FOC Instrument Science Report #090 15 Jan 1996 "Results of the Cycle 4 FOC UV Throughput Monitoring Program" by R. Jedrzejewski Abstract excerpted from the report: This report describes the monitoring of the UV throughput of the FOC by observing a spectrophotometric standard star through four filter combinations. It is found that the observations through the F210M filter show a slight decline in senstivity with time of approximately 4%/year. Observations through the other filters (F120M, F140M, F170M) show no significant trend. Comparison with measurements of the UV reflectivity of the WF/PC-1 pickoff mirror shows that the timescale for decay of contaminants in the hub region is of order 1 year.
