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1) ISIS 1 Electron N and T data maxmize
Resource ID:spase://VSPO/NumericalData/ISIS1/CEP/PT60S
Start:1969-01-30 00:00:00 Observatory:ISIS 1 Cadence:60 seconds
Stop:1971-06-01 00:00:00 Instrument:Cylindrical Electrostatic Probes Resource:NumericalData
ISIS 1 ionospheric electron density and temperature data at 1-5 min resolution

2) ISIS 1 1-min Position Data maxmize
Resource ID:spase://VSPO/NumericalData/ISIS1/Ephemeris/PT1M
Start:1969-01-30 00:00:00 Observatory:ISIS 1 Cadence:1 minute
Stop:1990-01-30 00:00:00 Instrument:ISIS1 Positions Resource:NumericalData
ISIS-1 satellite position and magnetic field model information.

3) ISIS 1 Swept-/Fixed-Averaged Ionograms maxmize
Resource ID:spase://VSPO/NumericalData/ISIS1/SFS/AveragedIonongrams
Start:1969-01-30 14:50:12 Observatory:ISIS 1 Cadence:
Stop:1983-12-30 15:19:33 Instrument:ISIS1 Swept-Frequency Sounder Resource:NumericalData
This data set consists of ISIS 1 (International Satellites for Ionospheric Studies)ionograms that have been obtained through a data restoration project. The ISIS ionograms, consisting of a fixed-frequency and a swept-frequency part, were digitized from the original ISIS telemetry tapes. The digitized sounder data consisting of 8-bit receiver-amplitude values collected at a 40 kHz rate contain the time and the frequency associated with each sounder pulse. The frequency of each sounder pulse is determined from a 3rd degree interpolation between the times of the frequency markers as identified in the sounder video during the A/D operation. Included in this data set are the average-resolution ionograms (averages of each 4 successive 40 kHz 8-bit values) in CDF format. Software to read and display the individual CDF files is available at These CDF files were produced at NSSDC from the original PI-provided ionogram data. Other ionogram data sets available at NSSDC include the full resolution ionograms and average ionograms both in the PI-provided (OS2) binary format, ASCII header files with pass-specific information and the PCM data which contain header, time, AGC, frequency-marker information and telemetry-level data from all other ISIS instruments. The binary average ionograms and the ASCII header files are available online at ISIS 1 and 2 data are available to the extent permitted by telemetry scheduling and the location of telemetry stations. A list of stations can be found at and their location on a worldmap is shown in (

4) ISIS-1 Topside Sounder Ionograms maxmize
Resource ID:spase://VWO/NumericalData/ISIS1/SFS/Ionogram.PT29S
Start:1969-01-30 14:50:12 Observatory:ISIS 1 Cadence:24 seconds
Stop:1983-12-30 15:19:33 Instrument:ISIS1 Swept-Frequency Sounder Resource:NumericalData
These ionograms were digitized from the original ISIS-1 7-track analog telemetry tapes using the facilities of the former Data Evaluation Laboratory at the NASA/GSFC. This data restoration project is headed by Dr. R.F. Benson (NASA/GSFC). Ionograms were digitized at the rate of 40,000 16-bit samples/sec. This sample rate is higher than the Nyquist frequency of 30 kHz. The sample frequency of 40 kHz provides a measurement every 25 microseconds corresponding to an apparent range (c*t/2) interval of 3.75 km. Each ionogram consists of a fixed-frequency and and a swept-frequency portion. The time resolution between ionograms is typically 29 seconds.

5) ISIS 1 CRC Electron Density Profiles maxmize
Resource ID:spase://VSPO/NumericalData/ISIS1/SFS/TOPS
Start:1969-02-01 15:50:12 Observatory:ISIS 1 Cadence:
Stop:1980-05-30 02:41:08 Instrument:ISIS1 Swept-Frequency Sounder Resource:NumericalData
This data set, provided by the Communications Research Centre (CRC) in Ottawa, Canada, consists of electron density profiles for the ionosphere above the F2 maximum (topside ionosphere). The data are computed from digital values of frequency and virtual height, scaled from ionograms that are measured by the ISIS 1 (International Satellites for Ionospheric Studies) Swept-Frequency Sounder. The data are ordered chronologically. Telemetry stations are not identified, but satellite location, Greenwich mean time of observation, solar zenith angle at the satellite, dip latitude at the satellite, total electron content down to the lowest height of topside signal reflection (normally near 300 km), and other relevant information is noted with 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. (

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