NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

Lunar Orbit X-ray Data on Magnetic Tape


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

Time span: 1972-04-20 to 1972-04-24


This data set, on magnetic tape, is composed of reduced data supplied by the PI. The fundamental data are the count rates, for each channel, for each of the three lunar-oriented detectors and the solar detector (the last was useless due the 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 on the tapes 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 16 lunar XRFS data are from 288242 seconds GET (Ground Elapsed Time, or time since launch), 20 April 1972 at 1:58 UT on the third orbit and the final data were taken at 696654 GET, 24 April 1972 at 19:25 UT on orbit 61.

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

  • Lunar Orbit X-Ray Data


  • Planetary Science: Geology and Geophysics


  • 72-031A-08A

Additional Information



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



NameRoleOriginal AffiliationE-mail
[] NASA Logo -