ANALYSIS OF HYDROGEN H-ALPHA OBSERVATIONS OF THE COMA OF COMET P HALLEY/

Ground-based Fabry-Perot observations of the hydrogen coma of comet P/ Halley in the Ha (6563 angstrom) line were acquired on 10 nights betwe en 1985 mid-December and 1986 mid-January. These observations are anal yzed using a Monte Carlo Particle Trajectory Model. Model calculations were undertaken for both the line profile and the two-dimensional Hal pha brightness on the sky plane. Model calculations accurately reprodu ced both the measured line profile and the integrated brightness obtai ned through the observing aperture. The H2O production rates determine d in this manner were compared with revised values derived from [O I] 6300 angstrom observations of comet Halley, also taken with the same i nstrument. For measurements obtained on the same day, these two H2O pr oduction rates are in excellent agreement. This agreement verifies and demonstrates the underlying consistency of the H2O photochemistry and coma outflow dynamics for comet Halley. Comparisons of these H2O prod uction rates were also made with H2O production rates determined by ot her independent observations of the H and OH comae, where the various measurements sampled different spatial scales and had different apertu re locations. Because of the different time delays and spatial averagi ng introduced by the different spatial scales and aperture locations, the derived H2O production rates will not be identical to the instanta neous H2O production rates at the nucleus. The derived H2O production rates determined on the same day from the different measurements were, nevertheless, in excellent agreement with only small differences that were qualitatively consistent with the expected time delays. Collecti vely these observations provide a nearly daily time coverage for the H 2O production rates from almost 50 days preperihelion to 130 days post perihelion with only one 18 day preperihelion gap.