high-speed software correlator. In March 2003 Metsähovi and Jodrell Bank observed at 22 GHz (as far as we know) the first international Mk4/Mk5A-compatible 1Gbps e-VLBI experiment. It was successfully correlated at JIVE with fringes detected on both H2O and continuum sources. Both Jodrell Bank and Metsähovi used MVDS to record Mk4 formatter data converted to VSI onto Linux hard disks. In June 2003 Metsähovi and Kashima obtained the first 2Gbit/s eVLBI fringes using VSI-standard disk recorders developed at Kashima amd Metsähovi. The experiment proved the easy scalability and interoperability of the VSI-based equipment even at multi-gigabit/s speeds. Geodetic VLBI Project The neighbouring Geodetic Observatory's project to start geodetic VLBI observations at Metsähovi is slowly advancing. The six new BBCs received from Signatron in April 2002 have been tested with BBCTEST.EXE during winter 2003. The S/X receiver built by TTI Norte, Santander, Spain, has also arrived and due to its heavy (>115kg) construction, it needs mechanical fitting to antenna pedestal. It features standard geodetic RCP-only S and X bands. The system temperature of this receiver is around 80 K when the LNAs are cooled to 15 K and the bulky feed system and polarizers are at room temperature. The construction of a larger, manually swappable secondary mirror for S/X observations using carbon fiber as the main material is currently on-going. The secondary mirror will need a new antenna support as well. The insufficient man-power of Geodetic Observatory is the most limiting factor for the project. The present approximation is that geodetic VLBI observations will start at Metsähovi within two years. Next Generation VLBI Project Since the termination of PCEVN project Metsähovi has continued the development of Metsähovi VSI Data System (MVDS). It is a simple and scalable multi-Gbps data acquisition system that adapts easily to the evolution of commodity PC technology. The VSIB data I/O PCI board has been complemented with Metsähovi Multi-Mode VSI Converter (MMM) which is based on universal VSI-H converter board, VSIC. These convert existing Mk4/VLBA formatter, VLBA sampler, and S2 DAS sampler signals into VSI-H for easy recording with any VSI-H-compatible recorder, including our VSIB board. The VSIB data I/O PCI board was tested in June 2002 by recording simultaneously data with both old recorder system and VSIB board system at Westerbork. The correlation of both data concluded identical fringes at JIVE. The board is VSI-H compatible and it supports bit stream assigments including all Mark5A 64/32/16/8 track formats. A total of one hundred of VSIB and VSIC boards has been manufactured in August 2002 and they are immediately available from Metsähovi. Several VSIB/VSIC systems have been delivered to stations in Australia, Germany, Italy, Japan, the Netherlands, and the United Kingdom where the systems are being used for disk and e-VLBI, fringe checks, single-dish spectral and pulsar work. For pricing and for several documents on the subject, please see the Web address 'http://kurp-www.hut.fi/vlbi/instr/'. Station Hardware/Software Field System Updates A new FS version 9.5.17 was installed at Metsähovi in November. New BBCs The testing of six new BBCs was received from Signatron has been done by the Geodetic Observatory. Curiously, all of them report "no1pps" to the FS, but nevertheless seem to receive 1pps and use it correctly. New H-Masers and Maser Room The temperature control system of our isolated maser "cave" has been revised multiple times by the local constructor. Currently it seems to succeed in keeping the temperature constant within +/-0.5C. The effectivity of humidity control is under current investigation. Our old EFOS-9 H-maser has been retired and the remnants have been sent back to Neuchatel Observatory. Two new Russian Kvarz H-masers replace it, with Kvarz-69 as the station frequency reference and Kvarz-70 as backup and---if necessary---autotuning Kvarz-69 by using automatic frequency control. Receivers The 22 GHz and 86 GHz receivers are functioning as before. The 43 GHz receiver is still being repaired for its broken RCP HEMT. A new pair of 43 GHz (LCP/RCP) HEMTs was purchased from the "YLINEN Electronics Ltd." in September. The HEMTs have already been installed but their required DC and bias arrangements are still due. Metsähovi has ordered a new dual-feed 80-115/150 GHz SIS receiver from Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS, Nizhny Novgorod). 80--115 GHz will be LCP/RCP while 150 GHz will be LCP only (using a 1/4-lambda plate to convert LCP to RX native polarization). The expected delivery will be in May 2003, with integration efforts continuing thru 2003. The new receiver will replace the old 86 GHz RX. Recorder It has been known since 2001 that some high-numbered recorder tracks are producing marginal recordings. Investigations in the end of September did not reveal anything new, the headstack is probably 2/3 worn but should be still usable. As a result (and as a result of an earlier decision not to perform thin/thick tape switching anymore) we decided to increase the thin tape vacuum from 6in to 9in. In February 2003 EVN session this seemed to help somewhat, and probably more lapping with thin tape will further improve recording quality. The second head installation is still pending. It is most probable that MH will not invest to old technology, i.e. buy new head stacks. VLBI Sessions in 2002--2003 Metsähovi participated in Nov-2002 and Feb-2003 22 GHz EVN sessions. Due to the limited staffing Metsähovi did not participate in any CMVA sessions in 2002--2003.