Seawinds Radiometer Brightness Temperature Calibration And Validation

The NASA SeaWinds scatterometer is a radar remote sensor which operates on two satellites; NASA\u27s QuikSCAT launched in June 1999 and on Japan\u27s ADEOS-II satellite launched in December 2002. The purpose of SeaWinds is to provide global measurements of the ocean surface wind vector. On QuikSCAT, a ground data processing algorithm was developed, which allowed the instrument to function as a QuikSCAT Radiometer (QRad) and measure the ocean microwave emissions (brightness temperature, Tb) simultaneously with the backscattered power. When SeaWinds on ADEOS was launched, this same algorithm was applied, but the results were anomalous. The initial SRad brightness temperatures exhibited significant, unexpected, ascending/descending orbit Tb biases. This thesis presents an empirical correction algorithm to correct the anomalous SeaWinds Radiometer (SRad) ocean brightness temperature measurements. I use the Advanced Microwave Scanning Radiometer (AMSR) as a brightness temperature standard to calibrate and then, with independent measurements, validate the corrected SRad Tb measurements. AMSR is a well-calibrated multi-frequency, dual-polarized microwave radiometer that also operates on ADEOS-II. These results demonstrate that, after tuning the Tb algorithm, good quality SRad brightness temperature measurements are obtained over the oceans

CrypTFlow: Secure TensorFlow Inference

We present CrypTFlow, a first of its kind system that converts TensorFlow inference code into Secure Multi-party Computation (MPC) protocols at the push of a button. To do this, we build three components. Our first component, Athos, is an end-to-end compiler from TensorFlow to a variety of semi-honest MPC protocols. The second component, Porthos, is an improved semi-honest 3-party protocol that provides significant speedups for TensorFlow like applications. Finally, to provide malicious secure MPC protocols, our third component, Aramis, is a novel technique that uses hardware with integrity guarantees to convert any semi-honest MPC protocol into an MPC protocol that provides malicious security. The malicious security of the protocols output by Aramis relies on integrity of the hardware and semi-honest security of MPC. Moreover, our system matches the inference accuracy of plaintext TensorFlow. We experimentally demonstrate the power of our system by showing the secure inference of real-world neural networks such as ResNet50 and DenseNet121 over the ImageNet dataset with running times of about 30 seconds for semi-honest security and under two minutes for malicious security. Prior work in the area of secure inference has been limited to semi-honest security of small networks over tiny datasets such as MNIST or CIFAR. Even on MNIST/CIFAR, CrypTFlow outperforms prior work

Sea Winds Radiometer (Srad) Brightness Temperature Calibration And Validation

NASA \u27s SeaWinds scatterometer, on Japan \u27s ADEOS-II satellite, is a special purpose radar remote sensor used to measure ocean surface wind vector (speed and direction). This paper presents the novel use of this instrument as a SeaWinds radiometer (SRad) to measure the ocean microwave emissions (brightness temperature). The derivation of the SRad radiometric transfer function is presented, which is used to calculate the apparent brightness temperature collected simultaneously with the radar scattering measurement. Results are presented for the on-orbit calibration and validation of the SRad brightness temperature algorithm performed using simultaneous measurements from the Advanced Microwave Scanning Radiometer (AMSR) also on the ADEOS-II. © 2005 IEEE

Seawinds Radiometer (Srad) On Adeos-Ii Brightness Temperature Calibration/Validation

NASA\u27s Sea Winds scatterometer, on Japan\u27s ADEOS-II satellite, is a special purpose radar remote sensor used to measure ocean surface wind vector. This paper presents the novel use of SeaWinds as a radiometer (SRad), to measure the ocean\u27s brightness temperature simultaneously with the radar backscattered power. The calibration/validation of the SRad ocean Tb data processing algorithm uses the Advanced Microwave Scanning Radiometer (AMSR) that also operates on ADEOS-II as a brightness temperature standard. Empirical on-orbit comparisons are presented for SRad and independent, simultaneous Tb measurements from AMSR. © 2005 IEEE

Chemical speciation and source apportionment of ambient PM2.5 in New Delhi before, during, and after the Diwali fireworks

Diwali is among the most important Indian festivals, and elaborate firework displays mark the evening's festivities. This study assesses the impact of Diwali on the concentration, composition, and sources of ambient PM2.5. We observed the total PM2.5 concentrations to rise to 16 times the pre-firework levels, while each of the elemental, organic, and black carbon fractions of ambient PM2.5 increased by a factor of 46.1, 3.7, and 5.6, respectively. The concentration of species like K, Al, Sr, Ba, S, and Bi displayed distinct peaks during the firework event and were identified as tracers. The average concentrations of potential carcinogens, like As, exceeded US EPA screening levels for industrial air by a factor of ~9.6, while peak levels reached up to 16.1 times the screening levels. The source apportionment study, undertaken using positive matrix factorization, revealed the fireworks to account for 95% of the total elemental PM2.5 during Diwali. The resolved primary organic emissions, too, were enhanced by a factor of 8 during Diwali. Delhi has encountered serious haze events following Diwali in recent years; this study highlights that biomass burning emissions rather than the fireworks drive the poor air quality in the days following Diwali.Comment: The manuscript is accepted for publication in Atmospheric Pollution Research. Present Status: Accepte

Near to Long-Wave Infrared Mercury Chalcogenide Nanocrystals from Liquid Mercury

International audienceHgTe nanocrystals are currently the most promising colloidal material for infrared detection, combining broadly tunable infrared absorption and photoconductive properties. Current synthesis leads to a limited amount of material and relies on a highly toxic water-soluble form of Hg. Here, we explore the possibility of using Hg thiolate as Hg source and demonstrate that the latter can be formed in situ from liquid Hg. The developed protocol allows large masses (7 g) and highly concentrated (100 g/L) synthesis, which is a step forward for the transfer of this material towards industry. The transport properties of the material have also been investigated and we observe a transition from p to n-type with size. We observe that the threshold of the p to n switch depends on the growth method which enables for a given size of nanocrystal the formation of p-n junction. This work has great potential to design infrared sensor with optimized charge dissociation

Pushing absorption of perovskite nanocrystals into the infrared

International audienceTo date defect-tolerance electronic structure of Lead halide perovskite nanocrystals is limited to optical feature in the visible range. Here, we demonstrate that IR sensitization of formamidinium lead iodine (FAPI) nanocrystals array can be obtained by its doping with PbS nanocrystals. In this hybrid array, absorption comes from the PbS nanocrystals while transport is driven by the perovskite which reduces the dark current compared to pristine PbS. In addition, we fabricate a field-effect transistor using a high capacitance ionic glass made of hybrid FAPI/PbS nanocrystal arrays. We show that the hybrid material has an n-type nature with an electron mobility of 2 x 10-3 cm2 V-1s-1. However, the dark current reduction is mostly balanced by a loss of absorption. To overcome this limitation, we couple the FAPI/PbS hybrid to a guided mode resonator, that can enhance the infrared light absorption