scholarly journals Optical Parameters Optimization for All-Time Star Sensor

Sensors ◽  
2019 ◽  
Vol 19 (13) ◽  
pp. 2960
Author(s):  
Wang ◽  
Wei ◽  
Li ◽  
Du ◽  
Zhang
Keyword(s):  
High Altitude ◽  
Background Radiation ◽  
Imaging System ◽  
Model Simulation ◽  
Parameters Optimization ◽  
Sensor Technology ◽  
Optical Parameters ◽  
Star Sensor ◽  
Cost Constraints ◽  
Sensor Detection

As an important development direction of star sensor technology, the All-Time star sensor technology can expand the application of star sensors to flight platforms inside the atmosphere. Due to intense atmospheric background radiation during the daytime, the commonly used star sensors operating in the visible wavelength range are significantly limited in their ability to detect stars, and hence the All-Time star sensor technology which is based on the shortwave infrared (SWIR) imaging system has become an effective research direction. All-Time star sensor detection capability is significantly affected by observation conditions and, therefore, an optimized selection of optical parameters, which mainly includes the field of view (FOV) and the detection wavelength band, can effectively improve the detection performance of All-Time star sensors under harsh observation conditions. This paper uses the model simulation method to analyze and optimize the optical parameters under various observation conditions in a high-altitude environment. A main parameter among those discussed is the analysis of detection band optimization based on the SWIR band. Due to the huge cost constraints of high-altitude experiments, we conducted experiments near the ground to verify the effectiveness of the detection band selection and the correctness of the SWIR star sensor detection model, which thereby proved that the optimization of the optical parameters for high altitudes was effective and could be used as a reference.

A Study of Exposure of Overall Background Radiation In Syangja District of Nepal

2017 ◽  
pp. 92-95
Author(s):  
T Timilsina ◽  
K. R. Poudel ◽  
P. R. Poudel
Keyword(s):  
High Altitude ◽  
Background Radiation ◽  
Significant Risk ◽  
Total Radiation ◽  
Radiation Level ◽  
The People ◽  
Public Exposure

This study presents general exposure of background radiation to the people living or visiting nine places of Syangja district. A portable GM counter was used to quantify the total radiation at those places. The findings of this study show variation of radiation level at different places. Comparatively large values of radiation counts are observed at high altitude places (Gurung Dada: 70.23 cpm and Pokhari Dada: 64.77 cpm). The value of radiation count inside room is comparatively larger than that at outside room for these places. Moreover, small value of radiation count is observed at river side (Bank of Aandhikhola river: 21.63 cpm). Little large values are observed near Saligram stones and ancient statue than at other regions of one historical/religious place. Hence, results show fluctuations of background radiation level for different places. Some places have comparatively large value of radiation count while some places have comparatively small value. But there is no any abnormal value of radiation counts for all sample places. So there is, generally, no significant risk of public exposure to the background radiation for sample places.The Himalayan Physics Vol. 6 & 7, April 2017 (92-95)

scholarly journals 4511 Bio-Compatible Implantable Oxygen Sensor Technology with Real-Time Monitoring of Surgical Flaps and Reimplantation

2020 ◽  
Vol 4 (s1) ◽  
pp. 93-93
Author(s):  
Preet Patel ◽  
Mohamed Ibrahim ◽  
Bruce Klitzman
Keyword(s):  
Oxygen Tension ◽  
Optical Sensors ◽  
Oxygen Sensor ◽  
Imaging System ◽  
Statistical Significance ◽  
Surgical Flaps ◽  
Tissue Oxygen Tension ◽  
Sensor Technology ◽  
Tissue Oxygen ◽  
Flap Viability

OBJECTIVES/GOALS: Current surgical flap and replantation monitoring techniques have limitations in detecting the pathologic state, calibration and cost-to-patient issues. Our hypothesis is that novel implantable oxygen sensors can provide a more efficient, accurate, and reliable monitoring of tissue oxygenation. METHODS/STUDY POPULATION: Experimental sensors were used with an exogenous remote used as a reader once implanted (Fig. 1) A rat tissue perfusion model with three regions of an SIEA flap as well as into adjacent control sites was made (Tip, Middle, and Base) Blood flow was greatest at the base, diminishing towards the Tip, thus creating a perfusion gradient. Changes in tissue oxygen tension PO2 were estimated by the steady-state fluorescence of the optical sensors using an IVIS imaging system. The sensors were used to collect data from days 0, 3, and 7 as a reading of Tissue Oxygen Tension (TOT) with ANOVA used to assess for statistical significance in blood oxygen data with respect to relative perfusion status. RESULTS/ANTICIPATED RESULTS: Inspired FiO2 was decreased from 100% to 12% with a corresponding change in the TOT readings from all sensors. (Fig. 2) The tip portion of the flap demonstrated the most profound detection of tissue necrosis, with the middle demonstrating the second most necrosis and the base demonstrating the least with correlating TOT sensor readings. (Fig. 3) Acute vascular compromise of the feeding blood vessels in the pedicle was immediately detected within 70 seconds (*p<0.05). (Fig. 4) DISCUSSION/SIGNIFICANCE OF IMPACT: This study introduces and validates a recent technique to monitor acute vascular occlusion, flap viability, and necrosis in the immediate postoperative period in a validated rodent model. Future directions of this novel technology will aim to reproduce these findings in clinical feasibility studies.

Measurement of Chlorophyll Content in Wheat Leaves Using Laser Scattering Image

2012 ◽  
Vol 485 ◽  
pp. 361-364
Author(s):  
Xiao Juan Zhang ◽  
Cui Hong Zhang ◽  
Yan Li
Keyword(s):  
Chlorophyll Content ◽  
Imaging System ◽  
Optical Parameters ◽  
Laser Scattering ◽  
Chlorophyll Contents ◽  
Spad Value ◽  
Functional Relations ◽  
Back Scattering ◽  
Scattering Image ◽  
Wheat Leaves

Laser back-scattering images of wheat leaves (green leaves, yellow leaves and dry leaves)are obtained with video imaging system, the optical parameters (absorption coefficient and reduced scatering coefficient)of the wheat leaves are reversed with diffusion approximation theory, the functional relations between optical parameters(at 670nm) and chlorophyll contents (SPAD value)of the leaves are studied. The results demonstrate that: wheat leaf optical parameters and chlorophyll content present linear correlation, it is feasible for determing plant chlorophyll content with laser back-scattering image technology. These researches are very valuable for diagnosis crop condition with the results of laser scattering image

scholarly journals Odin–OSIRIS detection of the Chelyabinsk meteor

2014 ◽  
Vol 7 (3) ◽  
pp. 777-780 ◽  
Author(s):  
L. A. Rieger ◽  
A. E. Bourassa ◽  
D. A. Degenstein
Keyword(s):  
High Altitude ◽  
Infrared Imaging ◽  
Imaging System ◽  
Stratospheric Aerosol ◽  
Processing Algorithm ◽  
Earth’S Atmosphere ◽  
Aerosol Loading ◽  
Infrared Imaging System ◽  
Earth's Atmosphere

Abstract. On 15 February 2013 an 11 000 ton meteor entered Earth's atmosphere southeast of Chelyabinsk, creating a large fireball at 23 km altitude. The resulting stratospheric aerosol loading was detected by the Ozone Mapping and Profiler Suite (OMPS) in a high-altitude polar belt. This work confirms the presence and lifetime of the stratospheric debris using the Optical Spectrograph and InfraRed Imaging System (OSIRIS) onboard the Odin satellite. Although OSIRIS coverage begins in mid-March, the measurements show a belt of enhanced scattering near 35 km altitude between 50° N and 70° N. Initially, enhancements show increased scattering of up to 15% over the background conditions, decaying in intensity and dropping in altitude until they are indistinguishable from background conditions by mid-May. An inversion is also attempted using the standard OSIRIS processing algorithm to determine the extinction in the meteoric debris.

Estimating Gyro Drift of Strapdown Inertial Navigation System Based on Star Sensor

2012 ◽  
Vol 566 ◽  
pp. 235-238
Author(s):  
Guang Tao Zhou ◽  
Gui Min Shi ◽  
Lei Zhang ◽  
Kai Li
Keyword(s):  
Navigation System ◽  
Inertial Navigation System ◽  
Model Simulation ◽  
Inertial Navigation ◽  
Strapdown Inertial Navigation System ◽  
Star Sensor ◽  
Integrated Navigation ◽  
Working Principle ◽  
Gyro Drift ◽  
Strapdown Inertial Navigation

In the strapdown inertial navigation system (SINS), gyro drift will result in navigation errors. A new algorithm based on star sensor is proposed in this paper to estimate gyro drift. The paper analyzed the working principle of star sensor and the technique of estimating gyro drift. Gyro drift can be estimated through the high-precision attitude information provided by a star sensor. Kalman filter is used in the integrated navigation model. Simulation results show that the proposed algorithm can estimate gyro drift accurately and improve the precision of SINS.

scholarly journals A Star Sensor On-Orbit Calibration Method Based on Singular Value Decomposition

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3301 ◽  
Author(s):  
Liang Wu ◽  
Qian Xu ◽  
Janne Heikkilä ◽  
Zijun Zhao ◽  
Liwei Liu ◽  
...  
Keyword(s):  
Singular Value Decomposition ◽  
Singular Values ◽  
Calibration Method ◽  
Angular Distance ◽  
Singular Value ◽  
Optical Parameters ◽  
Star Sensor ◽  
Calibration Methods ◽  
Value Decomposition ◽  
Svd Method

The navigation accuracy of a star sensor depends on the estimation accuracy of its optical parameters, and so, the parameters should be updated in real time to obtain the best performance. Current on-orbit calibration methods for star sensors mainly rely on the angular distance between stars, and few studies have been devoted to seeking new calibration references. In this paper, an on-orbit calibration method using singular values as the calibration reference is introduced and studied. Firstly, the camera model of the star sensor is presented. Then, on the basis of the invariance of the singular values under coordinate transformation, an on-orbit calibration method based on the singular-value decomposition (SVD) method is proposed. By means of observability analysis, an optimal model of the star combinations for calibration is explored. According to the physical interpretation of the singular-value decomposition of the star vector matrix, the singular-value selection for calibration is discussed. Finally, to demonstrate the performance of the SVD method, simulation calibrations are conducted by both the SVD method and the conventional angular distance-based method. The results show that the accuracy and convergence speed of both methods are similar; however, the computational cost of the SVD method is heavily reduced. Furthermore, a field experiment is conducted to verify the feasibility of the SVD method. Therefore, the SVD method performs well in the calibration of star sensors, and in particular, it is suitable for star sensors with limited computing resources.

Multifractal Analysis of Rainfall-Rate Datasets Obtained by Radar and Numerical Model: The Case Study of Typhoon Bolaven (2012)

2020 ◽  
Vol 59 (5) ◽  
pp. 819-840 ◽  
Author(s):  
J. Lee ◽  
I. Paz ◽  
D. Schertzer ◽  
D. I. Lee ◽  
I. Tchiguirinskaia
Keyword(s):  
Numerical Model ◽  
High Altitude ◽  
Korean Peninsula ◽  
Multifractal Analysis ◽  
Model Simulation ◽  
Rainfall Rate ◽  
Radar Rainfall ◽  
Significant Damage ◽  
Two Parameters

AbstractTyphoon Bolaven caused significant damage with severe rainfall all over South Korea, including Cheju Island, which received more than 250 mm in 2 days in August 2012. It was regarded as the most powerful storm to strike the Korean Peninsula in nearly a decade. The rainfall-rate datasets were obtained from S-band radar operated by the Korea Meteorological Administration to be analyzed and compared with the mesoscale Cloud Resolving Storm Simulator (CReSS) model simulation. Multifractal analysis was conducted to understand the structure of the rainfall rate with height in the typhoon system. The radar rainfall data presented with strong intermittency across scales at lower altitudes (1 and 2 km) and a more homogeneous rainfall field at high altitude (5 km) with two parameters (fractal codimension and multifractality index). The statistical scaling moment function and maximal singularities show clear significant differences between radar and the CReSS model.

scholarly journals Aerosol decadal trends – Part 1: In-situ optical measurements at GAW and IMPROVE stations

2013 ◽  
Vol 13 (2) ◽  
pp. 869-894 ◽  
Author(s):  
M. Collaud Coen ◽  
E. Andrews ◽  
A. Asmi ◽  
U. Baltensperger ◽  
N. Bukowiecki ◽  
...  
Keyword(s):  
Light Scattering ◽  
High Altitude ◽  
Optical Measurements ◽  
The Arctic ◽  
Optical Parameters ◽  
Absorption Coefficients ◽  
Least Squares Fit ◽  
Long Term Trends

Abstract. Currently many ground-based atmospheric stations include in-situ measurements of aerosol physical and optical properties, resulting in more than 20 long-term (> 10 yr) aerosol measurement sites in the Northern Hemisphere and Antarctica. Most of these sites are located at remote locations and monitor the aerosol particle number concentration, wavelength-dependent light scattering, backscattering, and absorption coefficients. The existence of these multi-year datasets enables the analysis of long-term trends of these aerosol parameters, and of the derived light scattering Ångström exponent and backscatter fraction. Since the aerosol variables are not normally distributed, three different methods (the seasonal Mann-Kendall test associated with the Sen's slope, the generalized least squares fit associated with an autoregressive bootstrap algorithm for confidence intervals, and the least-mean square fit applied to logarithms of the data) were applied to detect the long-term trends and their magnitudes. To allow a comparison among measurement sites, trends on the most recent 10 and 15 yr periods were calculated. No significant trends were found for the three continental European sites. Statistically significant trends were found for the two European marine sites but the signs of the trends varied with aerosol property and location. Statistically significant decreasing trends for both scattering and absorption coefficients (mean slope of −2.0% yr−1) were found for most North American stations, although positive trends were found for a few desert and high-altitude sites. The difference in the timing of emission reduction policy for the Europe and US continents is a likely explanation for the decreasing trends in aerosol optical parameters found for most American sites compared to the lack of trends observed in Europe. No significant trends in scattering coefficient were found for the Arctic or Antarctic stations, whereas the Arctic station had a negative trend in absorption coefficient. The high altitude Pacific island station of Mauna Loa presents positive trends for both scattering and absorption coefficients.

scholarly journals Design of thermal imaging continuous-zoom optical system

2021 ◽  
Vol 2127 (1) ◽  
pp. 012070
Author(s):  
A V Kryukov ◽  
Yu Yu Kachurin ◽  
Yu S Datiy
Keyword(s):  
Optical System ◽  
Thermal Imaging ◽  
Imaging System ◽  
Focal Length ◽  
Optical Parameters ◽  
Secondary System ◽  
System A ◽  
Detection And Identification ◽  
Objective System ◽  
Analytical Expressions

Abstract The report tells about the design of a middle wave infrared continuous-zoom imaging optical system. To capture the image in an «eye-type» infrared optical system a multi-element sensor is used. To increase the contrast of the thermal image the sensor is equipped with a cold aperture. The use of an optical system based on the continuous-zoom lens makes it possible to solve the problems of object detection and identification more effectively but requires taking into account some features of varifocal lenses. The optical system being analyzed in the report includes front zoom objective system and secondary imaging system. The front zoom optical system is composed of four groups and provides the focal length that is continuously changed with a large zoom ratio (15–20X) under the condition of a constant total length of the system. The secondary imaging system is designed for zoom system exit stop and sensor cold stop conjugation. The design technique represents analytical expressions and equations to obtain optical parameters of the front and secondary system components and the motion curves for movable groups.

A Dual Modality Dynamic Imaging System

2008 ◽  
Author(s):  
Mehmet Burcin Unlu ◽  
Yuting Lin ◽  
Orhan Nalcioglu ◽  
Gultekin Gulsen
Keyword(s):  
Imaging System ◽  
Optical Tomography ◽  
Dynamic Imaging ◽  
Optical Data ◽  
High Temporal Resolution ◽  
Optical Parameters ◽  
Combined System ◽  
Optical Contrast Agents ◽  
Animal Imaging ◽  
Wide Range

Diffuse optical tomography (DOT) is a recently emerging technique that uses arrays of sources and detectors to obtain spatially dependent optical parameters of tissue. DOT techniques have been applied for a wide range of applications, especially for breast and head as well as animal imaging. We have developed an integrated dynamic MR/DOT imaging system. This combined system can acquire MR and optical data simultaneously with a high temporal resolution. Hence, the enhancement kinetics of multiple MR and optical contrast agents can be monitored independently.

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