Hartebeesthoek (Hh) Station Report - TOG Meeting - March 2006


Session III - October 2005:

A total of only 3 experiments were recorded during this session, of which 1
was a user experiment, comprising some 45% of the 20 hours (16 hours C-band
and 4 hours L-band) of telescope time, and some 48% of the 1964 Gbytes
of recorded Mark5A data.  The average filling factor was about 75% with all
experiments destined for the JIVE correlator in this session.

The C-band network monitoring experiment was plagued with problems, with the
failure of a control box for the secondary reflector delaying the start by 
some 10 minutes and the RCP receiver going unstable due to a loose cable for
the last four and a half hours.  Again significant RFI was experienced
thoughout the L-band part of the session.


Session I - February/March 2006:

A total of 19 experiments were recorded during this session, of which 11 were
user experiments (including the target-of-opportunity experiments), comprising
some 84% of the 122 hours ( 13 hours C-band, 31 hours X-band, 41 hours 'M'-band
and 37 hours L-band) of telescope time, and some 89% of the 13623 Gbytes of
recorded Mark5A data.  The average filling factor was 85% with an extra disk
pack required to ship one experiment to Socorro.

In total only 50 minutes (<0.1%) of data were lost during the session due to
wind-stow of the antenna, but significant RFI was experienced throughout the
L-band part of the session.

Mark5A Recorder:

This recorder continues to perform extremely reliably now that we only switch
disk-packs between experiments.  All faults have been traced to individual
failed disks (including one pack with 3 failures which we think was dropped
in transit),  though none of these were in the astronomical disk pool.


Mark 4 Terminal:

Our IF distributor module continues to intermittently report zero for one
of the total power integrator "zero" levels, impacting only the "IF2"
system temperature which is only reported for diagnostic purposes.

Frequency Standards:

HartRAO continues to operate on our new EFOS-C maser (EFOS-28) which has
performed flawlessly since its installation almost two years ago.  Our old
EFOS-A maser (EFOS-6) is still operating as our backup standard.


Telescope Surface:

There has been no further progress on this issue since the last TOG meeting,
holographic mapping of the remaining surface errors is in process.


Receivers:

No changes to receivers have been made over the period since the last TOG
meeting.  However the new dual polarisation ambient 22GHz receiver is close
to final assembly with installation projected for early April.  Plans to
upgrade this receiver to cryogenic amplifiers are awaiting confirmation
that the surface accuracy is good enough for viable operation at this
frequency.


Other Hardware/Software:

Computer (and hence FS) control of the secondary reflector position to enable
switching between all the available receivers took a back seat to preparation
of a SKA site bid.  The hardware was further set-back by damage caused by a
lightning strike to the preliminary controller resulting in a return to the
drawing board.  Significant hardware testing/software optimisation will be
required to make this capability operational once the new hardware becomes
available.

A long standing problem in off-source flagging was traced to flicker in the
weather inputs to the pointing model which affected the command coordinates,
causing the antenna servo system to momentarily stop tracking.  This was
fixed just prior to the February/March session.


J.F.H. Quick
16 March 2006