Lunar Observations Research Articles

Empowering Astronomical Exploration: Advancement of New Moon Observation Devices in Sarawak, Malaysia

Understanding the motion of celestial objects is essential for space exploration. Observing the new crescent Moon requires advanced technological devices due to the moon’s position in the atmosphere and the refraction of sunlight on the horizon. Nowadays, theodolite and telescope applications are commonly used for new crescent moon sightings because they offer superior visibility compared to the naked eye. In Sarawak, the Falak Section holds the authority to observe the new crescent Moon to determine the beginning of the Hijree month. Thus, this study aims to examine the development of devices to observe the new moon crescent in the Sarawak Mufti Department. Qualitative methods are employed, involving the perspectives of astronomers and data on new crescent Moon observations using the observation devices in the Falak Section. From 1997 onwards, the Sarawak Mufti Department had three theodolites and seven telescopes specifically for new crescent moon observations. Additionally, there are 22 recorded data of new crescent Moon sightings using these devices. These findings indicate a direct correlation between the observation devices and the potential visibility of the new crescent Moon in Sarawak. This study will benefit the Sarawak Mufti Department in evaluating suitable devices for new crescent Moon observations, whether acquiring new devices or selecting devices for new crescent moon observations.

Characterization of the Small Robotic Telescope Instrument and Implementation at ITERA Lampung Astronomical Observatory

As time has passed, the technological advances used to run these telescope systems have become faster, more reliable, and more user-friendly. Institut Teknologi Sumatera (ITERA) has installed a small robotic telescope at the Meteorology–Climatology–Geophysics Observing Station in collaboration with an ASTELCO System. The telescope system is designed to make fully robotic observations and can operate in both interactive and unattended robotic modes. This study's primary focus is on the OZT-ALTS telescope robotic system with the optical system using triplet apochromatic lens technology manufactured by LZOS with a focal ratio of f/8 refractor design. The telescope mount is a German Equatorial (NTM-500 manufactured by ASTELCO) with a direct drive system with an absolute encoder, and it allows fully programmable tracking speeds with a typical slewing speed of 20°/sec and a tracking accuracy range of 0.3–1.0 arcsec. For the process of collecting moon observation images, we use Manta G-031B. The OZT-ALTS robotic telescope is now contributing to monitoring crescent moon observation and astronomical studies. This paper presents the scientific motivation behind the OZT-ALTS robotic telescope and the facility's specifications and unique features. Furthermore, we present to characterize the result of the hardware OZT-ALTS robotic telescope system to increase the mechanical and optical performance of the telescope system based on the in-situ test observations. Based on the result, setting the Gain on the camera at 3.5 e-/ADU is the limit for the CCD to produce good-quality output images by utilizing the entire dynamic range without saturation. We also present an example of the science we have performed with the OZT-ALTS robotic telescope. The OZT-ALTS can observe young crescent moon events in the daylight after implementing the CLAHE technique to enhance contrast objects. On the other hand, the OZT-ALTS can also observe WASP-16b and WASP-34b exoplanets by using the transit method to analyze the decreasing light curve when a planet passes between a star and its observer.

Light Scattering From High‐Porosity 3D Simulants of the Lunar Regolith at Small Phase Angles

AbstractLunar regolith consists of unconsolidated grains with high porosity, called the fairy castle structure. It is closely linked to the lunar opposition effect, which is the effect where brightness sharply increases as the phase angle approaches 0. However, owing to the Earth's gravity, it is difficult to reproduce the structure to study the physical characteristics of the lunar fairy castle structure in the laboratory. We designed a lunar fairy castle structure model for 3D printing. These models had high porosity and were simplified to tree‐like shapes. Various porous conditions of the surface were considered, represented by the number of trees, maximum trunk length, and maximum branch angle. In this study, a laboratory experiment was conducted to measure the reflectance of simulants with a fairy castle structure within a small phase angle range from 1.4 to 5.0. The result is analyzed for the sample porosity with the tangential slope of the reflectance S, which denotes the strength of the opposition effect. In addition, the results of this study were compared with lunar observation data. The porous samples exhibited a relatively large S value. The influence of branch length and attachment angle was very weak in this study. Samples with a porosity between 0.78 and 0.82 represent the similar S values to the lunar observation data, a mean porosity of lunar regolith. In conclusion, our findings suggest a potential correlation between porosity and the opposition effect in printed samples, proposing a new research approach for understanding the lunar opposition effect.

Early Mission Calibration Performance of NOAA-21 VIIRS Reflective Solar Bands

The Visible Infrared Imaging Radiometer Suite (VIIRS) is one of the key instruments on the recently launched NOAA-21 (previously known as JPSS-2) satellite. The VIIRS, like its predecessors on the SNPP and NOAA-20 satellites, provides daily global coverage in 22 spectral bands from 412 nm to 12 μm. The geometrically and radiometrically calibrated observations are the basis for many operational applications and scientific research studies. A total of 14 of the 22 bands are reflective solar bands (RSBs), covering photon wavelengths from 412 nm to 2.25 μm. The RSBs were radiometrically calibrated prelaunch and have been regularly calibrated on orbit through the onboard solar diffuser (SD) and scheduled lunar observations. The on-orbit SD’s reflectance change is determined by the onboard solar diffuser stability monitor (SDSM). We review the calibration algorithms and present the early mission performance of the NASA N21 VIIRS RSBs. Using the calibration data collected at both the yaw maneuver and regular times, we derive the screen transmittance functions. The visible and near-infrared bands’ radiometric gains have been stable, nearly independent of time, and so were the radiometric gains of the shortwave-infrared bands after the second mid-mission outgassing. Further, we assess the Earth-view striping observed in the immediate prior collection (Collection 2.0) and apply a previously developed algorithm to mitigate the striping. The N21 VIIRS RSB detector signal-to-noise ratios are all above the design values with large margins. Finally, the uncertainties of the retrieved Earth-view top-of-the-atmosphere spectral reflectance factors at the respective typical spectral radiance levels are estimated to be less than 1.5% for all the RSBs, except band M11 whose reflectance factor uncertainty is 2.2%.

Design and Analysis of a Moon-Based Earth-Radiation Measurement System

This research project envisions using a lunar observation platform to measure the full-wave (0.2~100 μm) and shortwave (0.2~4.3 μm) radiation of the Earth, achieving an accurate estimation of the overall radiation budget of the Earth. Based on the lunar platform, the system analyzes Earth’s radiation characteristics and geometric attributes, as well as the sampling properties of observation times. Informed by these analyses, an Earth-facing optical radiation measurement system tailored to these specifications is designed. The optical system adopts an off-axis three-mirror configuration with a secondary image plane, incorporating a field stop at the primary image plane to effectively suppress solar stray light, scattered lunar surface light, and background radiation from the instrument itself, ensuring the satisfactory signal-to-noise ratio, detection sensitivity, and observation duration of the instrument. At the same time, stringent requirements are imposed for the surface treatments of instrument components and temperature control accuracy to further ensure accuracy. Simulation analyses confirm that the design satisfies requirements, achieving a measurement accuracy of better than 1% across the entire optical system. This Moon-based Earth-radiation measurement system, with capabilities for Earth-pointing tracking, radiation energy detection, and stray-light suppression, furnishes a more comprehensive dataset, helping to advance our understanding of the mechanisms driving global climate change

Quantitative grain size estimation on airless bodies from the negative polarization branch

This work explores characteristics of the negative polarization branch (NPB), which occurs in scattered light from rough surfaces, with particular focus on the effects of fine particles. Factors such as albedo, compression, roughness, and the refractive index are considered to determine their influence on the NPB. This study compiles experimental data and lunar observations to derive insights from a wide array of literature. Employing our proposed methodology, we estimate the representative grain sizes on the lunar surface to be D ~ 1–2 µm, with D ≲ 2–4 µm, consistent with observed grain size frequency distributions in laboratory settings for lunar fines. Considering Mars, we propose that the finest particles are likely lacking (D ≫ 10 µm), which matches previous estimations. This study highlights the potential of multiwavelength, particularly near-infrared, polarimetry for precisely gauging small particles on airless celestial bodies. The conclusions provided here extend to cross-validation with grain sizes derived from thermal modeling, asteroid taxonomic classification, and regolith evolution studies.

Cosmic mysteries and the hydrogen 21-cm line: bridging the gap with lunar observations.

The hydrogen 21-cm signal is predicted to be the richest probe of the young Universe, including those eras known as the cosmic Dark Ages, the Cosmic Dawn (when the first star and black hole formed) and the Epoch of Reionization. This signal holds the key to deciphering processes that take place at the early stages of cosmic history. In this opinion piece, we discuss the potential scientific merit of lunar observations of the 21-cm signal and their advantages over more affordable terrestrial efforts. The Moon is a prime location for radio cosmology which will enable precision observations of the low-frequency radio sky. The uniqueness of such observations is that they will provide an unparalleled opportunity to test cosmology and the nature of dark matter using the Dark Ages 21-cm signal. No less enticing is the opportunity to obtain a much clearer picture of the Cosmic Dawn than that currently achievable from the ground, which will allow us to determine the properties of the first stars and black holes. This article is part of a discussion meeting issue 'Astronomy from the Moon: the next decades (part 2)'.

LIME: Lunar Irradiance Model of ESA, a new tool for absolute radiometric calibration using the Moon

Abstract. Absolute calibration of Earth observation (EO) sensors is key to ensuring long-term stability and interoperability, and it is essential for long-term global climate records and forecasts. The Moon provides a photometrically stable calibration source within the range of the Earth's radiometric levels and is free from atmospheric interference. However, to use this ideal calibration source, one must model the variation in its disc-integrated irradiance resulting from changes in Sun–Earth–Moon geometries. The Lunar Irradiance Model of the European Space Agency (LIME) is a new lunar irradiance model developed from ground-based observations acquired using a lunar radiometer operating from the Izaña Atmospheric Observatory near Mount Teide, located in Tenerife, Spain. Nightly top-of-atmosphere (TOA) irradiance is determined using the Langley plot method, and each observation is traceable to the international system of units (SI) through the radiometer calibration performed at the National Physical Laboratory (NPL). Approximately 590 lunar observations acquired between March 2018 and December 2022 currently contribute to the model parameter derivation, which builds on the widely used ROLO (Robotic Lunar Observatory) model analytical formulation. This paper presents the strategy used to derive LIME parameters: the characterisation of the lunar radiometer, the derivation of nightly top-of-atmosphere lunar irradiance and a description of the model parameter derivation, along with the associated metrologically rigorous uncertainty. The model output has been compared to PROBA-V, Pléiades and Sentinel-3B, as well as to the VITO implementation of the ROLO model. Initial results indicate that LIME predicts 3 %–5 % higher lunar-disc-integrated irradiance than the ROLO model for the visible and near-infrared channels. The model output has an expanded (k=2) radiometric uncertainty of ∼ 2 % at the lunar radiometer wavelengths, and it is expected that planned observations until at least 2024 further constrain the model parameters in subsequent updates.

A SABEDORIA LOCAL EM SISTEMAS AGROFLORESTAIS: O ESTUDO DE CASO NA VILA WANGA, SUBDISTRITO DE MOTOLING LESTE, REGÊNCIA DE MINAHASA DO SUL, INDONÉSIA

Purpose: The purpose of this study is to ascertain how the Wanga Village community manages land using agroforestry technologies. Based on the observations, different component kinds are found in the sites of the respondents. Agrisilviculture, agrosilvofishery, agrosilvopasture and agroforestry patterns employed by the residents of Wanga village. Method: The approach is a survey that combines field observations and interviewing methods. Purposive sampling was used to select respondents, and the indigenous inhabitants of Wanga Village who oversee agroforestry land met the selection criterion. Interviews with respondents using questionnaires. Following the research results, a descriptive analysis was conducted on the data. Results and conclusion: The Wanga Village community still uses an agroforestry technique to manage their land with the help of local knowledge. The agroforestry system in Wanga Village is still used to manage land utilizing the traditional knowledge of "mapalus" or "maendo," "toki bulu," and moon observation. Research implications: The way the residents of Wanga Village observe the "New Moon" phase which comes once a month when the moon is in the west, appears at sunset and the moon adopts the appearance of a crescent. The young quartile moon phase follows the "new moon" phase, which lasts for three days during which people are believed to not plant anything. After the young quartile phase, people wait six days for the big moon phase, during which they believe they cannot plant any fruit plants because they will not bear fruit. Originality/value: "Toki Bulu" is a community activity on agrosilvofishery land in providing fish food. Based on the results of interviews, the community's unique way of feeding fish is by "Toki Bulu" (tapping the feathers) first to call the fish. "Mapalus" is a social activity originating from Minahasa culture and is usually called mutual cooperation. "Mapalus" for the Tountemboan people is called "Maendo" which means taking the day or taking advantage of the day to work together with other people. The Wanga Village community still carries out this activity, especially in land preparation.

Standar Pos Observasi Bulan Kementerian Agama & BMKG (Analisis Terhadap POB. Blang Tiron, Bukit Pole Kompleks Perumahan PT. Perta Arun gas Lhokseumawe)

The implementation of the Rukyat hilal sighting includes an important concern for Muslims. Among the supports for the successful implementation of hilal sightings is the existence of standard and ideal hilal sightings. Based on the author's observations and interviews with reckoning and rukyat staff at the Lhokseumawe Ministry of Religion, POB Blang Tiron Bukit Pole housing complex PT. Perta Arun Gas Lhokseumawe still has not succeeded in seeing the new moon, especially for the sighting of the new moon at the beginning of Ramadan and the beginning of Shawwal (Idul Fitri). So that the POB Bukit Pole Blang Tiron housing complex PT. Perta Arun Gas Lhokseumawe has never printed data on the sighting of the new moon to the Indonesian Ministry of Religion's Hisab Rukyat Agency (BHR). This research uses qualitative methods with the type of research used is field research through direct observation in the field and uses theories taken from the literature in the form of books, journals and others to strengthen research. While the data collection technique uses descriptive analysis method. The research location is located at the Blang Tiron Moon Observation Post, Bukit Pole, Housing Complex of PT. Perta Arun Gas Lhokseumawe. The research results in this study are (1). Natural conditions of the Blang Tiron Bukit Pole Observation Post, Housing Complex of PT. Perta Arun Gas Lhokseumawe apparently has not met the standards set by the Ministry of Religion and the Meteorology, Climatology and Geophysics Agency (BMKG). (2). The success rate of Rukyat Hilal sightings at the POB Blang Tiron Bukit Pole Housing Complex PT. Perta Arun Gas Lhokseumawe still does not meet the average sighting of the new hilal as data on the hilal study spanning four years for the month of Ramadan and Shawwal 1438-1441 H/2017-2020 M.

Characterization and Absolute Calibration of the Far-infrared Field Integral Line Spectrometer for SOFIA

We present the characterization and definitive flux calibration of the Far-infrared Field Integral Line Spectrometer (FIFI-LS) instrument on board SOFIA. The work is based on measurements made in the laboratory with an internal calibrator and on observations of planets, moons, and asteroids as absolute flux calibrators made during the entire lifetime of the instrument. We describe the techniques used to derive flat fields, water vapor column estimates, detector linearity, spectral and spatial resolutions, and absolute flux calibration. Two sets of responses are presented, before and after the entrance filter window was changed in 2018 to improve the sensitivity at 52 μm, a wavelength range previously not covered by PACS on Herschel. The relative spectral response of each detector and the illumination pattern of the arrays of the FIFI-LS arrays are derived using the internal calibrator before each observational series. The linearity of the array response is estimated by considering observations of bright sources. We find that the deviation from the linearity of the FIFI-LS arrays affects the flux estimations by less than 1%. The flux calibration accuracy is estimated to be 15% or better across the entire wavelength range of the instrument. The limited availability of sky calibrators during each observational series is the major limiting factor of the flux calibration accuracy.

Total ozone variability and trends over the South Pole during the wintertime

Abstract. The Antarctic polar vortex creates unique chemical and dynamical conditions when the stratospheric air over Antarctica is isolated from the rest of the stratosphere. As a result, stratospheric ozone within the vortex remains largely unchanged for a 5-month period from April until late August when the sunrise and extremely cold temperatures create favorable conditions for rapid ozone loss. Such prolonged stable conditions within the vortex make it possible to estimate the total ozone levels there from sparse wintertime ozone observations at the South Pole. The available records of focused Moon (FM) observations by Dobson and Brewer spectrophotometers at the Amundsen–Scott South Pole Station (for the periods 1964–2022 and 2008–2022, respectively) as well as integrated ozonesonde profiles (1986–2022) and MERRA-2 reanalysis data (1980–2022) were used to estimate the total ozone variability and long-term changes over the South Pole. Comparisons with MERRA-2 reanalysis data for the period 1980–2022 demonstrated that the uncertainties of Dobson and Brewer daily mean FM values are about 2.5 %–4 %. Wintertime (April–August) MERRA-2 data have a bias with Dobson data of −8.5 % in 1980–2004 and 1.5 % in 2005–2022. The mean difference between wintertime Dobson and Brewer data in 2008–2022 was about 1.6 %; however, this difference can be largely explained by various systematic errors in Brewer data. The wintertime ozone values over the South Pole during the last 20 years were about 12 % below the pre-1980s level; i.e., the decline there was nearly twice as large as that over southern midlatitudes. It is probably the largest long-term ozone decline aside from the springtime Antarctic ozone depletion. While wintertime ozone decline over the pole has hardly any impact on the environment, it can be used as an indicator to diagnose the state of the ozone layer, particularly because it requires data from only one station. Dobson and ozonesonde data after 2001 show a small positive, but not statistically significant, trend in ozone values of about 1.5 % per decade that is in line with the trend expected from the concentration of the ozone-depleting substances in the stratosphere.

From Babylonian lunar observations to Floquet multipliers and Conley–Zehnder indices

In 1878, Hill found numerically, in his limiting case of the restricted three-body problem, the so-called Hill’s lunar problem, a planar direct periodic orbit with a period of one synodic month. By virtue of the spatial system’s invariance under a symplectic involution, whose fixed point set corresponds to the planar problem, we can assign to Hill’s orbit planar and spatial Floquet multipliers and planar and spatial Conley–Zehnder indices. We show that these have deep astronomical significance because, on the one hand, we relate the anomalistic month to the planar Floquet multipliers and the planar Conley–Zehnder index. On the other hand, we relate the draconitic month to the spatial Floquet multipliers and the spatial Conley–Zehnder index. Knowledge of this lunar month dates back to the Babylonians, who lived until around 500 BCE. In order to determine the indices, we analyze analytically the bifurcation procedure of the fundamental families of planar direct and retrograde periodic orbits (traditionally known as families g and f) from the rotating Kepler problem for very low energies.

Simulation Study of the Lunar Spectral Irradiances and the Earth-Based Moon Observation Geometry

As a radiant light source within the dynamic range of most spacecraft payloads, the Moon provides an excellent reference for on-orbit radiometric calibration. This research hinges on the precise simulation of lunar spectral irradiances and Earth-based Moon observation geometry. The paper leverages the Hapke model to simulate the temporal changes in lunar spectral irradiances, utilizing datasets obtained from the Lunar Reconnaissance Orbiter Camera (LROC). The research also details the transformation process from the lunar geographic coordinate system to the instantaneous projection coordinate system, thereby delineating the necessary observational geometry. The insights offered by this study have the potential to enhance future in-orbit spacecraft calibration procedures, thereby boosting the fidelity of data gathered from satellite observations.

Radio Instrument Package for Lunar Ionospheric Observation: A Concept Study

AbstractThe lunar ionosphere is a ∼100 km thick layer of electrically charged plasma surrounding the moon. Despite knowledge of its existence for decades, the structure and dynamics of the lunar plasma remain a mystery due to lack of consistent observational capacity. An enhanced observational picture of the lunar ionosphere and improved understanding of its formation/loss mechanisms is critical for understanding the lunar environment as a whole and assessing potential safety and economic hazards associated with lunar exploration and habitation. To address the high priority need for observations of the electrically charged constituents nikear the lunar surface, we introduce a concept study for the Radio Instrument Package for Lunar Ionospheric Observation (RIPLIO). RIPLIO would consist of a multi‐CubeSat constellation (at least two satellites) in lunar orbit for the purpose of conducting “crosslink” radio occultation measurements of the lunar ionosphere, with at least one satellite carrying a very high frequency (VHF) transmitter broadcasting at multiple frequencies, and at least one satellite flying a broadband receiver to monitor transmitting satellites. Radio occultations intermittently occur when satellite‐to‐satellite signals cross through the lunar ionosphere, and the resulting phase perturbations of VikHF signals may be analyzed to infer the ionosphere electron content and high‐ resolution vertical electron density profiles. As demonstrated in this study, RIPLIO would provide a novel means for lunar observation, with the potential to provide long‐term, high‐resolution observations of the lunar ionosphere with unprecedented pan‐lunar detail.

Spaceborne Relative Radiometer: Instrument Design and Pre-Flight Test

In order to simultaneously determine the values of total solar irradiance (TSI) and the Earth’s radiation at the top of the atmosphere (TOA) on board the Fengyun-3F satellite, a spaceborne relative radiometer (SRR) was developed. It adopts a dual-channel structure, including a solar radiometer channel (SR) with an unobstructed field of view (FOV) of 1.5° and an Earth radiometer channel (ER) with a wide field of view (WFOV) of 95.3° and a diameter of about 1900 km on the ground. Before the launch, both the SR and ER were calibrated. The SR, installed on the inner frame of the solar tracker of the SIM-II (solar irradiance monitor-II), is used to observe rapid changes in solar radiance with the SIAR (solar irradiance absolute radiometer), an electrical-substitution radiometer, on orbit. The ER is mounted on the U-shaped frame of the solar tracker, directly pointing in the nadir direction. Additionally, a dark space observation mode is used to determine the on-orbit background noise and lunar observation mode for on-orbit calibration. In this article, the instrument design and working principle of the SRR is first introduced, and an analysis of the measurement model of the ER, the WFOV channel of the SRR, is focused on. Finally, ground test results of the SRR are introduced.

The Conley–Zehnder indices of the spatial Hill three-body problem

We explore the interaction between the Conley–Zehnder index and bifurcation points of symmetric planar as well as spatial periodic orbits in the spatial Hill three-body problem. We start with the fundamental families of planar periodic orbits which are those of direct (family g) and retrograde periodic orbits (family f). Since the spatial system is invariant under a symplectic involution, whose fixed point set corresponds to the planar problem, planar orbits have planar and spatial Floquet multipliers, and planar and spatial Conley–Zehnder indices. When the Floquet multipliers move through a root of unity, new families of periodic orbits bifurcate and the index jumps. For very low energies, the families g and f arise dynamically from the rotating Kepler problem, and in a recent work (Aydin From Babylonian lunar observations to Floquet multipliers and Conley-Zehnder Indices) we determined analytically their indices. By their numerical continuations for higher energies, we determine the index of various families of planar and spatial periodic orbits bifurcating from g and f. Since these families can bifurcate again and meet each other, this procedure can get complicated. This index leads to a grading on local Floer homology. Since the local Floer homology and its Euler characteristic stay invariant under bifurcation, the index provides important information about the interconnectedness of such families, which we illustrate in form of bifurcation graphs. Since the solutions of Hill’s system may serve as orbits for space mission design or astronomical observations, our results promote the interaction between Symplectic Geometry and practical problems.

Activities to Promote the Moon as an Absolute Calibration Reference

The accuracy and consistency of Earth observation (EO) instrument radiometric calibration is a fundamental prerequisite for achieving accurate results and delivering reliable predictions. Frequent calibration and validation (Cal/Val) activities are needed during the instrument’s lifetime, and this procedure is often extended to historical archives. Numerous satellites in orbit and proposed future missions have incorporated lunar observation into their vicarious calibration components over recent years, facilitated by the extreme long-term photometric stability of the Moon. Since the birth of the first lunar calibration reference model, lunar-dependent calibration techniques have developed rapidly, and the application and refinement of the lunar radiometric model have become a welcome research focus in the calibration community. Within the context of the development of lunar observation activities and calibration systems globally, we provide a comprehensive review of the activities and results spawned by treating the Moon as a reference for instrument response and categorize them against the understanding of lunar radiometric reference. In general, this appears to be a process of moving from data to instruments, then back into data, working towards a stated goal. Here we highlight lunar radiometric models developed by different institutions or agencies over the last two decades while reporting on the known limitations of these solutions, with unresolved challenges remaining and multiple lunar observation plans and concepts attempting to address them from various perspectives, presenting a temporal development. We also observe that the methods seeking uncertainty reduction at this stage are rather homogeneous, lacking the combination of approaches or results from lunar surface studies conducted by many spacecraft missions, and joint deep learning methods to extract information. The factors that influence the accuracy of the measurement irradiance may be regulated when practical models arrive. As a central element in lunar calibration, the development of an absolute radiometric datum helps to better understand the Earth system.

Predicting new crescent moon visibility applying machine learning algorithms

The world's population is projected to grow 32% in the coming years, and the number of Muslims is expected to grow by 70%—from 1.8 billion in 2015 to about 3 billion in 2060. Hijri is the Islamic calendar, also known as the lunar Hijri calendar, which consists of 12 lunar months, and it is tied to the Moon phases where a new crescent Moon marks the beginning of each month. Muslims use the Hijri calendar to determine important dates and religious events such as Ramadan, Haj, Muharram, etc. Till today, there is no consensus on deciding on the beginning of Ramadan month within the Muslim community. This is mainly due to the imprecise observations of the new crescent Moon in different locations. Artificial intelligence and its sub-field machine learning have shown great success in their application in several fields. In this paper, we propose the use of machine learning algorithms to help in determining the start of Ramadan month by predicting the visibility of the new crescent Moon. The results obtained from our experiments have shown very good accurate prediction and evaluation performance. The Random Forest and Support Vector Machine classifiers have provided promising results compared to other classifiers considered in this study in predicting the visibility of the new Moon.

Dynamic space-time dark level correction approach for lunar radiometric calibration of the Lunar Observation Imaging Spectrometer.

Lunar radiometric calibration is used to solve the problem of consistent radiometric calibration for multiple satellite platforms and remote sensors. However, the dark level fluctuates when observing the Moon with a short-wave infrared spectrometer, which seriously affects the accuracy of lunar radiation data. In this work, we propose a dynamic space-time dark level correction approach to address the fluctuation of the dark level. This method employs cold space signals in space and time dimensions to estimate the dark level for each frame individually and to reduce errors due to environmental variations. Experiments on lunar observations at multiple phase angles were conducted, and the dark level correction results demonstrate that our proposed method is effective even in the short-wave infrared, and is also superior to currently existing techniques. For a single-band (1700nm) image of the full Moon, the mean background proportion of the proposed method is 1.00%, which is better than that of the static dark correction method (2.25%) and linear dark correction method (5.93%).