IMP 8 Cosmic Ray Data Newly Archived at NSSDC

Volume 13, Number 2, June 1997
By Joseph King

Since its launch in 1973, NASA's still-active Interplanetary Monitoring Platform (IMP) 8 spacecraft has produced a great deal of solar wind and magnetospheric magnetic field, plasma, and energetic particle (cosmic rays, etc.) data. The field and plasma data have been widely disseminated by IMP scientists and by NSSDC and have been used for studies involving themselves and data from a wide variety of spacecraft and ground-based sources. Most of these studies address the coupling of the magnetized solar wind with the Earth's magnetosphere, ionosphere, and atmosphere.

Two IMP 8 energetic particle data sets have very recently arrived at NSSDC for archiving and dissemination. The smaller of the two, from Drs. Cliff Lopate and John Simpson at the University of Chicago, holds on one CD-ROM 22 years of 15-min resolution count rate data of electrons, protons, alpha particles, and carbon-nitrogen-oxygen nuclei in several energy bins. Documentation includes coefficients and discussions of alternative approaches to the production of flux values from the count rates.

The larger of the two holds on five CD-ROMs/year 20-sec resolution electron, proton, alpha particle, and medium-Z count rates from the Energetic Particle Experiment (EPE) particle detectors of Drs. Donald Williams and Donald Mitchell and from the Charged Particle Measurement Experiment (CPME) particle detectors of Drs. Robert Decker and Tom Krimigis, all of the Johns Hopkins University Applied Physics Laboratory (JHU/APL). Since availability of concurrent magnetic field and plasma data is needed for many studies of these particle data, the makers of this data set included 15-sec Goddard Space Flight Center magnetometer data and 1-min Massachusetts Institute of Technology (MIT) plasma data, both also from IMP 8.

This larger data set is sometimes called the IMP MERGE data set and actually has a long history. Some five or so years ago, Dr. Pat Briggs of the Citadel, then a recent student of Dr. Tom Armstrong, University of Kansas, who is a CPME co-investigator, undertook the effort to define the data product, to assemble the needed data, to develop the needed software to correctly merge the multisource data, and to guide the actual production being carried out at JHU/APL. A set of 354 9-track tapes was created covering the period 1973 through 1989, and a copy of these tapes were archived with NSSDC. A minor glitch was then discovered in the merging of the magnetic field data, which resulted in further production work being put on hold. In more recent years under the leadership of Dr. Robert Decker, the software was fixed and the production resumed. This time, however, with the advance of technology, it was possible to target CD-ROMs instead of 9-track tapes to hold the data. Twenty-five years of these merge data will now fit on about 125 CD-ROMs, held in five "shoeboxes" as opposed to 500 magnetic tapes, which stack as a cylinder one foot in diameter and over 40 feet high.

NSSDC expects to make both these data sets network-accessible before the end of the year. Staff anticipate that the ready access to such definitive and well-documented data sets will broaden the use of IMP energetic particle data, mostly used until now by principal investigator teams and a handful of other researchers, to a level if not matching the field/plasma data use then at least representing a significant fraction thereof.

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Miranda Beall,, (301) 286-0162
Hughes STX, Code 633, NASA Goddard Space Flight Center
Greenbelt, MD 20771, U.S.A.

Erin D. Gardner,, (301) 286-0163
Hughes STX, Code 633, NASA Goddard Space Flight Center
Greenbelt, MD 20771, U.S.A.

NASA home page GSFC home page GSFC organizational page

Author:Miranda Beall
Curators: Erin Gardner and Miranda Beall
Responsible Official: Dr. Joseph H. King, Code 633
Last Revised: 26 JUNE 1997 [EDG]