New IMP 8 Data Set Created at NSSDC

Volume 14, Number 3, September 1998

By Joesph King and Natalia Papitashvili

Over the past 20 years the Interplanetary Monitoring Platform (IMP ) 8 team at the University of Maryland has been providing to NSSDC on magnetic tape selected processed data from their IMP 8 investigation. This investigation consists of two detector systems for measuring energetic charged particles: the Electrostatic Energy-Charge Analyzer (EECA) and the UltraLow Energy Telescope (ULET). The ULET system failed a few months after launch, but the EECA continues to provide important data after 25 years of operation in space. The EECA is described in detail at

The data came to NSSDC in IBM-binary format into 1991 and then in VAX- binary format thereafter. Each "normal" data record contains 11-min resolution EECA count rates and pulse height data enabling determination of the physical parameters listed in the following paragraph. In addition, each record contains much ancillary and engineering information of little potential value for science data users. Finally, each record has many words devoted to data from the ULET instrument, where such words are meaningfully filled for only the first five years of the IMP 8 life. In addition, each "normal" record was followed by zero, one or many special ULET records according to how many energetic particles were pulse-height-analyzed by ULET during the 11 minutes covered by the normal data record. (How many such ULET records followed a given normal record was given in a data word of the normal records.)

EECA parameters derivable are fluxes of: singly ionized ions in five energy/ charge windows of lower limits between 130 and 740 keV/Q, doubly charged ions in the same five keV/Q windows plus another at 65 keV/Q, ions with charge states between 5 and 8 in the same six keV/Q windows as for doubly charged ions plus another at 37 keV/Q; ions with charge states above about 10 at 37 and 65 keV/Q windows, and 600-860 keV electrons. Some of the fluxes are spin-integrated while others are in 90-deg quadrants about the spacecraft spin vector (which is normal to the ecliptic plane).

Over the years that these data accumulated off line at NSSDC, in their binary formats with mixed EECA and ULET data in normal records and variable numbers of ULET-specific records following each normal record and with many other information items of little or no value to researchers, there were virtually no requests for or access to them. To make the unmined science potential of the long series of EECA data more readily accessible and usable by the research community, NSSDC undertook to create a new ASCII, EECA-specific, network-accessible data set holding the EECA data and just the supporting material (data words) needed to make these EECA data correctly usable by potential scientist-users. This effort was supported by the University of Maryland team (Fred Ipavich and John Paquette) who provide feedback on NSSDC's selection of data words to be retained and on the precision (for example, F7.2, E10.3) to be retained in converting words from binary to ASCII representation. The University of Maryland also helped in clarifying certain ambiguities in the documentation originally provided by the University of Maryland to NSSDC many years earlier.

The newly organized and formatted data are now accessible through SPyCAT from NDADS, where they are held in 3-6 MB monthly data files. Because of the relatively small volume of these monthly files, NSSDC did not g-zip them as it had done with earlier higher volume data sets. Of course, the original University of Maryland EECA/ULET data set from which this data set was created will be retained at NSSDC. Should the demand arise, NSSDC could create from it an equivalent five-year ULET data set.

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Editor:Miranda Beall
Programmer: Erin Gardner
Responsible Official: Dr. Joseph H. King, Code 633
Last Revised: 12 FEB 99 [DRW]
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