Rocket Borne Long-slit UV Spectroscopy of Comet Hale-Bopp

J. B. McPhate, S. R. McCandliss, P. D. Feldman, E. B. Burgh, R. Pelton (JHU)

A sounding rocket observation of comet Hale-Bopp was conducted on 1997 April 6 03:51 UT, when the comet was at heliocentric and geocentric distances of 0.92 and 1.39 AU, respectively. The instrument consisted of a 40 cm f/15.5 Dall-Kirkham telescope, a sealed 400 mm Rowland circle spectrograph with a holographically ruled, astigmatism corrected grating, and a microchannel plate (MCP) detector with a double-delay-line anode. A long slit (7  tex2html_wrap_inline105  260, 7.1 tex2html_wrap_inline105 tex2html_wrap_inline111  km  tex2html_wrap_inline105  2.6 tex2html_wrap_inline105 tex2html_wrap_inline119  km at the comet) located at the focus of the telescope served as the entrance pupil to the spectrograph. Spectral resolution of tex2html_wrap_inline121 5 Å was achieved over the entire bandpass (1280-1850 Å). The spatial resolution of the telescope was tex2html_wrap_inline121 1 (1000 km at the comet). All optical surfaces were coated with MgF tex2html_wrap_inline125 over Al and the spectrograph was sealed with a 2 mm thick CaF tex2html_wrap_inline125 window, eliminating contamination by HI tex2html_wrap_inline129 1216. The effective area of the instrument over the majority of the bandpass was 10-15 cm tex2html_wrap_inline131 .

During the observation the slit sampled the coma along the sun-comet line from tex2html_wrap_inline121 9 tex2html_wrap_inline105 tex2html_wrap_inline139  km sunward to tex2html_wrap_inline121 2 tex2html_wrap_inline105 tex2html_wrap_inline119  km tailward. Emissions from O, C, S and CO are detected with almost all emissions showing a sunward enhancement. O1 tex2html_wrap_inline129 1304, C1 tex2html_wrap_inline151 1561 and 1657 emissions fill the aperture and show little evidence of a peaked distribution. Several multiplets of S1 are observed over a gradient of optical depths. The optically thin S1 lines show a spatial distribution peaked at the nucleus while the most optically thick line shows no evidence of a peaked distribution. Numerous bands of the CO Fourth Positive system (A tex2html_wrap_inline153 -X tex2html_wrap_inline155 ) are present in the data and all show a peaked distribution, although the stronger transitions are less peaked than the weaker ones. The forbidden O1 tex2html_wrap_inline129 1356 transition is detected and exhibits a spatial profile similar to that of the CO Fourth Positive bands. C2 tex2html_wrap_inline129 1335 is detected with a spatial profile enhanced in the tailward direction.