HyperSCAN (Hyper Spectral Camera ANalyzer) is a hyperspectral imager which monitors the Earth’s environment and also an educational platform to integrate college students’ ideas and skills in optical design and data processing. The advantages of HyperSCAN are that it is designed for modular design, is compact and lightweight, and low-cost using commercial off-the-shelf (COTS) optical components. The modular design allows for flexible and rapid development, as well as validation within college lab environments. To optimize space utilization and reduce the optical path, HyperSCAN’s optical system incorporates a folding mirror, making it ideal for the constrained environment of a CubeSat. The use of COTS components significantly lowers pre-development costs and minimizes associated risks. The compact size and cost-effectiveness of CubeSats, combined with the advanced capabilities of hyperspectral imagers, make them a powerful tool for a broad range of applications, such as environmental monitoring of Earth, disaster management, mineral and resource exploration, atmospheric and climate studies, and coastal and marine research. We conducted a spatial-resolution-boost experiment using HyperSCAN data and various hyperspectral datasets including Urban, Pavia University, Pavia Centre, Botswana, and Indian Pines. After testing various data-fusion deep learning models, the best image quality of these methods is a two-branches convolutional neural network (TBCNN), where TBCNN retrieves spatial and spectral features in parallel and reconstructs the higher-spatial-resolution data. With the aid of higher-spatial-resolution multispectral data, we can boost the spatial resolution of HyperSCAN data.

Abstract A line of mesoscale convective systems (MCSs) accompanied by hails with strong updraft may produces favorable weather conditions for high flash rates and sprite occurrences. On 18–20 May, 2018, we observed a total of 287 transient luminous events (TLEs) in the Taiwan campaign. After analyzing flashes from Earth Networks Total Lightning Network (ENTLN), the observation region has a maximum CG flash rate 115.1 min-1 (95.1 min-1 for –CGs and 20.0 min-1 for + CG) within a single cell of MCSs on May 20 within a radius 55 km. We investigated the TLEs activity associated with the multi-cells in the MCS, and found that sudden increases of TLEs are associated with the merging stage of new and old cells and the dissipating stage of cell. The flashes associated with TLEs with halo emissions have a tendency of large peak current. The TLEs with their parent flashes and extremely high peak currents (200, 244, 261, 267, 311, 357 kA) were shown, and most of events have common optical features of sprite halos and clusters of sprites structures.

Most of the lightning appears below the cloud or inside the cloud. Unlike conventional lightning, blue jets and gigantic jets (GJ) produce upward discharge since electric discharge occurs as a form of cloud-to-air leader. We analyzed a gigantic jet recorded in the 2022 Taiwan campaign. For our color photograph recorded in the observation, high spatial resolution (150 m) at a close distance (140 km) resolves the important spatial features of the GJ phenomena. First, the GJ propagated upwardly as the fully developed jet with a maximum height of ~80 km above the cloud top ~17 km. After the fully developed stage, the subsequent leader reached its top height of ~30 km with a width of 0.5–1.0 km. The subsequent leader attempted but failed to develop from leader to fully developed jet. The subsequent leader may be interpreted as a negative stepped leader associated with cloud rebrightening, similar to the subsequent stroke in the multi-stroke lightning. Besides, the relatively higher IC flash rates associated with the rise of cloud tops benefit the required meteorological conditions for developing gigantic jets.

Abstract A short‐term (30 days before an earthquake) prediction of an earthquake is a big challenge in seismology. As a first step, we apply deep learning to the ionospheric total electron content (TEC) data between 2003 and 2014 to detect the seismo‐ionospheric precursors of M ≥ 6.0 earthquakes in Taiwan. The bidirectional Long Short‐Term Memory (Bi‐LSTM) network is employed to use observed input data (features) to obtain the sequential TEC variations. The five input features are sequential vectors of TEC, the geomagnetic index Dst, the solar activity index F10.7, sunspot number (SSN), and solar emission index Lyman‐α. The daily values of F10.7, SSN, and Lyman‐α are converted into hourly values, depending on the solar elevation angle. The calculated hourly TEC variations can be more precisely predicted with this data conversion. We calculate the normalized difference of errors between two 15‐day adjacent stages as the “relative error”. Three trained models with the best discrimination between the relative errors of earthquake and no‐earthquake cases are chosen as classifiers. These three classifiers are then used to have a majority vote to declare whether the 30‐day period is related to the preparation of an earthquake or not. The results show that all 22 positive cases (earthquakes) are successfully predicted, giving a true positive rate of 100%. Among the 19 negative cases (normal cases), 10 of them are true negative.” Overall, a high accuracy of 78.05% is obtained.

The JAXA’s Martian Moons Exploration (MMX) mission is planned to reveal the origin of Phobos and Deimos. It will remotely observe both moons and return a sample from Phobos. The nominal instruments include the TElescopic Nadir imager for GeOmOrphology (TENGOO) and Optical RadiOmeter composed of CHromatic Imagers (OROCHI). The scientific objective of TENGOO is to obtain the geomorphological features of Phobos and Deimos. The spatial resolution of TENGOO is 0.3 m at an altitude of 25 km in the quasi-satellite orbit. The scientific objective of OROCHI is to obtain material distribution using spectral mapping. OROCHI possesses seven wide-angle bandpass imagers without a filter wheel and one monochromatic imager dedicated to the observation during the landing phase. Using these two instruments, we plan to select landing sites and obtain information that supports the analysis of return samples. Graphical Abstract

Recent efforts to compare the sprite ratios with theoretical results have not been successfully resolved due to a lack of theoretical results for sprite streamers in varying altitudes. Advances in the predicted emission ratios of sprite streamers with a simple analytic equation have opened up the possibility for direct comparisons of theoretical results with sprite observations. The study analyzed the blue-to-red ratios measured by the ISUAL array photometer with the analytical expression for the sprite emission ratio derived from the modeling of downward sprite streamers. Our statistical studies compared sprite halos and carrot sprites where the sprite halos showed fair agreement with the predicted ratios from the sprite streamer simulation. But carrot sprites had lower emission ratios. Their estimated electric field has a lower bound of greater than 0.4 times the conventional breakdown electric field (E k ). It was consistent with the results of remote electromagnetic field measurements for short delayed or big/bright sprites. An unexpectedly lower ratio in carrot sprites occurred since sprite beads or glow in carrot sprites may exist and contribute additional red emission.

After almost thirty years’ efforts on studying transient luminous events (TLEs), ground-based observation has confirmed the TLE family, including elves, halos, sprites, and blue jets, etc. The typical elve has the shortest emission time (<1 ms) in comparison with other TLEs. The second shortest is the halo emission. Although elves and halos are supposed to be more frequent than sprites, ground campaigns still have less probability of recording their images due to their fleeting and short emission. Additionally, the submillisecond imaging of elves, halos, and sprite halos helps us resolve their electro-optic dynamics and morphological features, but few have been reported in the literature. Our study presents the 10,000 fps imaging frames on elves, halos and sprite halos, compares their similarity and disparity, and analyzes their parent lightning properties with associated VLF and ELF data.

The Ionospheric Dynamics Exploration and Attitude Subsystem Satellite (IDEASSat/ INSPIRESat-2) is a three-unit (U) CubeSat developed with the objective of providing in-situ measurements of the Earth's ionosphere in order to quantify both global scale ionospheric variability and small scale irregularities. The science payload is the Compact Ionospheric Probe (CIP) - an all in one in-situ plasma sensor developed at Taiwan National Central University (NCU), which is the miniaturized version of the larger Advanced Ionospheric Probe (AIP) that is carried and operational aboard the 450 kg FORMOSAT-5 spacecraft. The spacecraft has been developed by NCU in partnership with the International Satellite Program in Research and Education (INSPIRE) consortium, and is funded by the Taiwan National Space Organization (NSPO), Ministry of Science and Technology, and Ministry of Education as part of the first national effort to encourage small satellite development at Taiwan universities. The development of IDEASSat offers students a hands-on opportunity to learn about space science and technology and will work in conjunction with FORMOSAT-5 and INSPIRESat-1 to provide ionospheric observations spanning different altitudes and local times. The IDEASSat spacecraft subsystems are a combination of commercial off the shelf (COTS) and self-developed components designed by NCU in partnership with other INSPIRE member universities. IDEASSat is expected to be launched in late 2020. In this report, we describe the IDEASSat mission and spacecraft design, as well as unique lessons learned as part of the development process. (C) 2020 COSPAR. Published by Elsevier Ltd. All rights reserved.

Multi-band observation of transient luminous events (TLEs) is one of the useful methodologies to be employed in sprite campaigns. Here, we show a method to estimate the Boltzmann vibrational temperature of N2 (B3Πg) by analyzing the 630nm-filtered, N2 1P-filtered and 762 nm-filtered images of TLEs. Our advanced method is validated in compassion with derived relative vibrational distributions by sprite spectrum (Kanmae et al., 2007). The imager recorded N2 1P-filtered emission (I1P, 623 – 754 nm) of TLEs indicates the intensity of N2 1P Δv=3 and partial with Δv=2 where dominated emissions with upper state vibrational number v=4, 5 and 6, i.e., N2 1P (4, 2), (4, 1), (5, 2) and (6, 3). The imager recorded 630 nm-filtered emissions (I630) were contributed primarily from N2 1P (10, 7) with v=10 while N2 1P (3, 1) for 762 nm-filtered emissions (I762) with v=3. Hence, we calculated the emission ratios of I630 to I1P, I630 to I762 and I762 to I1P. The emission ratios of I630 to I1P, I630 to I762 and I762 to I1P also reflect the relative vibrational distributions of vibrational levels with LOW v=3 (I762), MIDDLE v=4, 5, 6 (I1P, 623 – 754 nm), and HIGH v=10 (I630). Therefore, we use the Boltzmann temperature for indicating the relative vibrational distributions of the specified group (LOW/MIDDLE/HIGH) of N2 (B3Πg) vibrational levels. For ISUAL recorded sprites, the average brightness of N2 1P (I1p), 762 nm (I762) and 630 nm (I630) emission was 2.3, 0.6 and 0.02 MR. The N2 (B3Πg) vibrational temperatures (Tv) were estimated to be 2800 K, 3200 K and 4300 K for multi-band emission ratios of I630/ I1p, I630/ I762 and I762/ I1p. For observed elves, the average brightness I1p, I762 and I630 were 170, 50 and 3 kR. The estimated Tv values were 3700 K, 3700 K and 3800 K for ratios I630/ I1p, I630/ I762 and I762/ I1p. For observed gigantic jets, the derived Tv values were 3000 – 5000 K for a ratio I762/ I1p. Through N2 (B3Πg) Tv analyses from emission ratios of ISUAL multi-band observation, we derived the N2 (B3Πg) vibrational temperature that ranges between 3000 and 5000 K or higher in TLEs. Accuracy and variations of derived N2 (B3Πg) Tv are also discussed while the relative population of vibrational levels in the Boltzmann equilibrium are also compared with past spectra observation. The details are shown in the publication (https://doi.org/10.1029/2019JA027311).

We present a multi-instrument experiment to study the effects of tropospheric thunderstorms on the mesopause region and the lower ionosphere. Sodium (Na) lidar and ionospheric observations by two digital ionospheric sounders are used to study the variation in the neutral metal atoms and metallic ions above thunderstorms. An enhanced ionospheric sporadic E layer with a downward tidal phase is observed followed by a subsequent intensification of neutral Na number density with an increase of 600 cm−3 in the mesosphere. In addition, the Na neutral chemistry and ion-molecule chemistry are considered in a Na chemistry model to simulate the dynamical and chemical coupling processes in the mesosphere and ionosphere above thunderstorms. The enhanced Na layer in the simulation obtained by using the ionospheric observation as input is in agreement with the Na lidar observation. We find that the intensification of metallic layered phenomena above thunderstorms is associated with the atmospheric tides, as a result of the troposphere-mesosphere-ionosphere coupling.

One of the main challenges for the observation of a transient luminous event (TLE) is to observe TLEs in different emission bands. Here, we show TLEs recorded using the ISUAL 427.8 nm, 630 nm, N-2 1P (623-750 nm) and 762-nm-filtered imager, and we analyze the 630-nm-filtered, N-2 1P-filtered, and 762-nm-filtered images of TLEs for estimating the N-2 (B-3 Pi(g)) Boltzmann vibrational temperature in comparison with the theoretical N-2 1P spectrum. For ISUAL recorded sprites, the average brightness of N-2 1P (I-1p), 762 nm (I-762), and 630 nm (I-630) emission was 2.3, 0.6, and 0.02 MR. The N-2, (B-3 Pi(g)) vibrational temperatures (T-v) was estimated to be 2800 K, 3200 K, and 4300 K for multiband emission ratios of I-630/I-1p, I-630/I-762, and I-762/I-1p. For observed elves, the average brightness I-1p, I-762, and I-630 were 170, 50, and 3 kR. The estimated T-v, values were 3700 K, 3700 K, and 3800 K for ratios I-630/I-1p, I-630/I-762, and I-762/I-1p. For observed gigantic jets, the derived T-v values were 3000-5000 K for a ratio I-762/I-1p. Through N-2 (B-3 Pi(g)) T-v analyses from emission ratios of ISUAL multiband observation, we derived the N-2 (B-3 Pi(g)) vibrational temperature that ranges between 3000 and 5000 K or higher in TLEs. Accuracy and variations of derived N-2 (B-3 Pi(g)) T-v are also discussed while relative population of vibrational levels in the Boltzmann equilibrium are also compared with past spectra observation.

Several lithosphere-atmosphere-ionosphere coupling (LAIC) models have been proposed to explain observed precursors before strong earthquakes, such as atmospheric conductivity anomalies and ionospheric total electron content (TEC) variations. These coupling models include (a) radon ionization leading to charged aerosols and change of load resistance in the global atmospheric electric circuit, (b) an electric coupling model of stressed rock-atmosphere-ionosphere based on experimental evidence of stressed rock currents, and (c) ionosphere dynamics with an imposed zonal electric field. Here, we summarize our modeling of stressed-rock-atmosphere-ionosphere coupling for the LAIC process. A physical mechanism of electrical coupling between the atmosphere and surface charge in the fault region is proposed. We also discuss other possible seismic anomalies before and after the earthquake and suggest that in future electric field measurements are used to validate the possible existence of electric activities associated with an earthquake preparation region.

The blue luminous events (BLEs) recorded by ISUAL (Imager of Sprites and Upper Atmospheric Lightning) radiate unambiguous middle ultraviolet to blue emissions (230-450 nm) but contain dim red emissions (623-754 nm). The BLE appears to be dot-like on one ISUAL image with an integration time of 29 ms. A few BLEs develop upward into blue jets/starters or type II gigantic jets (GJs). The associated sferics of the BLEs in the extremely low frequency to very low frequency band and in the low-frequency band exhibit similar patterns to the narrow bipolar events (NBEs) identified in the very low frequency and low-frequency band. The ISUAL BLEs are conjectured to be the accompanied light emissions of the NBEs. Both upward and downward propagating current obtained from the associated sferics of the BLEs have been found. The source heights of the six BLEs related to negative NBEs are estimated in the range of 16.2-17.8 km. These six events are suggested to occur between the upper positive charge layer and the negative screen charge layer on the top of the normally electrified thunderstorm. The six blue starters, one blue jet, and one type II GJ are inferred to be positive upward discharges from their associated sferics in the extremely low frequency to very low frequency band. Based on the simultaneous radio and optical observations, a NBE is conjectured to be the initiation discharge with rapidly flowing current within the thunderstorm, while a blue jet/starter or a type II GJ is suggested to be the ensuing discharge with slowly varying current propagating upward from the thunderstorm.

This paper reports on the recent developments in spectroimagers for sprite campaigns in Taiwan. We first introduce two types of spectroimagers, the slit and slitless types, and discuss their advantages and shortcomings. Next we explore the instrument development and procedures undertaken for this study. In 2006, a slit spectroimager was installed for a sprite campaign and on 15 August of that year, two sprite spectra were recorded using the slit spectroimager along with seven sprites, one halo, one ELVES emission and two jets. By the end of 2015, a slitless spectroimager had been successfully constructed and was ready to conduct additional investigations. On 7 May 2016, a sprite spectrum was recorded using the slitless spectroimager. Following an examination of the calibrations (comprising detection region field of view, wavelength calibration, and response curve), data analysis, and additional calibrations (comprising elevation and azimuthal angles, atmospheric transmittance, and theoretical wavelength calculations) performed in this study, we present the results from our observed sprite spectra using the slit and slitless spectroimagers.

Ulysses magnetic and plasma data are used to study hourly scale Alfvenic fluctuations in the solar polar wind. The calculated energy ratio R-vA(2) (cal) of inward to outward Alfven waves is obtained from the observed Walen slope through an analytical expression, and the observed R-vA(2) (obs) is based on a direct decomposition of original Alfvenic fluctuations into outward-and inward-propagating Alfven waves. The radial variation of R-vA(2) (cal) shows a monotonically increasing trend with heliocentric distance r, implying the increasing local generation or contribution of inward Alfven waves. The contribution is also shown by the radial increase in the occurrence of dominant inward fluctuations. We further pointed out a higher occurrence (similar to 83% of a day in average) of dominant outward Alfvenic fluctuations in the solar wind than previously estimated. Since R-vA(2) (cal) is more accurate than R-vA(2) (obs) in the measurement of the energy ratio for dominant outward fluctuations, the values of R-vA(2) (cal) in our results are likely more realistic in the solar wind than those previously estimated as well as R-vA(2) (obs) in our results. The duration ratio R-T of dominant inward to all Alfvenic fluctuations increases monotonically with r, and is about two or more times that from Voyager 2 observations at r >= 4 au. These results reveal new qualitative and quantitative features of Alfvenic fluctuations therein compared with previous studies and put constraints on modeling the variation of solar wind fluctuations.