Lunar Orbiter Mission Research Articles

Analysis of boulders population around a young crater using very high resolution image of Orbiter High Resolution Camera (OHRC) on board Chandrayaan-2 mission

The Orbiter High Resolution Camera (OHRC) is a very high spatial resolution panchromatic camera (0.45–0.70 μm) on-board Chandrayaan-2 orbiter. Its spatial resolution of 0.25 m from 100 km altitude is highest among all lunar orbiter missions. A simple crater with substantial boulder population was observed in an OHRC image of a region near Boguslawsky E crater. Boulders are distinctly seen in this image because of high spatial resolution of 0.28 m and low sun elevation angle (6°) which enhanced the boulders' shadows. We have identified and mapped >2000 boulders around this young un-named simple crater (74.9216° S, 54.5148° E). It is observed that the OHRC is capable of extending the lower limit of size for identifiable boulders below 1 m. The distributions of mapped boulders are studied and compared with previous studies. It was found that the coefficient values estimated by fitting power laws to various distributions, such as size-frequency, size-range, etc., are well within the ranges reported in literature for craters distributed on lunar surface around the landing sites. Weibull distribution was also fit to the data, and the fitting coefficients were compared with the values obtained in similar studies. The crater age was estimated to be in the range of 50‐90 Ma using empirical relations, and comparison with areal density of other craters near lunar landing sites. This study also provides a glimpse of the low-light imaging capability of the OHRC showing inside the shadow regions, which were illuminated by reflected light from adjoining areas.

Petrology and geochemistry of lunar feldspathic meteorite Northwest Africa 11111: Insights into the lithology of the lunar farside highlands

AbstractWe performed a petrological, mineralogical, and geochemical study of the lunar feldspathic meteorite Northwest Africa (NWA) 11111. This meteorite contains several types of lithic clasts, including feldspathic clasts, mafic‐rich clasts, granulites, impact melt breccias, minor basaltic clasts, and highly evolved clasts cemented in a recrystallized fine grain matrix. Both mineral chemistry and geochemical characteristics indicate a lunar origin for NWA 11111. The bulk analysis suggests that NWA 11111 is a typical feldspathic lunar meteorite, which is consistent with its large population of anorthositic clasts and plagioclase fragments. A comparison of geochemical data made by lunar orbiter missions indicates that this meteorite was likely launched from the Feldspathic Highland Terrane on the lunar farside. The chemical zoning, coupled with extensive exsolution lamellae (up to 20 μm in width) occurring in pyroxene across three sections of NWA 11111, demonstrates that this meteorite contains components derived from the surface to about 10 km of lunar crust. Magnesian anorthosite clasts are commonly present in the meteorite, indicating that magnesian anorthosite probably represents an important lithology in the lunar farside crust. Basaltic clasts in NWA 11111 range from a very low‐Ti to a low‐Ti mare basalt, possibly representing cryptomare on the lunar farside. Although a KREEPy signature for NWA 11111 is not evident, highly evolved clasts containing various silica polymorphs and/or K‐feldspar are present. They may originate from late‐stage residual liquids. Lithic clasts and mineral fragments within NWA 11111 provide new insights into the diversity of lunar crust lithology and magmatic processes on the lunar farside. This meteorite also offers rocky materials from a wide vertical section of lunar crust.

NASA Prepares To Drill for the “Oil of Space”

“We’re going to the Moon, and we’re going there to stay this time,” has become a NASA mantra as the US competes with other countries, including China and Russia (https://jpt. spe.org/esa-roscosmos-to-mine-oxygen-water-from-moon-rocks-as-nasa-eyes-first-artemis-lunar-mission), to be the first to put humans on the Moon and Mars. The race will rely heavily on using resources available on the planetary bodies - or in-situ resource utilization (ISRU). Chief among these is water, which has been called “the oil of space.” As NASA prepares for Artemis mission astronauts to land on the Moon in 2024, it will fly at least two preliminary missions to look for water and gather information about the lunar south pole. The Polar Resources Ice-Mining Experiment (PRIME-1) and Volatiles Investigating Polar Exploration Rover (VIPER) missions, which will be launched in late 2022 and 2023, respectively, will be the first missions to study ISRU on another celestial body. They will also mark the first time NASA will robotically sample and analyze for ice from below the surface. And they will use technologies transferred and adapted from oil and gas exploration. Reconnaissance Missions Data from nearly 3 decades of lunar orbiter and impactor missions suggest that the Moon’s “soils,” particularly at its south pole and other regions, could contain hundreds of millions of gallons of water that could eventually be harvested and converted to oxygen, fuel, or drinkable water for human use on the Moon, Mars, and beyond. But, at what concentrations? In what kinds of soils? And is the water in a form that’s accessible? Most of the information we have about the presence of water-ice on the Moon comes from orbital measurements. The only direct evidence acquired to date came in 2009 from a sensing satellite aboard a spacecraft that was purposely crashed in the Cabeus crater. The material ejected as a result of the impact was analyzed with a spectrometer to reveal the presence of 5.6%±2.9% water-ice by mass. The form, distribution, composition, and quantity of the water-ice remain largely uncertain. The only way to reduce this uncertainty is to obtain ground-truth data by drilling exploratory boreholes in the crater. This will be the purpose of the PRIME-1 and VIPER missions. PRIME-1 will last a week to 10 days, during which a robot will deploy a drill and mass spectrometer to harvest and preliminarily evaluate moon-ice for quality and regional heights and to determine how much of the ice is lost to a process known as sublimation, wherein the water transforms directly from solid ice into vapor, rather than first going through a liquid phase. In addition to ice, PRIME-1 will gather samples including rock samples to help date the sequence of impact events on the Moon, core tube samples to capture ancient solar wind trapped in regolith layers (unconsolidated, inorganic rocky material), and paired samples of material to characterize the presence of volatiles and to assess geotechnical differences between materials inside and outside permanent shadows. The samples will be returned to Earth and studied to characterize and document the regional geology, including the small, permanently shadowed regions. The data from the mission will help scientists understand how a mobile robot to be used on the subsequent VIPER mission can search for water at the Moon’s pole, and how much water may be available to use as NASA plans to establish a sustainable human presence on the Moon by the end of the decade (Fig. 1).

An investigation of potential pyroclastic deposits on the southeast limb of the Moon

We investigated the physical and spectral properties of potential dark mantling deposits (PDMDs) previously and newly identified on the SE limb of the Moon, near the craters Humboldt and Petavius. The goals of this investigation were to constrain the composition and mode of emplacement of these poorly studied deposits, to identify interdeposit variations, and to use these results to draw conclusions about regional and subsurface geologic processes. Our investigation involved an assessment of both the physical properties (size, texture, morphology) and spectral properties (albedo, absorption bands, color ratios) utilizing remote sensing data from multiple lunar orbital missions. We found that many of the SE Limb deposits previously identified as possibly pyroclastic in origin were likely effusively emplaced. However, we also identified several likely pyroclastic deposits, including three not previously mapped. We found that the volcanic deposits across the study area comprise three major spectral groups: one similar to Mare Fecunditatis, one similar to Mare Australe, and one similar to known glassy pyroclastic deposits elsewhere on the Moon. We conclude that volcanism across the SE limb was likely fed from at least two distinct magma source regions, and that the type and extent of surface expression of this volcanic activity was possibly influenced by regional variations in crustal thickness. Our documentation and analysis of the complex volcanic history in this region of the Moon supports ongoing efforts to develop increasingly detailed interpretations of the volcanic history of the entire Moon.

Feasibility of quasi-frozen, near-polar and extremely low-altitude lunar orbits

Designing long-duration lunar orbiter missions is challenging due to the Moon's highly nonlinear gravity field and the third-body perturbations induced by the Earth, Sun and other large bodies. The absence of a Lunar atmosphere has offered the possibility for mission designers to search for extremely low-altitude, quasi-stable lunar orbits. In addition to the reduced amount of propellant required for station-keeping maneuvers, these orbits present great opportunities for unique scientific studies such as high resolution imaging and characterization of the polar ice deposits in deep craters. Prior to the GRAIL mission, mission planning for Lunar orbiters had suffered from inaccuracies, mainly due to the lack of an accurate Lunar gravity model, which resulted in severe deviations with respect to the spacecraft's nominal orbit.We study station-keeping feasibility for spacecraft in near-polar and extremely low-altitude, quasi-frozen orbits around the Moon, that are perturbed by a high-fidelity lunar gravity model and third-body effects from the Earth and Sun. For several candidate orbits, we compare the trade-space between mission duration and ΔV budget, considering impulsive maneuvers applied once every ‘N∈{2,6,10,14,18}’ orbits at periselene or aposelene. Additionally, we investigate the propulsive cost for different orbit insertion dates, the location of impulsive corrections for arresting argument of periselene (ω) drift, and controlling periselene altitude.

Multi-band Polarimetry of the Lunar Surface. III. Polarization Phase Curve

Polarimetry of the Moon reveals characteristics of the lunar regolith such as the size and composition of regolith grains, which are useful in understanding the surface properties and to determine landing sites for future lunar missions. As part of the Korea Pathfinder Lunar Orbiter (KPLO) mission, the wide-angle polarimetric camera (PolCam) will perform polarimetric measurements of the Moon for the first time from the lunar orbit. Because the degree of linear polarization is a function of the phase angle, it is necessary to observe the same region multiple times at various phase angles to construct the phase curve of polarization and derive the map of maximum polarization (Pmax). Any unexpected discontinuities of observing runs or an abrupt termination of the mission may cause the scientific goals of the PolCam to be unachievable. Here, we investigated how to recover the polarimetric phase curve when the observational data set is incomplete. Using ground-based polarimetry data, we explored the parameter space of the fitting formula of the phase curve and show that the formula can be reduced into a single parameter form. Assuming several cases of incomplete measurements, we constructed Pmax maps and investigated the allowable range of the phase-angle coverage. We show that Pmax can be estimated with a root-mean-square discrepancy less than 0.5%p when the maximum phase angle covered is greater than 90°.

Early Phase Contingency Trajectory Design for the Failure of the First Lunar Orbit Insertion Maneuver: Direct Recovery Options

To ensure the successful launch of the Korea pathfinder lunar orbiter (KPLO) mission, the Korea Aerospace Research Institute (KARI) is now performing extensive trajectory design and analysis studies. From the trajectory design perspective, it is crucial to prepare contingency trajectory options for the failure of the first lunar brake or the failure of the first lunar orbit insertion (LOI) maneuver. As part of the early phase trajectory design and analysis activities, the required time of flight (TOF) and associated delta-V magnitudes for each recovery maneuver (RM) to recover the KPLO mission trajectory are analyzed. There are two typical trajectory recovery options, direct recovery and low energy recovery. The current work is focused on the direct recovery option. Results indicate that a quicker execution of the first RM after the failure of the first LOI plays a significant role in saving the magnitudes of the RMs. Under the conditions of the extremely tight delta-V budget that is currently allocated for the KPLO mission, it is found that the recovery of the KPLO without altering the originally planned mission orbit (a 100 km circular orbit) cannot be achieved via direct recovery options. However, feasible recovery options are suggested within the boundaries of the currently planned delta-V budget. By changing the shape and orientation of the recovered final mission orbit, it is expected that the KPLO mission may partially pursue its scientific mission after successful recovery, though it will be limited.

A Deep Space Orbit Determination Software: Overview and Event Prediction Capability

This paper presents an overview of deep space orbit determination software (DSODS), as well as validation and verification results on its event prediction capabilities. DSODS was developed in the MATLAB object-oriented programming environment to support the Korea Pathfinder Lunar Orbiter (KPLO) mission. DSODS has three major capabilities: celestial event prediction for spacecraft, orbit determination with deep space network (DSN) tracking data, and DSN tracking data simulation. To achieve its functionality requirements, DSODS consists of four modules: orbit propagation (OP), event prediction (EP), data simulation (DS), and orbit determination (OD) modules. This paper explains the highest-level data flows between modules in event prediction, orbit determination, and tracking data simulation processes. Furthermore, to address the event prediction capability of DSODS, this paper introduces OP and EP modules. The role of the OP module is to handle time and coordinate system conversions, to propagate spacecraft trajectories, and to handle the ephemerides of spacecraft and celestial bodies. Currently, the OP module utilizes the General Mission Analysis Tool (GMAT) as a third-party software component for highfidelity deep space propagation, as well as time and coordinate system conversions. The role of the EP module is to predict celestial events, including eclipses, and ground station visibilities, and this paper presents the functionality requirements of the EP module. The validation and verification results show that, for most cases, event prediction errors were less than 10 millisec when compared with flight proven mission analysis tools such as GMAT and Systems Tool Kit (STK). Thus, we conclude that DSODS is capable of predicting events for the KPLO in real mission applications.

Uncertainty Requirement Analysis for the Orbit, Attitude, and Burn Performance of the 1st Lunar Orbit Insertion Maneuver

In this study, the uncertainty requirements for orbit, attitude, and burn performance were estimated and analyzed for the execution of the 1st lunar orbit insertion (LOI) maneuver of the Korea Pathfinder Lunar Orbiter (KPLO) mission. During the early design phase of the system, associate analysis is an essential design factor as the 1st LOI maneuver is the largest burn that utilizes the onboard propulsion system; the success of the lunar capture is directly affected by the performance achieved. For the analysis, the spacecraft is assumed to have already approached the periselene with a hyperbolic arrival trajectory around the moon. In addition, diverse arrival conditions and mission constraints were considered, such as varying periselene approach velocity, altitude, and orbital period of the capture orbit after execution of the 1st LOI maneuver. The current analysis assumed an impulsive LOI maneuver, and two-body equations of motion were adapted to simplify the problem for a preliminary analysis. Monte Carlo simulations were performed for the statistical analysis to analyze diverse uncertainties that might arise at the moment when the maneuver is executed. As a result, three major requirements were analyzed and estimated for the early design phase. First, the minimum requirements were estimated for the burn performance to be captured around the moon. Second, the requirements for orbit, attitude, and maneuver burn performances were simultaneously estimated and analyzed to maintain the 1st elliptical orbit achieved around the moon within the specified orbital period. Finally, the dispersion requirements on the B-plane aiming at target points to meet the target insertion goal were analyzed and can be utilized as reference target guidelines for a mid-course correction (MCC) maneuver during the transfer. More detailed system requirements for the KPLO mission, particularly for the spacecraft bus itself and for the flight dynamics subsystem at the ground control center, are expected to be prepared and established based on the current results, including a contingency trajectory design plan.

Electron content near the lunar surface using dual-frequency VLBI tracking data in a single lunar orbiter mission

In VLBI observations of Vstar, a subsatellite of the Japanese lunar mission SELENE, there were opportunities for lunar grazing occultation when Vstar was very close to the limb of the Moon. This kind of chance made it possible to probe the thin plasma layer above the Moon's surface as a meaningful by-product of VLBI, by using the radio occultation method with coherent radio waves from the S/X bands. The dual-frequency measurements were carried out at Earth-based VLBI stations. In the line-of-sight direction between the satellite and the ground-based tracking station where VLBI measurements were made, the effects of the terrestrial ionosphere, interplanetary plasma and the thin lunar ionosphere mixed together in the combined observables of dual-frequency Doppler shift and phase shift. To separate the variation of the ionospheric total electron content (TEC) near the surface of the Moon from the mixed signal, the influences of the terrestrial ionosphere and interplanetary plasma have been removed by using an extrapolation method based on a short-term trend. The lunar TEC is estimated from the dual-frequency observation for Vstar from UT 22:18 to UT 22:20 on 2008 June 28 at several tracking stations. The TEC results obtained from VLBI sites are identical, however, they are not as remarkable as the result obtained at the Usuda deep space tracking station.

Active moon: evidences from Chandrayaan-1 and the proposed Indian missions

Chandrayaan-1, the polar Lunar orbiter mission of Indian Space Research Organization, successfully carried out study of Moon’s environment and surface processes for a period of about nine months during 2008–2009. The results obtained by the mission established (i) A tenuous but active hydrosphere (ii) Volcanically active and geologically dynamic Moon and (iii) Global melting of Moon’s surface regions and formation of magma ocean early in the history of Moon. Chandrayaan-1 was equipped with a dozen instruments, including an impact probe, which housed three additional instruments. The results obtained by four instruments viz. Chandra’s Altitudinal Composition Explorer, Moon Mineral Mapper (M3), Solar Wind Monitor and Synthetic Aperture Radar gave an insight into an active hydrosphere, with several complex processes operating between lunar surface and its environment. These inferences are based on identification of H, OH, H2O, CO2, Ar etc. in the lunar atmosphere. There are indications that several young (~2 to100 Ma) volcanic regions are present on the Moon as shown by integrated studies using Terrain Mapping Camera and M3 of Chandrayaan-1 and data from other contemporary missions i.e. Kaguya and Lunar Reconnaissance Orbiter. These data establish that Moon has a dynamic and probably still active interior, in contrast to the generally accepted concept of dormant and quiet Moon. Discovery of Mg spinel anorthosites and finding of kilometer sized crystalline anorthosite exposures by M3 support the formation of global magma ocean on Moon and differentiation early in its evolutionary history. Furthermore, X-ray Spectrometer data showed anorthositic terrain with composition, high in Al, poor in Ca and low in Mg, Fe and Ti in a nearside southern highland region. This mission provided excellent opportunity for multilateral international cooperation and collaboration in instrumentation and observation in which a dozen countries participated and contributed to the success of the mission. The Mars Orbiter Mission, for study of Martian atmosphere and ionosphere was launched on 5th November, 2013 and is already on its way to Mars. This will be followed by Chandrayaan-2, a well equipped Orbiter-Lander-Rover mission. This article summarises a few results obtained by Chandrayaan-1, which changed some of the concepts about Moon's evolutionary history.

High-priority lunar landing sites for in situ and sample return studies of polar volatiles

Our understanding of the Moon has advanced greatly over the last several decades thanks to analyses of Apollo samples and lunar meteorites, and recent lunar orbital missions. Notably, it is now thought that the lunar poles may be much more enriched in H2O and other volatile chemical species than the equatorial regions sampled during the Apollo missions. The equatorial regions sampled, themselves, contain more H2O than previously thought. A new lunar mission to a polar region is therefore of great interest; it could provide a measure of the sources and processes that deliver volatiles while also evaluating the potential in situ resource utilization value they may have for human exploration. In this study, we determine the optimal sites for studying lunar volatiles by conducting a quantitative GIS-based spatial analysis of multiple relevant datasets. The datasets include the locations of permanently shadowed regions, thermal analyses of the lunar surface, and hydrogen abundances. We provide maps of the lunar surface showing areas of high scientific interest, including five regions near the lunar north pole and seven regions near the lunar south pole that have the highest scientific potential according to rational search criteria. At two of these sites—a region we call the “Intercrater Polar Highlands” (IPH) near the north pole, and Amundsen crater near the south pole—we provide a more detailed assessment of landing sites, sample locations, and exploration strategies best suited for future human or robotic exploration missions.

Ground Contact Analysis for Korea's Fictitious Lunar Orbiter Mission

In this research, the ground contact opportunity for the fictitious low lunar orbiter is analyzed to prepare for a future Korean lunar orbiter mission. The ground contact opportunity is basically derived from geometrical relations between the typical ground stations at the Earth, the relative positions of the Earth and Moon, and finally, the lunar orbiter itself. Both the cut-off angle and the orbiter's Line of Sight (LOS) conditions (weather orbiter is located at near or far side of the Moon seen from the Earth) are considered to determine the ground contact opportunities. Four KOMPSAT Ground Stations (KGSs) are assumed to be Korea's future Near Earth Networks (NENs) to support lunar missions, and world-wide separated Deep Space Networks (DSNs) are also included during the contact availability analysis. As a result, it is concluded that about 138 times of contact will be made between the orbiter and the Daejeon station during 27.3 days of prediction time span. If these contact times are converted into contact duration, the duration is found to be about 8.55 days, about 31.31% of 27.3 days. It is discovered that selected four KGSs cannot provide continuous tracking of the lunar orbiter, meaning that international collaboration is necessary to track Korea's future lunar orbiter effectively. Possible combinations of world-wide separated DSNs are also suggested to compensate for the lack of contact availability with only four KGSs, as with primary and backup station concepts. The provided algorithm can be easily modified to support any type of orbit around the Moon, and therefore, the presented results could aid further progress in the design field of Korea's lunar orbiter missions.

You Saw the Whole of the Moon: The Role of Imagination in the Perceptual Construction of the Moon

The author offers a short history of how our perceptual relationship with the Moon has changed over time. Examples of lunar imaging by Early Renaissance painter Jan Van Eyck, Leonardo da Vinci, Galileo, 19th-century photographer James Nasmyth and NASA's Ranger and Lunar Orbiter missions of the 1960s reveal ways in which our perception of the Moon has changed. Images of the Moon produced by technology remain far from “complete”—they are akin to fragments, sketches or models, providing information upon which the imagination can build. How we imagine the Moon, the author argues, is symbiotically linked with our representations of it; we only perceive the truly complete, whole Moon in the non-localized zone of our imaginations.

The lunar moho and the internal structure of the Moon: A geophysical perspective

Extraterrestrial seismology saw its advent with the deployment of seismometers during the Apollo missions that were undertaken from July 1969 to December 1972. The Apollo lunar seismic data constitute a unique resource being the only seismic data set which can be used to infer the interior structure of a planetary body besides the Earth. On-going analysis and interpretation of the seismic data continues to provide constraints that help refine lunar origin and evolution. In addition to this, lateral variations in crustal thickness (~ 0–80 km) are being mapped out at increasing resolution from gravity and topography data that have and continue to be collected with a series of recent lunar orbiter missions. Many of these also carry onboard multi-spectral imaging equipment that is able to map out major-element concentration and surface mineralogy to high precision. These results coupled with improved laboratory-based petrological studies of lunar samples provide important constraints on models for lunar magma ocean evolution, which ultimately determines internal structure. Whereas existing constraints on initial depth of melting and differentiation from quantitative modeling suggested only partial Moon involvement (< 500 km depth), more recent models tend to favor a completely molten Moon, although the former cannot be ruled out sensu stricto. Recent geophysical analysis coupled with thermodynamical computations of phase equilibria and physical properties of mantle minerals suggest that the Earth and Moon are compositionally distinct. Continued analysis of ground-based laser ranging data and recent discovery of possible core reflected phases in the Apollo lunar seismic data strengthens the case for a small dense lunar core with a radius of < 400 km corresponding to 1–3% of lunar mass.

LUNAR CARTOGRAPHY: PROGRESS IN THE 2000S AND PROSPECTS FOR THE 2010S

LUNAR CARTOGRAPHY: PROGRESS IN THE 2000S AND PROSPECTS FOR THE 2010S

Integrating advanced mobility into lunar surface exploration

With growing knowledge of the lunar surface environment from recent robotic missions, further assessment of human lunar infrastructures and operational aspects for surface exploration become possible. This is of particular interest for the integration of advanced mobility assets, where path planning, balanced energy provision and consumption as well as communication coverage grow in importance with the excursion distance. The existing modeling and simulation tools for the lunar surface environment have therefore been revisited and extended to incorporate aspects of mobile exploration. An extended analysis of the lunar topographic models from past and ongoing lunar orbital missions has resulted in the creation of a tool to calculate and visualize slope angles in selected lunar regions. This allows for the identification of traversable terrain with respect to the mobile system capabilities. In a next step, it is combined with the analysis of the solar illumination conditions throughout this terrain to inform system energy budgets in terms of electrical power availability and thermal control requirements. The combination of the traversability analysis together with a time distributed energy budget assessment then allows for a path planning and optimization for long range lunar surface mobility assets, including manned excursions as well as un-crewed relocation activities. The above mentioned tools are used for a conceptual analysis of the international lunar reference architecture, developed in the frame of the International Architecture Working Group (IAWG) of the International Space Exploration Coordination Group (ISECG). Its systems capabilities are evaluated together with the planned surface exploration range and paths in order to analyze feasibility of the architecture and to identify potential areas of optimization with respect to time-based and location-based integration of activities.

Analysis of Delta-V Losses During Lunar Capture Sequence Using Finite Thrust

To prepare for a future Korean lunar orbiter mission, semi-optimal lunar capture orbits using finite thrust are designed and analyzed. Finite burn delta-V losses during lunar capture sequence are also analyzed by comparing those with values derived with impulsive thrusts in previous research. To design a hypothetical lunar capture sequence, two different intermediate capture orbits having orbital periods of about 12 hours and 3.5 hours are assumed, and final mission operation orbit around the Moon is assumed to be 100 km altitude with 90 degree of inclination. For the performance of the on-board thruster, three different performances (150 N with of 200 seconds, 300 N with of 250 seconds, 450 N with of 300 seconds) are assumed, to provide a broad range of estimates of delta-V losses. As expected, it is found that the finite burn-arc sweeps almost symmetric orbital portions with respect to the perilune vector to minimize the delta-Vs required to achieve the final orbit. In addition, a difference of up to about 2% delta-V can occur during the lunar capture sequences with the use of assumed engine configurations, compared to scenarios with impulsive thrust. However, these delta-V losses will differ for every assumed lunar explorer`s on-board thrust capability. Therefore, at the early stage of mission planning, careful consideration must be made while estimating mission budgets, particularly if the preliminary mission studies were assumed using impulsive thrust. The results provided in this paper are expected to lead to further progress in the design field of Korea`s lunar orbiter mission, particularly the lunar capture sequences using finite thrust.

Development of Precise Lunar Orbit Propagator and Lunar Polar Orbiter's Lifetime Analysis

Korea Aerospace Research Institute, Deajeon 305-600, KoreaTo prepare for a Korean lunar orbiter mission, a precise lunar orbit propagator; Yonsei precise lunar orbit propagator (YSPLOP) is developed. In the propagator, accelerations due to the Moon’s non-spherical gravity, the point masses of the Earth, Moon, Sun, Mars, Jupiter and also, solar radiation pressures can be included. The developed propagator’s performance is validated and propagation errors between YSPOLP and STK/Astrogator are found to have about maxi-mum 4-m, in along-track direction during 30 days (Earth’s time) of propagation. Also, it is found that the lifetime of a lunar polar orbiter is strongly affected by the different degrees and orders of the lunar gravity model, by a third body’s gravitational attractions (especially the Earth), and by the different orbital inclinations. The reliable lifetime of circular lunar polar orbiter at about 100 km altitude is estimated to have about 160 days (Earth’s time). However, to estimate the reasonable lifetime of circular lunar polar orbiter at about 100 km altitude, it is strongly recommended to consider at least 50 × 50 degrees and orders of the lunar gravity field. The results provided in this paper are expected to make further progress in the design fields of Korea’s lunar orbiter missions.

Global mapping of iron and titanium oxides in the lunar megaregolith and subsurface

This paper reports mapping results obtained by remote sensing analysis of iron and titanium oxides in the megaregolith under the lunar Highlands regolith and in the subsurface under the Mare and South Pole Aitken basin regolith. FeO and TiO2 images were mosaicked from data extracted from the 1994 Clementine lunar orbiter mission from 60°N to 60°S. These images were then used to study the ejecta blanket for each of 2059 craters analysed. Average weight percentage values for each crater ejecta blanket were interpolated to derive underlying global province maps for FeO and TiO2. The Moon was divided into five provinces to balance the needs of analysis and simplicity. Division of global TiO2 weight percentages in the five megaregolith/subsurface provinces matched the observed distribution of that at the surface. In contrast, division of lunar FeO into five provinces revealed unexpectedly elevated iron concentrations (3.8 – 6.4%) in some areas of the Highland megaregolith. This province of elevated iron oxide is termed Highland II.