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Photometry and Colorimetry of Planets and Satellites
... The first photoelectric photometry of the satellites was performed by Kuiper at the favorable opposition of 1956 (Harris, 1961). His results are listed in the table below. ...
... Kuiper (Harris, 1961) 12.1 7 0.1 0.6 0.052 Kuiper (Harris, 1961) Deimos 13.3 7 0.1 0.6 0.055 Pascu (1973) 11.8 7 0.1 0.069 Pascu (1973) Deimos 12.84 70.05 0.084 Zellner and Capen (1974) 11.9 7 0.2 0.063 Zellner and Capen (1974) Markedly red in the NIR D-type Grundy and Fink (1991), Deimos 0.5-1.0 mm Subdued at 0.55 mm? ...
... Kuiper (Harris, 1961) 12.1 7 0.1 0.6 0.052 Kuiper (Harris, 1961) Deimos 13.3 7 0.1 0.6 0.055 Pascu (1973) 11.8 7 0.1 0.069 Pascu (1973) Deimos 12.84 70.05 0.084 Zellner and Capen (1974) 11.9 7 0.2 0.063 Zellner and Capen (1974) Markedly red in the NIR D-type Grundy and Fink (1991), Deimos 0.5-1.0 mm Subdued at 0.55 mm? ...
This article intends to review the different studies of the Mars satellites Phobos and Deimos realized by means of ground-based telescopic observations as well in the astrometry and dynamics domain as in the physical one. This study spans the first period of investigations of the Martian satellites since their discovery in 1877 through the astrometry and the spectrometry methods, mainly before the modern period of the space era. It includes also some other observations performed thanks to the Hubble Space Telescope. The different techniques used and the main results obtained for the positionning, the size estimate, the albedo and surface composition are described.
... Several compilations of UBV planetary magnitudes were published around 50 years ago. Those by Harris (1961), de Vaucouleurs (1964 and Irvine et al. (1968) are especially notable. Furthermore, Lockwood, Jerzykiewicz and their colleagues have monitored the narrow band magnitudes of several solar system bodies from the mid-twentieth century until the present (e.g., Lockwood and Jerzykiewicz, 2006). ...
... Equation 2 12 indicates that value as M 1 (0) where the '1' indicates one AU and '0' indicates that the phase angle, α, is zero. M 1 (α) is the magnitude when α is not zero and thus the brightness is diminished in accordance with the illumination phase function which is represented by the following polynomial (Harris, 1961). ...
Complete sets of reference magnitudes in all 7 Johnson-Cousins bands (U, B, V, R, I, Rc and Ic) and the 5 principal Sloan bands (u', g', r', i', and z') are presented for the 8 planets. These data are accompanied by illumination phase functions and other formulas which characterize the instantaneous brightness of the planets. The main source of Johnson-Cousins magnitudes is a series of individualized photometric studies reported in recent years. Gaps in that dataset were filled with magnitudes synthesized in this study from published spectrophotometry. The planetary Sloan magnitudes, which are established here for the first time, are an average of newly recorded Sloan filter photometry, synthetic magnitudes and values transformed from the Johnson-Cousins system. Geometric albedos derived from these two sets of magnitudes are consistent within each photometric system and between the systems for all planets and in all bands. This consistency validates the albedos themselves as well as the magnitudes from which they were derived. In addition, a quantity termed the delta stellar magnitude is introduced to indicate the difference between the magnitude of a planet and that of its parent star. A table of these delta values for exo-planets possessing a range of physical characteristics is presented. The delta magnitudes are for phase angle 90 degrees where a planet is near the greatest apparent separation from its star. This quantity may be useful in exo-planet detection and observation strategies when an estimate of the signal-to-noise ratio is needed. Likewise, the phase curves presented in this paper can be used for characterizing exo-planets. Finally, magnitudes for the proposed Planet Nine are estimated, and we note that P9 may be especially faint at red and near-IR wavelengths.
... Un très grand nombre de composés chimiques ont été identifiés et confirmés par la suite. D'abord la glace d'eau a été rapidement identifiée (Kuiper, 1957;Harris, 1961) sous forme cristalline et amorphe Mishra et al., 2021a;King et al., 2022). La majorité des débats porte sur la nature des composés associés à la glace d'eau, des composés hydratés tels que les sulfates de magnésium et sodium ont été proposés (McCord et al., 1998; ainsi que l'acide sulfurique (Carlson et al., 2002. ...
... Water ice has quickly been identified by ground-based spectroscopy (Kuiper, 1957;Harris, 1961) because the similarity between spectra of Europa and those of pure water ice was remarkable, especially when comparing the position and shape of the characteristics absorption bands. A small distortion of the bands were observed, especially for spectra of the trailing side, involving a potential 'non ice' component. ...
This research work focuses on the microphysical characterization of ice present on the surface of different planetary bodies. Studying the microphysical state of the ice consists in characterizing the chemical and structural properties such as the volume proportion of the components, the size of their grains, the porosity or the surface roughness. These properties allow us to understand the formation mode and the processes governing the temporal evolution of these surfaces. At the end of this thesis, two objects were the target of these investigations: Mars and Europa, a satellite of Jupiter. To do so, we use the physical principles describing the interactions between light and matter and in particular the theoretical framework of radiative transfer. The radiation transfer equations allow to model the phenomena of absorption, reflection and scattering of light during its interaction with the surface materials.This work is organized in three distinct parts. The first part is devoted to the description of radiation transfer, the concepts and important physical quantities are defined to lead to some examples of models commonly used by the scientific community. The model used in this work, the so-called photometric Hapke model, is widely described. The advantages of this approach lie in the fact that this model is analytical and easily invertible. The inversion of a physical model consists in using it to find the physical parameters allowing to reproduce as accurately as possible a data, in our case an observation of the surface. The concepts and methods of inversions are also presented in this section. A comparison between different inversion methods is proposed to select the most suitable methods for the problems encountered.The second part is dedicated to the characterization of the surface of Europa, one of the ice satellites of Jupiter. The scientific background gives an overview of the current knowledge about the properties of the surface and ends with the remaining questions: what is the chemical composition of the surface? How does it vary from one geological structure to another? What processes promote this composition? To answer these questions we use the data obtained by the NIMS spectro-imager during the Galileo mission. We have combined the Hapke model and a Bayesian inversion approach to test, for the first time, a very large number of different representations of the surface from 15 chemical compounds that have been proposed so far by previous studies. We show that there is a multitude of different surface representations that produce a similar fit to the data.The third part is devoted to the study of the ices of Mars via the use of the data of the recent ExoMars-TGO mission and in particular the NOMAD infrared spectrometer. The acquisition of the first data of the mission coincides with the beginning of this thesis, so an instrumental calibration work was necessary. A calibration method for the NOMAD nadir channel data has been proposed and published. A first analysis of the data allows to highlight the instrumental capacity to detect surface ice. These data will then allow to undertake a work of characterization and temporal follow-up of the microphysical properties of the ice on Mars.
... Several compilations of UBV planetary magnitudes were published around 50 years ago. Those by Harris (1961), de Vaucouleurs (1964 and Irvine et al. (1968) are especially notable. Furthermore, Lockwood, Jerzykiewicz and their colleagues have monitored the narrow band magnitudes of several solar system bodies from the mid-twentieth century until the present (e.g., Lockwood and Jerzykiewicz, 2006). ...
... Equation 2 12 indicates that value as M 1 (0) where the '1' indicates one AU and '0' indicates that the phase angle, α, is zero. M 1 (α) is the magnitude when α is not zero and thus the brightness is diminished in accordance with the illumination phase function which is represented by the following polynomial (Harris, 1961). ...
Complete sets of reference magnitudes in all 7 Johnson-Cousins bands (U, B, V, R, I, Rc and Ic) and the 5 principal Sloan bands (u', g', r', i', and z') are presented for the 8 planets. These data are accompanied by illumination phase functions and other formulas which characterize the instantaneous brightness of the planets. The main source of Johnson-Cousins magnitudes is a series of individualized photometric studies reported in recent years. Gaps in that dataset were filled with magnitudes synthesized in this study from published spectrophotometry. The planetary Sloan magnitudes, which are established here for the first time, are an average of newly recorded Sloan filter photometry, synthetic magnitudes and values transformed from the Johnson-Cousins system. Geometric albedos derived from these two sets of magnitudes are consistent within each photometric system and between the systems for all planets and in all bands. This consistency validates the albedos themselves as well as the magnitudes from which they were derived. In addition, a quantity termed the delta stellar magnitude is introduced to indicate the difference between the magnitude of a planet and that of its parent star. A table of these delta values for exo-planets possessing a range of physical characteristics is presented. The delta magnitudes are for phase angle 90 degrees where a planet is near the greatest apparent separation from its star. This quantity may be useful in exo-planet detection and observation strategies when an estimate of the signal-to-noise ratio is needed. Likewise, the phase curves presented in this paper can be used for characterizing exo-planets. Finally, magnitudes for the proposed Planet Nine are estimated, and we note that P9 may be especially faint at red and near-IR wavelengths.
... The studies [16,19,25,26,37,38] indicated the existence of cycles in the change of Jupiter's brightness, with periods ranging from 3 to 25 years. The data on determining the integral stellar magnitude of the planet before 1933 [9], complemented by the results of [10,29] and our observations [51,58], have allowed us to prepare for analysis of 255 individual measurements of Jupiter's disk in the V band. The accuracy of determining the absolute stellar magnitude of the planet, based on our data with the reference to the photometric standard α Lyr, was better than 2% for all years and ranged from 1 to 15% based on the data of [9,10,29]; the internal error of each measurement series was lower than 4% in all cases. ...
... The data on determining the integral stellar magnitude of the planet before 1933 [9], complemented by the results of [10,29] and our observations [51,58], have allowed us to prepare for analysis of 255 individual measurements of Jupiter's disk in the V band. The accuracy of determining the absolute stellar magnitude of the planet, based on our data with the reference to the photometric standard α Lyr, was better than 2% for all years and ranged from 1 to 15% based on the data of [9,10,29]; the internal error of each measurement series was lower than 4% in all cases. ...
To identify temporal variations of the characteristics of Jupiter’s cloud layer, we take into account the geometric modulation caused by the rotation of the planet and planetary orbital motion. Inclination of the rotation axis to the orbital plane of Jupiter is 3.13°, and the angle between the magnetic axis and the rotation axis is β ≈ 10°. Therefore, over a Jovian year, the jovicentric magnetic declination of the Earth φm varies from–13.13° to +13.13°, and the subsolar point on Jupiter’s magnetosphere is shifted by 26.26° per orbital period. In this connection, variations of the Earth’s jovimagnetic latitude on Jupiter will have a prevailing influence in the solar-driven changes of reflective properties of the cloud cover and overcloud haze on Jupiter. Because of the orbit eccentricity (e = 0.048450), the northern hemisphere receives 21% greater solar energy inflow to the atmosphere, because Jupiter is at perihelion near the time of the summer solstice. The results of our studies have shown that the brightness ratio Aj of northern to southern tropical and temperate regions is an evident factor of photometric activity of Jupiter’s atmospheric processes. The analysis of observational data for the period from 1962 to 2015 reveals the existence of cyclic variations of the activity factor Aj of the planetary hemispheres with a period of 11.86 years, which allows us to talk about the seasonal rearrangement of Jupiter’s atmosphere.
... Indeed, at zero-phase angle, the values 0, ½, and 1 for the k parameter correspond to opposition limb effects of cosine brightening, uniform disk brightness, and the cosine darkening brightness of a perfect Lambert surface, respectively. In the visible spectral range, the full Moon has k = 0.5 (uniform disk brightness) (Harris 1961). For k = 1, the Minnaert expression (1) reduces to ...
... Guthnick's observations could show in 1925 that the Galilean moons are tidally locked (Ulivi and Harland 2007, p. xli). The first photoelectric photometry-based information on the Galilean moon's brightness was published by Stebbins (1927) (augmented by Harris, 1961) which also confirmed synchronous rotation. Pickering (1908:77) connected albedo and density, and suggested that the three inner satellites are covered by white sand. ...
... Indeed, at zero-phase angle, the values 0, ½, and 1 for the k parameter correspond to opposition limb effects of cosine brightening, uniform disk brightness, and the cosine darkening brightness of a perfect Lambert surface, respectively. In the visible spectral range, the full Moon has k = 0.5 (uniform disk brightness) (Harris 1961). For k = 1, the Minnaert expression (1) reduces to ...
... Guthnick's observations could show in 1925 that the Galilean moons are tidally locked (Ulivi and Harland 2007, p. xli). The first photoelectric photometry-based information on the Galilean moon's brightness was published by Stebbins (1927) (augmented by Harris, 1961) which also confirmed synchronous rotation. Pickering (1908:77) connected albedo and density, and suggested that the three inner satellites are covered by white sand. ...
... A common albedo feature among Europa, Ganymede, and Callisto is the contrast between the leading and 3 The Late Heavy Bombardment, also referred to as the Lunar cataclysm, is a putative event thought to have occurred approximately 4.1 to 3.8 Ga during which a large number of impact craters may have formed on the Moon and on other terrestrial planets. trailing hemispheres (e.g., Stebbins & Jacobsen 1928;Harris 1961;Johnson 1971;Blanco & Catalano 1974;Morrison et al. 1974;Millis & Thompson 1975;Nash & Johnson 1979). This pattern has been discussed in relation to the fact that the energetic plasmas trapped in the Jovian magnetosphere preferentially hit the trailing hemispheres, although the details of the interactions between the surfaces and energetic particles remain uncertain. ...
... On the other hand, it is feasible to observe rotational variation (at near full phases) of outer bodies, including the Galilean moons and Mars, even from Earth. For the Galilean moons, we considered datasets from Millis & Thompson (1975) (MT75) among the literature of ground-based observations of Galilean moons (e.g., Stebbins & Jacobsen 1928;Harris 1961;Johnson 1971;Blanco & Catalano 1974;Morrison et al. 1974;Nash & Johnson 1979). ...
A reasonable basis for future astronomical investigations of exoplanets lies
in our best knowledge of the planets and satellites in the Solar System. Solar
System bodies exhibit a wide variety of surface environments, even including
potential habitable conditions beyond Earth, and it is essential to know how
they can be characterized from outside the Solar System. In this study, we
provide an overview of geological features of major Solar System solid bodies
with minor atmospheres (i.e., the Terrestrial Moon, Mercury, the Galilean
moons, and Mars) that affect surface albedo at local to global scale, and we
survey how they influence point-source photometry in UV, visible, and near IR
(i.e., the reflection-dominant range). We simulate them based on recent mapping
products and also compile observed light curves where available. We show a
5-50% peak-to-trough variation amplitude in one spin rotation associated with
various geological processes including heterogeneous surface compositions due
to igneous activities, interaction with surrounding energetic particles, and
distribution of grained materials. Some indications of these processes are
provided by the amplitude and wavelength dependence of variation in
combinations of the time-averaged spectra. We also estimate the photometric
precision needed to detect their spin rotation rates through periodogram
analysis. Our survey illustrates realistic possibilities for inferring the
detailed properties of solid exoplanets with future direct imaging
observations.
... Prior to the Voyager mission's first flyby of the Jupiter system, Io's unusual color and low near-UV reflectance in Earth-based imagery (Harris 1961;Minton 1973;Murray 1975) and narrow-band spectrophotometry (Johnson & McCord 1970;Johnson 1971;Wamsteker 1973;Nelson & Hapke 1978) were variably suggested to reflect polysulfides (Johnson & McCord 1971), elemental sulfur (Wamsteker et al. 1974), sulfur-rich salt evaporite deposits featuring irradiation-produced color centers (Fanale et al. 1974;Nash & Fanale 1977;Fanale et al. 1977), and mixtures of metastable sulfur allotropes and possibly evaporite salts (Nelson & Hapke 1978). Voyager's discovery of active volcanism (Morabito et al. 1979) and volcanic SO 2 gas (Pearl et al. 1979) at Io led to the focus on plausible volcanic species and the quick identification of condensed surficial SO 2 (Hapke 1979;Fanale et al. 1979;Smythe et al. 1979) via previously unidentified infrared bands (Cruikshank et al. 1978;Pollack et al. 1978) and a UV absorption maximum near 280 nm measured by the International Ultraviolet Explorer (IUE) (Bertaux & Belton 1979;Nelson et al. 1980). ...
Io's intense volcanic activity results in one of the most colorful surfaces in the solar system. Ultraviolet and visible-wavelength observations of Io are critical to uncovering the chemistry behind its volcanic hues. Here, we present global, spatially resolved UV-visible spectra of Io from the Space Telescope Imaging Spectrograph on the Hubble Space Telescope (HST), which bridge the gap between previous highly resolved imagery and disk-integrated spectroscopy, to provide an unprecedented combination of spatial and spectral detail. We use this comprehensive dataset to investigate spectral endmembers, map observed spectral features associated with SO frost and other sulfur species, and explore possible compositions in the context of Io surface processes. In agreement with past observations, our results are consistent with extensive equatorial SO frost deposits that are stable over multi-decade timescales, widespread sulfur-rich plains surrounding the SO deposits, and the enrichment of Pele's pyroclastic ring and the high-latitude regions in metastable short-chain sulfur allotropes.
... Although difficult to accomplish, Mercury has been observed multiple times with groundbased telescopes (e.g., Harris 1961;Moroz 1965;Irvine et al. 1968;McCord and Adams 1972;Vilas and McCord 1976;Vilas et al. 1984;Vilas 1985Vilas , 1988Sprague et al. 1994Sprague et al. , 2002Emery et al. 1998;Cooper et al. 2001;Warell and Blewett 2004;Ksanfomality et al. 2007). Although early ground-based observations did not detect absorption features in the VIS-NIR spectral range (e.g., McCord and Clark 1979;Vilas et al. 1984;Warell and Blewett 2004), Warell et al. (2006) attributed weak absorption features to Fe 2+ in high-Ca clinopyroxene and concluded that Mercury's surface is heterogeneous and exhibits an iron-poor mineralogy. ...
Launched onboard the BepiColombo Mercury Planetary Orbiter (MPO) in October 2018, the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) is on its way to planet Mercury. MERTIS consists of a push-broom IR-spectrometer (TIS) and a radiometer (TIR), which operate in the wavelength regions of 7-14 μm and 7-40 μm, respectively. This wavelength region is characterized by several diagnostic spectral signatures: the Christiansen feature (CF), Reststrahlen bands (RB), and the Transparency feature (TF), which will allow us to identify and map rock-forming silicates, sulfides as well as other minerals. Thus, the instrument is particularly well-suited to study the mineralogy and composition of the hermean surface at a spatial resolution of about 500 m globally and better than 500 m for approximately 5-10% of the surface. The instrument is fully functional onboard the BepiColombo spacecraft and exceeds all requirements (e.g., mass, power, performance). To prepare for the science phase at Mercury, the team developed an innovative operations plan to maximize the scientific output while at the same time saving spacecraft resources (e.g., data downlink). The upcoming fly-bys will be excellent opportunities to further test and adapt our software and operational procedures. In summary, the team is undertaking action at multiple levels, including performing a comprehensive suite of spectroscopic measurements in our laboratories on relevant analog materials, performing extensive spectral modeling, examining space weathering effects, and modeling the thermal behavior of the hermean surface.
... Section 7 summarizes the paper and presents our conclusions. An appendix describes More than 50 years ago Harris (1961) summarized the available observations and analyses of planetary brightness. Those studies began in the 1800s with visual magnitudes actually estimated by the human eye. ...
Improved equations for computing planetary magnitudes are reported. These formulas model V-band observations acquired from the time of the earliest filter photometry in the 1950s up to the present era. The new equations incorporate several terms that have not previously been used for generating physical ephemerides. These include the rotation and revolution angles of Mars, the sub-solar and sub-Earth latitudes of Uranus, and the secular time dependence of Neptune. Formulas for use in The Astronomical Almanac cover the planetary phase angles visible from Earth. Supplementary equations cover those phase angles beyond the geocentric limits. Geocentric magnitudes were computed over a span of at least 50 years and the results were statistically analyzed. The mean, variation and extreme magnitudes for each planet are reported. Other bands besides V on the Johnson-Cousins and Sloan photometric systems are briefly discussed. The planetary magnitude data products available from the U.S. Naval Observatory are also listed. An appendix describes source code and test data sets that are available on-line for computing planetary magnitudes according to the equations and circumstances given in this paper. The files are posted as supplementary material for this paper. They are also available at SourceForge under project https://sourceforge.net/projects/planetary-magnitudes/ under the 'Files' tab in the folder 'Ap_Mag_Current_Version'.
... The clouds of Titan are distinctly red in the visible -a fact noted from groundbased observations many decades ago (Harris, 1961), and confirmed by Voyager observations. In addition, high resolution spectroscopy of the Titanian clouds exists, as do near ultraviolet spectra from the International Ultraviolet Explorer, groundbased microwave observations, and Voyager infrared continuum spectroscopy. ...
Voyager discovered nine simple organic molecules in the atmosphere of Titan. Complex organic solids, called tholins, produced by irradiation of simulated Titanian atmosphere are consistent with measured properties of Titan from ultraviolet to microwave frequencies, and are the likely main constituents of the observed red aerosols. The tholins contain many of the organic building blocks central to life on Earth. At least 100 m and possibly kms thickness of complex organics have been produced on Titan during the age of the solar system, and may exist today as submarine deposits beneath an extensive ocean of simple hydrocarbons.
... In their homogeneous, multiple-Iayered and plane-parallel model, these authors consider the asymmetry factor (g) and single scattering albedo (07s) independent the optical depth. Additionally, they assume a Legendre polynomial series for the phase function commonly applied in planetary atmospheres (Chandrasekhar, 1960;Busbridge, 1960;Harris, 1961;Sobolev, 1963;Goody, 1964;Irvine, 1963Irvine, /64, 1975. Here, the phase function is also taken independent of the optical depth. ...
The relative extinction of solar and infrared radiation by dry and clean air molecules, has been eatimated through a theoretical determination of the ratio referred ordinarily as the Greenhouse Parameter (GP). In a first approach, it was calculated assuming that terrestrial air only conaists of a simple mixture of oxygen and nitrogen. The method used here is based on the application, in an inverse procedure, of an homogeneous, plane-parallel, and time-independent grey model, which employs the Eddington approximation as a solution to the radiative transfer equation, both in the solar and the infrared spectral regions and, which has the GP value as an input free parameter. The best value of the GP was estimated calibrating the local temperature profile for four types oí. uniform surface (anow, desert, vegetation and ocean), with average albedos known in these spectral regiona, adopting air surface temperature values which were chosen for an assumed micro or local climatological environment according to an average radiative criterion. With this result, it was possible for an estimation of the infrared opacity for the air layer implicated in this model and al.so the mean extinction coefficient in this spectral range to be calculated. The resulta predicted are compared with resulta obtained indirectly from the data provided by other authors. Although its validation is constrained solely to the radiative model applied it seems that the value of the GP obtained ia more accurate than the one initially available.
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... orange to the eye when seen in a large tele-Initial attempts at identification failed, but scope, and early multicolor photometry at on the eve of the discovery by Voyager I of visual wavelengths (Harris, 1961) showed active volcanism on lo, the absorption band that it is indeed the reddest object in the was identified as the va + v, vibrational Solar System. The first distinct feature de-combination band of solid sulfur dioxide on H 2 S AND H 2 0 ON JO band, additional observations at higher spectral resolution in this region allied to laboratory studies of sulfur dioxide frosts have been used to identify the (2v, + v2) and 2v3 bands of SO 2 , as well as isotopic bands due to 34S'602 and 32S'80160 ). ...
The analysis of the 2.5-5.0μm spectra of Io, using detailed laboratory studies of plausible surface ices, shows that Io's surface most likely contains H2S and H2O mixed with SO2. The 3.85 and 3.91μm bands in the Io spectra can be assigned to the ν1 fundamental mode in H2S clusters and isolated molecules in an SO2 ice. The 2.97 and 3.15μm bands coincide with the ν3 and ν1 vibrations of clusters of H2O molecules complexed with SO2. The observations are well matched by the spectra of SO2 ices containing 3% H2S and 0.1% H2O and which has been formed by condensation onto a 100K surface. The shifts and splitting of the absorption bands seen in the Io spectrum and the fact that solid H2S is observed in the surface material of Io at temperature and pressure conditions above its sublimation point can only be explained by the mixed-molecular ices model. -Authors
... mag [De Vaucouleurs, 1964]. De Vaucouleurs [1964], integrating photographic observations by King [1923] and Livlander [1933] and photoelectric observations by Johnson andGardiner [1955], De Vaucouleurs [1960], and Harris [1961], showed that the mean visual phase curve was well described by a linear phase law. He reported a magnitude V = -1.52 ± 0.01 and a phase coefficient of +0.015 mag/deg. ...
Two studies of the photometric behavior and physical properties of the surface and atmosphere of Mars are presented: (1) Temporal variations in the size distribution of atmospheric dust from observations by the Mars Exploration Rovers Spirit and Opportunity Navigation Cameras; (2) Analysis of the scattering properties of the martian surface using Hubble Space Telescope (HST) images of Mars. The Navcams are panchromatic stereoscopic imaging systems. An improved Navcam calibration pipeline was developed to provide absolute radiometric calibration with an absolute accuracy
We now know Io to be a world of superlatives among solar system bodies. It experiences the strongest orbital resonances, exhibits the greatest volcanic activity, sustains the most rapidly escaping atmosphere, and lies deep within the most powerful magnetosphere. This chapter synopsizes the centuries of studies that revealed Io’s remarkable properties, but highlights how the fundamental interconnectedness between these distinct properties were revealed only in recent decades. In fact, the revelation of links between seemingly unrelated planetary phenomena placed Io in the position to revolutionize planetary science. Before Io, who might have hypothesized that orbital peculiarities could drive volcanoes, shrink moons and power aurora? Io’s example forces planets and moons to be studied as coupled as systems, from celestial mechanics through interiors, surfaces, and atmospheres to magnetospheres.
We expose and analyze the proposed models of the visual magnitude of the Moon for large phase angles (>150º). We devised a method to determine the luminance and illuminance per unit angular length of the lunar crescent as a function of position and phase angles.
From our investigation of the behavior of changes in the visible brightness of Jupiter observed since 1850, it follows that the 22.3-year Hale magnetic cycle of solar activity produces the dominating influence on the processes taking place in the troposphere at a level of forming the upper boundary of clouds. The maximum values of the integral brightness of Jupiter fall on the solar cycle with the highest value of the Wolf number for the last 165 years (around 1957). The lowest estimates of brightness were obtained in 1855, when the Wolf number in the 12th solar-activity cycle was smallest. The analysis of the reflectance of Jupiter’s hemispheres in the visible spectral range for 1962–2015 revealed the alternating increase in the brightness of southern and northern tropical and middle regions for one rotation period of Jupiter about the Sun. Such a change in brightness and the increase in the activity of different hemispheres of the planet may indicate the periodic global alteration in the circulation system, the structure of cloud layers, and the overcloud haze. This suggests the interrelation between the observed variations in the reflectance of the considered latitudinal belts of Jupiter and the change in the axial tilts of the planet itself and its magnetic field to the orbital plane, i.e., the seasonal alteration in the atmosphere. The comparison of the temporal dependence of the activity factor Aj of the Jovian hemispheres in the visible spectral range with the change in the solar-activity index R shows that, from 1962 to 1995, these parameters almost synchronously changed, though the response of the visible cloud layer somewhat lagged behind the regime of exposure of the atmosphere to the Sun. The analysis shows that, when the planet is moving along the orbit, the reflectance of Jupiter’s hemispheres varies in response to the 21-percent change in the exposure of different hemispheres with a lag of 6 years. Such a lag coincides with the radiation- relaxation time of the hydrogen–helium atmosphere under the Jovian conditions. Desynchronization in their behavior that occurred after 1997 may be explained by the unbalanced influence of the three mentioned causes on the atmosphere of the planet.
Remote observations of the surfaces of airless planetary objects are fundamental to inferring the physical structure and compositional makeup of the surface material. A number of forward models have been developed to reproduce the photometric behavior of these surfaces, based on specific, assumed structural properties such as macroscopic roughness and associated shadowing. Most work of this type is applied to geometric albedos, which are affected by complicated effects near zero phase angle that represent only a tiny fraction of the net energy reflected by the object. Other applications include parameter fits to resolved portions of some planetary surface as viewed over a range of geometries. The spherical albedo of the entire object (when it can be determined) captures the net energy balance of the particle more robustly than the geometric albedo. In most treatments involving spherical albedos, spherical albedos and particle phase functions are often treated as if they are independent, neglecting the effects of roughness. In this paper we take a different approach. We note that whatever function captures the phase angle dependence of the brightness of a realistic rough, shadowed, flat surface element relative to that of a smooth granular surface of the same material, it is manifested directly in both the integral phase function and the spherical albedo of the object. We suggest that, where broad phase angle coverage is possible, spherical albedos may be easily corrected for the effects of shadowing using observed (or assumed) phase functions, and then modeled more robustly using smooth-surface regolith radiative transfer models without further imposed (forward-modeled) shadowing corrections. Our approach attributes observed “powerlaw” phase functions of various slope (and “linear” ranges of magnitude-vs.-phase angle) to shadowing, as have others, and goes in to suggest that regolith-model-based inferences of composition based on shadow-uncorrected spherical albedos overestimate the amount of absorbing material contained in the regolith.
In this chapter, we deal with the ways in which the objects described in Chapter 2 can be observed and the conditions affecting those observations.
For reference purposes, the earth’s surface at sea level may be represented by revolving an ellipse of eccentricity, e, and major axis, a
e, about the polar axis. The flattening factor, f, or ellipticity, is related to the eccentricity, e,by the equation
(5-1),
The flattening factor is alternatively called the ellipticity or the oblateness factor. The major axis, a
e, is the equatorial radius, which is related to the polar radius, a
p, by the equation
{a_p} = {a_e}\left( {1 - f} \right) = {a_e}{\left( {1 - {e^2}} \right)^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}}} (5-2)
and the mean radius, < a> is given by
\left\langle a \right\rangle = {\left( {a_e^2{a_p}} \right)^{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-\nulldelimiterspace} 3}}} (5-3).
Voyager discovered nine simple organic molecules in the atmosphere of Titan. Complex organic solids, called tholins, produced by irradiation of simulated Titanian atmosphere are consistent with measured properties of Titan from ultraviolet to microwave frequencies, and are the likely main constituents of the observed red aerosols. The tholins contain many of the otganic building blocks central to life on Earth. At least 100 m and possibly kms thickness of complex organics have been produced on Titan during the age of the solar system, and may exist today as submarine deposits beneath an extensive ocean of simple hydrocarbons.
Results of polarimetric observations of Saturn’s satellite Rhea obtained in the range of phase angles from 0.76° to 5.96° are presented. The observations were carried out in the WR spectral band (550–750 nm) at the 2.6-m telescope equipped with a single-channel photometer–polarimeter at the Crimean Astrophysical Observatory in the period from March 23, 2012, to May 2, 2014. From the results of the observations, the phase dependence of linear polarization of Rhea was built. The parameters of this dependence are compared to those of the high-albedo satellites of Jupiter, Japetus, and medium-albedo satellites of Uranus. The obtained results are discussed in terms of the currently available models of the light scattering by regolith surfaces.
This article reviews the principal techniques that have been used to estimate the surface pressure on Mars. The basic physics behind each technique is outlined and illustrated with simplified examples. An attempt is made to evaluate the reliability of each technique and its use to date. The problem is outlined in section 1; the older techniques (polarimetry and photometry) are examined in section 2; the spectroscopic method, wherein at least two CO2 absorption bands are used to derive both the CO2 abundance and the surface pressure, is reviewed in section 3. The conclusions, summarized in section 4, are principally (1) that the polarimetric and photometric techniques are not nearly so reliable as has been generally supposed, and (2) that, although the spectroscopic method should ultimately settle the problem, the data thus far available do not yield good accuracy in either the CO2 content or the total pressure.
Photometric observations of the Galilean satellites were carried out in the spectral region 0.30–1.1 μ during the 1967, 1968, and 1969 apparitions of Jupiter. Both relative reflectivities (one satellite relative to another) and spectral reflectivities (satellite relative to the Sun) were obtained. A spectral feature between 0.5 and 0.6 μ appears in the J1 vs. J4 relative curve. This feature arises primarily from a feature in J1's spectral reflectivity. J1's spectral reflectivity also has a steep decrease toward shorter wavelengths (0.3 to 0.5 μ) and a dip at 0.8 μ (which also appears in J4's curve). J2, J3, and J4 all have very similar spectral reflectivities, with flatter curves than J1 in the 0.3 μ to 0.5 μ region and no appreciable dip from 0.5 to 0.6 μ. All the satellite reflectivities exhibit a decrease at wavelengths beyond 1.0 μ. The spectral reflectivities of the satellites do not match those of either the Moon or Mars. Neither the 0.95-μ band found in the Moon's reflectivity or the 1.0-μ band in Mars' reflectivity is present in the satellite curves. The lack of such diagnostic bands makes identification of the satellite's surface composition very difficult based on spectral reflectivity alone.
Near-infrared spectra (0.8-2.5-micron) of Triton and Pluto reveal six
absorption bands attributed to the methane molecule. Additional
considerations of temperature, spatial variability on the surfaces of
these bodies, and the character of the absorption bands indicates that
frozen methane is the principal contributor to the spectral signatures
observed. Triton shows an additional absorption band which is
tentatively identified as molecular nitrogen, probably in the liquid
state. The red color observed for both of these objects in the
photovisual spectral region (0.3-1.0-micron) may result from
photochemical derivatives of methane and nitrogen, known from laboratory
work to have such coloration.
The intensities of dark jovian clouds belts and bright zones are changeable. The normally dark South Equatorial Belt was so bright from late 1963 into 1964 and again in 2009–2010 that Jupiter’s integrated luminosity increased measurably. Conversely, darkening of the normally bright Equatorial Zone during 1963 and 2006–2007 may have significantly reduced the integrated luminosity. Surprisingly, the planet seems to have dimmed when the North Temperate Belt brightened from 2002 until 2007. The mean absolute magnitudes of Jupiter measured photoelectrically during the past 48 years at zero phase angle in the UBVRI band passes are U, −8.106 ± 0.005; B, −8.540 ± 0.004; V, −9.395 ± 0.003; R, −9.854 ± 0.005 and I, −9.718 ± 0.006. The geometric albedo peaks in V at 0.535 ± 0.005. The brightest apparent magnitude of the planet in the V-band is −2.94, the faintest is −1.66 and the B–V color index is +0.855. While the U, B and V values are similar to the accepted values very little has been published about R and I filter measurements. These long wavelengths represent an important part of the spectrum that significantly impacts Jupiter’s radiation budget.
The globe of Saturn is brighter than previously reported as indicated by its absolute opposition magnitudes in the UBVRI band passes which are −7.080, −7.842, −8.914, −9.587 and −9.606, respectively. The geometric albedo in V is 0.501 and it peaks in the R filter at 0.567. The brightest apparent magnitude of the system in the V-band is −0.61 and the faintest is +1.31. The B–V color index can be as blue as +0.93 and as red at +1.12.
Quantifying relative differences in regolith optical maturation rates is critical to interpreting multispectral reflectance measurements of airless bodies. In this study, normalized reflectance measurements of crater ejecta blankets and rays are used as indicators of the relative state of regolith maturation on Mercury and the Moon, as well as for a comparison of surface reflectance. Characterization of craters with high-reflectance ejecta from Lunar Reconnaissance Orbiter Camera and Mercury Dual Imaging System orbital mosaics indicates that the optical maturation rate is up to 4 times faster on Mercury than on the Moon. Observations also show that there are fewer immature craters (per unit area) on Mercury than on the Moon, and suggest a younger average age for mercurian rayed craters than for lunar rayed craters. A comparison of crustal reflectance of immature material yields a ratio of 1.9 ± 0.4 for the average photometrically normalized reflectance of lunar material to that of mercurian material. The difference in reflectance is attributed primarily to differences in composition between the lunar highlands and average surface material on Mercury. The new observations of immature craters per unit area and surface reflectance of immature materials are consistent with previous proposals that regolith maturation rates are faster on Mercury than the Moon, and but here we quantify the relative rate from empirical observations for the first time.
Infrared photometry of Amalthea (JV) indicates that it is at a temperature of 155±15 K and has a raduis of 120±30 km. There is no evidence for substantial heating by the Jovian radiation belts.
In this review paper we first discuss the dimensions of major ring features and of the disk of the planet. We then summarize the observed photometric parameters, and because frozen H2O appears to be a major ring constituent, we compare the appropriate photometric properties of various forms of snow with those of the ring. We examine several ring models, noting certain characteristics that any model should supply. In our view, a physical means of accounting for the observed ring thickness of ∼2 km is a prime requirement. There appears to be one model that presents no clear observational or theoretical inconsistency. Finally, we list certain problems whose solutions should broaden our knowledge of the ring system.
It is proposed that a large temperature inversion exists in the atmosphere of Titan due to absorption of solar radiation by small “dust” particles. A very simplified preliminary analysis indicates that this inversion model can expain the high infrared brightness temperatures in the absence of a greenhouse effect.
Absorption features arose at 0.42 and 0.52 microns when spectral reflectance measurements were conducted for elemental sulfur allotrope mixtures produced by the exposure of the cyclooctal S(8) allotrope of sulfur to X-rays; while these features due to the presence of short-chain molecules are stable at low temperatures, they fade upon warming of the sample. The hypothesis that X-rays in the Jovian environment would cause other allotropic forms of sulfur to revert to S(8) is contradicted by the fact that these features are not present in S(8) at the same temperature that had not been exposed to X-rays. 33 refs.
At the 8900 A wavelength of the CCD and photoelectric photometry obtained for Triton in 1987, where than moon's methane absorption might be reflected as a strong contrast, no rotational lightcurve has been noted to a level of below 0.02 mag, in contradiction of Franz's (1981) apparent lightcurve of 0.06 mag observed in 1977. Triton's photoelectrically determined 1987 V magnitude is consistent with the most reliable of previous measurements, exhibiting no clear indication of long-term change. 15 refs.
Saturn satellites spectrophotometric observations at UV, visible and near IR, noting reflection spectra data
This chapter sets the scene for the current investigation of Titan with Cassini---Huygens, by reviewing the steps that took us there, from the first glimpses through a small telescope to the satellite observations passing by the first hints of an atmosphere about a 100 years ago.
We list the main scientific tasks which can be solved aboard the ISS on the basis of UV-polarimetric observations. The tasks are the following: 1) the determination of spectral values of the complex refractive index of cloud particles; 2) the investigation of the nature of photometric details of discs of planets with thick atmospheres; 3) the monitoring of the long-period changes of optical properties of planetary atmospheres and the elucidation of the possible mechanism of the occurrence of the changes; 4) solving the problem of strong-absorbing Axel particles to which the effects of the UV-absorption in planetarey atmospheres are attributed; 5) the investigation of the thickness of hydrogen atmospheres of comets; 6) the elucidation of the causes of variations of the ozone layer thickness and temperature conditions on a global scale; 7) the improvement of the spectral values of the imaginary part of the refractive index of the martian aerosol and its optical thickness, as well as the effective radius of particles.
Presented here are analyses of the photometric measurements acquired by the imaging system on the MESSENGER spacecraft during its three flybys of Mercury, in particular the dedicated sequence of photometric measurements obtained during the third flyby. A concise, analytical approach is adopted for characterizing the effects of scattered light on the images. This approach works well for wavelengths shorter than 700nm but breaks down at the longer wavelengths where the scattering behavior of the imaging system is more complex. Broadband spectral properties are commensurate with ground-based observations for spectra acquired at phase angles less than 110°; photometric corrections to a common illumination and viewing geometry provide consistent results for those phase angles. No phase reddening is apparent in the image-derived spectra. A bolometric albedo of 0.081 is derived over the wavelength range of the imaging system.
An attempt is made to determine the rotation state of Hyperion with a model developed from the dynamics outlined by Wisdom et al. (1984). The results of these dynamical investigations demonstrate the chaotic nature of Hyperion's rotation and are consistent with the satellite having a uniform density distribution.
The empirically derived phase curves of terrestrial planets strongly distinguish between airless Mercury, cloud-covered Venus, and the intermediate case of Mars. The function for Mercury is steeply peaked near phase angle zero due to powerful backscattering from its surface, while that for Venus has 100 times less contrast and exhibits a brightness excess near 170° due to Mie scattering from droplets in the atmosphere. The phase curve of Mars falls between those of Mercury and Venus, and there are variations in luminosity due to the planet’s rotation, seasons, and atmospheric states. The phase function and geometric albedo of the Earth are estimated from published albedos values. The curves for Mercury, Venus and Mars are compared to that of the Earth as well as theoretical phase functions for giant planets. The parameters of these different phase functions can be used to characterize exoplanets.
Disk-resolved reflectance spectra of the surface of Mercury (longitudes 240–300°), obtained in the visual (vis) and near-infrared (NIR) spectral region, are presented and analyzed. The observations were made at the 2.6-m Nordic Optical Telescope with the ALFOSC low-resolution spectrograph on 20 and 22 June 1999 in the wavelength range 520–970 nm with a footprint size of 700 km on the mid-disk of Mercury. A method which enables more accurate correction for telluric line absorptions and atmospheric extinction than that applied on previously published vis–NIR spectra of Mercury is introduced. The resulting reflectance spectra are remarkably linear, lack significant absorption features, and have optical slopes comparable to remotely sensed lunar pure anorthosites. The relation between spectral slope and photometric geometry found by Warell (2002, Icarus 156, 313–317) is confirmed and is explained as caused by strongly backscattering particles with embedded submicroscopic metallic iron in a mature regolith. With the theoretical maturation model of Hapke (2001, J. Geophys. Res. 106 (E5), 10039–10073) an abundance of 0.05–0.3 wt% submicroscopic metallic iron in the regolith for silicate grain sizes in the range 10–80 μm is determined, implying a ferrous iron content in mafic minerals intrinsically lower than that of the lunar highlands. A binary crustal composition model with anorthite linearly mixed with pyroxene provides better spectral fits than a pure anorthitic composition. Comparison with mature lunar pure anorthosite spectra yields a confident upper limit to the FeO content of 3 wt% under the assumption that the surfaces are similarly matured, but this figure probably represents a considerable overestimate. The average mercurian regolith does not seem to be substantially more weathered than the most mature lunar highland soils in terms of abundance of submicroscopic metallic iron, indicating that a steady-state maturation level has been reached. However, the strong relation between optical spectral slope and photometric geometry may imply that the majority of regolith particles are more fine-grained than their lunar counterparts and that the regolith is admixed with complex agglutinate weathering products which are more abundant and more transparent than those of the lunar highlands. This is consistent with more energetic impacts and a higher rate of impact melt production in an iron-poor regolith. An observed relation between the spectral slope and latitude provides evidence that the Ostwald ripening process may be operating at equatorial latitudes on Mercury.
Observational determinations of the absolute spectral reflectivities of visually distinct regions of Jupiter are presented. The observations cover the 3390–8400 Å region at 10 Å resolution, and they are compared with observations using 150–200 Å filters in the 3400–6400 Å range. The effective reflectivities for several regions (on the meridian) in the 3400–8400 Å range are: South Tropical Zone, 0.76±0.05; North Tropical Zone, 0.68±0.08; South Equatorial Belt, 0.63±0.08; North Equatorial Belt, 0.62±0.04; and the Great Red Spot, 0.64±0.09. Reflectivities near the limb are also observed. The appropriate blue and red reflectivities are tabulated in support of the Pioneer 10 and 11 imaging photopolarimeter experiments. For the regions listed above, equivalent widths of molecular bands vary as: CH4 (6190 Å), 14–16 Å; CH4 (7250 Å), 77–86 Å; and NH3 (7900 Å), 87–95 Å. Significant differences from the results of C. B. Pilcher, R. G. Prinn, and T. B. McCord (“Spectroscopy of Jupiter: 3200 to 11200 Å,” J. Atmos. Sci.30, 302–307.)
Photoelectric measurements of the monochromatic flux from Jupiter in the region from 3400 to 10 000 Å are reported. From these measurements and published data for the ultraviolet and infrared outside the region of measurement a bolometric geometrical albedo of 0.28 was obtained. With an adopted bolometric phase integral of 1.6 the bolometric Bond albedo is then found to be 0.45, corresponding to a temperature of equilibrium with absorbed sunlight of 105°K.If the difference between this temperature and the radiometric temperature of 128°K is due to heat from the interior the mantle is probably melted. Rough calculations suggest that even with convective cooling the initial contraction energy could explain the present radiometric temperature. Radioactivity, meteor bombardment, tidal friction, and magnetic field decay do not appear to be feasible alternative energy sources for the radiometric temperature.A simple interpretation of the radiometric temperature is that Jupiter is radiating only absorbed sunlight with a temperature of 145°K and emissivity of 0.27.
We present results of a five-filter photometric study of Mercury's integral phase curve in the Johnson–Cousins UBVRI system, performed with the 0.90-m Westerlund Telescope in Uppsala, Sweden. CCD observations were made of the integrated disk for the phase angle range 22–152°, and the study is the first to cover the extended visible spectrum of Mercury. The observations are analyzed with Hapke's semi-empirical radiative transfer-based light-scattering model and photometric quantities are derived. A statistically significant phase reddening effect of -9±6mmag/deg/μm is determined for Mercury based on color index observations, which is similar to that of the Moon. Phase coefficients fit to integral absolute magnitude data and Hapke models in combination with color index data provide a phase reddening effect of -11±13mmag/deg/μm which does however not provide statistically significant evidence for its presence. Phase coefficients indicate that phase reddening may be decreasing in magnitude with wavelength. As for the case with the Moon, the value of the phase integral increases with wavelength, but at an eight times higher rate. This value is consistent with the difference in the rate of change in the spectral slope–emission angle relation for the two bodies. We attribute these differences with Mercury's redder spectral slope and an increase with wavelength of the backscattering lobe amplitude in the double Henyey–Greenstein particle phase function formulation. The normal albedo of integral Mercury at 1064nm, pertinent to the return pulse energy of the BepiColombo laser altimeter (BELA), is estimated to 0.23±0.06 with a range of 0.13–0.33 for 99% of the surface.
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