Accuracy in starphotometry

Abstract: Starphotometry, or stellar spectrophotometry, is a passive remote sensing method for retrieving the spectral optical depth of the atmosphere, and a night counterpart of sunphotometry. Despite all the technological advances, robust and accurate starphotometry remains a challenge that has limited its evolution. The general objective in this work is to inspire trust and interest in starphotometry by improving its reliability, its measurement accuracy and by identifying particular cases where it outperforms sunphotometry (which is in fact starphotometry with the star being our Sun). In order to achieve such an objective we need to better understand the detailed nature of specific starphotometry attributes: the different spectral classes of stars, the properties of weaker reference sources, the consequences of a larger telescope aperture, a smaller Field of View (FOV)

A microbolometer-based far infrared radiometer to study thin ice clouds in the Arctic

A far infrared radiometer (FIRR) dedicated to measuring radiation emitted by clear and cloudy atmospheres was developed in the framework of the Thin Ice Clouds in Far InfraRed Experiment (TICFIRE) technology demonstration satellite project. The FIRR detector is an array of 80 × 60 uncooled microbolometers coated with gold black to enhance the absorptivity and responsivity. A filter wheel is used to select atmospheric radiation in nine spectral bands ranging from 8 to 50 µm. Calibrated radiances are obtained using two well-calibrated blackbodies. Images are acquired at a frame rate of 120 Hz, and temporally averaged to reduce electronic noise. A complete measurement sequence takes about 120 s. With a field of view of 6°, the FIRR is not intended to be an imager. Hence spatial average is computed over 193 illuminated pixels to increase the signal-to-noise ratio and consequently the detector resolution. This results in an improvement by a factor of 5 compared to individual pixel measurements. Another threefold increase in resolution is obtained using 193 non-illuminated pixels to remove correlated electronic noise, leading an overall resolution of approximately 0.015 W m−2 sr−1. Laboratory measurements performed on well-known targets suggest an absolute accuracy close to 0.02 W m−2 sr−1, which ensures atmospheric radiance is retrieved with an accuracy better than 1 %. Preliminary in situ experiments performed from the ground in winter and in summer on clear and cloudy atmospheres are compared to radiative transfer simulations. They point out the FIRR ability to detect clouds and changes in relative humidity of a few percent in various atmospheric conditions, paving the way for the development of new algorithms dedicated to ice cloud characterization and water vapor retrieval

Accuracy in starphotometry

Abstract: Starphotometry, or stellar spectrophotometry, is a passive remote sensing method for retrieving the spectral optical depth of the atmosphere, and a night counterpart of sunphotometry. Despite all the technological advances, robust and accurate starphotometry remains a challenge that has limited its evolution. The general objective in this work is to inspire trust and interest in starphotometry by improving its reliability, its measurement accuracy and by identifying particular cases where it outperforms sunphotometry (which is in fact starphotometry with the star being our Sun). In order to achieve such an objective we need to better understand the detailed nature of specific starphotometry attributes: the different spectral classes of stars, the properties of weaker reference sources, the consequences of a larger telescope aperture, a smaller Field of View (FOV)

Synchronized Starphotometry and Lidar measurements in the High Arctic

The sunphotometry-lidar synergy has proven to be effective for the characterization of aerosol events in the High Arctic. Sunphotometry measurements, however, are limited to the day-time periods. Starphotometry, based on the extinction of bright-star radiation, can mitigate the lack of aerosol optical depth (AOD) measurements during the Polar Night. In this work we present several examples of the coincident starphotometry-lidar measurements at Eureka, Canada (79°59'N, 85°56'W) obtained in Feb-Mar 2011. We show a correlation between fine (sub-micron) and coarse (super-micron) mode AOD dynamics from starphotometry and the backscatter profiles and depolarization ratio values from the lidar data

Climate Change Is Increasing the Risk of the Reemergence of Malaria in Romania

The climatic modifications lead to global warming; favouring the risk of the appearance and development of diseases are considered until now tropical diseases. Another important factor is the workers’ immigration, the economic crisis favouring the passive transmission of new species of culicidae from different areas. Malaria is the disease with the widest distribution in the globe. Millions of people are infected every year in Africa, India, South-East Asia, Middle East, and Central and South America, with more than 41% of the global population under the risk of infestation with malaria. The increase of the number of local cases reported in 2007–2011 indicates that the conditions can favour the high local transmission in the affected areas. In the situation presented, the establishment of the level of risk concerning the reemergence of malaria in Romania becomes a priority

The Risk of Emerging of Dengue Fever in Romania, in the Context of Global Warming

(1) Background: Few studies to date have assessed the influences induced by climate change on the spatial distribution and population abundance of Aedes albopictus using the latest climate scenarios. In this study, we updated the current distribution of Ae. albopictus mosquitoes and evaluated the changes in their distribution under future climate conditions, as well as the risk of dengue virus emergence in Romania. (2) Methods: Under the two scenarios: High scenario (HS) when no drastic measures to reduce the effects of global warming will be taken, or they are not effective and low scenario (LS) when very stringent greenhouse control measures will be implemented. (3) Results: The results estimate an increase in temperatures in Romania of up to 2.6 °C in HS and up to 0.4 °C in LS, with an increase in the period of virus replication within the vector from June to October in HS and from May to September in LS. Moreover, in 2022, Ae. albopictus was reported in a new county, where it was not identified at the last monitoring in 2020. (4) Conclusions: The rapid spread of this invasive species and the need to implement monitoring and control programs for the Aedes population in Romania are emphasized

MACAO-VLTI adaptive optics systems performance

International audienc

Silver Nanoparticles Synthesized from <i>Abies alba</i> and <i>Pinus sylvestris</i> Bark Extracts: Characterization, Antioxidant, Cytotoxic, and Antibacterial Effects

In recent years, phytofunctionalized AgNPs have attracted great interest due to their remarkable biological activities. In the present study, AgNPs were synthesized using Abies alba and Pinus sylvestris bark extracts. The chemical profile of these bark extracts was analyzed by LC-HRMS/MS. As a first step, the synthesis parameters (pH, AgNO3 concentration, ratio of bark extract and AgNO3, temperature, and reaction time) were optimized. The synthesized AgNPs were characterized by ATR-FTIR spectroscopy, DLS, SEM, EDX, and TEM. Their antioxidant, cytotoxic, and antibacterial properties were evaluated by the DPPH, ABTS, MTT, and broth microdilution assays, respectively. Abies alba and Pinus sylvestris bark extract-derived AgNPs were well-dispersed, spherical, small (average particle size of 9.92 and 24.49 nm, respectively), stable (zeta potential values of −10.9 and −10.8 mV, respectively), and cytotoxic to A-375 human malignant melanoma cells (IC50 = 2.40 ± 0.21 and 6.02 ± 0.61 μg/mL, respectively). The phytosynthesized AgNPs also showed antioxidant and antibacterial effects