The recent surge in the development of low-cost, miniaturised technologies provides a significant opportunity to develop miniaturised hyperspectral imagers at a fraction of the cost of currently available commercial set-ups. This article introduces a low-cost laboratory-based hyperspectral imager developed using commercially available components. The imager is capable of quantitative and qualitative hyperspectral measurements, and it was tested in a variety of laboratory-based environmental applications where it demonstrated its ability to collect data that correlates well with existing datasets. In its current format, the imager is an accurate laboratory measurement tool, with significant potential for ongoing future developments. It represents an initial development in accessible hyperspectral technologies, providing a robust basis for future improvements.

Recent advances in smartphone technologies have opened the door to the development of accessible, highly portable sensing tools capable of accurate and reliable data collection in a range of environmental settings. In this article, we introduce a low-cost smartphone-based hyperspectral imaging system that can convert a standard smartphone camera into a visible wavelength hyperspectral sensor for ca. £100. To the best of our knowledge, this represents the first smartphone capable of hyperspectral data collection without the need for extensive post processing. The Hyperspectral Smartphone’s abilities are tested in a variety of environmental applications and its capabilities directly compared to the laboratory-based analogue from our previous research, as well as the wider existing literature. The Hyperspectral Smartphone is capable of accurate, laboratory- and field-based hyperspectral data collection, demonstrating the significant promise of both this device and smartphone-based hyperspectral imaging as a whole.

Using exceptionally accurate measurements of the speed of sound in argon, we have made estimates of the difference between thermodynamic temperature, T , and the temperature estimated using the International Temperature Scale of 1990, T ₉₀ , in the range 118 K to 303 K. Thermodynamic temperature was estimated using the technique of relative primary acoustic thermometry in the NPL-Cranfield combined microwave and acoustic resonator. Our values of ( T − T ₉₀ ) agree well with most recent estimates, but because we have taken data at closely spaced temperature intervals, the data reveal previously unseen detail. Most strikingly, we see undulations in ( T − T ₉₀ ) below 273.16 K, and the discontinuity in the slope of ( T − T ₉₀ ) at 273.16 K appears to have the opposite sign to that previously reported.

Lava lakes provide a rare opportunity to study conduit flow processes through direct observation of the exposed magma surface. The recent lava lake activity at Masaya volcano (Nicaragua), which commenced in 2015, displayed several unusual phenomena. We report on the dynamics of this rapidly convecting lake, which, to the best of our knowledge manifested the highest lava flow velocities ever reported for a lava lake: 13.7–16.4 m s⁻¹, in addition to unusual fluid dynamic behavior involving alteration in surface flow direction. We studied this system with multiparametric and high time resolution remote sensing measurements, performed during June 2017, including ultraviolet camera observations of SO₂ emission rates, near infrared thermal camera measurements and video analyses of the lake surface. Median SO₂ emission rates of 3.1 (±0.8) and 3.7 (±0.9) kg s⁻¹ were found, which are lower than previously published estimates, and could represent challenging remote sensing conditions or a waning in lava lake activity. Video analyses enabled characterization of frequent bursts of approximately hemispherical spherical-cap bubbles on the surface with diameters ranging 0.6–8.5 m (median of 2.6 m), and calculation of individual bubble masses, which contribute to active bubble bursting values estimated at 1.9 to 3.9 kg s⁻¹. We show that only a small fraction, 7–17%, of total emission volumes are contributed by these bubbles, based on estimated emission rates of 22.5 and 26.9 kg s⁻¹. Furthermore, periodicity analysis reveals regular 200–300 s oscillations in SO₂ emissions. These are not shared by any of our other datasets and particularly during the contemporaenously acquried thermal data, hence, we tentatively assign an atmospheric causal generation mechanism, driven by atmospheric transport and turbulence phenomena, such as eddying. Overall, we highlight the uniquely high velocity and fluid dynamic behavior of Masaya lava lake.

Near infrared thermal cameras can provide useful low-cost imaging systems for high temperature applications, as an alternative to ubiquitous mid-/long-wavelength infrared systems. Here, we present a new Raspberry Pi-based near infrared thermal camera for use at temperatures of ≈>500 °C. We discuss in detail the building of the optical system, calibration using a Sakuma-Hattori model and quantification of uncertainties in remote temperature retrievals. We then present results from the deployment of the system on Masaya Volcano, Nicaragua, where the active lava lake was imaged. Temperatures reached a maximum of 1104 ± 14 °C and the lake radiative power output was found to range between 30 and 45 MW. To the best of our knowledge, this is the first published ground-based data on the thermal characteristics of this relatively nascent lava lake, which became visible in late 2015.