This data set, provided by the Communications Research Centre (CRC) in Ottawa, Canada, consists of electron density profiles derived from Alouette 1 Sweep-Frequency Sounder measurements for the ionosphere above the F2 maximum (topside ionosphere). The data set is in chronological order, and includes about 27,000 profiles obtained primarily during the period 1963 to 1967. The electron density profiles were computed from digital values of frequency and virtual height, which had in turn been scaled from the ionograms. Profiles were selected because of their scientific interest. Telemetry stations are not identified, but satellite location, time of observation, solar zenith angle at the satellite, magnetic dip at the satellite, total content down to the lowest altitude of topside ionospheric reflection, and other relevant information are listed for each profile. The format gives sequences of numbers for each point scaled from the ionogram. These sequences include electron density at the successive points, and the coefficients a2, b3, b4, b5, etc. from which geometric heights can be calculated, using formulas 40 and 41 in J. E. Jackson, "The reduction of topside ionograms to electron-density profiles," Proceedings of the IEEE., p. 960, June 1969. These formulas can also be used to calculate interpolated density-height values. A CRC interpolation program (available at NSSDC) can be used with this data set. These data make up a very small portion of the recorded Alouette 1 ionograms. Latitudinal coverage is widespread, but data at longitudes near 80 deg W are more numerous than others. The data were originally provided on 9-track, 1600-bpi, odd-parity, EBCDIC tape written on a MODCOMP-4 computer. NSSDC prepared an ASCII version using the Jackson formulas to compute electron density profiles.