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Mulholland, J. D.

Publications and source records attributed to Mulholland, J. D..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Lunar dynamics and observational coordinate systems

The state of the art in lunar dynamics studies is summarized by a partial review of papers presented at a recent COSPAR meeting. The following general conclusions are made from the papers: (1) a comprehensive system of fundamental lunar craters is now feasible. Its coordinates can be determined by combining spacecraft, laser, and radar data. The quality of this system is well in par with those of systems based on earth-based observations. (2) Progress toward very high-precision ephemeris measurements has been very impressive, with fitting errors reduced to a few meters. Physical libration modeling techniques, a major obstacle to further improvement, are in the process of refinement. The lunar figure and planetary attraction were found to influence librations. (3) A combination of new techniques and revolutionized old techniques has a potential for achieving a still higher precision in lunar dynamics studies.

Mulholland, J. D.↗
NASA NTRS1973

Lunar laser ranging data deposited in the National Space Science Data Center: Filtered observations for 1971 July through 1971 December and unfiltered photon detections for 1972 January through 1972 June

Documentation to be used in conjunction with data deposited in the National Space Science Data Center is presented which concerns the filtered observations obtained during laser ranging operations between the McDonald Observatory and the Apollo 11, 14, and 15 reflectors, and the unfiltered photon detections. As part of the Lunar Laser Ranging Experiment, three widely separated reflector arrays were placed on the moon. Laser ranging equipment, both ground based on lunar based, is described, and coordinates of the intersection of the polar and transverse axes of the telescope are given. Filtered and unfiltered data are defined and discussed.

Mulholland, J. D.↗
NASA NTRS1973

Analysis of the first laser echoes obtained on the reflector of Luna 21

The international program of lunar telemetry, which has been in operation for three and one-half years, is intended to supply basic information for study of the lunar motion and the internal physics of the moon and the earth, particularly with reference to movement of the pole and displacements of plates. Laser echoes were obtained on Jan. 23, 1973 from the French reflector placed on the moon by Luna 21. Two series of firings, made with a 3-J laser radiated by the 2.7-m telescope of the McDonald Observatory (Texas) made it possible to identify significant echoes of an intensity comparable to those obtained with the reflector set down by Apollo 15. The path time measurements are compatible with normal coordinates.

Abalakin, V. K.↗
NASA NTRS1973

Linear change of variable in normal systems.

Linear transformations of variable in differential correction processes cannot always be accomplished in the equations of condition, yet may be desirable to reduce high correlations. The means by which this may be accomplished in the system of normal equations is derived and the process reduced to a very simple computational algorithm.

Mulholland, J. D.↗
NASA NTRS1972

Numerical isolation of flaws in the lunar theory.

The general concept of a numerical study of the lunar motion is examined and a particular case is discussed in greater detail than was possible in an earlier paper. Particular emphasis is placed upon the distinction to be made between model inadequacies and numerical artifacts, since either type of problem may be present in a given study, but the sensitivity to one or the other depends on the methodology used.

Mulholland, J. D.↗
NASA NTRS1972

Measures of time in astronomy.

Astronomically-important measures of time are discussed with their definitions, their intended purposes, and areas of viability or obsolescence. Several different kinds of year are defined. Earth rotation time is described in terms of sidereal and solar time and in terms of universal time (UT) for which four different levels are defined corresponding to different approximations of 'uniform' time. The formal definition of ephemeris time, consisting of a defined rate and epoch, is discussed and some unorthodox criticisms are presented. Uses of broadcast time are noted. In the discussion of what measure of time should be used in astronomical applications, it is stated that, at present, all dynamical applications should use a measure of time based on atomic clock time.

Mulholland, J. D.↗
NASA NTRS1972

Measurement of physical librations using laser retroreflectors.

Discussion of the applicability to lunar physics of the libration measurements obtained from the Apollo lunar laser ranging experiment, and assessment of the data obtained with respect to their adequacy for providing the desired information. A review of measurement principles and lunar properties is followed by an evaluation of the status of data collection.

Mulholland, J. D.↗
NASA NTRS1972

Laser ranging retroreflector

The lunar laser ranging retroreflector (LRRR) experiments to define the motion of the moon in its orbit are described, and the properties of the LRRR arrays and ground-station operation are discussed. It is concluded that primary benchmarks on the lunar surface are provided by the Apollo 11 and 14 arrays, and the placement of the Apollo 15 reflector.

Faller, J. E.↗
NASA NTRS1972

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

The technique of laser ranging to a reflector fixed on the lunar surface is discussed. The causes for initial low rate of data acquisition are explained. The documentation to be used in conjunction with the deposition of the filtered data in the National Space Science Data Center are documented. Filtered data obtained during laser operations between the McDonald Observatory and the reflector at Tranquility Base during the interval September 1969 through June 1970 are presented. The unfiltered photon detections for the succeeding six months are examined.

Mulholland, J. D.↗
NASA NTRS1972

Geodesy results obtainable with lunar retroreflectors.

Retroreflector packages have been carried to the moon by the Apollo 11, Apollo 14, and Apollo 15 missions, as well as by Luna 17. Laser ranging from the earth onto these packages should eventually yield information on polar motions and crustal movements accurate to a few centimeters, and on UT1 to 100 microsec. Present (1971) error of the range measurements is 30 cm, but accuracy to 3 cm should be obtainable with improvements in methods and equipment.

Faller, J. E.↗
NASA NTRS1971

The lunar laser ranging experiment

With data from two or more well-located observing stations, the lunar range can be corrected accurately for the effects of polar motion and fluctuations in the earth's rotation rate. Very accurate corrections can be made for the earth tides at each station. It appears that the use of lasers giving roughly 0.1-msec pulse lengths is highly desirable. With them, single-shot ranging accuracies of about 3 cm are expected. The actual lunar range results will be analyzed by fitting a numerical integration for the lunar motion to the data. A mathematical model for lunar range is given. Tests of the theory of gravitation are considered.

Bender, P. L.↗
NASA NTRS1971

The use of the Earth-Moon system as a radio tracking facility

The use of the earth-moon system for radio tracking has several potentially useful aspects, from a scientific standpoint: extension of the baseline by two orders of magnitude, absence of lunar atmosphere, higher-velocity parallax with a longer period, and the moon's more modellable rotation. The facility would be a convenient base station for other research, not directly involving the tracking capability, but utilizing its orbiting data link features.

Mulholland, J. D.↗
NASA NTRS1971

Laser ranging retroreflector

Laser ranging retroreflector deployed on lunar surface to study lunar librations for defining precisely lunar orbits and studying earth planetary structure - Apollo 14 flight

Alley, C. O.↗