Instrument Information
IDENTIFIER urn:nasa:pds:context:instrument:multi-host.dbp::1.1
NAME DUAL BEAM PHOTOMETER
TYPE PHOTOMETER
DESCRIPTION Instrument Overview===================The dual beam photometer is designed to provide object and skyphotoelectric photometry through a series of 24 filters. The lightpasses through a field lens and then through a 24-position filterwheel the positions of which are selectable by means of a steppermotor. The next element in the optical path is a chopping mirrorwhich alternates at a rate of 24 Hz between the object and a nearbypatch of sky. The resulting beam then enters the detector. Achoice among three different available detectors was made on thebasis of the required sensitivity and wavelength range for the givenobject. The three available detectors include a high quantumefficiency GaInAs photomultiplier, an S-20 photomultiplier, and anS-1 photomultiplier.
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REFERENCES McCord, T.B., A Double Beam Astronomical Photometer, Applied Optics, vol. 7, pp.475-478, 1968.