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M. S. Sahu (NASA/GSFC & AURA/NOAO), W. Landsman (Raytheon/ITSS), F.C. Bruhweiler (CUA), J. Linsky (U Colorado), I. Hubeny (NASA/GSFC), M. Barstow (U Leicester), J. Holberg (U Arizona), T. Gull (NASA/GSFC), C. Bowers (NASA/GSFC), D. Lindler (ACC/GSFC), T. Lanz (NASA/GSFC), K. Feggans (ACC/GSFC)
Does the D/H ratio vary within ~ 100~pc of the Sun? If it does, what is the range of these variations? Are the D/H variations correlated to any physical property of the absorbing cloud? To answer these questions we have begun a project to obtain high-precision D/H abundance ratios in the Local Interstellar Medium within ~ 100~pc (Sahu et al. 1999, ApJ 523, L159). For this purpose, we primarily use HST-Space Telescope Imaging Spectrograph (STIS) data towards nearby hot, white dwarfs (WDs). The advantages of using STIS for this study are: (1) The high velocity resolution of STIS in the UV (~ 2 km~s-1 in the E140H and E230H modes) allows the velocity structure in the sightline to be resolved and reliable component-to-component variations can be studied (2) WDs provide a strong, smooth UV continuum against which other diagnostic interstellar absorption lines can be measured. The wider wavelength coverage (~ 200Å\ per setting) of STIS in the high-resolution E140H mode allows important interstellar lines such as N~{\sc i}, Si~{\sc ii}, O~{\sc i} and S~{\sc ii} to be measured in addition to D~{\sc i} and H~{\sc i}, at no extra cost in HST time (3) The superior echelle scatter and background corrections possible with the 2-dimensional STIS-MAMA detectors allow more accurate D/H determinations from WD spectra.\\ In this poster, we present a status report of our project along with some recent results.