European VLBI Network - TOG Meeting, Wettzell, 1 April 2004

Station Report for Jodrell Bank & Cambridge Telescopes

Alastair Gunn
Paul Burgess

November 2003 Session

The session comprised 11 experiments at C-band using the Lovell
telescope for the first time at this frequency, and 5 experiments
at L-band, again on the Lovell telescope. The total allocated
observing time was 184 hours, of which 119.5 were at C-band and
63.5 were at L-band. At C-band, 1h57m (1.6%) of time was lost due to
equipment failures (either problems with tape vacuum or telescope
drives). A further 4h14m (3.5%) was lost due to high winds. At
L-band, a total of 57m (1.5%) data were lost due to equipment
failure (vacuum loss). Thus, for the entire session, we suffered a
total data loss of 3.9% (1.6% due to equipment, 2.3% due to weather).

Whilst setting up for L-band observations we found a fault in our
final LO synthesiser which compromised all Lovell observations at
C-band. The synthesiser suffered a 220 kHz offset and the drift
made correlation impossible. This failure is not included in the
above statistics. A new Agilent E4400B synthesiser has been installed
as the second LO and set up under FS-9.6.9.  A new upconvertor unit
has been built and both units will be installed in January 2004.

February 2004 Session

This session comprised 4 experiments at K-band using both the Mk2
and Cambridge antennas, 6 C-band experiments on the Lovell telescope
(of which 4 included Cambridge) and 8 L-band experiments on the
Lovell (of which 6 included Cambridge). The total allocated observing
time was 283.5 hrs; 28 hrs on Mk2, 128.5 hrs on Lovell and 127 hrs
on Cambridge. Problems with recabling the Mk5 unit for double-head-stack
operations meant that the NME experiments, ea029 and kah1 failed for
the Lovell telescope. Other data loss was caused by vacuum failure
and an error in the MERLIN schedule for eb027b. The total lost time
at the telescope, including the Mk5 failure, was 2 hrs for Mk2,
15h6m for Lovell and 3 hrs for Cambridge, making a total loss of
20h6m (7.1%).

Mk5 and near-real-time VLBI tests

The first Mark5 recorder has been integrated-in and tested on several
occasions. We have built 7 disk packs. Several software upgrades,
and one firmware upgrade have been done. Jodrell Bank has recently
participated in a series of tests as preliminary stages for
near-real-time VLBI over the Internet. On Monday 24th November
2003 fringes were obtained between Jodrell Bank Mk2 and Westerbork,
correlated at JIVE Dwingeloo. The data had a bandwidth of 16MHz sampled
at 2 bits giving a total data rate of 64Mbps over the existing Jodrell
link. The received data were stored on disk at JIVE (but not at the
transmitting end).

Technical Developments

A second Mark5 unit has been purchased and tested locally. It has
'unofficial' status until further funds allow purchase of the matching
JIVE unit. A prototype FS PC has been built to replace the older ones,
as several of the IO cards are obsolete. Debian Linux 'woody' has been
installed as per J. Quick/GSFC instructions. A second CNS GPS receiver
will be commissioned shortly. It should provide a reduced dUT error of
35ns down from 45ns. Local 1Gbps network switches and cards have been
installed. Jodrell's data link has been upgraded to the full 155MBps.
The VLBI dedicated fibre is progressing.