The McDonald photoelectric occultation observation program

Since 1968 an assiduous program of photoelectric observation of occultations of stars by the Moon has been pursued at McDonald Observatory. A total of about 600 events has been observed of which 254 have been published and a second list is in preparation. Timings derived from the reductions have errors of the order of 1 ms corresponding to a positional uncertainty in the lunar limb of typically 80 cm. Results are routinely communicated to the ephemerides offices.In about 140 events the fringe pattern due to diffraction by the lunar limb is sufficiently well defined to permit a determination of the slope near the point of occultation. A statistical discussion of these data is given. In all except a few cases, the slopes are numerically less than 15°, though 7 cases with slopes between 30° and 40° have been found. The relations between numbers of observations and contact angle, and between errors of slope determination and contact angle are discussed. The distribution of slope data with contact angle seems adequately explained. When slope data are collected by position angle consistently large and consistently small values show a tendency to group in a pattern suggesting a connection with observed large scale features on the lunar limb.The influence of lunar limb irregularities of a scale of a few meters on observed diffraction patterns and inferred timings is discussed. Multichannel observations should be of value in removing ambiguities. The use of occultation observations for the discovery of multiple stars and for the measurement of angular diameters of stars is mentioned. Future developments proposed for the project are considered.The project has involved contributions by a considerable number of individuals from the staff and student body at Austin, Texas, from the staff at McDonald Observatory, from visiting scientists and from the Laser Ranging Group. These contributions are acknowledged in the paper. The work has been supported by NSF Grants GP-21204 and GP-32263X.Communication presented at the conference on Lunar Dynamics and Observational Coordinate Systems held January 15–17, 1973 at the Lunar Science Institute, Houston, Tex., U.S.A.     

Selenographic control

Evaluation of selenographic data obtained with use of different observational means require the formulation of rigorous algorithms connecting the systems of coordinates, which the various methods have been referred to. The lunar principal axes of inertia are suggested as most appropriate for reference in lunar mapping and selenographic coordinate catalogues. The connection between the instantaneous axis of lunar rotation (involved in laser ranging, radar studies, astronomical observations from the surface of the Moon and VLBI observations of ALSEPs), the ecliptic system of coordinates (which in reductions of observations was considered as fixed in space), the Cassini mean selenographic coordinates (to which physical libration measures were referred), the lunar principal axes of inertia and the invariable plane of the solar system is discussed.On leave from the University of Manchester, England.Lunar Science Institute Contribution No. 138.Communication presented at the Conference on Lunar Dynamics and Observational Coordinate Systems, Held January 15–17, 1973, at the Lunar Science Institute, Houston, Tex., U.S.A.     

Scientific rationale for the D-CIXS X-ray spectrometer on board ESA's SMART-1 mission to the Moon

The D-CIXS X-ray spectrometer on ESA's SMART-1 mission will provide the first global coverage of the lunar surface in X-rays, providing absolute measurements of elemental abundances. The instrument will be able to detect elemental Fe, Mg, Al and Si under normal solar conditions and several other elements during solar flare events. These data will allow for advances in several areas of lunar science, including an improved estimate of the bulk composition of the Moon, detailed observations of the lateral and vertical nature of the crust, chemical observations of the maria, investigations into the lunar regolith, and mapping of potential lunar resources. In combination with information to be obtained by the other instruments on SMART-1 and the data already provided by the Clementine and Lunar Prospector missions, this information will allow for a more detailed look at some of the fundamental questions that remain regarding the origin and evolution of the Moon.     

The Chandrayaan-1 X-ray Spectrometer: First results

We present X-ray fluorescence observations of the lunar surface, made by the Chandrayaan-1 X-ray Spectrometer during two solar flare events early in the mission (12th December 2008 and 10th January 2009). Modelling of the X-ray spectra with an abundance algorithm allows quantitative estimates of the MgO/SiO₂ and Al₂O₃/SiO₂ ratios to be made for the two regions, which are in mainly basaltic areas of the lunar nearside. One of these ground tracks includes the Apollo 14 landing site on the Fra Mauro Formation. Within the 1σ errors provided, the results are inside the range of basaltic samples from the Apollo and Luna collections. The Apollo 14 soil composition is in agreement with the results from the January flare at the 1σ uncertainty level. Discrepancies are observed between our results and compositions derived for the same areas by the Lunar Prospector gamma-ray spectrometer; some possible reasons for this are discussed.     

Scientific objectives and selection of targets for the SMART-1 Infrared Spectrometer (SIR)

The European SMART-1 mission to the Moon, primarily a testbed for innovative technologies, was launched in September 2003 and will reach the Moon in 2005. On board are several scientific instruments, including the point-spectrometer SMART-1 Infrared Spectrometer (SIR). Taking into account the capabilities of the SMART-1 mission and the SIR instrument in particular, as well as the open questions in lunar science, a selection of targets for SIR observations has been compiled. SIR can address at least five topics: (1) Surface/regolith processes; (2) Lunar volcanism; (3) Lunar crust structure; (4) Search for spectral signatures of ices at the lunar poles; and (5) Ground truth and study of geometric effects on the spectral shape. For each topic we will discuss specific observation modes, necessary to achieve our scientific goals. The majority of SIR targets will be observed in the nadir-tracking mode. More than 100 targets, which require off-nadir pointing and off-nadir tracking, are planned. It is expected that results of SIR observations will significantly increase our understanding of the Moon. Since the exact arrival date and the orbital parameters of the SMART-1 spacecraft are not known yet, a more detailed planning of the scientific observations will follow in the near future.     

Improvement of the numerical lunar ephemeris with laser ranging data

Analysis of lunar laser ranging data is underway at several institutions. We describe here our efforts at improving the numerical ephemeris of Moon, based on over three years' span of data. Orbit generation and correction procedures are discussed briefly. Comparisons of the new ephemeris with observations and with a widely available ephemeris are illustrated. The standard deviation of the observation residuals is 7 m.Communication presented at the conference on Lunar Dynamics and Observational Coordinate Systems held January 15–17, 1973 at the Lunar Science Institute, Houston, Tex., U.S.A.     

Lunar Prospector measurements of secondary electron emission from lunar regolith

We present the first in situ measurements of the secondary electron emission efficiency of lunar regolith, utilizing Lunar Prospector measurements of secondary electrons emitted from the negatively charged night side and accelerated upward by surface electric fields. By comparing measurements of secondary currents emitted from the surface and incident primary electron currents, we find that the secondary yield of lunar regolith is a factor of ∼3 lower than that measured for samples in the laboratory. This lower yield significantly affects current balance at the lunar surface and the resulting equilibrium surface potentials. This information must be folded into models of the near-surface plasma sheath, in order to predict the effects on dust and other components of the lunar environment, and ultimately determine the importance for surface exploration and scientific investigations on the Moon.     

Effects of the physical libration of the moon on lunar orbiters

Lunar physical libration, which is true oscillation of lunar equator in the space, alters the lunar gravitational field in the space coordinate system and affects the orbiting motion of lunar orbiters (hereafter called as lunar satellites) correspondingly. The effect is very similar to that of the precession and nutation on the earth satellites, and a similar treatment can be used. The variations in the gravitational force and in the orbit perturbation solution are clearly given in this paper together with numerical illustrations.     

Russian lunar ephemeris EPM-ERA 2012

The paper describes the lunar ephemeris EPM-ERA 2012. It is a part of the Ephemerides of Planets and the Moon (EPM) developed at the Institute of Applied Astronomy (IAA) of the Russian Academy of Sciences (RAS). In order to construct EPM-ERA 2012, 17580 lunar laser ranging (LLR) observations for 1970–2012 have been processed including 21 observations from the Lunokhod 1 reflector found by the Lunar Reconnaissance Orbiter (LRO) at the end of 2010. EPM-ERA 2012 is compared with American ephemerides DE403, DE405, DE421 ephemeris, and the French ephemeris INPOP10. The possibility of the use of the ephemeris EPM-ERA 2012 to address contemporary problems of ephemeris astronomy is considered.     

Rotation of the moon and lunar coordinate systems

The need for precise definition of lunar reference systems is stressed and the principles on which systems of lunar coordinates could be based are established. Differences between coordinate systems defined by the dynamical properties of the lunar configuration and the rotational motion of the lunar globe about its centre of gravity are outlined, and rigorous mathematical formulae relating those systems have been developed. The principles of reduction of measurements are outlined and in the Appendix the absolute coordinates obtained for 700 lunar features are presented.Paper presented to the NATO Advanced Study Institute on Lunar Studies, Patras, Greece, September 1971.     

Density cavity observed over a strong lunar crustal magnetic anomaly in the solar wind: A mini-magnetosphere?

We present observations of what may be the inner region of a lunar mini-magnetosphere. If so, these likely represent the first such observations. Previous studies of solar wind interaction with lunar crustal magnetic fields found increased particle fluxes associated with magnetic amplifications, suggesting a shock/sheath region. The central density cavity expected in the inner mini-magnetosphere (if analogous to other planetary magnetospheres) has proven elusive. We now present Lunar Prospector fly-throughs of a density cavity near a strong crustal magnetic source in the solar wind, and compare these unique observations with typical orbits in the solar wind and wake. We observed the density cavity on two consecutive orbits on July 14, 1999 with optimal viewing geometry, downstream from one of the strongest lunar crustal sources (an anomaly centered at 235E, 20S), during very unusual solar wind conditions. We found no other similar features in the solar wind in 7 months of low-altitude orbits, suggesting that fully formed lunar mini-magnetospheres are rare and/or difficult to observe from orbit.     

On the standardization of the selenodetic frame of reference

Strict solving of various selenodetic and astrometric problems is possible in the case when positions of lunar surface points are given in a common system of reference. Such a system can be realised by composing the fundamental catalogue of selenodetic reference points. Principles of establishing a lunar standard frame of reference are discussed.Communication prepared for the conference on Lunar Dynamics and Observational Coordinate Systems held January 15–17, 1973 at the Lunar Science Institute, Houston, Tex. U.S.A.     

Was there ever a Terminal Lunar Cataclysm?: With lunar viscosity arguments

About 30 years ago there was a suggestion by several able scientists at the California Institute of Technology that the Moon had undergone a Terminal Lunar Cataclysm. This meant that most of the early impact cratering had been concentrated strongly at about the time of formation of the Imbrium basin. This solution was discussed in many papers and the idea of a cataclysm gradually faded away. In about 1990 it was again revived by several scientists. The idea of a Terminal Lunar Cataclysm at about the time the Imbrium basin was formed was advanced albeit in a somewhat different manner. The present paper has been written to analyze the various observations and interpretations that have been advanced to permit a cataclysm. It is concluded that the three main proposals, which, if correct, would have permitted a cataclysm to have occurred, are each faulty and not consistent with such a cataclysm. To demonstrate this conclusion it was necessary to determine absolute ages of various lunar features. This meant, in part, determinations of the existence and nature of lunar crustal viscosity consistent with times of formation of six lunar basins. The results of such studies yielded an internally consistent model which requires a long period from the original formation of the Moon at about 4.5 byr to a time slightly earlier than that of the formation of the Imbrium basin at about 3.84 byr. On this model there is no indication of a clustering of events and it is concluded that a Terminal Lunar Cataclysm never occurred.     

月球物理天平动对环月轨道器运动的影响

月球物理天平动是月球赤道在空间真实的摆动，会导致月球引力场在空间坐标系中的变化，从而引起环月轨道器(以下称为月球卫星)的轨道变化，这与地球的岁差章动现象对地球卫星轨道的影响类似．采用类似对地球岁差章动的处理方法，讨论月球物理天平动对月球卫星轨道的影响，给出相应的引力位的变化及卫星轨道的摄动解，清楚地表明了月球卫星轨道的变化规律，并和数值解进行了比对，从定性和定量方面作一讨论．     

ALSEP-quasar differential VLBI

A program of ALSEP-Quasar Very Long Baseline Interferometry (VLBI) is being carried out at the Jet Propulsion Laboratory. These observations primarily employ a 4-antenna technique whereby simultaneous observations with two antennas at each end of an intercontinental baseline are used to derive the differential interferometric phase between a compact extragalactic radio source (usually a quasar) and a number of ALSEP transmitters on the lunar surface. A continuous ALSEP-quasar differential phase history over a few hour period will lead to milliarcsecond angular accuracy in measuring the lunar position against the quasar reference frame if suitable calibration measurements are obtained. Development of this application of the 4-antenna technique has been underway at JPL for more than a year and is now producing high quality data utilizing Deep Space Network (DSN) stations in Australia, Spain, and Goldstone, California as well as the STDN Apollo station at Goldstone. These high accuracy observations are of value to tie the lunar ephemeris to a nearly inertial extragalactic reference frame, to test gravitational theories, and to measure the Earth-Moon tidal friction interaction.This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration.     

Prognosis of TiO2 abundance in lunar soil using a non-linear analysis of Clementine and LSCC data

We suggest a technique to determine the chemical and mineral composition of the lunar surface using artificial neural networks (ANNs). We demonstrate this powerful non-linear approach for prognosis of TiO₂ abundance using Clementine UV-VIS mosaics and Lunar Soil Characterization Consortium data. The ANN technique allows one to study correlations between spectral characteristics of lunar soils and composition parameters without any restrictions on the character of these correlations. The advantage of this method in comparison with the traditional linear regression method and the Lucey et al. approaches is shown. The results obtained could be useful for the strategy of analyzing lunar data that will be acquired in incoming lunar missions especially in case of the Chandrayaan-1 and Lunar Reconnaissance Orbiter missions.     

The advanced Moon micro-imager experiment (AMIE) on SMART-1: Scientific goals and expected results

The advanced Moon micro-imager experiment (AMIE) is the imaging system on board ESA mission to the Moon SMART-1; it makes use of a miniaturised detector and micro-processor electronics developed by SPACE X in the frame of the ESA technical programme. The AMIE micro-imager will provide high resolution CCD images of selected lunar areas and it will perform colour imaging through three filters at 750, 915 and 960 nm with a maximum resolution of 46 m/pixel at the perilune of 500 km. Specific scientific objectives will include (1) imaging of high latitude regions in the southern hemisphere, in particular the South Pole Aitken basin (SPA) and the permanently shadowed regions close to the South Pole, (2) determination of the photometric properties of the lunar surface from observations at different phase angles (physical properties of the regolith), (3) multi-band imaging for constraining the chemical and mineral composition of the surface, (4) detection and characterisation of lunar non-mare volcanic units, (5) study of lithological variations from impact craters and implications for crustal heterogeneity. The AMIE micro-imager will also support a Laser-link experiment to Earth, an On Board Autonomous Navigation investigation and a Lunar libration experiment coordinated with radio science measurements.     

United States lunar mapping — a basis for and result of project apollo

This paper includes 3 related presentations on United State lunar mapping made to the International symposium A Hundred Years of Lunar Mapping at Athens, Greece in May 1978. It reviews Project Apollo's role as both stimulas to and beneficiary of lunar mapping. Lunar cartographic technology and products employed and produced by the U.S. Defense Mapping Agency and its predecessor organizations, are discussed.Presented at the IAU-COSPAR Julius Schmidt Symposium on 100 Years of Lunar Mapping held at Lagonissi, Greece, 25–27 May, 1978.     

Comparison of the analytical results from the surveyor,Apollo, and Luna missions

The principal chemical element composition and inferred mineralogy of the powdered lunar surface material at seven mare and one terra sites on the Moon are compared. The mare compositions are all similar to one another and comparable to those of terrestrial ocean ridge basalts except in having higher titanium and much lower sodium contents than the latter. These analyses suggest that most, if not all, lunar maria have this chemical composition and are derived from rocks with an average density of 3.19 g cm^–3. Mare Tranquillitatis differs from the other maria in having twice the titanium content of the others.The chemical composition of the single highland site studied (Surveyor 7) is distinctly different from that of any of the maria in having much lower amounts of titanium and iron and larger amounts of aluminium and calcium. Confirmation of these general characteristics of lunar highland material has come from recent observations by the Apollo 15 Orbiter. The inferred mineralogy is 45 mole percent high anorthite plagioclase and the parent rocks have an estimated density of 2.94 g cm^–3. The Surveyor 7 chemical composition is the principal contributor to present estimates of the overall chemical composition of the lunar surface.Presented at the NATO Advanced Study Institute on Lunar Studies, Patras, Greece, September 14–25, 1971. This paper is an expanded and updated version of a paper presented at the Apollo 12 Lunar Science Conference, Houston, Texas, January 11–14, 1971, and published in the Proceedings of this Conference (Turkevich, 1971).     

Lunar surface mass distribution from dynamical point-mass solution

Combined efforts of the Jet Propulsion Laboratory and Aerospace Corporation have provided a front side lunar gravity field using the Doppler tracking data from the United States Lunar Orbiters IV and V. Data reduction was accomplished with a model which included all dynamical motion due to gravitational perturbations, as well as all tracking geometries. The field is represented as a grid of 580 surface mass points which are contoured and show correlations with various lunar surface features.This paper presents the results of one phase of research carried out at the Jet Propulsion Laboratory, California Institute of Technology, under Contract No. NAS 7-100, sponsored by the National Aeronautics and Space Administration.