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Lunar Orbit X-Ray Data


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

Time span: 1971-07-30 to 1971-08-04


This data set is composed of reduced data supplied by the PI. The fundamental data are count rates, for each channel, for each of the 3 lunar-oriented detectors and the solar detector (the last was useless due to saturation effects), as a function of lunar position. The data are time ordered. Fortran programs are included to help the user in the preliminary analysis of these data.

The data are stored in two tables; the first gives the data for the instrument in normal mode and the second in extended mode, in which the energy boundaries measured by the first detector are doubled. The values give the measurement mode of the instrument, the time, orbit, spacecraft position and orientation, and the event counts, normally for 8-second intervals, for the three proportional counters and the solar monitor. The normal energy range for the first 7 channels of the first three counters (detector 1 unfiltered, detector 2 magnesium filter, and detector 3 aluminum filter) was between 0.75 and 2.75 keV, broken into seven equal energy ranges: 0.75-1.04, 1.04-1.32, 1.32-1.61, 1.61-1.89, 1.89-2.18, 2.18-2.46, and 2.46-2.75 keV. The solar monitor measured the range from approximately 1 to 3 keV, divided into seven equal intervals. An eighth channel recorded all x-ray events with energies higher than the upper level.

Each row in the table represents one set of measurements and contains 45 numbers in the order: one integer (I3) designated NFLAG [The values of NFLAG are: 14, normal mode; 96 calibration mode; 144, energy boundaries for detector 1 doubled; 224, calibration mode with energy range for detector 1 doubled]; eight real numbers (F11.2, 7F9.2) designated ANS(1) through ANS(8) [ground elapsed time in seconds, orbit number, selenographic latitude, selenographic longitide, altitude, pitch angle, yaw angle, roll angle]; and 36 integers (I5, 35I6) forming an array designated ISPEC(I,J), where I ranges from 1 to 4 and represents the counter used: I=1, detector 1, beryllium windowed counter, no filter; I=2,detector 2, beryllium windowed, magnesium filtered counter; I=3,detector 3, beryllium windowed, aluminum filtered counter; and I=4, solar monitor ; and J ranges from 1 to 9 and represents the energy channel: J=1-7, seven energy regions into which the energy readings were divided; J=8, all x-ray events above the upper level discriminator; and J=9, all non X-ray events. The ISPEC values are ordered in each row as ISPEC(1,1), ISPEC(1,2), ISPEC(1,3), etc. The first Apollo 15 lunar XRFS data are from 306608 seconds GET (Ground Elapsed Time, or time since launch), 30 July 1971 at 2:44 UT on the fourth orbit and the final data were taken at 794934 GET, 4 August at 18:23 UT on the 73rd orbit.

These data have been read from the tapes and put online in tabular form as part of the Lunar Data Project at the NSSDC, this data set and more information is available at:

Alternate Names


    • Planetary Science: Geology and Geophysics


    • 71-063A-09A

    Additional Information



    Questions and comments about this data collection can be directed to: Dr. David R. Williams



    NameRoleOriginal AffiliationE-mail
    Mr. Richard L. SchmadebeckData ProviderNASA Goddard Space Flight Center
    Mr. Richard L. SchmadebeckGeneral ContactNASA Goddard Space Flight Center
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