Michael Wise / TKP Plenary Meeting / December 3, 2012
LOFAR
LOFAR
4
Rollout of Final NL Stations
3.2 Asynchronous RSP Boards
As reported in a previous progress report, a problem has been identified with the start-up
of the RSP boards on a given station at the beginning of an observation. This problem can
cause significantly (~30%) reduced signal-to-noise ratios compared to baselines with
‘good’ stations. The problem was already traced in part to behaviour where one or more
RSP boards on a station can start 5 nsec earlier or later than the remaining boards. This
difference gives 180 degrees phase error at 100MHz (200MHz clock). The net effect of the
problem is an error in the pointing and a net reduction in the sensitivity of the station,
ranging from 30% to 100%. Further investigation traced the problem down to the Rb-
clocks in the stations: the clock signal inside the Rb clock is distributed to several signal
outlets, but a temperature dependent phase difference between these outlets to which the
RSP boards are connected causes unpredictable phase relations. To remedy this effect,
clock distribution was moved to a SyncOptic board (already under development for the
core single clock project, see section 3.5). This board was successfully tested on CS401 in
May.
The next step was to produce a series of these SyncOptic boards for both core stations
and remote stations. The boards were delivered in the last week of August, and underwent
integration and final testing at ASTRON in early September. All Dutch stations, core and
remote, were outfitted with SyncOptic boards in September and early October.
SyncOptic boards were installed as an experiment in the Effelsberg station, DE601, in the
week of November 12 to 16. This station was selected because a) the clock system at
DE601 showed erratic behaviour, and b) the station is sufficiently close to ASTRON to
permit traveling to the station in case of complications.
3.3 Station Rollout Schedule
At the time of writing, construction of three Dutch stations, RS409, RS305, and RS407, is
completed, with the stations being on-line (RS305) or being brought on-line (RS407 and
RS409). Of the remaining four NL stations, two, RS310 and RS210 are expected to be
completed before the end of 2012. The location of the Buinen station (RS404) has become
uncertain due to archaeological finds nearby. The remaining station, RS410, is expected to
come online in 2013 due to delays associated with obtaining the necessary building
permits. Table 1 gives the current expected rollout schedule for the remaining NL stations.
Table 1: Estimated rollout schedule for remaining LOFAR stations.
Station ID Location Status Completion
RS404 Buinen Location uncertain 2013
RS310 Onna Construction started Q4 2012
RS210 Weerselo Construction started Q4 2012
RS410 Wolvega Location uncertain 2013
(courtesy M. Gerbers & N. Ebbendorf)
§ Four remaining NL remote
stations under construction
§ RS310 and RS210 are
expected to be completed
before the end of 2012
§ RS404 location uncertain due
to archaeological finds nearby
§ RS410 delayed due to
building permit issues
LOFAR station RS310 (Zuidveen/Onna)
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