Hartebeesthoek (Hh) Station Report - TOG Meeting - November 2009


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.  However funding has now been secured to
pursue a bearing replacement through a US telescope manufacturer and the
contract will be signed shortly.  We are hoping that the 26m will return to
service by the middle of 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 in geodetic VLBI operations.


Session II - May/June 2009:

No participation due to 26m telescope bearing failure.


Session III - October/November 2009:

No participation 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 the L-band receiver has been re-installed following the
replacement of both of the cryogenice LNAs (after the failure of the RCP
HEMT amplifier.)  We are now busy replacing the cryogenic LNAs in the S-band
receiver, with the X-band receiver due to receive a similar re-furbishment
thereafter.  Both sets of cryogenic LNAs extracted will be re-used in the
new S/X prime focus receiver for the 15m.


Other Hardware/Software:

Field System:    FS9.10.2 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 final 10G backbone link
segment in a path through to London is due to enter service later today, though
two bottle-necks (one here on our local-lead and the other at the Ubuntunet
peering point in London) still need resolution.  However we would hope to be
able to stream data at 1Gbps as soon as the 26m antenna returns to service.

J.F.H. Quick
24 November 2009