Hartebeesthoek (Hh) Station Report - TOG Meeting - June 2005


Session I - February/March 2005:

A total of 9 experiments were recorded during this session, of which 7 were
user experiments, comprising some 88% of the 88 hours ( 24 hours S/X-band,
10 hours C-band and 54 hours L-band) of telescope time, and some 72% of the
3743 Gbytes of recorded Mark5A data, plus 1 thin tape sent to Socorro.
The average filling factor of the disk-packs was much higher at 71% though
again we needed 4 disk-packs rather than the nominal 3 to send the NMEs
through timeously. ( Note that with the FTP fringe checks the NMEs no
longer require urgent shipment - so disk-pack utilisation should improve.)

Only half an hour (0.6%) of data was lost during the session due to failure
of the antenna servo system (though this fault continued on after all sources
had set), but significant RFI was experienced throughout the L-band part of the
session.


Session II - June 2005:

A total of 10 experiments were recorded during this session, of which 6 were
user experiments, comprising some 88% of the 78 hours (70 hours L-band
and 8 hours C-band) of telescope time, and some 89% of the 5652 Gbytes
of recorded Mark5A data.  The average filling factor was 86% only since
the last pack was not full as all experiments were destined for the JIVE
correlator in this session.

An hour and a half (2%) of data was lost during the session due to operator
error and Mark5A recorder problems (in particular where an automatic bank
switch went wrong - though it is not clear if all of this data is lost.)
Again significant RFI was experienced thoughout the L-band part of the
session.


Mark5A Recorder:

This recorder continues to perform reasonably reliably though we have had some
problems due to faulty disks, and due to mis-timing of a disk-pack switch on
during an automatic bank switch.


Mark 4 Terminal:

We experienced a problem with our Mark 4 decoder where it continuously
rebooted, which was traced finally to a failing 5V power supply in the Mark 4
rack.  Our IF distributor module has recently started reporting zero for the
total power integrator "zero" level, which we have yet to investigate.

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 progress on this issue since the last TOG meeting, though
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.  However components are on order to equip the telescope with a dual
polarisation ambient 22GHz receiver (currently being designed), hopefully
before the October session, with partial funding in the current financial
year to upgrade this to cryogenic amplifiers.

Further progress has been made towards computer (and hence FS) control of the
secondary reflector position to enable switching between all the available
receivers and to allow better optimisation for most feeds (which are mounted
off-axis except for 12.2 GHz.)  Only hardware testing/software optimisation 
is still required to make this capability operational.


J.F.H. Quick
28 June 2005