Hartebeesthoek (Hh) Station Report - TOG Meeting - November 2004 Session II - May/June 2004: A total of 6 experiments were recorded during this session, of which only 2 were user experiments, comprising some 59% of the 34 hours (19.5 hours C-band and 14.5 hours L-band) of telescope time, but only some 46% of the 3469 Gbytes of recorded Mark5A data (due to a 1GB/s fringe test). However Bologna rules, combined with network monitoring experiment urgent shipping, resulted in an average filling factor of only 53% of the disc-pack capacity thus requiring 5 DPs instead of a nominal 3. No data was lost during the session (in part since the antenna control electronics failure occurred during a fortuitous gap in the NME schedule) from equipment failures/mis-configuration or weather, apart from our usual persistant RFI at 1643 MHz in the L-band experiments. Session III - October/November 2004: A total of 7 experiments were recorded during this session, of which 4 were user experiments, comprising some 79% of the 61 hours ( 29.5 hours C-band and 31.5 hours 4.5/5cm) of telescope time, and some 75% of the 2909 Gbytes of recorded Mark5A data. Bologna rules, combined with network monitoring experiment urgent shipment, again resulted in an average filling factor of only 55% of disc-pack capacity thus requiring 4 DPs instead of 3. Again no data was lost as such during the session due to equipment failire or weather, except perhaps for the last experiment where the RCP IF level was incorrectly set about 5dB too high which will impact at least on the amplitude calibration/sampler statistics. Mark5A Recorder: HartRAO took delivery of a further 20 disc packs from Conduant populated with 160GB disks just in time for the May session. Of these 5 were used in the May session and 4 in the November session leaving 11 on site for future use ie. some 2-3 session's worth. Meanwhile a further 5 disc-packs have been populated with locally sourced 180GB discs for a total of 20 such packs for IVS use of which 18 have now been fed into the geodetic pool. Of the 160 discs purchased locally we have now had a total of 3 failures which have been replaced under warranty. All recording now takes place on disc-pack except where either the correlator cannot support Mark5 (ie. Socorro) or where Antarctic stations are involved ie. correlation may not occur for several months. Mark 4 Terminal: One video converter (VC2) developed an intermittent short on the logic board resulting in the TPI readout being stuck at full range which appears to have resolved after some fiddling with the wiring underneath the board. Frequency Standards: HartRAO continues to operate on our new EFOS-C maser (EFOS-28) which has performed flawlessly since its installation over a year ago. Telescope Surface: All the new surface panels on our 26m antenna have now been aligned optically using steel tape and a theodolite and the secondary reflector has been moved onto the axis of the main dish, all whilst pointing at zenith. Peformance of the antenna at the shorter wavelengths has steadily improved throughout this process and now is essentially flat across the wavebands currently available, a nett improvement of over 100% at 12.2GHz. A 12GHz single-baseline interferometer is now operational between the main 26m antenna and a 3m satellite dish using our ATNF Multibeam correlator and we hope to start holographic mapping of the remaining surface errors shortly. Receivers: No changes to receivers have been made over the period since the last TOG meeting apart from our 12.2GHz receiver being moved on axis. However funding has been set aside for us to equip the telescope with a dual polarisation ambient 22GHz receiver (currently being designed) with proposed funding in the next financial year to upgrade this to cryogenic amplifiers. Significant progress has been made towards computer (and hence FS) control of the secondary reflector position to enable switching between all available receivers and to allow better optimisation for most feeds (which are mounted off-axis except for 12.2 GHz.) Only some cabling and integration work is still necessary, currently waiting on manpower otherwise occupied on SKA-bid RFI monitoring equipment construction. Other issues: There are persistant rumors of a South African "Pathfinder" instrument to be developed at the proposed SKA site in the Northern Cape and various numbers are being bandied about with regard to project. Current ideas revolve around a small D, medium N instrument with collecting area at least equal to Parkes but with baselines out to a few kilometers, operating up to 1,7 GHz with array synthesis feeds allowing multiple simultaneous beams within a few square degree patch of sky. Responses to questionaire: TABLE II 1) New receivers available None 2) Changes or new measurements of the SEFD (system noise in Jy) (for example we are missing information on Jodrell Bank Mark2 at 90cm, Noto and Urumqi at 49cm, Metsahovi, please check the S/X entry) Measured changes in SEFD due to surface upgrade/setting LCP RCP 6.0cm SEFD: 795 / 780 Jy 5.0cm SEFD: 680 / 700 Jy 4.5cm SEFD: 660 / 880 Jy (<-- these values questionable) 3.5cm SEFD: - not yet determined. 3) Changes in polarization characteristics None 4) Check and update if necessary the frequency range of each telescope at UHF band (30+ cm) (Footnote % in Table II) No UHF receiver at Hh. 5) Plans to built new receivers? (2005) Plan to introduce control of secondary reflector to allow full frequency agility. (2005) Plan to add a(n ambient) 1.3cm dual polarisation receiver. 6) TABLE III: Frequency Agility Please check and update the information on receiver agility No change as yet. 7) Table IIIA Check and update if necessary the frequency range at 21cm No coverage at 21cm, 18cm frequency range is 1580-1750 MHz 8) Table IIIb Please check and update the frequency range for 6.0/6.7 GHz. Values indicated with (*) on that table are taken from the current (Sep 2004) freq.dat table. 5900-6170 / 6170-6750 J.F.H. Quick 16 November 2004