The theory of reflectance and emittance spectroscopy is based on the fundamental principles of radiative transfer (the propagation of energy in the form of electromagnetic radiation) in particulate media. This chapter outlines key models for radiative transfer in particulate media that can be forward-modeled to predict reflectance and emittance spectra or inverted to obtain the abundance of geologic materials from remote observations. The models are rooted in the optical properties of geologic materials, namely the complex index of refraction, and the scattering of light controlled by particulate texture, shape, and size. The chapter is divided into reflectance modeling and emittance modeling because of the key difference in the origin of the electromagnetic radiation: external to the grain’s surface and internal to the grain’s surface, though the principles are common across this division. The key models presented for reflectance spectroscopy are the Hapke model for scattering and reflectance and the Shkuratov model for reflectance. For emittance spectroscopy, the Hapke model forms the backbone upon which hybrid models incorporating Mie T-matrix concepts are integrated.

The Cassini Visual Infrared Mapping Spectrometer (VIMS) spans a wavelength range of 0.34 to 5.2 µm. Executing numerous close targeted flybys of the major moons of Saturn, as well as serendipitous flybys of the smaller moons, VIMS gathered millions of spectra of these bodies during its 13-year mission, some at spatial resolutions of a few hundred meters. The surfaces of the inner moons are dominated by water ice, while Iapetus, Hyperion, and Titan have substantial amounts of dark materials, including hydrocarbons, on their surfaces. Phoebe is grayer in color in the visible than Saturn’s other low-albedo moons. The surfaces of the inner small moons are also dominated by water ice, and they share compositional similarities to the main rings. The optical properties of the main moons are affected by particles from Saturn’s rings: the inner moons are coated by the E-ring, which originates from cryoactivity on Enceladus, while Iapetus and Hyperion are coated by particles from the Phoebe ring. Cassini VIMS detected previously unknown volatiles and organics on these moons, including CO2, H2, organic molecules as complex as aromatic hydrocarbons, nano-iron, and nano-iron oxides.

Visible and near-infrared reflectance spectroscopy using reflected sunlight is an ideal tool for remote detection of many compounds. Surfaces can be measured in the field at close range (mm), or from a distance with aircraft or spacecraft. The technology works throughout the Solar System. Advancements have recently been made in sensor calibration and atmospheric correction, enabling faster and more accurate calibration to surface reflectance (or apparent surface reflectance). Parallel to these advancements have been advancements in radiative transfer models, including a better understanding of the scattering effects of submicrometer particles and the ability to model those effects. There has also been progress in spectral analysis, including methods to rapidly analyze imaging spectrometer data to identify and map hundreds of compounds. Finally, with the advancements in computer technology, both in compute speed and in storage, analysis of very large imaging spectrometer data sets is now feasible in a relatively short time. With some additional development, imaging spectroscopy could be used in real time or near real time applications, including exploration of resources to autonomous robots such as spacecraft rovers searching for resources or life on remote planets and satellites.

This chapter provides definitions of contrasting classical and medieval approaches to meteorology. It outlines the relevant works of Aristotle, as well as the means by which selections from these were transferred to Roman writers. The roles of Pliny and Virgil are considered, together with their own reception by early medieval writers. A key point is that patristic writers, especially Augustine, integrated this knowledge of the natural world into Christian teachings on cosmology. However, Aristotle’s arguments on meteorology were primarily transmitted to Latin Europe in Islamicate versions, and came accompanied by new information on astronomy. The chapter then offers an account of the transition from classical, theoretical models of climate to more detailed calculation of planetary movements and their alleged meteorological effects. An important argument is that early medieval scientific work is often presented in diagrams and tables, themselves found in monastic works on the ecclesiastical year, and are easy to miss or underestimate.

Chapter 7 considers astrometeorology as an established branch of knowledge, within the context of fourteenth-century developments in astronomy and technology. Mechanical clocks were prominent products of these advances, as were more accurate astrolabes and planetary tables. Most successful of the latter were the Alfonsine Tables, used by the authors of new and more ambitious treatises of astrometeorology, such as Firminus de Bellavalle. The chapter analyses the new approaches taken by inventors like Richard of Wallingford and scholars like John of Eschenden, and traces the growing prominence of Merton College, Oxford, in this field. Eschenden’s fame as a forecaster was boosted by his claim to have predicted the great plague of 1348. Related to this is the survival of his weather forecasts for 1348 to 1374. The chapter considers the rise of weather observation, and the survival of records from Lincolnshire, Oxford, Wurzburg and Basel, as evidence of a drive to give astrometeorology an empirical backing. It concludes that astrometeorology grew as an area of expert practice, despite the attacks that critics such as Nicole Oresme made against the reliability of all forms of astrology.

Chapter 3 gives an account of the transmission of Islamicate meteorology into Northern and Western Europe. An early phase was the collection and study of the texts known as the Alchandrean Corpus, which provided short introductions to topics within astronomy and mathematics. The chapter then considers twelfth-century translations of more advanced works, and especially of treatises on weather-forecasting. The contributions of Petrus Alfonsi, and the reception of Latin translations of Arabic versions of the works of Ptolemy, are discussed. The chapter argues that it was this period that saw the creation of Latin, Christian forms of astrologically based weather forecasting. Moreover, this was no transitory fashion, and the new, astrometeorology remained dominant until the seventeenth century. Central to this new science was the application of fundamental works by Ptolemy, and this is considered in detail. The final part of the chapter gives an outline of the works of Islamicate astrometeorology that were translated into Latin, and especially of the theories of al-Kindi. The conclusion is that Latin writers and translators searched out works on weather forecasting, and rapidly began to produce their own versions.

Chapetr 4 traces the reception and adaptation of Islamicate meteorology by writers and scientists in Northern and Western Europe. Fundamental to this was the growing body of planetary tables, based on versions of Ptolemy’s work, which made it possible to calculate the positions of the planets with much greater accuracy. The chapter traces the works of Latin astrometeorology that drew on this ability, and gives outlines of the processes involved in making actual weather forecasts, according to rival methods. Pioneers were Hermann of Carinthia, Robert of Ketton and John of Seville, who all made translations and then issued new treatises on the subject. Manuscript evidence for the transmission of this new astrometeorology is discussed. The roles of astrological textbooks, especially the Book of Nine Judges, are considered. The concluding part of the chapter weighs up the popularity of astrometeorological forecasting across Europe by the early thirteenth century, and argues that it was closely associated with the emergence of a new, highly technical, scientific discourse.

This chapter begins with an account of the roles of Charlemagne and Alcuin in supporting the study of computus and astronomy in the Carolingian Empire. It then offers an outline of the expanded astronomical and meteorological information found in Carolingian ‘encyclopedias’ of computus. A key problem for users of these collections was the lack of accurate astronomical observations and calculations, which enforced continuing dependence on lists of short-term ‘signs’ of coming weather, mostly derived from Pliny. One attempt to improve the range of knowledge available took the form of beautifully illuminated versions of Aratus’ long poem, in volumes known as Aratea. The dissemination of this body of information is traced through analyses of surviving manuscripts, which demonstrate the resources being devoted to the subject across mainland Europe. Separate consideration is given to Anglo-Saxon England, where Viking conquests and wars had caused serious disruption, and where the teaching of Abbo of Fleury, and his pupil Byrhtferth, was crucial. The chapter argues that possession of superior astronomical and meteorological knowledge was highly vaued by rulers in both secular and spiritual spheres.

The Conclusion traces the importance of astrometeorological forecasts from the seventeenth century onwards. It finds surprising evidence that they finally disappeared only in the nineteenth century, despite increasing criticism. In fact, one of the attackers mourned the continuing high sales of Moore’s almanac in the 1830s. A central finding is that the increasing rejection of astrology in the eighteenth century, and the attacks on astrometeorology, led to the absence of any accepted basis for making weather forecasts. This problem, together with ongoing demand for knowledge of coming weather, led to the revival of old-fashioned weather-signs. The support given by Tycho Brahe and Johannes Kepler to both astrometeorology and the keeping of waether records is considered, as are early modern treatises on weather prediction. A detailed study of English 18th-century almanacs shows use of weather journals and instruments such as barometers, alongside traditional astrometeorological methods. The final conclusion is that it was only the production of FitzRoy’s new, ‘practical’ system of forecasting the weather that finally ended the age of medieval meteorology.

Chapter 5 traces the evidence for the practice of astrometeorology by scholars and professionals in the service of the European elite. This phenomenon faced criticism from those who feared the rise of judicial astrology and the associated threat of demonic intervention. The chapter analyses the level of meteorological knowledge displayed by scholars such as William of Conches, adviser to Geoffrey of Anjou. William knew works attributed to Masha’allah as well as Seneca, and deployed the new, scientific terminology that spread in the twelfth century. A key point is that works like William’s depict secular rulers as keenly interested in understanding and predicting the weather. From this the chapter moves on to the more advanced astrometeorological teachings of Abraham Ibn Ezra, a Jewish scholar from al Andalus who travelled across Italy and Spain. One of his innovations was to provide tables of mathematical values to be applied to astrometeorological configurations, making forecasting much simpler. This was to be followed by others in the thirteenth century. The chapter ends with comment on the scarcity of surviving twelfth-century copies of these works.

This chapter first explores how early medieval writers, and especially Isidore and Bede, made fundamental contributions to a new understanding of the natural world and its workings. They both quarried classical works for factual information and empirical observations, and placed these within a Christian cosmological model. An outline is given of the monastic science of ‘computus’, which was fundamental for teaching on natural philosophy and for theories about the weather in particular. Summaries of introductory works by both Isidore and Bede demonstrate their respective meteorological models; Bede’s views on the powers of the planets are covered in detail. Special attention is given to Bede’s The Reckoning of Time and the complex information on astronomy and meteorology which it expounds. An important conclusion is that Bede produced an understanding of weather as the intelligible and predictable result of astronomical and climatic factors. Overall, the chapter argues that classically derived natural philosophy and Christian cosmology were successfully integrated, and that the two together provided the basis for a new approach to weather and its prediction.

Chapter 6 traces the spread of astrometeorology and detailed weather forecasting amongst the lay and ecclesiastical elite. It discusses the distinctions made between varying forms of astrology, before analysing a treatise attributed to Robert Grosseteste. This offers a worked example of a weather forecast for 15 April 1249. The chapter argues that such forecasts were in accord with other works by Grosseteste. It goes on to consider the place of accepted forms of astrology in thirteenth-century university study. An important point is that Aquinas’ Summa Theologiae established weather forecasting as distinct from divination. Equally important is the evidence of the Mirror of Astronomy attributed to Albertus Magnus. This discusses astrometeorology in detail, and gives a list of approved works on the subject. The chapter concludes that this endorsement was very important, given the growing concern about necromancy and divination. Analysis of contemporary enclyclopedias demonstrates the authors’ very cautious acceptance of the basics of astrometeorology. In contrast, secular rulers such as Frederick II openly employed astrologers like Michael Scot and Guido Bonatti, whose contributions to astrometeorology are discussed.