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- 2019
- low-temperature electronics
- differential operational amplifier
- LTspice environment
- differential stage
- common-mode rejection ratio
- junction field-effect transistors
- Electronic Science and Technology
- Don State Technical University
- Southern Federal University
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The Ice, Cloud, and Land Elevation Satellite – 2 mission: A global geolocated photon product derived from the Advanced Topographic Laser Altimeter System
摘要： The Ice, Cloud, and land Elevation Satellite – 2 (ICESat-2) observatory was launched on 15 September 2018 to measure ice sheet and glacier elevation change, sea ice freeboard, and enable the determination of the heights of Earth's forests. ICESat-2's laser altimeter, the Advanced Topographic Laser Altimeter System (ATLAS) uses green (532 nm) laser light and single-photon sensitive detection to measure time of flight and subsequently surface height along each of its six beams. In this paper, we describe the major components of ATLAS, including the transmitter, the receiver and the components of the timing system. We present the major components of the ICESat-2 observatory, including the Global Positioning System, star trackers and inertial measurement unit. The ICESat-2 Level 1B data product (ATL02) provides the precise photon round-trip time of flight, among other data. The ICESat-2 Level 2A data product (ATL03) combines the photon times of flight with the observatory position and attitude to determine the geodetic location (i.e. the latitude, longitude and height) of the ground bounce point of photons detected by ATLAS. The ATL03 data product is used by higher-level (Level 3A) surface-specific data products to determine glacier and ice sheet height, sea ice freeboard, vegetation canopy height, ocean surface topography, and inland water body height.
关键词： Laser altimeter,Ice sheets,Altimetry,ICESat-2,Sea ice,Photon counting,Remote sensing,Cryosphere
更新于2025-09-16 10:30:52
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Replacing GRACE/GRACEa??FO C30 with satellite laser ranging: Impacts on Antarctic Ice Sheet mass change
摘要： Satellite laser ranging (SLR) observations have long been relied upon for measuring changes in Earth’s dynamic oblateness, C20. This major component of Earth’s time-variable gravity field is not well-observed by the GRACE and GRACE-FO missions, leading to the common practice of replacing their values with those obtained by SLR. The C30 coefficient, which has a large impact on the recovered Antarctic Ice Sheet mass changes, is shown here to be poorly observed by GRACE/GRACE-FO when either mission is operating without two fully functional accelerometers. The GRACE spacecraft pair operated nominally until October 2016 when one accelerometer was powered off due to battery limitations, while GRACE-FO is currently excluding one accelerometer from the data processing due to elevated noise levels. Beginning with the launch of LARES in 2012, SLR-derived C30 values are suitable for replacing any problematic GRACE/GRACE-FO estimates, enabling the accurate recovery of Antarctic Ice Sheet mass changes, among others.
关键词： mass change,Antarctic Ice Sheet,C30,GRACE-FO,satellite laser ranging,GRACE
更新于2025-09-16 10:30:52
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Dynamic simulation and experimental study of a variable speed photovoltaic DC refrigerator
摘要： A variable speed photovoltaic direct-current (DC) refrigerator (VSPVDR) system is proposed in this paper. In the VSPVDR system, the photovoltaic (PV) cells are directly connected to the compressor without batteries and inverter, and the DC compressor speed changes with the radiation intensity. In the paper, a dynamic model is presented to simulate the behavior of the VSPVDR, and several prototype experiments are conducted to validate the model. On this basis, the impacts of the compressor speed control strategy, ambient temperature and the radiation intensity have been studied. Compared with the fixed speed mode, the cooling capacity of the variable speed mode increases by 32.76% and the average PV utilization efficiency increases by 45.69%. When ambient temperature increases, the average cooling capacity decreases significantly, but the increase of average power consumption is not obvious, which reveals that the ambient temperature has greater influence on the cooling capacity and has less influence on the power consumption. The radiation intensity has a significant impact on system performance. When the radiation intensity increases, the cooling capacity increases significantly.
关键词： Ice making,Variable speed,DC compressor,Photovoltaic cooling
更新于2025-09-16 10:30:52
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Precision and Bias Comparison Between Laser and Radar Altimetry Data in the Amundsen Sea Embayment and the Lambert-Amery System of Antarctica
摘要： This article focuses on the precision and bias of laser altimetry data [Ice, Cloud, and Land Elevation Satellite (ICESat)] and radar altimetry data (Envisat) L2 products during the contemporary period from 2003 to 2008 in the Amundsen Sea Embayment (ASE) in West Antarctica (an ice loss region) and the Lambert-Amery System (LAS) in East Antarctica (an ice gain region). We used the crossover method to obtain the elevation differences between ICESat tracks, Envisat tracks, and between ICESat and Envisat tracks. The crossover points were generated and the difference of each crossover pair was calculated as raw data. The standard deviations were then computed from the raw data in a grid cell for both ICESat and Envisat. The precision of both satellites varied as a function of the surface slope in the abovementioned two regions, from 6.6 to 16.6 cm for the ICESat data and from 0.11 to 0.35 m for the Envisat data. The crossover points from ICESat-Envisat showed a mean bias of 0.55 ± 4.00 m for the ASE and 0.45 ± 0.99 m for the LAS, in accordance with the penetration depth of the radar altimetry. The relationship between the precision of the satellite measurements with the slope of the ice sheet and the ice velocity in the study area showed that the regions with gentle slopes and low velocity obtained a better precision of altimetry data.
关键词： Antarctica,Envisat,bias,precision,Ice, Cloud, and Land Elevation Satellite (ICESat)
更新于2025-09-12 10:27:22
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109 Evaluation of the Efficacy and Safety of Fractional Picosecond 1064-nm Laser Treatment for Skin Rejuvenation
摘要： Gold (Au) colloids are becoming ubiquitous across biomedical engineering, solar energy conversion, and nano-optics. Such universality has originated from the exotic plasmonic effect of Au colloids (i.e., localized surface plasmon resonance (LSPRs)) in conjunction with the versatile access to their synthetic routes. Herein, we introduce a previously undiscovered usage of Au colloids for advancing cryoprotectants with significant ice recrystallization inhibition (IRI). Oligopeptides inspired by the antifreeze protein (AFP) and antifreeze glycoprotein (AFGP) are attached onto the surface of well-defined Au colloids with the same sizes but different shapes. These AF(G)P-inspired Au colloids can directly adsorb onto a growing ice crystal via the synergistic interplay between hydrogen bonding and hydrophobic groups, in stark contrast to their bare Au counterparts. Dark-field optical microscopy analyses, benefitting from LSPR, allow us to individually trace the in situ movement of the antifreezing Au colloids during ice growth/recrystallization and clearly evidence their direct adsorption onto the growing ice crystal, which is consistent with theoretical predictions. With the assistance of molecular dynamics (MD) simulations, we evidently attribute the IRI of AF(G)P-inspired Au colloids to the Kelvin effect. We also exploit the IRI dependence on the Au colloidal shapes; indeed, the facet contacts between ice and Au colloids can be better than the point-like counterparts in terms of IRI. The design principles and predictive theory outlined in this work will be of broad interest not only for the fundamental exploration of the inhibition of ice growth but also for enriching the application of Au colloids.
关键词： gold colloids,antifreezing proteins,dark-field microspectroscopy,oligopeptides,Ice recrystallization inhibition
更新于2025-09-11 14:15:04
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Laser-Induced Fluorescence Emission (L.I.F.E.) as Novel Non-Invasive Tool for In-Situ Measurements of Biomarkers in Cryospheric Habitats
摘要： Global warming affects microbial communities in a variety of ecosystems, especially cryospheric habitats. However, little is known about microbial-mediated carbon fluxes in extreme environments. Hence, the methodology of sample acquisition described in the very few studies available implies two major problems: A) high resolution data require a large number of samples, which is difficult to obtain in remote areas; B) unavoidable sample manipulation such as cutting, sawing, and melting of ice cores that leads to a misunderstanding of in situ conditions. In this study, a prototype device that requires neither sample preparation nor sample destruction is presented. The device can be used for in situ measurements with a high spectral and spatial resolution in terrestrial and ice ecosystems and is based on the Laser-Induced Fluorescence Emission (L.I.F.E.) technique. Photoautotrophic supraglacial communities can be identified by the detection of L.I.F.E. signatures in photopigments. The L.I.F.E. instrument calibration for the porphyrin derivates chlorophylla (chla) (405 nm laser excitation) and B-phycoerythrin (B-PE) (532 nm laser excitation) is demonstrated. For the validation of this methodology, L.I.F.E. data were ratified by a conventional method for chla quantification that involved pigment extraction and subsequent absorption spectroscopy. The prototype applicability in the field was proven in extreme polar environments. Further testing on terrestrial habitats took place during Mars analog simulations in the Moroccan dessert and on an Austrian rock glacier. The L.I.F.E. instrument enables high resolution scans of large areas with acceptable operation logistics and contributes to a better understanding of the ecological potential of supraglacial communities in the context of global change.
关键词： chlorophyll,glacial melt,laser-induced fluorescence emission (L.I.F.E.),ice,cryospheric habitats,phycoerythrin,non-invasive
更新于2025-09-11 14:15:04
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Near-Real Time Detection of the Re-Opening of the Weddell Polynya, Antarctica, from Spaceborne Infrared Imagery
摘要： A hole in the Antarctic sea ice cover, the Weddell Polynya, unexpectedly re-opened in winter 2017 for the first time since 1976. Models suggest that the polynya opened because warm oceanic water moved up to the surface, melting the ice from below. Here three temperature thresholds applied to near-hourly spaceborne infrared imagery (AVHRR) successfully detect the appearance of a warm spot up to five days before the polynya opened in June and September 2017. Traditional sea ice concentration and thickness criteria could only detect the polynya once it was open. An automatised warning system, using near-real time passive monitoring of warm spots, would allow researchers to reroute vessels or autonomous sensors in order to finally study the polynya as a whole when it opens again, from its preconditioning to its impacts on the climate system.
关键词： AVHRR,infrared imagery,Weddell Polynya,sea ice concentration,sea ice thickness,Antarctic sea ice
更新于2025-09-10 09:29:36
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An improved algorithm for polar cloud-base detection by ceilometer over the ice sheets
摘要： Optically thin ice and mixed-phase clouds play an important role in polar regions due to their effect on cloud radiative impact and precipitation. Cloud-base heights can be detected by ceilometers, low-power backscatter lidars that run continuously and therefore have the potential to provide basic cloud statistics including cloud frequency, base height and vertical structure. The standard cloud-base detection algorithms of ceilometers are designed to detect optically thick liquid-containing clouds, while the detection of thin ice clouds requires an alternative approach. This paper presents the polar threshold (PT) algorithm that was developed to be sensitive to optically thin hydrometeor layers (minimum optical depth τ ≥ 0.01). The PT algorithm detects the first hydrometeor layer in a vertical attenuated backscatter profile exceeding a predefined threshold in combination with noise reduction and averaging procedures. The optimal backscatter threshold of 3 × 10?4 km?1 sr?1 for cloud-base detection near the surface was derived based on a sensitivity analysis using data from Princess Elisabeth, Antarctica and Summit, Greenland. At higher altitudes where the average noise level is higher than the backscatter threshold, the PT algorithm becomes signal-to-noise ratio driven. The algorithm defines cloudy conditions as any atmospheric profile containing a hydrometeor layer at least 90 m thick. A comparison with relative humidity measurements from radiosondes at Summit illustrates the algorithm's ability to significantly discriminate between clear-sky and cloudy conditions. Analysis of the cloud statistics derived from the PT algorithm indicates a year-round monthly mean cloud cover fraction of 72 % (±10 %) at Summit without a seasonal cycle. The occurrence of optically thick layers, indicating the presence of supercooled liquid water droplets, shows a seasonal cycle at Summit with a monthly mean summer peak of 40 % (±4 %). The monthly mean cloud occurrence frequency in summer at Princess Elisabeth is 46 % (±5 %), which reduces to 12 % (±2.5 %) for supercooled liquid cloud layers. Our analyses furthermore illustrate the importance of optically thin hydrometeor layers located near the surface for both sites, with 87 % of all detections below 500 m for Summit and 80 % below 2 km for Princess Elisabeth. These results have implications for using satellite-based remotely sensed cloud observations, like CloudSat that may be insensitive for hydrometeors near the surface. The decrease of sensitivity with height, which is an inherent limitation of the ceilometer, does not have a significant impact on our results. This study highlights the potential of the PT algorithm to extract information in polar regions from various hydrometeor layers using measurements by the robust and relatively low-cost ceilometer instrument.
关键词： optically thin ice clouds,cloud-base detection,polar regions,mixed-phase clouds,ceilometer
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Monitoring the Cryosphere for Commerce and Transportation
摘要： Changes in the Arctic sea ice present opportunities and challenges for commerce and transportation. Monitoring and forecasting the conditions and changes in the sea ice to increase the environmental intelligence in the Arctic is a critical component of the infrastructure required to exploit these opportunities. The Joint Polar Satellite System (JPSS) provides global coverage from five sensors of a variety of environmental parameters including observations of cryosphere. JPSS provides these observations on an operational basis 24x7 and will continue these observations through the 2030’s. The JPSS Proving Ground and Risk Reduction (PGRR) program is facilitating an initiative to increase or improve the use and value of cryosphere data products in user products, services, and application or service areas [1]. JPSS aims to evaluate and demonstrate the use of sea ice products for monitoring and forecast applications and work with the user communities to understand how these applications support commerce and transportation in the Arctic.
关键词： Arctic,U.S. Government Agencies,Monitoring,Satellites,Sea Ice
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Assessment of Simulated Compact Polarimetry of the High Resolution Radarsat Constellation Mission SAR Mode for Multiyear and First Year Sea Ice Characterization
摘要： Synthetic Aperture Radar (SAR) remote sensing has become a valuable tool for sea ice characterization. Operational sea ice monitoring usually relies on SAR data from single- or dual-polarized beam modes such as the ScanSAR mode of RADARSAT-2. However, such imagery cannot accurately discriminate certain sea ice types and open water states at all times during the year. Thus, the recently proposed compact polarimetric (CP) SAR configuration for Earth observation could be a compromised choice for operational sea ice observation. This configuration will be included in the future RADARSAT Constellation Mission (RCM). In this study, simulated CP SAR data of the RCM High Resolution (HR) SAR mode is evaluated for sea ice classification. Results indicate promising performance of the RCM HR mode for First Year Ice (FYI) and Multiyear Ice (MYI) classification using CP SAR data.
关键词： RCM,compact polarimetric SAR,sea ice
更新于2025-09-10 09:29:36