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0.5-second Encyclopedia Data Merged with Ephemeris


Availability: At NSSDC, Ready for Offline Distribution (or Staging if Digital)

Time span: 1967-07-29 to 1969-01-19


This data set is one of three identical-format data sets from the Orbiting Geophysical Observatories (OGOs) 2, 4, and 6, otherwise known as POGO 1, 2, and 3 (P is for Polar). This important source of scalar data for geophysicists modeling the Earth's magnetic field has been previously available only in highly decimated form, or for specific local times or geographic regions. The low-altitude, polar-orbiting OGOs collected data from all local times, in contrast to Magsat which collected data from only two local times. Magsat however, carried vector magnetometers in addition to a scalar magnetometer.

With reconstructed programs, the entire set of POGO Encyclopedia data was merged with the ephemeris data by the Geomagnetics Group at GSFC, and is available on 10 CD-Recordable disks. The data consist of time, latitude, longitude, altitude, and scalar magnitude of the magnetic field.

The POGO data, from three spacecraft, are available from October 1965 to April 1971. The magnetometer was part of a large satellite with several other experiments on board. These scalar measurements were taken with a rubidium vapor magnetometer at the end of a 6-meter boom. The following information gives the satellite names, launch dates, inclinations, and perigee/apogee heights.

OGO 2 -- Oct. 14, 1965, 87.3 degrees, 410 / 1510 km; OGO 4 -- July 28, 1967, 86.0 degrees, 410 / 910 km; OGO 6 -- June 5, 1969, 82.0 degrees, 400 / 1100 km.

OGO 2 collected data until October 2, 1967. Due to an early failure in the attitude control system, the data are limited to dusk local times when the orbit was in full sunlight. OGO 4 collected data almost continuously until January 19, 1969. OGO 6 operated almost continuously until August 29, 1970 then sporadically until June 1971, although the latest data included are for April 26, 1971. OGO 2 and 4 sampled data at a rate of .5 seconds, and OGO 6 collected data every .288 seconds. The error associated with the POGO data from all known sources was determined to be 5.63 nT.

The three separate spacecraft components of the combined POGO Encyclopedia Data with Ephemeris each have their own NSSDC data set ID.

The OGO 2 data set ID is 65-081A-05I, and it consists of 1 CD containing 371 MB in 4 files.

The OGO 4 data set ID is 67-073A-06B, and it consists of 3 CDs containing 1189 MB in 11 files.

The OGO 6 data set ID is 69-051A-21A, and it consists of 6 CDs containing 2557 MB in 14 files.

These data also appear in NSSDC's WWW CD-ROM Catalog at

Alternate Names

  • 0.5-s Encyclopedia Data & Ephemer


  • Space Physics: Magnetospheric Studies


  • 67-073A-06B

Additional Information



Questions and comments about this data collection can be directed to: Dr. H. Kent Hills



NameRoleOriginal AffiliationE-mail
Dr. Michael E. PuruckerData ProviderNASA Goddard Space Flight

Selected References

  • Langel, R. A., Processing of the total field magnetometer data from the OGO-2 satellite, NASA-GSFC, X-612-67-272, Greenbelt, MD, June 1967.
  • Langel, R. A., Near-Earth magnetic disturbance in total field at high latitudes 1. Summary of data from OGO's 2, 4, and 6, J. Geophys. Res., 79, No. 16, 2363-2392, doi:10.1029/JA079i016p02363, June 1974.
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