AAO Newsletter October 1996 - Page 13
Optical designers probably will not mourn the demands for generous backfocal
distances, and similarly the mechanical engineers for the requirements
of supporting the not inconsiderable weight of the detector head. The IPCS
requirements dominated a generation of spectrograph camera designs.
Dick Hunstead and Max Pettini were allocated the IPCS for an observing
run in November 1995. It was not intended to be the final run of the IPCS,
but the general feeling developed that this was likely to be the last one.
Tests in preparation for the last run indicated that the detector was
delivering its specified performance levels after nearly 20 years and numerous
modifications. Factors that help explain this include the following. Professor
Alec Boksenberg and the IPCS engineering design team selected proven available
technology and, where necessary, developed novel technical solutions to
overcome instrumental effects. In an age of fast track instruments and
short life cycles, the value of 20 years continuity of support from original
members of the design team such as John Fordham of UCL and earlier Tony
Jordan of RGO should not be underestimated.
The last night of the IPCS was spent with the detector doing what it
was designed for, observing absorption lines in quasars. The integration
was started and with the detector slowly accumulating counts, we left the
control room to view the comet Schwassinann-Wachmann 3 from the catwalk.
It was a dark clear night after a hot Australian day with the warm breeze
and a beautiful comet hanging in the western sky it proved to be an appropriate
night for the IPCS to end its observing career.
Here are a number of scientific highlights from two decades of observations
with the IPCS:
The IPCS was a major optical detector for nearly 20 years, and the only
panoramic optical photoelectric detector available for spectroscopy for
10 years. It is not likely that any future detector will match this record.
The absence of readout noise and large format maintained the popularity
of the IPCS well after the efficiency of the detector was superseded. A
number of the projects listed above could not have been achieved with the
CCD detectors available at the time as they had significant readout noise.