Data StreamThe Apollo seismic experiment data were acquired from July 21,1969 to Sept.30,1977 on the Moon. The observed data were digitized on the Moon and directly sent to the Earth in pulse-coded modulation [PCM], a type of frequency modulation [FM]. On the Earth, 13 ground tracking stations distributed worldwide received the data, and recorded these digital data on 7-or 14-track, analog, open-real magnetic tapes (range tapes) as FM signal.
From July 21,1969 to Feb.29,1976, the range tapes created at each tracking station were sent to NASA Johnson Space Center (JSC) and processed for analysis and archiving. At JSC, the data on range tapes were processed using a CDC3200 telemetry system, time-edited and recorded on digital computer-compatible tapes. Then, the digital tapes were processed on a Univac 1108 computer, and the data from each ALSEP experiment were separately on 7-track magnetic tapes (PI tapes).
As the Apollo program continued and more ALSEP stations were operating, the increased data flow impacted the Univac 1108 computer. For this reason, after April 1973, the processing procedure was modified to use the CDC3200 exclusively, and ALSEP 24-hour time-edited save tapes (ARCSAV tapes) were created. The ARCSAV tapes contain data from all the ALSEP instruments, and five ARCSAV tapes were generated daily for the 5 Apollo landing sites between April 1973 and February 1976. The PI tapes were also created using the CDC3200.
Up to March 1973, the range tapes from JSC were sent to the Goddard Space Flight Center for a permanent archive. From April 1973 to February 1976, the ARCSAV tapes were also sent to Washington National Records Center (WNRC). However, their existences can't be almost identified presently.
After Mar.1, 1976, the range tapes created at tracking stations were sent to University of Texas in Galveston (UT), where newer, smaller, and more versatile computers and equipment could be used. At UT, the range tapes were processed, and the data were stored on Work tapes using workflow similar to that used at JSC. The Work tapes were 9-track tapes which contained the ALSEP time-edited data, and they were used for archiving instead of the ARCSAV tapes until the termination of the ALSEP operation (Sept.30, 1977).
During the 1990's, the contents of the original 7-track PI tapes for PSE (Passive Seismic Experiment), produced at JSC, were reformatted and copied to 8-mm video cassette (Exabyte) tapes at the University of Texas at Austin with a help of the Institute of Space and Astronautical Science (ISAS), Japan. The 9-track tapes (the Normal-bit-rate and High-bit-rate Work tapes) stored at the University of Texas were also converted to Exabyte tapes. Normal-bit-rate Work Tape files contain all the ALSEP instrument data from Mar.1, 1976 to Sept.30, 1977, and High-bit-rate Work Tape files contain only the Passive Listening Mode data of LSPE (Lunar Surface Profiling Experiment) from the Apollo 17 station when the station was operating at high-bit-rate. After the conversion of the tapes, Exabyte tapes were sent to ISAS and archived there.
This retrieval system created at ISAS contains all digital copies of the Exabyte tape files transferred from UT. The digital data are decoded and stored in ASCII format in our relational database. All the active seismic observational data (Active Seismic Experiment (ASE) and active LSPE) were sent to the ISAS from Dr. Matthew Brzostowski. He obtained them from National Space Science Data Center (NSSDC) and reformatted them from the original archiving format to SEG-Y format. In this system, the SEG-Y format data and ASCII data of the original seismic observations are archived. Please see the following figure to view the entire data stream of the ALSEP data flow.
ReferencesJ. R. Bates, W. W. Lauderdale, H. Kernaghan
ALSEP Termination Report
NASA Reference Publication 1036 (1979).
Catalog of Lunar Seismic Data from Apollo Passive Seismic Experiment on 8-mm Video Cassette (Exabyte) Tapes
University of Texas Institute for Geophysics Technical Report No.118 (1992).
M. Brzostowski, A. Brzostowski
Archiving the Apollo active seismic data
The Leading Edge 28, pp.414-416 (2009).
S. Nagihara, Y. Nakamura, L. R. Lewis, D. R. Williams, P. T. Taylor, E. J. Grayzeck, P. Chi, G. K .Schmidt
Search and Recovery Efforts for the ALSEP Data Tapes
Abstract of 42nd Lunar and Planetary Science Conference #1103 (2011).