Infrared and Other Instrumentation projects that I have been involved with

MkI, MkII and MkIII Infrared Photometers

The MkI photometer was constructed while I was at RGO, in 1971, and had a 3-bladed mirror focal-plane chopper and two interchangeable Dewars containing a PbS detector for JHKL and a Low bolometer for MNQ (MNRAS, 164, 155, 1973). Later, a stepwise-oscillating mirror chopper was added and the PbS detector was replaced by InSb. The MkII photometer was a copy made at SAAO for use with the 0.75m telescope. The MkIII was built for use with the chopping secondary on the 1.9m telescope in 1981 (MNASSA 44, 45, 1985) and uses the original JHKL filters from the MkI. The first online reduction programme (Nova minicomputer ca 1979) was by LA Balona and the later PC-based software was by P.A. Whitelock.

Filter-wheel Spectrometer

The FWS used a continuously variable filter to give 1% resolution from 1 to 4 microns. It had a InSb detector (MNASSA 41, 68, 1982). Nova software by P.A. Whitelock.

Chopping Secondary

A 7-inch diameter F50 chopping secondary was designed for the 1.9m telescope in 1980. It is driven by push-pull moving coil units mounted on a baseplate which themselves oscillate. Detailed mechanical design by D.T. Ellis. Electronics designed by G.F. Woodhouse (MNASSA 41, 81, 1982). The mirrors of the oscillating secondary and MkIII photometer were gold coated in 1998.

J-band Ebert-Fastie Spectrometer

This instrument used a Ford Aerospace photodiode to give coverage from about 0.8 to 1.6 microns with a resolution of about 1500. It was used for a spectrum of SN1987A (MNRAS 234, 5p, 1988). The preamplifier was an integrating Hall-type, reset by a FET switch across the feedback capacitor.

IRCAM JHKL HgCdTe Camera

The IRCAM used a Philips 64 x 64 HgCdTe CCD array with "loophole" interconnects between the layers. This was the only chip available to us at the time because of US export regulations. The detector material was sensitive to about 4.1 microns. The camera had scales of 1"/mm and 0.5"/mm. This detector was never very satisfactory. The photodiodes were circular and the fill factor x QE was low. In addition, there were problems with non-uniform thresholds in the mosfet switching circuitry and with the charge transfer efficiency. Although the array was used on several occasions, the quality of the data was too low for it to be competitive. It was described in MNASSA, 50, 58, 1991. Transputer programme mostly by D.B. Carter.

PANIC JHK PtSi Camera

The PANIC camera used a 1040 x 1040 interlaced Mitsubishi monolithic array with about 50% fill factor. Three different arrays were used. The QE at K was very low - about 2% for two of the arrays. It was only 1% for the array that behaved the best - problems were experienced with trapping and loss of charge in the others. The array had a CCD-like readout. The charges from a given line were dumped into vertical CCDs which operated not once, but many times, to overcome the charge transfer inefficiency associated with the narrow channels. The horizontal CCD was quite conventional. There are 4 outputs. PANIC was described in A.G. Davis Philip et al (eds), IAU Symposium 167, Kluwer Academic Publishers, Dordrecht, p.109. This camera was used for the much-publicised observations of the Comet Shoemaker Levy collision with Jupiter and for the Galactic Centre Variable Star Survey. Transputer programme mostly by D.A. Carter.

PICNIC JHK Camera

The PtSi chip of the PANIC camera was replaced by a PICNIC 256 x 256 HgCdTe chip in 1998. The Transputer programme is by D.A. Carter. This system has been improved by the addition of an "Offner Relay" with cold stop (June 1999), with ray-tracing help from D. O'Donoghue and K. Smit. (MNASSA, 58, 147, 1999)

InSb JHKnbL Camera

An infrared survey camera using an engineering-grade InSb 512 x 512 Aladin array that can operate at 3.6 microns (narrow-band L) was constructed for use on the IRSF 1.4m telescope. It was driven by a SDSU controller and Linux PC, with final recording on DVD-ROMs. An Offner relay system (with design help from D O'Donoghue) incorporated a cold stop. Cooling was via a closed-cycle CTI-Helix refrigerator, the detector operating at 35K and the remainder of the optics at 61K. A control programme (KISS.C) interacted with the controller and the telescope automatic, allowing automatic dithering and co-adding multiple exposures. An automatic reduction pipeline was also developed. This work was reported in MNASSA, 63, 28, 2004.

CCD Acquisition Camera

This instrument uses an EEV frame-transfer CCD cooled by a 3-stage thermoelectric stack. It is driven by a SAAO-Rutherford Transputer-based controller. The picture is displayed on the 480 x 640 256-colour VGA screen of a PC. Later versions of the programme, written by others, allowed autoguiding and seeing measurement. These cameras are used with simple focal reducers for field acquisition on the 1m and 1.9m telescopes.

CCD on Unit Spectrograph

I devised a design using an existing Wynn-designed Maksutov camera, originally intended for use with a McGee electronographic image tube, coupled to a long-format SITE chip. The cryostat has a silica window mimicking that of the image tube, which forms part of the camera design. The cryostat, which is angled at 45 degrees, is coupled by a "cold finger" to an upright Dewar containing liquid nitrogen.


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