NSSDC Starts Serving Compressed Data from NDADS

Volume 13, Number 4, December 1997
By Joseph King and Natalia Papitashvili

NSSDC has received from the Johns Hopkins University's Applied Physics Laboratory (APL) a set of 115 CD-ROMs holding 20-sec resolution data from four Interplanetary Monitoring Platform (IMP) 8 experiments (magnetometer/Goddard Space Flight Center [GSFC], plasma/Massachusetts Institute of Technology [MIT], two energetic particle instruments/APL). This data set was described in some detail in the June 1997 newsletter and is more fully described at http://nssdc.gsfc.nasa.gov/space/helios/imp8.html.

The data on the CD-ROMs were in 86-MB VAX/binary files covering 12 days each. To promote both the accessibility and usability of these data, NSSDC has converted them to one-day ASCII files of 16 MB each, compressed them using the gzip routine in a UNIX environment, and loaded them to the NASA Data Archive and Distribution Service (NDADS), the main near-line mass storage environment. Typical compression factors realized with gzip range between 10 and 20. (IMP telemetry gaps have fill data that compress more than real data.)

This effort represents the first time NSSDC has loaded compressed data to NDADS with the expectation that users will be able to download these zipped files to their computers and unzip them at their sites. This understanding is based on the wide and multiplatform availability of gzip/gunzip software and some initial user feedback. A readily available file will be posted by NSSDC to guide persons who need these data but who are less familiar with gzip software. Also, full ASCII forms of a few 20-sec records will be made available so that users can ensure the correct operation of their unzip software.

In addition to the authors, key NSSDC staffers involved in this activity have been Barbara Rowland, Vanessa Myers, and Muriel Taylor.

Data from the IMP 8 satellite, pictured above, has been compresseed and loaded to NDADS for downloading with gzip/gunzip software.

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Miranda Beall, beall@nssdca.gsfc.nasa.gov, (301) 286-0162
Raytheon STX, Code 633, NASA Goddard Space Flight Center
Greenbelt, MD 20771, U.S.A.

Erin D. Gardner, gardner@nssdca.gsfc.nasa.gov, (301) 286-0163
Raytheon STX, Code 633, NASA Goddard Space Flight Center
Greenbelt, MD 20771, U.S.A.



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Author:Miranda Beall
Curators: Erin Gardner and Miranda Beall
Responsible Official: Dr. Joseph H. King, Code 633
Last Revised: 26 JAN 98 [EDG]