The data acquired by the lunar laser ranging experiment are described for the six months period ending 31 December, 1972. The data are contained on two files of a binary tape written in card image format, using a CDC 6400/6600 computer. Photon detections, and unfiltered photon stops are included

Mulholland, J. D.

Shelus, P. J.

English

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https://ntrs.nasa.gov/search.jsp?R=19740020187 2020-03-23T07:38:34+00:00Z
Lunar Laser Ranging Data Deposited in the
National Space Science Data Center:
Filtered Observations for
1972 July through 1972 December
and
Unfiltered Photon Detections
for 1973 January through 1973 July
J. Derral Mulholland
Peter J. Shelus
University of Texas at Austin
Research Memorandum in Astronomy
197 4 July
I
I. Introduction
The lunar laser ranging experiment (LURE) project at McDonald
Observatory has been active for almost five years, providing beyond a
doubt the unique opportunity to acquire successfully precise ranging
ldata I'o.: t :li c ar th-moon system.
'vrom the experiment's inception, the LURE Team has recognized
tle obligation to make these data available to the scientific
community in a reasonably usable form, and we have agreed upon a time-
schedule that strives for a fair compromise between timely release
and priority of the members of the LURE Team. This report is the
documentation to be used in conjunction with the deposition in the
National Space Science Data Center (NSSDC) of the filtered data obtained
during lunar laser ranging operations at McDonald Observatory for the
six months ending 1972 December 31 and the unfiltered photon detections
I'or tlie succeeding six months.
The laser ranging equipment is mounted on the 272 cm (107-inch)
reflector at the McDonald Observatory, Fort Davis, Texas. The physical
installation has been so thoroughly described in the literature (e.g.
Silverberg and Currie 1972, Silverberg 1974) that it seems unnecessary
to dwell on it here. The nominal coordinates for this instrument, based
on high-order land survey ties to the SAO Organ Pass Tracking Station, are
geocentric radius p = 6374.665 km
east longitude X = +255.97779 degrees
geocentric latitude cp'= +30.50320 degrees
These refer to the intersection of the polar and transverse axes of
the telescope. The center of the primary mirror, as the telescope
2tracks across the sky, describes a circle of radius 305 cm whose
plane is normal to the polar axis.
The nominal coordinates for the reflectors are
Tranquility Fra Mauro Hadley
selenocentric radius p=1735.730 km 1736.680 1735.64
east longitude X=+23.485 degrees -17.4628 +3.673
latitude P=+0.642 degrees -3.6680 +26.094
based on data supplied by NASA/MSC during tracking operations during
the Apollo missions. Improved telescope and reflehctor coordinates are
available, see Bender, et al (1973).
The second of two French retroreflector arrays was deployed on
the lunar surface on the Soviet roving vehicle Lunakhod 2, landed by
the Luna 21 spacecraft in January, 1973. Shortly after, it was observed
by a Franco-American effort at the McDonald Observatory (Abalakin et al
1973). A second series of McDonald observations was obtained a
month later, after a considerable traverse by the rover. Due to the
motion, these observations are of no practical value beyond giving
assurance that the reflector array was usable and permitting some very
tenuous discussion of the use of very short data arcs for determining
reflector coordinates (Mulholland, et al 1973). These observations
(together with the unsucessful attempts at this reflector) made at
McDonald have been included in the unfiltered observations for this semi-
annual data deposition under the reflector identifier 4.
II. Data Description
The data are contained on two files of a binary magnetic tape
3written in card image format, using a CDC 6400/6600 computer. It is
written with odd parity at 800 bpi. Two types of cards are present,
distinguished by an alphabet character in column 1 (Mulholland, 1971).
The letter Z designates a "run" card, giving environmental and operational
parameters for a series of shots. Except for clock epoch error,
these will not customarily be required for application of the range
data, but serve to provide information on the observing conditions
and the state of the equipment. Most users will find them helpful
only as separators between observing sessions. The letter P in
column 1 represents a "shot" card, containing the result of a single
laser firing. A word of warning is in order to the unwary users. Some
of the specified data items may not be available. In the card images,
a blank field is a "no information" indicator. Actual null values will
be represented by zero punches.
The first data file contains the photon detections which have
been obtained by a data filtering procedure developed at the University
of Texas (Abbot, et al; 1973). This process is based on the assumption
of the linearity of 0-C residuals over a relatively short time interval
and relies on Poisson statistics for establishing a level of confidence
in a collection identified by the filter. Application of the process
results in the identification of the observations during the subject
interval.
The potential user should be aware that the laser cannot be
relied upon to produce a simple pulse shape. There sometimes is a
complex and/or biased structure within the pulse. Therefore, residuals
derived from signal photons are not necessarily expected to show a
Gaussian distribution. The uncertainties assigned are based on the sum
of the pulse half-width and the measured uncertainty in calibrating
the electronic system. Beginning with the April-May, 1972 lunation,
a letter code appears in column 32 (formerly unused) of the "Z" card
imagewhich provides an estimate for the accuracy of the electronic
calibration correction. The following code is used:
A - better than ±200 picoseconds
B - ±200 to ±400 picoseconds
C - +400 to ±600 picoseconds
D - ±600 to ±1000 picoseconds
E - + 1.0 to ±1.5 nanoseconds
F - +1.5 to ±2.0 nanoseconds
G - ±2.0 to ±4.0 nanoseconds
I1 - worse than ±4.0 nanoseconds
The calibrations were performed by E. C. Silverberg.
The second data file contains the unfiltered photon stops.
It is most important that the potential user observe the designation
"unfiltered." By this, we mean that the real data are heavily inter-
spersed with noise photons from any of the various sources of stray
light. Any attempt to use these data in a simple Gaussian application
would probably result in a solution closely adhering to the prediction
ephemeris used to control the detector range gating. Some filtering
process needs to be applied to these data before effective use can
be made of them. The unfiltered data may be of direct utility or
interest to those potential users who may wish to replace our filter
criteria with their own.
511. Acknowledgements
The data described herein were generated at the McDonald
Observatory through the collective efforts of the LURE Team and
numerous supporting personnel at their several institutions. The
team is composed of C. O. Alley and D. G. Currie (U. of Md.), P. L.
Bender and J. E. Faller (JILA), R. H. Dicke (Princeton U.), D. H.
Eckhardt (AFCRL), W. M. Kaula (UCLA), J. D. Mulholland and E. C.
Silverberg (McDonald Obs. and U. of Tex.), H. H. Plotkin (NASA/GSFC),
J. G. Williams (JPL). Executive Secretary is A. T. Strickland
(NASA HQTRS). This report and the data tapes described herein were
prepared under NASA Grant NGR 44-012-219.
6Abalakin, V. K., Calane, O., Kokurin, Y. L., Mulholland, J. D.,
Orszag, A., and Silverberg, E. C., C. R. Acad. Sci. Paris
27( 13, 673 (1973).
Abbot, R. I., Shelus, P. J., Mulholland, J. D., and Silverberg, E. C.
1973, "Laser Observations of the Moon: Identification and
Construction of Normal Points for 1969-1971" Astron. J.,
78, 78L .
Bender, P. L., Currie, D. G., Dicke, R. H., Eckhardt, D. H., Faller,
J. E., Kaula, W. M., Mulholland, J. D., Plotkin, H. H.,
Poultney, S. K., Silverberg, E. C., Wilkinson, D. T., Williams
J. G. and Alley, C. 0. 1973, "The Lunar Laser Ranging Experiment,"
Science 182, 229.
Mulholland, J. D. 1971, "Proposed Standards for Distribution and
Documentation of Lunar Laser Ranging Data " COSPAR Bulletin,
No. 61 (March).
Mulholland, J. D., Shelus, P. J., and Silverberg, E. C. 1973, COSPAR
Bull. 68, 27.
Silverberg, E. C., 1974. "Operation and Performance of a Lunar Laser
Ranging Station," Applied Optics, 13, 565.
Silverberg, E. C., and Currie, D. G. 1972, "A Description of the Lunar
Ranging Station at McDonald Observatory" Space Research XII
(Akademie-Verlag, Berglin) .


Lunar laser ranging data deposited in the National Space Science Data Center:  Filtered Observations for July through December 1972 and unfiltered photon dections for January through July 1973

Lunar laser ranging data deposited in the National Space Science Data Center: Filtered Observations for July through December 1972 and unfiltered photon dections for January through July 1973

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