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M.K. Bird, R. Dutta-Roy (Univ.\ Bonn), S.W. Asmar, T.A Rebold (JPL-CalTech)
Doppler data from the {\sl Voyager 1} radio occultation of Titan were reprocessed in an attempt to detect an ionosphere. The original analysis (Lindal {\sl et al.}, 1983) provided only upper bounds on the peak electron density of 3000~cm-3 (ingress: evening terminator) and 5000~cm-3 (egress: morning terminator). The raw recordings were used to generate a longer baseline prior to occultation ingress (S-band and X-band data available) and after occultation egress (only S-band). The primary result was a positive detection of Titan's ionosphere with a maximum electron density of 2400±500~cm-3 at an altitude of 1180±150 km. There is a hint that this main peak actually splits into two layers, as would be expected from numerical models of Titan's upper ionosphere that invoke both photoionization and energetic electron impacts. Convincing detections of the main ionospheric peak were also obtained using only the S-band data for both ingress and egress.