Solar Phase Research Articles

The Combined Effects of ENSO and Solar Activity on Mid-Winter Precipitation Anomalies Over Southern China

Both the El Niño-Southern Oscillation (ENSO) and the 11-years solar cycle had been identified as important factors that may influence the wintertime southern China precipitation (SCP). However, the interactions between these two factors remain less noticed. In this study, the combined effects of the ENSO and the solar activity on mid-winter (January) SCP are investigated using observational and reanalysis data. Results suggest that both the ENSO and the solar activity are positively correlated with the SCP, although exhibiting distinct spatial patterns. Under different combinations of the ENSO and solar phases, the SCP anomalies show superposition of these two factors to some extent. Generally, the ENSO-related SCP anomalies tend to be enhanced (disturbed) when the ENSO and the solar activity are in-phase (out-of-phase). But this solar modulation effect appears more clear and significant under cold ENSO (cENSO) phase rather than under warm ENSO (wENSO) phase. Further analysis suggests, during the wENSO phase, solar influences on the Northern Hemisphere circulation are generally weak with little significance. In contrast, during the cENSO phase, the solar effect resembles the positive phase of the Arctic Oscillation but with an evident zonal asymmetric component. Its manifestation over the Asia-Pacific domain features by negative geopotential height anomaly over the West Asia and positive geopotential height anomaly over the East Asian coast, a pattern that is favorable for the SCP, thus causing a significant solar modulation on the cENSO-related precipitation anomalies. Further, the potential physical causes of solar effects on circulation are also discussed. Our results highlight the importance of considering solar cycle phase when ENSO is used to predict the East Asian winter climate.

Improving the efficiency of solar drying unit with PCM (Paraffin wax)

The renewable energy source like solar is been used in this projects to produce more efficiency in a solar dryer. It is one the most reliable energy source and that does not pollute the environment and green house free emission. In this project work we use sunlight to dry the crops and to preserve the dry fruits we are using sunlight. The motivation of the work is to use a solar dryer with phase change material. With the help of PCM we can able to increase the efficiency of solar dryer because of increasing the contact area of the crops with PCM during off sunlight. In this project work we use indirect solar radiation principle because PCM will absorb the solar radiation and that will be emitted during the night time. A absorber plate is used to absorb the solar radiation. Once after receiving the radiation from the sun that is been transferred to the chamber where the crops are been provided. In that chamber we will be having the PCM box that will be in solid state and once after receiving the solar radiation phase change will be taking place from solid to liquid phase. Once the sun starts to set off the solar radiation will not be available so during that time PCM is used to transfer the heat. The moisture present in the crop is been removed with the help of the heated air. With the help of the above information the crop drying process is been evaluated with the help of calculation.

Categorization of Coronal Mass Ejection-driven Sheath Regions: Characteristics of STEREO Events

Abstract We present a comprehensive statistical analysis of 106 sheath regions driven by coronal mass ejections and measured near 1 au. Using data from the STEREO probes, this extended analysis focuses on two discrete categorizations. In the first categorization, we investigate how the generic features of sheaths change with their potential formation mechanisms (propagation sheaths and expansion sheaths), namely, their associations with magnetic ejectas (MEs), which are primarily propagating or expanding in the solar wind. We find propagation sheaths to be denser and driven by stronger MEs, whereas expansion sheaths are faster. Exploring the temporal profiles of these sheaths with a superposed epoch technique, we observe that most of the magnetic field and plasma signatures are more elevated in propagation sheaths relative to expansion sheaths. The second categorization is based on speed variations across sheaths. Employing linear least-squares regression, we categorize four distinct speed profiles of the sheath plasma. We find that the associated shock properties and solar cycle phase do not impact the occurrence of such variations. Our results also highlight that the properties of the driving MEs are a major source of variability in the sheath properties. Through logistic regression, we conclude that the magnetic field strength and the ME speed in the solar wind frame are likely drivers of these speed variations.

A photometric study of members of the NEOs Atiras population

The observation of objects of the Atiras population is a challenge due to the narrow time-window in which observations are possible and, even so, at very low altitudes. This is due to the orbit of these objects, internal to that of the Earth. In this work we present the results of a photometric observational campaign of Atiras aiming to determine their physical parameters using the rotational light curve, the solar phase curve and the photometric spectrum. The period and amplitude have been determined for the asteroids (163693) Atira, (413563) 2005 TG45 and 2017 YH. In the case of (163693) Atira, we have determined a plausible rotational period P=3.1532±0.0001, where the composite light curve presents structure usually related to the presence of a companion, as it has been suggested by radar observations of this asteroid. For asteroids (163693) Atira, (413563) 2005 TG45, (481817) 2008 UL90 and 2018 JB3 it was possible to derive the absolute magnitude and the phase coefficient. The obtained values are similar to those observed for asteroids with intermediate to low albedo. Finally, for asteroid (163693) Atira we have obtained a featureless photometric spectrum which is compatible in the Carvano taxonomic scheme with the Xp, Dp or Cp classes. No appreciable surface variations were observed for this object.

Spread F echoes variability along solar flux and seasonality conditions over the 50-MHz radar on Christmas Island/ Espalhe a variabilidade dos ecos de F ao longo do fluxo solar e das condições de sazonalidade no radar de 50 MHz na Ilha Christmas

Perturbations in the amplitude (or phase) of radio signals are caused by irregularities in the ionospheric electron density. Ionospheric structures can disrupt the propagation of radio waves, and are commonly observed, for instance, by ionospheric vertical radio sounders (ionosondes). For historical reasons, the signatures of ionospheric irregularities in different types observations (optical, radio, in-stu ) are referred to as equatorial spread F (ESF). Previous studies show that the occurrence rate can be greatly affected by solar and magnetic conditions. Observations during the period of 2003 to 2012 of nighttime echoes made from the 50-MHz radar on Christmas Island (2.0 o N, 157.4 o W) have revealed time and altitude pattern distribution along the descending phase of solar cycle 23 and the recent extended solar minimum phase. We present the study of spread F echoes as a function of solar flux conditions and seasonality in order to quantify their variability. Under higher solar flux conditions, echoes reach higher altitudes but decay earlier. Only during solar minimum conditions the echoes exist throughout the whole night, since the post?reversal anti?zonal background electric field is weaker. Thus, irregularities during solar maximum will be dominated by dynamics near the time of the PRE. Since the population of irregularities during solar minimum exists throughout the whole night, post?reversal ionospheric conditions may play a role in the morphology of plasma irregularities, especially with the coincidentally weaker PRE during solar minimum. Peak time occurrence of echoes along the current period show a well defined pattern, meanwhile the peak altitude occurrence of echoes show a slight regular pattern.

Geomagnetic Storm Occurrence and Their Relation With Solar Cycle Phases

AbstractUsing a time series of geomagnetic storm events between 1957 and 2019, obtained by selecting storms where −50 nT, we have analyzed the probability of occurrence of moderate, intense, and severe events. Considering that geomagnetic storms can be modeled as stochastic processes with a log‐normal probability distribution over their minimum index, the dataset was separated according to solar cycle (SC) and SC phases, and the distributions of events were fitted through maximum likelihood method in order to characterize the occurrence of storms in each cycle and phase, and then compare those occurrences to the SC24. Our results show that there is a strong dependence between the occurrence of intense storms, with −100 nT, and the strength of the SC measured by the sunspot numbers. In particular, SC24 is very similar to SC20. However, when comparing the occurrence of storms by SC phases, events tend to show similar activity toward the minimum phase and have significant differences in the maximum phases. By looking at the value—the fit log‐normal distribution “width” parameter—characteristic of the occurrence rate of storms, we have found that the (the sigma value in the descending phase of one cycle) shows the highest correlation () with (the sigma value in the maximum phase of the next cycle) which allows us to estimate the occurrence rate of storms for SC25 to be similar to those of SC21 and SC22, suggesting a more intense cycle than the one that just ended.

Effectiveness and safety of levilimab in combination with methotrexate in treatment of patients with active rheumatoid arthritis resistant to methotrexate monotherapy (double-blinded randomized placebo controlled phase III clinical study SOLAR)

Levilimab is anti-interleukin-6 receptor (IL6R) monoclonal antibody. The article presents data obtained during 24 weeks of the SOLAR phase III study.Objective: to confirm efficacy and safety of levilimab in combination with methotrexate (MTX) in patients with methotrexate resistant active rheumatoid arthritis (RA).Patients and methods. 154 adult patients, aged ≥18 years with the diagnosis of RA (ACR/EULAR 2010) and confirmed disease activity at screening despite treatment with MTX for at least 12 weeks (in a stable dose 15-25 mg/week). Patients were randomized 2:1 in levilimab (162 mg once a week, subcutaneously) + MTX (n=102) or placebo + MTX (n=52) group.The hypothesis of superiority of levilimab over placebo was tested for two co-primary efficacy endpoints: proportion of subjects who achieved ACR20 at week 12 and proportion of subjects who achieved low disease activity (LDA) of RA (DAS28-CRP <3.2) at week 24. Safety was assessed through monitoring of adverse events (AEs).Results and discussion. Seventy (68.6%) subjects who received levilimab and 20 (38.5%) who received placebo achieved ACR20 response at week 12. Fifty three (52%) subjects who received levilimab and 3 (5,8%) subjects who received placebo achieved LDA at week 24. The most common adverse events (reported in ≥5% of subjects) in levilimab and placebo arms, respectively were (by decreasing frequency): blood c holesterol increase (24% vs 12%), alanine aminotransferase elevation (11% vs 8%), lymphocyte count decrease (9% vs 8%), blood total bilirubin increase (11% vs 0%), blood triglycerides increase (10% vs 2%), aspartate aminotransferase elevation (7% vs 4%), positive interferon-gamma release assay (IGRA) with M.tuberculosis antigen blood test (5% vs 6%), absolute neutrophil count decrease (8% vs 0%). No deaths were occurred.Conclusion. The study confirmed superior efficacy of levilimab + MTX over placebo + MTX in subjects with MTX resistant active RA. Levilimab showed favorable safety profile and low immunogenicity. No new important safety risks were detected.

On Charon’s Far-ultraviolet Surface Reflectance

Abstract We present the first measurements of Charon’s far-ultraviolet (FUV) surface reflectance, obtained by the Alice spectrograph on New Horizons. We find no measurable flux shortward of 1650 Å, and Charon’s geometric albedo is <0.019 (3σ) at 1600 Å. From 1650 to 1725 Å, Charon’s geometric albedo increases to 0.166 ± 0.068 and remains nearly constant until 1850 Å. As this spectral shape is characteristic of H2O ice absorption, Charon is the first Kuiper Belt object with a H2O ice surface to be detected in the FUV. Charon’s geometric albedo is ∼3.7 times lower than Enceladus’s at these wavelengths but has a very similar spectral shape. We attribute this to similarities in their surface compositions and the difference in absolute reflectivity to a high concentration or more-absorbing contaminants on Charon’s surface. Finally, we find that Charon has different solar phase behavior in the FUV than Enceladus, Mimas, Tethys, and Dione, with a stronger opposition surge than Enceladus and a shallower decline at intermediate solar phase angles than any of these Saturnian satellites.

The Sun’s Magnetic (Hale) Cycle and 27 Day Recurrences in the aa Geomagnetic Index

Abstract We construct a new solar cycle phase clock which maps each of the last 18 solar cycles onto a single normalized epoch for the approximately 22 yr Hale (magnetic polarity) cycle, using the Hilbert transform of daily sunspot numbers (SSNs) since 1818. The occurrences of solar maxima show almost no discernible Hale cycle dependence, consistent with the clock being synchronized to polarity reversals. We reengineer the Sargent R27 index and combine it with our epoch analysis to obtain a high time resolution parameter for 27 day recurrence in aa, 〈acv(27)〉. This reveals that the transition to recurrence, that is, to an ordered solar wind dominated by high-speed streams, is fast, with an upper bound of a few solar rotations. It resolves an extended late declining phase which is approximately twice as long on even Schwabe cycles as odd. Galactic cosmic ray flux rises in step with 〈acv(27)〉 but then stays high. Our analysis also identifies a slow-timescale trend in SSN that simply tracks the Gleissberg cycle. We find that this trend is in phase with the slow-timescale trend in the modulus of sunspot latitudes, and in antiphase with that of the R27 index.

Natural Night Sky Brightness during Solar Minimum

Abstract In 2018, Solar Cycle 24 entered into a solar minimum phase. During this period, 11 million zenithal night sky brightness (NSB) data were collected at different dark sites around the planet, including astronomical observatories and natural protected areas, with identical broadband Telescope Encoder and Sky Sensor photometers (based on the Unihedron Sky Quality Meter TLS237 sensor). A detailed observational review of the multiple effects that contribute to the NSB measurement has been conducted with optimal filters designed to avoid brightening effects by the Sun, the Moon, clouds, and other astronomical sources (the Galaxy and zodiacal light). The natural NSB has been calculated from the percentiles for 44 different photometers by applying these new filters. The pristine night sky was measured to change with an amplitude of 0.1 mag/arcsec2 in all the photometers, which is suggested to be due to NSB variations on scales of up to months and to be compatible with semiannual oscillations. We report the systematic observation of short-time variations in NSB on the vast majority of the nights and find these to be related to airglow events forming above the mesosphere.

Preparation and properties of composite phase change material based on solar heat storage system

Solar phase change hot water storage tank is a kind of storage / exothermic system with solar energy as heat source and phase change heat storage material. It can store heat during the day, continue to operate at night with stored heat without consuming other energy. Because of the poor thermal conductivity of solid-liquid phase heat storage materials, carbon fiber is added to enhance the thermal conductivity of phase change materials. Stearic acid is used as phase change material, carbon fiber as heat transfer material and ethyl cellulose as auxiliary material to prepare carbon fiber / stearic acid composite phase change material. Carbon fiber / stearic acid in the mass ratio of 7.5:92.5 is the optimal material and the chemical compatibility, phase change temperature, phase change latent heat, thermal conductivity and thermal stability of carbon fiber / stearic acid are measured by using SEM, XRD and DSC. From the DSC test, the latent heat capacity was determined as 192.6 J/g and the phase change temperature as 67.7°C. Thermal conductivity was measured as 0.4011 W/m⋅K. The storage / exothermic experimental system of carbon fiber / stearic acid composite phase change material is built. The melting process and solidification process of the composite phase change material are tested, and the storage / exothermic characteristics are analyzed. SEM and DSC analysis results revealed that the PCM had high thermal stability. XRD revealed that the binary eutectic mixture had good chemical stability. Thus, the new PCM possessed high latent heat with good thermal and chemical stabilities making it a potential phase change material for solar heat storage applications.

Pluto in Glory: Discovery of Its Huge Opposition Surge

AbstractNear‐infrared observations of the Pluto Charon system were captured with the Palomar High Angular Resolution Observer (PHARO) adaptive optics (AO) system on the 200‐inch Hale telescope during the historically small solar phase angles in 2018–2019. Both objects exhibit large opposition surges of ∼30%–35% in the last half degree of solar phase angle, which is among the largest observed for icy moons and other Kuiper Belt Objects. In addition, Pluto's surge is exceptionally steep. Pluto's unusual phase curve may be due to an unusual surface texture caused by seasonal volatile transport and active geologic processes. These observations enable accurate determination of Pluto's geometric albedo in the JHK filter system, which we find to be 0.86 ± 0.04, 0.59 ± 0.05, and 0.39 ± 0.04 for Pluto, respectively, and 0.68 ± 0.06 for Charon in the J filter.

Solar activity modulates the El Niño‐Southern Oscillation‐induced precipitation anomalies over southern China in early spring

AbstractThe present study identifies an evident solar cycle modulation upon the spatial pattern of the El Niño‐Southern Oscillation (ENSO) impact on the southern China precipitation in early spring (February–March). During high/low solar activity (HS/LS) years, the significant positive correlation between the wintertime Niño 3.4 index and the precipitation in the following early spring mainly locates at the southeastern China/Yangtze River Valley (SEC/YRV). Our analysis also suggests that the precipitation anomalies show asymmetries between ENSO warm and cold events under both solar phases. In HS years, the ENSO warm events‐related rainfall anomalies over the southern China are weak, but during the ENSO cold events significant dry anomalies appear at the SEC region. In LS years, significant wet anomalies over the YRV region are found during the ENSO warm events, whilst the rainfall anomalies are insignificant for the ENSO cold events. These modulations on precipitation are mediated by the changes in the ENSO‐associated anomalous western North Pacific anticyclone/cyclone, which may be attributed to the solar modulations on the ENSO‐associated sea surface temperature anomalies. Our results highlight that the level of solar activity should be taken into account when ENSO is used as a predictor for the precipitation over East Asia. [Correction added on 18 June 2021, after first online publication: The text for the abstract and graphical abstract were interchanged in the original‐published article. This updated version rectifies the error.]

A Review on Thermal Properties Improvement of Phase Change Materials and Its Combination with Solar Thermal Energy Storage

This article summarizes measures to enhance the solar phase change thermal energy storage (TES), starting from two key points in solar phase change TES research: solar phase change materials (PCM) and solar phase transition devices. First, different types of PCM and their advantages and disadvantages are introduced. To improve thermal performance, the research progress of different dimensional thermal conductivity additives, photothermal composite phase change materials (CPCM), and phase change microcapsules is reviewed. Then, the characteristics of commonly used solar phase transition TES devices and the research status of solar energy device improvement with fins and multistage phase transition TES are summarized for the past few years. It is hoped to provide methods and ideas for the design and research of solar phase change TES systems, and to increase the overall heat transfer properties through the combination of multiple optimization methods. Finally, the future direction and research focus of solar phase change TES technology are put forward.

Optimal forecasting of thermal conductivity and storage in parabolic trough collector using phase change materials

Renewable energy is one of the cleaner energy generation strategies practiced all over the world to reduce environmental impacts and waste based on current sustainability in economic practices. Solar energy is one kind of renewable sources of energy practiced for different application. The thermal storage system in solar energy is one of the least practiced methods in research, and the utilization of solar energy in the thermal application is attaining higher responses and is quite possible. In this paper, solar heat generation is attained by solar parabolic trough collector using phase change materials. The ideology behind this research is to develop a thermal energy storage system using solar collectors and phase change materials. A composition mixture of MgCl2. 6H2O phase change materials used as the fluid medium in trough collector and thermal efficiency of the material is evaluated. For effective optimization, an imperialist competitive algorithm is used for optimizing the thermal efficiency of the solar collectors. The thermal efficiency of the collector is numerically experimented in the running platform of Mat Lab and executed in terms of heat gain, heat loss, and thermal efficiency of the parabolic trough collector, respectively. The efficiency of the proposed framework is 85%, and the current framework just has 80% efficiency. The heat loss in the proposed framework is lower than that of the current system, distinguished as 4200 W and 4520 W, respectively. It is shown from the research study that the proposed PCM composition is an optimal method for generating heat energy in solar parabolic trough collectors.

The 11 year solar cycle UV irradiance effect and its dependency on the Pacific Decadal Oscillation

The stratospheric, tropospheric and surface impacts from the 11 year ultraviolet solar spectral irradiance (SSI) variability have been extensively studied using climate models and observations. Here, we demonstrate using idealized model simulations that the Pacific Decadal Oscillation (PDO), which has been shown to impact the tropospheric and stratospheric circulation from sub-decadal to multi-decadal timescales, strongly modulates the solar-induced atmospheric response. To this end, we use a high-top version of the coupled ocean–atmosphere Norwegian Climate Prediction Model forced by the SSI dataset recommended for Coupled Model Intercomparison Project 6. We perform a 24-member ensemble experiment over the solar cycle 23 in an idealized framework. To assess the PDO modulation of the solar signal, we divide the model data into the two PDO phases, PDO+ and PDO−, for each solar (maximum or minimum) phase. By compositing and combining the four categories, we hence determine the component of the solar signal that is independent of the PDO and the modulation of the solar signal by the PDO, along with the solar signal in each PDO phase. Reciprocally, we determine the PDO effect in each solar phase. Our results show that the intensification of the polar vortex under solar maximum is much stronger in the PDO− phase. This signal is transferred into the troposphere, where we find a correspondingly stronger polar jet and weaker Aleutian Low. We further show that the amplification of the solar signal by the PDO− phase is driven by anomalous meridional advection of solar-induced temperature anomalies over northern North America and the North Pacific, which contributes to a decreased meridional eddy heat flux and hence to a decreased vertical planetary wave flux into the stratosphere.

Thermal optimization of a novel thermo-optically responsive SS-PCM coatings for building enclosures

Building energy consumption constitutes approximately 40% of total energy usage in the US. zero energy buildings (ZEBs) have received much attention in the last decade as they can alleviate some of the negative impacts that buildings have on the environment. New materials and systems are emerging that can help regulate building enclosure heat losses and gains in a passive manner, possibly leading to more cost effective ZEBs. A novel thermo-optically responsive solid–solid phase change material (SS-PCM) coating has been developed to help offset heat gains or losses in building enclosures. The study investigates the optical and thermal processes of the SS-PCM, as well as the synergies among different layers within the enclosure system, through a series of numerical simulations. The impacts of the solar incoming angle and phase transition temperature on the absorptivity of the SS-PCM, which have a significant influence on the optical and thermal transfer processes, are explored. The feasibility and benefits of using the SS-PCM system in building enclosures under both warm and cold climates are investigated. Simulation results: (1) confirm the potential of the SS-PCM coatings to reduce undesirable heat exchange through building enclosure in all orientations and identify the roof as the preferred location of installing the SS-PCM system; (2) substantiate the thermal benefits of the system throughout the year and determine the optimal phase transition temperature of the SS-PCM with maximal energy saving; and (3) demonstrate more thermal benefits and energy saving of the SS-PCM coatings in warm climates compared to cold climates, which has been a challenge for most of existing passive solar facades.

Postmidnight mid-latitude ionospheric trough position oscillations during solar cycle 24

In this work, the Global Ionospheric Maps (GIMs) are used to analyze the behavior of the mid-latitude ionospheric trough (MIT) during the solar cycle 24 (2008–2019). This analysis is performed for the Northern and Southern Hemispheres at different local times: 00, 02 and 04 LT. We study the MIT position dependence on the phase of the solar cycle, seasonal, and geomagnetic activity during the post-midnight period. We find that the MIT position shows an interhemispheric asymmetry. Its equatorward movement from low to high solar activity is about 3 ° and 1 ° for Northern and Southern Hemisphere respectively for the three local times analyzed. There is also a clear seasonal variation, the shift between winter and summer is around 3 ° and 1 ° at 00 LT and 6 ° and 4 ° at 04 LT for the Northern and Southern Hemispheres, respectively. In general, the MIT position reaches the highest geomagnetic latitude in winter, without variation with local time. However, in summer it takes the lowest geomagnetic latitude, moving towards the equator from 00LT to 04LT. The MIT position moves equatorward under disturbed geomagnetic conditions, and the difference between the MIT position during quiet and perturbed days is greater in the Northern than in the Southern Hemisphere. In addition, the periodicity of the variability of the MIT position for both Hemispheres versus the solar wind speed and IMF Bz-component are analyzed using the wavelet transform, showing a clear dependence between them during the descending and minimum solar phase at 13.5 and 27-day time scales.

A comprehensive optimization of phase change material in hybrid application with solar chimney and photovoltaic panel for simultaneous power production and air ventilation

Ventilation process is a significant requirement of healthy life-style and its importance was further highlighted through the recent Covid-19 global outbreak. Solar chimney is a natural indoor air ventilator without the requirement of any electricity power consumption. Hybrid solar chimney, photovoltaic panel, and phase change material (SC-PV-PCM) is investigated in this study (see graphical abstract) as the most recent newly proposed technology which is able to provide simultaneous natural ventilation and electricity in an effective manner. The contribution of this research is to identify the most efficient characteristics of phase change material (PCM) for this unique application using a comprehensive 3D validated numerical simulation. It is note that, the desirable phase change material should be able to enhance the efficiency of the ventilation process and power generation simultaneously. Hence, in order to reach the aim of this research, the impact of many effective parameters of phase change material including conductivity, melting point, heat capacity, and its enthalpy on both ventilation features of the solar chimney and electrical efficiency of solar panel is investigated for the mentioned (SC-PV-PCM) hybrid technology. Besides, the economic characteristics of the above system is evaluated as well. The simulation is performed under transient real weather conditions of Hong Kong (solar radiation intensity, ambient temperature, sky temperature, and wind speed) through the month of June from sunrise until sunset.

Optical-to-NIR magnitude measurements of the Starlink LEO Darksat satellite and effectiveness of the darkening treatment

Aims. We aim to measure the Sloan r′, Sloan i′, J, and Ks magnitudes of Starlink’s STARLINK-1130 (Darksat) and STARLINK-1113 low Earth orbit (LEO) communication satellites and determine the effectiveness of the Darksat darkening treatment from the optical to the near-infrared (NIR). Methods. Four observations of Starlink’s LEO communication satellites, Darksat and STARLINK-1113, were conducted on two nights with two telescopes. The Chakana 0.6 m telescope at the Ckoirama observatory (Chile) observed both satellites on 5 Mar. 2020 (UTC) and 7 Mar. 2020 (UTC) using a Sloan r′ and Sloan i′ filter, respectively. The ESO VISTA 4.1 m telescope with the VIRCAM instrument observed both satellites on 5 Mar. 2020 (UTC) and 7 Mar. 2020 (UTC) in the NIR J-band and Ks-band, respectively. Results. The calibration, image processing, and analysis of the Darksat images give r ≈ 5.6 mag, i ≈ 5.0 mag, J ≈ 4.2 mag, and Ks ≈ 4.0 mag when scaled to a range of 550 km (airmass = 1) and corrected for the solar incidence and observer phase angles. In comparison, the STARLINK-1113 images give r ≈ 4.9 mag, i ≈ 4.4 mag, J ≈ 3.8 mag, and Ks ≈ 3.6 mag when corrected for range, solar incidence, and observer phase angles. The data and results presented in this work show that the special darkening coating used by Starlink for Darksat has darkened the Sloan r′ magnitude by 50%, Sloan i′ magnitude by 42%, NIR J magnitude by 32%, and NIR Ks magnitude by 28%. Conclusions. The results show that both satellites increase in reflective brightness with increasing wavelength and that the effectiveness of the darkening treatment is reduced at longer wavelengths. This shows that the mitigation strategies being developed by Starlink and other LEO satellite operators need to take into account other wavelengths, not just the optical. This work highlights the continued importance of obtaining multi-wavelength observations of many different LEO satellites in order to characterise their reflective properties and to aid the community in developing impact simulations and developing mitigation tools.