Comet P/Halley neutral gas density profile along the Vega-1 trajectory measured by the Neutral Gas Experiment
Two complementary gas analyzers comprised the Neutral Gas Experiment (NGE) on the two Vega spacecraft sent to comet Halley. Although no significant mass spectra were obtained, data returned from the Vega-1 experiment have permitted the determination of the total neutral gas density profile along the spacecraft trajectory during the comet encounter. Discounting small fluctuations, the FIS instrument measured a density profile which varied approximately as the inverse radial distance squared. Data from the EIS instrument yielded a series of calibration points; e.g. the neutral density at a radial distance of 105 km was about 104 cm−3. The combined data provided a calibrated total density profile, and implied a neutral production rate of 11030 molecules/second (assuming an outflow velocity of 1 km s−1) during the hours prior to the spacecraft encounter.
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- Hsieh, K.C., Curtis, C.C., Fan, C.Y., Hunten, D.M., Ip, W.-H., Keppler, E., Richter, A.K., Umlauft, G., Afonin, V.V., Erö, J., Jr., Somogyi, J.A.: 1987, Astron. Astrophys. (this issue)Google Scholar