2 National Optical Astronomy Observatories

The ultraviolet spectrum (1145–1720 Å) of the distant quasar Q 0302–003 (z = 3.286) was observed at 1.8 Å resolution during 10 orbits of the Hubble Space Telescope with the Space Telescope Imaging Spectrograph. A total integration time of 23,280 s was obtained. The spectrum clearly delineates the Gunn-Peterson He II absorption trough, produced by He II Lyα along the line of sight over the redshift range z = 2.78 − 3.28. Interpretation of the results was facilitated by modeling based on Keck HIRES spectra of the