LIMITING ACCURACY OF FOS WAVELENGTH

R. BOHLIN, M. SIRK, and G. HARTIG
SPACE TELESCOPE SCIENCE INSTITUTE


Instrument Science Report CAL/FOS044
October 1987



ABSTRACT

Analysis of new data indicates that the FOS interne.1 caiibration
lampe produce spectra tha.t are systema.tically offset from spectra of
an external lamp wbich fully illumina.tes the spectrograph
optics. Evidence ii presented that these offeets are unstable and that
uncertainties in the offsets may limit tbe a.ccuracy of the wavelength
calibra.tion on orbit. Possible corrective mea.sures arc suggested.