Hartebeesthoek (Hh) Station Report - TOG Meeting - June 2010


Following the failure of the main polar shaft bearing on 3 October 2008, the
26m has been locked into a meridian transit position, which precludes us
from recording useful VLBI data.  Repair work on the 26m telescope commenced
on site in the middle of March, with the foundations of the temporary support
structure for the bearing change now completed  and is expected to finish in
mid-to-late July 2010.  In the interim we are continuing 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 I - March 2010:

No participation due to 26m telescope bearing failure.


Session II - May/June 2010:

No participation possible due to 26m telescope bearing failure.


Mark5A Recorder:

Although we have procured all the components necessary for the conversion of
the recorder into a Mark5B, we will postpone making such a change until after
we are able to produce VLBI data again.


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.  No
significant repairs/upgrades were done to the terminal over this period.

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.


Telescope Surface:

There has been no further progress on this issue since the last TOG meeting,
holographic mapping of the remaining surface errors has obviously stalled for
the moment.


Receivers:

There have been no changes to our receiver complement since the last TOG
meeting, though both the S-band and X-band receivers have been re-installed
following the replacement of the cryogenice LNAs (with the original HEMT
amplifiers destined for re-use in new S/X prime focus receiver for the 15m.)


Other Hardware/Software:

Field System:    FS9.10.4 running on FS Linux 7 (Debian "etch") kernel 2.6.18-6
Mark5A version:  2007y222d02h 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 has been postponed.


Connectivity:

Additionally, whilst the 26m VLBI capability has been unavailable, improvements
in our Internet connectivity have continued apace.  The only known remaining
1Gbps bottle-neck is the Ubuntunet/GeANT peering link in London which should
be addressed shortly.  Hence we would hope to be able to stream e-VLBI data
up to at least 512Mbps on a test basis as soon as the 26m antenna returns to
service.

J.F.H. Quick
18 May 2010