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Filtered and Unfiltered Laser Photon Detections


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

Time span: 1969-08-20 to 1981-06-24


This collection consists of data from the Apollo lunar laser ranging experiments from Apollos 11, 14, and 15. The data were written originally on a CDC 6600 computer. Each physical record contains 64 logical records. An additional four characters were appended at the end of each physical record when the original tapes were duplicated on an IBM 7094 computer.

The logical records are 80 characters in length. There are two types of logical data: run data, designated by the character "Z" occurring at the beginning of the records, and shot data, designated by the character "P".

The run data recorded include a Julian date, clock error, ambient temperature (Celsius), ambient relative humidity (percent saturation), wind speed, laser energy (J*10), laser frequency (Hz*10**10), pulse length (s*10**10), observational resolution (s*10**10), photo multiplier dark count (kHz), number of shots fired in the run, and several other parameters.

The shot data recorded include the Julian date, the observed time delay (s), the observational uncertainty (s*10**10), the electronic calibration delay (s*10**10), the geometric delay (s*10**10), the ambient presure (mb*10), and other parameters.

The filtered data consist of photon detections submitted to a data filtering procedure assuming linearity of O-C residuals (the difference between the observed and calculated position) over a relatively short time interval and relying on Poisson statistics for the level of confidence in a collection identified by the filter.

The unfiltered data are real data heavily interspersed with noise photons from any of the various sources of stray light. An attempt to use the data in a simple Gaussian application would result in a solution closely adhering to the prediction ephemeris used to control the detector range grating. Some filtering process must be applied to the data for effective use.

The data provider cautions users that during the reporting interval many of the data items specified in the record format were not available. The data value provided in these cases is a null value.

Alternate Names

  • Photon Det Data(Filtd + Unfiltd)


  • Earth Science: Geophysics/Geodesy
  • Planetary Science: Celestial Mechanics


  • 69-059C-04C
  • 71-008C-09A
  • 71-063C-08A

Additional Information



Questions and comments about this data collection can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Dr. J. Derral MulhollandData ProviderUniversity of Texas, Austin
Dr. J. Derral MulhollandGeneral ContactUniversity of Texas, Austin

Selected References

  • Mulholland, J. D., et al., Lunar laser ranging data deposited in the National Space Science Data Center: Filtered observations for September 1969 through June 1970 and unfiltered photon detections for July through December 1970, U. of Texas, Res. Mem. in Astronomy, 72-003, Jan. 1972.

Related Information

Lunar Ranging at McDonald Observatory

Lunar Ranging at McDonald Observatory

McDonald Laser Ranging Station (University of Texas)
Current Lunar Laser Ranging Data Sets

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