INTERNAL FOS Pt-Cr-Ne CALIBRATION LAMPS
Performance in the Far UV

M. SIRK and R. UOHLIN
SPACE TELESCOPE SCIENCE INSTITUTE

Instrument Science Report CAL/FOS014 22 MARCH, 1985



Abstract


Adequate wavelength calibrations are obtainable for H13 from 15 and
14 lines from the normal and cross-strapped lamps, respectively, with
a RMS difference of 0.065Ä. However. the five lines between 1169 and
1220Ä, which should be prominent in PtCr--Ne lamps, cannot be
identified in H13 spectra of 400s duration (lOOs per quarter step)
from the internal lamps. The attenuation of the far UV lines is
probably caused by the poor focus of these wavelengths, due to the
rapidly increasing index of refraction of the MgF2 lens of the larnps
below isooÄ. The lack of short wavelength lines leads to an
uncertainty in the wavelength scale that is as bad as 80 km s1 at
JJSOA. or about 10 times worse than the typical error at longer
wavelengths.