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Estimates of the maximum duration of communications blackout are presented for a proposed Pioneer Venus mission involving a multiprobe entry targeted to individual impact sites. Calculations of the inviscid flow about the probes have been made using both finite-rate chemistry and equilibrium chemistry computer codes. Equilibrium boundary-layer calculations, including ablation, are also presented both with and without the presence of alkali metal contaminants from the heat shield. Methods are described for estimating maximum electron density in the inviscid wake and the recirculation region at the base of the probes. The results presented provide a conservative basis for planning for storage and subsequent telemetry of data during the entry phase of the mission. Nomenclaturee = electron charge / = frequency m = electron mass N e = electron number density R -radius vv = probe mass y = normal distance from body | 8 = probe ballistic coefficient 7 £ = entry angle 5 = shock standoff distance e 0 = electric permittivity of free space B c = cone half-angle Subscripts B = base cr = critical e = boundary-layer edge n = nose p = plasma s = shoulder