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.     

Thermal study of the unilluminated surface of the waning moon

A program of lunar infrared radiometry which uses large area scanning is described. Procedures for atmospheric attenuation correction and data reduction to temperature by relative radiometry are outlined. The scan data of the waning Moon taken during ten evenings in the 10- to 12-µm window are presented as isothermal contour maps of the lunar disc. More than 160 areas of anomalous thermal emission have been found in the lunar darkside data. These are tabulated and are also shown on an accompanying map. An error analysis, derived from accuracy estimates of the independent parameters, is included.     

Independent selenocentric system of coordinates by large-scale star-calibrated lunar photography

The selenocentric coordinates of 263 craters and one mountain are given. The scale and orientation of the selenocentric coordinates system is determined by star-calibrated lunar photographs obtained with the long-focus horizontal telescope. The origin of the system is defined by the theory of the motion of the Moon. The physical libration is taken into account for the reduction of the coordinates system to the principal axes of the lunar inertia. The reference stars coordinates are reduced to the FK4 system. The position of the lunar mass centre is determined by LURE-2 theory, the rotation parameters are taken from the Migus tables (Migus, 1980).     

In Situ Biological Contamination Studies of the Moon: Implications for Planetary Protection and Life Detection Missions

NASA and ESA have outlined visions for solar system exploration that will include a series of lunar robotic precursor missions to prepare for, and support a human return to the Moon, and future human exploration of Mars and other destinations, including possibly asteroids. One of the guiding principles for exploration is to pursue compelling scientific questions about the origin and evolution of life. The search for life on objects such as Mars will require careful operations, and that all systems be sufficiently cleaned and sterilized prior to launch to ensure that the scientific integrity of extraterrestrial samples is not jeopardized by terrestrial organic contamination. Under the Committee on Space Research’s (COSPAR’s) current planetary protection policy for the Moon, no sterilization procedures are required for outbound lunar spacecraft, nor is there a different planetary protection category for human missions, although preliminary COSPAR policy guidelines for human missions to Mars have been developed. Future in situ investigations of a variety of locations on the Moon by highly sensitive instruments designed to search for biologically derived organic compounds would help assess the contamination of the Moon by lunar spacecraft. These studies could also provide valuable “ground truth” data for Mars sample return missions and help define planetary protection requirements for future Mars bound spacecraft carrying life detection experiments. In addition, studies of the impact of terrestrial contamination of the lunar surface by the Apollo astronauts could provide valuable data to help refine future Mars surface exploration plans for a human mission to Mars.     

Insight-building models for lunar range and range rate

The analysis of range or Doppler data between sites on the Earth and Moon requires an accurate computation of the lunar orbit and detailed models of the orientation of the Earth and Moon. Models constructed to understand range and range rate can lack detail, but if they include the largest lunar orbit variations, tracking stations on a rotating Earth, and lunar sites on a synchronously rotating Moon, then they will display the largest effects for orbit elements, Earth orientation, tracking station locations, and lunar site coordinates. The range and range rate are expanded into periodic series. To understand accurate solutions, the largest periodic terms that are sensitive to various solution parameters indicate the sensitivity of data to solution parameters and the time spans needed for their determination. Conclusions include: cylindrical coordinates work well for sites on the rapidly rotating Earth, but Cartesian coordinates are more natural for the synchronously rotating Moon since the series for the three coordinate projections are distinct. For range and range rate data, daily, semimonthly, monthly, and longer periods are present. For Doppler data, the daily periods may be stronger and more useful than the long periods, particularly for terms associated with the terrestrial tracking station. Doppler data do not determine the lander coordinate toward the Earth well. Observational strategies for range and Doppler data are not identical. For all data types, one wishes a variety of hour angles, lunar declinations, times of month, and longer periods. A long span of high-quality range data can improve the lunar orbit, orientation of the Earth’s equator, and physical librations. The locations of new lunar sites or new tracking stations can be determined from shorter spans of data.     

Star-Calibrated lunar photography

Accuracy in the determination of the absolute coordinates of lunar features or the physical libration of the Moon can be greatly improved by a technique providing lunar photographs on starcalibrated plates. An outline of the photographic technique and the computer programme for the reduction of the plates is given. In the Appendix the technical details of the double slide plate carrier which, adjusted to the Data Corporation Camera, secures high quality stellar images, are presented.Work supported in part by Contract F61052-68-C-0002 between Air Force Cambridge Research Laboratories (OAR), U.S. Air Force and the Department of Astronomy, University of Manchester.     

Optimization of lunar occultations for determining the positions of point-like X-ray sources

In view of the scheduled satellite mission EXOSAT (European X-Ray Observatory Satellite) of ESA (European Space Agency) the lunar occultation technique to determine the position of point-like X-ray sources is investigated. An error analysis for the source coordinates resulting from this technique is presented and an occultation strategy is proposed to achieve optimum lunar occultations. The analysis takes into account the errors of the space coordinates of the satellite and the Moon, the unevenness of the lunar surface, the intensities of source and background, the apparent angular velocity of the Moon as seen from the satellite, the finite sizes of the preoccultation position error boxes of the X-ray sources and the inaccuracies in the satellite orbit correction manoeuvres necessary to achieve the occultations.     

Computer simulation of observations of stars from the moon using the polar zenith telescope of the Japanese project ILOM

The paper briefly describes the purpose and features of the Japanese project ILOM (In-situ Lunar Orientation Measurement) in which it is planned to install the zenith telescope with a CCD lens on one of the poles of the Moon for the observation of stars in order to determine the physical libration of the Moon (PhLM). The studies presented in this paper are the result of the first stage of the theoretical support of the project:

1. The compilation of the list of stars within the field of view of the telescope during the precessional motion of the lunar pole.
2. Modeling and analysis of the behavior of stellar tracks during the observation period.
3. Simulation and testing of the sensitivity of the measured selenographic star coordinates to changes in the parameters of the dynamic model of the Moon and the elastic parameters of the lunar body.

Direct and inverse PhLM problems are discussed. Within the scope of the direct problem visible “daily parallels” and one-year star tracks are calculated. Their behavioral features when observed from the lunar surface are shown. At this stage of the simulation selenographic star coordinates for the four models of the gravitational field of the Moon have been compared, i.e., the model constructed on the basis of the lunar laser ranging (LLR), GLGM-2, LP150Q, and SGM100h. It is shown that even when comparing modern models LP150Q and SGM100h stellar tracks differ from the arc by more than 10 ms of arc. At the stage of the inverse problem, the manifestation of viscoelastic properties of the Moon in selenographic coordinates has been studied. In the spectrum of the simulated residual differences harmonics have been identified which can serve as indicators to refine parameters, Love number k ₂ and the delay time characterizing the viscous properties of the lunar body.     

Calibration of 35 pic-du-midi photographs of the moon

The measured and calibrated coordinates of selenodetic control points on 35 Pic-du-Midi negatives obtained by the method of star-calibrated lunar photography (cf. Moutsoulas, 1970) are presented in this paper.Paper dedicated to Professor H. C. Urey on the occasion of his 80th birthday on 29 April 1973.Work supported under Contract F 61052-68-C-0002 and Grant AFOSR-72-2261 between the Aerospace Office of Scientific Research, U.S. Air Force, and the University of Manchester in England.     

Coordinates of the centre of the figure of lunar marginal zone

On the basis of large-scale star-calibrated lunar photographs the rectangular selenoequatorial coordinates of the centre of the figure of lunar marginal zone have been obtained with reference to its mass centre, the position of which has been computed by the ephemerides j = 2 and LURE-2. A new definition method of lunar mass centre coordinates by photographic observation in system j = 2 and LURE-2 is proposed.     

Diurnal physical temperature at Sinus Iridum area retrieved from observations of Chinese Chang’E-1 microwave radiometer

According to the incidence and azimuth angles of the Sun during observations of Chinese Chang’E-1 (CE-1) lunar satellite, brightness temperatures (Tb) at different lunar local time observed by the CE-1 multi-channel radiometers, especially at the Sinus Iridum (i.e. Bay of Rainbow) area, are collected from the transformation between the principal and local coordinates at the observed site, which demonstrates the Tb distribution and its diurnal variation. Based on a three-layer radiative transfer model of the lunar media, the CE-1 Tb data at 19.35 and 37.0 GHz channels are applied to invert the physical temperatures of both the dust and the regolith layer at Sinus Iridum area, where might be the CE-3 landing site, at different lunar local times. The physical temperature variations with the lunar local time and other geophysical parameters of lunar layered media are discussed.     

Tidal pattern instabilities on multi-moon planets

The equilibrium tide-generating forces in the lunar orbital plane of a planet of radius R are calculated for the case of N moons of mass Mi orbiting the planet at instantaneous polar coordinates (Di, αi). For the case of a single moon, there are only two high tides. For the case of two moons, it is found that there can exist a critical lunar orbital distance at which two high tides become unstable with respect to formation of three high tides. Bifurcation diagrams are presented which depict how the angular positions of the high and low tides on the planet vary with the lunar distances and lunar separation angle. Tidal stability diagrams, which illustrate the stability regions for various tidal patterns as a function of lunar distances and lunar separation angle, are presented for various values of D₂/D₁ and M₂/M₁. Generally speaking, the aforementioned tidal instability, and hence the propensity for formation of three high tides on a two-moon planet, exists over a significant range of lunar distances and separation angles provided that M₂/M₁∼³(D₂/D₁). For the case of N>2 moons, the tidal stability diagram becomes more complex, revealing a diversity of potential tidal patterns.     

Accurate integration of geostationary orbits with Burdet's focal elements

The theory of Burdet's focal elements is outlined. The differential equations are presented, and the initial value problem is described together with the transformation to rectangular coordinates and classical elements. The focal elements are well defined for zero eccentricity and inclination. They can be adopted for the computation of elliptic, parabolic and hyperbolic motion. For the numerical integration of near-geostationary orbits a comparison of the efficiency is made between focal elements, KS theory and rectangular coordinates. For this class of orbits, a higher accuracy has been obtained by integrating elements than integrating rectangular coordinates.     

The improvement of the lunar ephemeris

At present the fundamental lunar ephemeris is based on Brown's theory of the motion of the Moon with improvements based on the bypassing of Brown's Tables, the removal of the great empirical term, the substitution of the relevant constants of the IAU system of astronomical constants and the retransformation of Brown's series in rectangular coordinates to spherical coordinates. Even so this ephemeris does not represent adequately the recent range and range-rate radio observations, and it will be inadequate for use in the analysis of laser observations of corner reflectors on the Moon. Numerical integrations for these purposes have already been made at the Jet Propulsion Laboratory, but improved theoretical developments are also required; new solutions of the main problem are in hand elsewhere. Work at H.M. Nautical Almanac Office is aimed at obtaining improved values of the constants of the lunar orbit by a rediscussion of occultation observations made since 1943 and at the redevelopment of the series for the planetary perturbations using more precise theories of the motion of the Sun and planets. The techniques and preliminary results of exploratory numerical integrations were briefly described.Presented at the Conference on Celestial Mechanics, Oberwolfach, Germany, 17–23 August, 1969.     

Long-term perturbations due to a disturbing body in elliptic inclined orbit

In the current study, a double-averaged analytical model including the action of the perturbing body’s inclination is developed to study third-body perturbations. The disturbing function is expanded in the form of Legendre polynomials truncated up to the second-order term, and then is averaged over the periods of the spacecraft and the perturbing body. The efficiency of the double-averaged algorithm is verified with the full elliptic restricted three-body model. Comparisons with the previous study for a lunar satellite perturbed by Earth are presented to measure the effect of the perturbing body’s inclination, and illustrate that the lunar obliquity with the value 6.68^∘ is important for the mean motion of a lunar satellite. The application to the Mars-Sun system is shown to prove the validity of the double-averaged model. It can be seen that the algorithm is effective to predict the long-term behavior of a high-altitude Martian spacecraft perturbed by Sun. The double-averaged model presented in this paper is also applicable to other celestial systems.     

The mapping of lunar radar scattering characteristics

This is the first of four articles describing a comprehensive series of radar maps of the entire visible lunar hemisphere carried out at wavelengths of 3.8 and 70 cm and analyzing the echoes in both orthogonal senses of circular polarization. In this paper, the basic techniques of delay-Doppler mapping by radar are developed, and the particular steps employed in mapping the Moon are outlined. Succeeding articles present the results obtained and discuss the way in which these results relate to other, nonradar measurements as well as to the actual lunar surface properties.     

Lunar Penetrating Radar onboard the Chang'e-3 mission

Lunar Penetrating Radar(LPR) is one of the important scientific instruments onboard the Chang'e-3 spacecraft. Its scientific goals are the mapping of lunar regolith and detection of subsurface geologic structures. This paper describes the goals of the mission, as well as the basic principles, design, composition and achievements of the LPR. Finally, experiments on a glacier and the lunar surface are analyzed.     

Detection and computation of the amount of atmospheric wave-front tilt in the application of adaptive optics technology to lunar laser ranging

For dealing with the problem of too few photons in the return wave in lunar laser ranging, the effect of the atmospheric turbulence is studied. The principles of the two tracking algorithms, cross correlation and absolute difference are studied and programs are written, which are tested with solar data. Collected image data of the interested area on the lunar disc are given. The integrated tilt signals of the atmospheric wave front obtained are treated by different methods under different conditions and the algorithms are compared as to their effectiveness.     

Lunar dust and lunar simulant activation and monitoring

Abstract— NASA plans to resume human exploration of the Moon in the next decade. One of the pressing concerns is the effect that lunar dust (the fraction of the lunar regolith <20 μm in diameter) will have on systems, both human and mechanical, due to the fact that various problems were caused by dust during the Apollo missions. The loss of vacuum integrity in the lunar sample containers during the Apollo era ensured that the present lunar samples are not in the same condition as they were on the Moon; they have been passivated by oxygen and water vapor. To mitigate the harmful effects of lunar dust on humans, methods of “reactivating” the dust must be developed for experimentation, and, ideally, it should be possible to monitor the level of activity to determine methods of deactivating the dust in future lunar habitats. Here we present results demonstrating that simple grinding, as a simple analog to micrometeorite crushing, is apable of substantially activating lunar dust and lunar simulant, and it is possible to determine the level of chemical activity by monitoring the ability of the dust to produce hydroxyl radicals in aqueous solution. Comparisons between ground samples of lunar dust, lunar simulant, and quartz reveal that ground lunar dust is capable of producing over three times the amount of hydroxyl radicals as lunar simulant and an order of magnitude more than ground quartz.     

The measurement of lunar altitudes by photography—I. Estimating the true lengths of shadows

This paper provides a discussion of all known sources of error in the apparent length of a lunar shadow recorded photographically and measured with a microdensitometer. The discussion is general but is illustrated by reference to sunrise shadows of various lengths cast by the lunar Straight Wall. Measurements of shadow lengths made between half-density points of a microdensitometric scan along a shadow may contain systematic errors due to the non-linearity of the characteristic of the photographic emulsion. The most important sources of systematic-error are seeing (especially in the case of short shadows), penumbrae, and uncertain selenographic coordinates. Other errors, due to seeing, effects at a shadow-tip, and procedures of measurement, are also important but probably apply in a more nearly random manner.