DOPPLER-INFERRED LAUNCH ANGLES OF GLOBAL ACOUSTIC RAY PATHS

Doppler measured at Ascension Island from a moving acoustic source at Heard Island is used to compute the azimuth of the acoustic path at th e source. This method yields a launch angle of 268.06+/-0.1 degrees as compared to the geodesically derived launch angle (allowing for Earth flattening and horizontal refraction) of 268.05 degrees. Although the Doppler-derived launch azimuths should theoretically be able to resol ve the small angular differences between acoustic paths to hydrophones to the West and East of Ascension, this proved not to be the case.