Low cost equipment for astronomical spectroscopy

The purpose of this paper is to show how we can obtain spectra for different astronomical objects using low coat equipment. Where a high-efficiency diffraction grating named “The Star Analyzer” was used by the International Astronomical Center (IAC) in Abu Dhabi, UAE to get the spectrum of different astronomical objects. Balmer series was readily visible when observing an “A” type star. TiO absorptions lines were distinguished by observing an “M” type star. Methane absorption lines were visible by observing Uranus and Neptune. Whereas HI and HeI emission lines were detected by observing a blue hypergiant. In addition, C2 Swan band absorption lines were identified by observing a red giant carbon star. This type of observation is very interesting for public outreach as well as university students, because it shows astrophysical principles for public and students practically and by using low cost equipment.

The Hubble PanCET program: Transit and Eclipse Spectroscopy of the Hot-Jupiter WASP-74b

Planets are like children with each one being unique and special. A better understanding of their collective properties requires a deeper understanding of each planet. Here we add the transit and eclipse spectra of hot-Jupiter WASP-74b into the ever growing data set of exoplanet atmosphere spectral library. With six transits and three eclipses using the Hubble Space Telescope and Spitzer Space Telescope (Spitzer), we present the most complete and precise atmospheric spectra of WASP-74b. We found no evidence for TiO/VO nor super-Rayleigh scattering reported in previous studies. The transit shows a muted water feature with strong Rayleigh scattering extending into the infrared. The eclipse shows a featureless blackbody-like WFC3/G141 spectrum and a weak methane absorption feature in the Spitzer 3.6 μm band. Future James Webb Space Telescope follow-up observations are needed to confirm these results.

Mapping methane plumes at very high spatial resolution with the WorldView-3 satellite

The detection of methane emissions from industrial activities has been identified as an effective climate change mitigation strategy. These industrial emissions, such as from oil and gas (O&amp;G) extraction and coal mining, typically occur as large plumes of highly concentrated gas. Different satellite missions have recently shown potential to map such methane plumes from space. In this work, we report on the great potential of the WorldView-3 (WV-3) satellite mission for methane mapping. This relies on its unique very high spatial resolution (up to 3.7 m) data in the shortwave infrared part of the spectrum, which is complemented by a good spectral sampling of the methane absorption feature at 2300 nm and a high signal to noise ratio. The proposed retrieval methodology is based on the calculation of methane concentration enhancements from pixel-wise estimates of methane transmittance at WV-3 SWIR band 7 (2235–2285 nm), which is positioned at a highly-sensitive methane absorption region. A sensitivity analysis based on end-to-end simulations has helped to understand retrieval errors and detection limits. The results have shown the good performance of WV-3 for methane mapping, especially over bright and homogeneous areas. The potential of WV-3 for methane mapping has been further tested with real data, which has led to the detection of 26 independent point emissions over different methane hotspot regions such as the O&amp;G extraction fields in Algeria and Turkmenistan, and the Shanxi coal mining region in China. In particular, the detection of very small leaks (< 100 kg/h) from oil pipelines in Turkmenistan shows the game-changing potential of WV-3 to map industrial methane emissions from space.

DETECTION OF METHANE PLUMES IN HYPERSPECTRAL IMAGES FROM SENTINEL-5P BY COUPLING ANOMALY DETECTION AND PATTERN RECOGNITION

Reducing methane emissions is essential to tackle climate change. Here, we address the problem of detecting large methane leaks using hyperspectral data from the Sentinel-5P satellite. For that we exploit the fine spectral sampling of Sentinel-5P data to detect methane absorption features visible in the shortwave infrared wavelength range (SWIR). Our method involves three separate steps: i) background subtraction, ii) detection of local maxima in the negative logarithmic spectrum of each pixel and iii) anomaly detection in the background-free image. In the first step, we remove the impact of the albedo using albedo maps and the impact of the atmosphere by using a principal component analysis (PCA) over a time series of past observations. In the second step, we count for each pixel the number of local maxima that correspond to a subset of local maxima in the methane absorption spectrum. This counting method allows us to set up a statistical a contrario test that controls the false alarm rate of our detections. In the last step we use an anomaly detector to isolate potential methane plumes and we intersect those potential plumes with what have been detected in the second step. This process strongly reduces the number of false alarms. We validate our method by comparing the detected plumes against a dataset of plumes manually annotated on the Sentinel-5P L2 methane product.

Short-lived storms inside long-lived cyclones: Simulations of the 2020 storm in the South Temperate Belt

&lt;p&gt;Convective storms on Jupiter usually develop in the cyclonic side of the jets or inside cyclones (Vasavada and Showman, 2005). On 31 May 2020 a convective storm developed inside a small cyclone (3&amp;#186; in longitudinal extent) in the South Temperate Belt at planetographic latitude 30&amp;#186;S. The storm outbreak was captured by amateur astronomer Clyde Foster becoming widely known as Clyde&amp;#8217;s spot. The storm was observed 2.5 days later by JunoCam with images displaying an apparent cyclonic structure with two main lobes and high-clouds observable in the methane absorption band. Analysis of these observations show the storm in a decaying phase with associated weak winds. Observations over the following months combined with prior observations (2 years) obtained by JunoCam, HST, IRTF and amateur observers show the long-term evolution of the cyclone before and after the convective eruption. The short-lived storm made the cyclone to display large changes in morphology and colour but not in its size or latitude, except for small fluctuations around a mean latitude and mean drift rate. Ground-based infrared observations at 5 &amp;#956;m show the region where the vortex was located characterized by a weakly warm radiance several months after the convective outbreak, indicating a relative clearing of clouds and haze. We have used the Explicit Planetary Isentropic-Coordinate (EPIC) numerical model (Dowling et. al., 1998) to simulate the cyclone and the effects of convective storms of different strengths and durations on it. These simulations were partially guided by our previous study of a similar convective storm in a different type of cyclone: an elongated structure known as the STB Ghost at the same latitude in 2018 (I&amp;#241;urrigarro et. al., 2020). Both storms and cyclones were different in terms of their size, morphology and later evolution, but our simulations suggest that in both cases the convective eruptions were of similar power but with different lifetimes indicating that the energy source is water moist convection. We compare these storms and simulations with a similar convective storm observed in 1979 by Voyager 2 at 38&amp;#186;S that quickly evolved into a Folded-Filamentary Region and investigate the outcome of convective storms at different latitudes from these simulations.&lt;/p&gt;&lt;p&gt;References:&lt;/p&gt;&lt;p&gt;Dowling et al., 1998. The Explicit Planetary Isentropic-Coordinate (EPIC) Atmospheric Model, Icarus, 132, 221-238.&lt;/p&gt;&lt;p&gt;I&amp;#241;urrigarro et al., 2020. Observations and numerical modelling of a convective disturbance in a large-scale cyclone in Jupiter&amp;#8217;s South Temperate Belt, Icarus, 336, 113475.&lt;/p&gt;&lt;p&gt;Vasavada and Showman, 2005. Jovian atmospheric dynamics: an update after Galileo and Cassini, Reports on Progress in Physics, 68, 1935-1996.&lt;/p&gt;

Variations in spectral reflectivity and vertical cloud structure of Jupiter’s Great Red Spot

&lt;p&gt;The Great Red Spot (GRS) of Jupiter is a large anticyclonic vortex present in the Jovian atmosphere. First observed in the XVII century, it is almost constantly located at 22&amp;#176;S and it is arguably one of the main atmospheric phenomena in the Solar System. Despite having been widely studied, the nature of the chromophore species that provide its characteristic colour to the GRS&amp;#8217;s upper clouds and hazes is still unclear, as well as its creation and destruction mechanisms.&lt;/p&gt;&lt;p&gt;In this work we have analysed images provided by the Hubble Space Telescope&amp;#8217;s Wide Field Camera 3 between 2015 and 2019, with a spectral coverage from the ultraviolet to the near infrared, including two methane absorption bands. These images have undergone a photometric process of cross calibration, ensuring a consistent correlation among the images corresponding to different visits and years. From such calibrated images, we have obtained the spectral reflectivity of the GRS and its surroundings, with particular emphasis on a few, dynamically interesting regions.&lt;/p&gt;&lt;p&gt;We used the NEMESIS radiative transfer suite to retrieve the main atmospheric parameters (particle vertical and size distributions, refractive indices&amp;#8230;) that are able to explain the observed spectral reflectivity of the selected regions. Here we report the spatial and temporal variations on such parameters and their implications on the GRS overall dynamics.&lt;/p&gt;

Methane in the atmosphere, methanotrophs and development of oil and gas industry

Dynamics of methane content alterations in the Earth's atmosphere in the conditions of globalization is analyzed and methane emission sources are estimated. Oil and gas industry is proved to be the most important anthropogenic source of atmospheric methane growth. Natural mechanisms of methane concentration regulation in the biosphere are considered. Particular attention is paid to the process of methane absorption by methanotrophic microorganisms and peculiarities of their functioning in extreme conditions. Methodology for reducing methane technogenic inflow into the atmosphere using methanotrophs is proposed. The book is addressed to oil and gas industry employees and everyone interested in the behavior of methane in the atmosphere, especially in connection with the atmospheric pollution and natural degradation of pollutants.

Application of Derivative Transform Spectroscopy in Gas Detection

Digital filtering technique is of great significance in real-time signal processing and analysis, but the stability, efficiency and flexibility of filter algorithm are important indicators to reflect its application value. In this paper, an adaptive derivative transformation based on Savitzky-Golay filter algorithm was proposed for laser absorption spectroscopy analysis. To demonstrate this analysis algorithm, first-order and second-order derivative spectroscopy are evaluated for the analysis of infrared methane absorption spectra, and compared with the original direct absorption spectral signals. The results indicated that the proposed signal processing algorithm has good performance on noise suppression and spectral resolution improvement, and the 2nd derivative spectroscopy shows better de-noising efficiency.

An examination of enhanced atmospheric methane detection methods for predicting performance of a novel multiband uncooled radiometer imager

To evaluate the potential for a new uncooled infrared radiometer imager to detect enhanced atmospheric levels of methane, three different analysis methods were examined. A single-pixel brightness temperature to noise-equivalent delta temperature (NEdT) comparison study performed using data simulated from MODTRAN6 revealed that a single thermal band centered on the 7.68 µm methane feature leads to a detectable brightness temperature difference exceeding the sensor noise level for a plume of about 17 ppm at ambient atmospheric temperature compared to an ambient plume with no enhanced methane present. Application of a normalized differential methane index method, a novel approach for methane detection, demonstrated how a simple two-band method can be utilized to detect a plume of methane that is 10 ppm above ambient atmospheric concentration and −10 K from ambient atmospheric temperature with an 80 % hit rate and 17 % false alarm rate. This method was capable of detecting methane with similar levels of success as the third method, a proven multichannel method, matched filter. The matched-filter approach was performed with six spectral channels. Results from these examinations suggest that given a high enough concentration and temperature contrast, a multispectral system with a single band allocated to a methane absorption feature can detect enhanced levels of methane.