Hartebeesthoek (Hh) Station Report - TOG Meeting - January 2011


The repair of the Hartbeesthoek 26m telescope has been completed and it was
returned to service as a VLBI instrument on the 28th July 2010.  Meanwhile
we continue to tool up the 15m KAT prototype antenna with a cooled dual
polarisation S/X prime-focus receiver for use (primarily) in geodetic VLBI
operations.


Session III - Oct/Nov 2010:

The 26m telescope returned to routine EVN service with this session, which
turned out to be very quiet with only some 6 (+1 e-EVN) experiments scheduled,
of which 4 (+1 e-EVN) were user experiments, comprising some 92% of the 78.5
hours (18 hours L-band and 60.5 hours S/X-band) of "recording" time and some
78% of the 5252 Gbytes of recorded data.  The average filling factor of the
disk-packs was about 87%, mainly due to the small size of the 3 experiments
destined for the JIVE correlator, since the Socorro pack actually over-flowed
and the last two scans were shipped electronically.

Only 5 minutes of data (ie. <<1%) was lost (due to some local ANTCN software
failure) though we also experienced our usual L-band RFI and some new strong
RFI at S-band which we are still investigating.


Mark5(A/B+) Recorders:

Although we have procured all the components necessary for the conversion of
the recorder into a Mark5B+, we are waiting for a suitable gap to install the
upgrade.  We have now also procured a second Mark5B+ recorder, plus the parts
necessary to upgrade both recorders to Mark5C in due course.

During the hiatus when disk-packs sat at Hartebeesthoek unused, some 3 packs
experienced disk failures, including one where two disks failed.  Two of these
have been repaired by disk replacement (since that is cheaper for us than
shipping to/from the correlator) and the third is awaiting the second disk
(after a replacement failed new out of the box !!)  The Hitachi 500GB disks
seem to be the main culprits.


Mark 4 Terminal:

Similarly components necessary for the conversion of the Mark4 formatter into
a VSI sampler suitable for use with a Mark5B+ recorder have been purchased but
not installed, pending the conversion of the Mark 5 recorder itself.  During
this period, two video converters have developed LO faults, of which one has
been repaired by cannabilising the buffer amplifier out of a long defunct
spare.  We have also developed an intermitten fault in our IF distribution
module which is under investigation.


DBBC Terminals:

Due to a capital injection from an unexpected source, we are in the process
of ordering two DBBC units from HAT-Lab s.r.i. for delivery in about 6 months.
This should enable us (with the second Mark5B+ recorder mentioned above) to
operate both antennas simultaneously for VLBI in due course, thereby hopefully
improving on our current Astronomical/Geodetic scheduling woes.


Frequency Standards:

HartRAO continues to operate on our new EFOS-C maser (EFOS-28) which has
performed flawlessly since its installation over five years ago.  Our old 
EFOS-A maser (EFOS-6) is non-functional, with the replacement of the internal
vacion pump still pending.  However the capital injection mentioned above
is sufficient for us to also purchase a new maser and we are busy canvassing
potential suppliers.


26m Telescope Surface:

There has been no further progress on this issue since the last TOG meeting,
holographic mapping of the remaining surface errors having taken a back seat
to the recommissioning of the telescope and its receivers.


Receivers:

There have been no changes to our receiver complement since the last TOG
meeting, though both the C-band and 6.7GHz Methanol receivers have been re-
installed following the replacement of the cryogenic expanders (which failed
during the 26m telescope down time.)


Other Hardware/Software:

Field System:    FS9.10.4 running on FS Linux 7 (Debian "etch") kernel 2.6.18-6
Mark5A version:  2007y223d08h running on Debian "etch" kernel 2.6.18-6
Mark5B+ version: 2007y222d04h running on Debian "etch" kernel 2.6.18-6

Computer (and hence FS) control of the secondary reflector position to enable
fast switching between all the available receivers is now operational, but the
proposed upgrade to a physical linear position encoder is still pending.


e-VLBI / Connectivity:

With the return of the 26m to service, Hartebeesthoek agreed to join the ranks
of the e-EVN starting with a C-band ToO observation on 30th September, and then
as a routine part of the array from October onwards, initially at 896Mbps and
subsequently at the full 1024Mbps.

Over this period we have been involved in some 5 e-EVN sessions (+ 1 e-VLBI
during the Oct/Nov 2010 disk session), 4 at C-band, 1 at L-band, for a total
of some 90 (+ 8) hours of telescope time.

Significant new C-band RFI was experienced during these sessions, but this
has since been traced to a Military Intelligence link, originally set up for
the World Cup, which has now been switched off.


J.F.H. Quick
27 January 2011