CAL/FOS Instrument Science Report 090 4/93 A Quick Reference Guide to the Appropriate File for a Particular Date and Instrumental Configuration by Charles D. Keyes and Cynthia J. Taylor Abstract excerpted from the Report: Complete tabulations of the currently installed FOS flat field reference files for all combinations of spectral element and aperture at each specified USE_AFTER date are presented in a convenient matrix format. A user-oriented summary of all FOS flat field observations and references to their detailed analyses are also provided. For more information, please contact the above authors.