FOS APERTURE WHEEL REPEATIBILITY
m
R. HARNS AND R. DOWNES
Applied Research Corporation
	Instrument Science Report	CAL/FOS046	October, 1988


ABSTRACT

Rep.atibility of the FOS aperture wheel was measured in the ambient
calibration of imlarch 1988. Cross-correlation of the eiuission line
spectra revealed a systematic drift in the X position of the
spectra. Ov.r a -160 minute time interval, the spectra drifted
linearly by 0.1 pixels for all three apertures measured. The trend is
similar to that seen in Narch 1983, althougb the magnitude of the
present drift is 9reater. A possible source of the drift ja
therznaJ. shifts due to the warm up of the electronics imniediately
following hi.gh voltage turn on.