SPECTROSCOPY OF ADDITIONAL VISIBLE PROTO-PLANETARY NEBULAE

> in this proposal, more time is being requested for bhrivnak.swsppn01 > this proposal requests an upgrade from priority 3 for bhrivnak.swsppn01 the goal of this proposal is to determine the chemical properties of the dust shells of protoplanetary nebulae through a study of their shortwavelength infrared spectra. four sources comprise the original priority 2 proposal, and a few ppn have been observed by others on gto proposals. in this proposal, we request additional observations to obtain a representative sample of both oxygen and carbonrich sources; in this way, we will be able to determine the general properties of the dust shells of these transitional objects. spectra in the wavelength interval 2.5 to 45 microns cover the regions which contain features in both oxygenrich (9.7 microns and isodiscovered features at 2045 microns) and carbonrich (21 and 30 micron and pah features) objects. we propose to observe both types. they all have visible counterparts, and we have extensive supporting groundbased observations of each of these. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]