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Medicina station ------------------
The hardware and Venix operating system have been purchased to install the new PC Field System and replace the old computer HP1000 computer.
This year two new heads have been mounted on the MK3 tape drive because the old ones wore out.
A polarimeter design is in progress.
Future upgrades should allow the telescope to work properly up to 43GHz and quicly switch between receivers. To start with a new L band receiver design is in progress. It will be at the primary focus and will replace the old and huge one, placed in secondary focus. In this way we gain room to permanently allocate and position all receivers.
Temperature sensors mounted on antenna legs have been completely changed with new ones, so more accurate and reliable measurements can be performed with respect to pointing degradation.
Alessandro Orfei
|--------------------------------------| | NEWS ABOUT ITALIAN MKII CORRELATOR | |--------------------------------------|
In 1988 The Istituto di Radioastronomia of Bologna got a MKII type Block 0 correlator from Caltech. The system was very old in technology because it was built in the seventies. The correlator has been operational for short periods only due to maintainance problems - especially in the control computer. Today the MKII standard is out from the official EVN VLBI scheduling. However, there is still interest in using the the MKII standard at Medicina and Noto because it represents a very cheap way to observe in "ad hoc" experiments using an operative data acquisition terminal. A full time working correlator is needed - this represents the natural element to complete an Italian network. In this context the first action is to ressurect the old Block 0 correlator. Expert help is expected within the next few month in the form of a Chinese colleague from Shangay Observatory. A new computer was bought and the operation should be completed in mid 1994. At the same time we are evaluating the possibility of building a new compact and cheap correlator using advanced technology. FPGA devices seem to fit the conditions imposed, in particular the on field re-programmable type. Costs are not very high despite the use of a few samples. Reprogram possibilities are very useful characteristics in order to simplify the debugging process and it allows some possibilities not offered by traditional strategies. A final decision on this project should be taken before the end of this year.
Gino Tuccari
Bonn Correlator -----------------
The Mark III correlator at Bonn is in the middle of its expansion. The purchase of three new drives and the expansion of the correlator is being done in collaboration with the geodesy group (Frankfurt/Bonn) and is aimed at providing Mark IV correlation capability to Astrono- my and Geodesy, once the Mark IV correlator developement has been succesfully finished. The old Mark III correlator from 1982 is ex- pected to have survived the years out of operation without damage. We tested a major fraction of the correlator boards in a test crate and found normal behavior. Some rewireing still needs to be done. The new cooling system is completed.
Three new tape drives are subject to acceptance testing at Interfero- metrics at the same time as the TWG meeting takes place. We ex- pect them in Bonn later this month. The new tape drives will be upgraded to thin tape operation capability after delivery in Bonn. Together with the drives in operation already we will then have six drives with VLBA-style electronics (5 Metrum, 1 Penny & Giles), and four drives to be upgraded succesively (3 in operation, 1 in the lab to be worked on).
Copying the Mark III archive tapes to DAT casettes makes good pro- gress. We have copied already between a third and half of the A-tape liberary.
Tape handling at the Bonn correlator now makes regular use of the NRAO "TRACK" program at Socorro. Initial problems with the Internet line seem to be overcome now. The program makes tape storage and shipping much more transparent and error proof.
The computer center at MPI has finally switched off the two Convex machines. Post processing is done now on workstations (Sun and HP/Apollo)
Klaus Ruf
Effelsberg ------------
The VLBI test observations at 86 GHz of July 1992 have been succes- fully repeated in April 1993, including a transatlantic baseline with Haystack. First results look promising!
Work has started on the multi-frequency receiver (15, 22, and 43 GHz). Possibly it can be finished by end of next year.
We have ordered a VLBA data acquisition terminal at Interferome- trics. Delivery is scheduled for February and end of April 1994 for the acquisition rack and the tape drive respectively.
Klaus Ruf
Jodrell Bank --------------
Jodrell local observing continues to function reliably at 90,50, 6 and 1.3cm wavelengths. The Sigma-Tau maser is working well, and a minor modification has been made to improve IF level. The three MK2 video cassette systems will remain installed for at least one year.
The VLBA terminal with DarFS software is now working reliably, however remote observing with the Cambridge 32m dish remains a problem despite several successful fringe tests. Reasons for this appear to be varied, due to the complex nature of the link system. Several new phase cal units have been made here, and one will shortly be installed permanently at Cambridge. This should make it much easier to be sure the links are correct.
During the joint EVN-MERLIN 18cm session in June data were recorded on the MkIII (Lovell telescope signal) and VLBA terminal (Cambridge telescope signal). Simultaneous tape changes and the use of different field systems/control computers on each DAR led to some interesting logistical problems! The main credit goes to the students who made the ``double-speed'' tape changes possible. We eagerly await news from the Bonn correlator w.r.t. fringes!
Jodrell now distributes calibration data in ANCAL format. This includes an antenna gain card and FT factor. The internet link to Jodrell has been upgraded to 64kbaud. This had markedly improved e-mail, news and ftp reliability. The last VAX was shut down in June and so our DECnet/SPAN link has gone. Communications are now entirely based on the Internet TCP/IP line. Post-processing relies on a substantial Sun workstation cluster which includes several SPARC-10 dual processor machines.
Paul Burgess and Mike Garrett.
Onsala Space Observatory --------------------------
The PC Field System is running and tested but still not running the DAR. We will phase out our old Modcomp computers for antenna control for the 25 meter telescope and we are waiting for a PC system to take care of that. It is hoped to connect the PC FS in the autumn.
Biorn Nilsson
NOTO ------
1) The station is now equiped with a VLBA terminal. Until the September 1993 session only 4 BBCs have been available, two more should arrive by october '93. In addition we need the ground base unit for phase cal.
2) The terminal is driven by a new PC486 50MHz running the VENIX operating system. The new MkIV Field System has been tested with both the VLBA and MkIII recorders, as well as the VLBA terminal. It works fine in both configurations.
3) The antenna pointing is still performed by the old HP1000. During the observations two schedules must be used, one for the PC486 and one for the HP1000 containing only the "source" and "!time" SNAP commands. A new program for antenna pointing running on a PC running MS-DOS has been developped, but communication software between the two PC's is still in progress. The new program will permit automatic antenna pointing using the MKIV Field System.
4) Fringes have been found for the new 18cm and the 327 MHz receivers. They were used for the first time during the November 1992 session.
Corrado Trigilio
Metsahovi (Jan 1993 - Jul 1993) ---------------------------------
VLBA terminal: The terminal appeared to work OK in Jun 1993 session -- D. Graham found fringes in at least one experiment. Currently we have 11 base band converters and are constructing 5 more.
In the June session we had problems with formatter timing, and we will build a station timing module for the September session and hope that the problems go away.
Receivers: the 22 GHz receiver is performing well and a beam chopper will be installed to enable pointing checks on program sources and more accurate amplitude calibration.
Design of the 43 GHz receiver will begin as the manpower constraints permit. One of the two HEMT amplifiers are on loan at the Onsala Space Observatory.
DARFS, AIPS: DARFS version v0.94 was adapted to the Metsahovi environment and some minor problems were corrected.
Further work on the 15OCT92 version of AIPS on a 486 PC running Mach 3.0 with BSD 4.3 UNIX has been put on hold for now. Tape handling and XAS server need more work but the small and medium DDT tests were passed and all the tasks were successfully built.
Jouko Ritakari Kaj Wiik Ari Mujunen