scholarly journals Analysis and Reduction of Solar Stray Light in the Nighttime Imaging Camera of Luojia-1 Satellite

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1130 ◽  
Author(s):  
Xing Zhong ◽  
Zhiqiang Su ◽  
Guo Zhang ◽  
Zhigang Chen ◽  
Yao Meng ◽  
...  
Keyword(s):  
High Sensitivity ◽  
Light Signal ◽  
Stray Light ◽  
Direct Sunlight ◽  
Detection Failure ◽  
Imaging Camera ◽  
Secondary Scattering ◽  
Order Of Magnitude ◽  
Nighttime Light ◽  
Design Requirements

As one of the experimental payloads on Luojia-1 satellite, the nighttime imaging camera works with a high sensitivity to acquire nighttime light on earth. Solar stray light is a fatal problem for optical satellite works in the polar orbit, even for nighttime scene imaging, resulting in image saturation and light signal detection failure. To solve this problem, an analysis of the range of solar incident angles was conducted firstly. Based on the result, a special-shaped baffle was designed to avoid direct sunlight incidence. Moreover, the capability of stray light elimination of the lens was enhanced by an order of magnitude via optimizing the internal structure. An evaluation of secondary scattering stray lights into the camera from surrounding parts was performed based on a real satellite model. The results showed that the stray light elimination reaches a 10−10 order, meeting design requirements. Utilizing on-orbit images, the ability of satellites in illuminated areas to obtain artificial lights in dawn-dusk area was verified, proving the effectiveness of the stray light elimination design.

scholarly journals High Sensitive Night-time Light Imaging Camera Design and In-orbit Test of Luojia1-01 Satellite

Sensors ◽  
2019 ◽  
Vol 19 (4) ◽  
pp. 797 ◽  
Author(s):  
Zhiqiang Su ◽  
Xing Zhong ◽  
Guo Zhang ◽  
Yanjie Li ◽  
Xiaojun He ◽  
...  
Keyword(s):  
Integrated Design ◽  
Remote Sensing Data ◽  
High Sensitivity ◽  
Stray Light ◽  
Modulation Transfer ◽  
Night Time ◽  
Camera Design ◽  
Design Requirements ◽  
Imaging Performance ◽  
Better Than

Luojia1-01 satellite is the first scientific experimental satellite applied for night-time light remote sensing data acquisition, and the payload is an optical camera with high sensitivity, high radiation measurement accuracy and stable elements of interior orientation. At the same time, a special shaped hood is designed, which significantly improved the ability of the camera to suppress stray light. Camera electronics adopts the integrated design of focal plane and imaging processing, which greatly reduces the volume and weight of the system. In this paper, the design of the optical camera is summarized, and the results of in-orbit imaging performance tests are analyzed. The results show that the dynamic modulation transfer function (MTF) of the camera is better than 0.17, and the SNR is better than 35 dB under the condition of 10 lx illuminance and 0.3 reflectivity and all indicators meet the design requirements. The data obtained have been widely applied in many fields such as the process of urbanization, light pollution analysis, marine fisheries detection and military.

scholarly journals Nonlinear Hydraulic Pressure Response of an Improved Fiber Tip Interferometric High-Pressure Sensor

Sensors ◽  
2020 ◽  
Vol 20 (9) ◽  
pp. 2548
Author(s):  
Wei Huang ◽  
Zhe Zhang ◽  
Jun He ◽  
Bin Du ◽  
Changrui Liao ◽  
...  
Keyword(s):  
High Pressure ◽  
Nonlinear Response ◽  
Arc Discharge ◽  
High Sensitivity ◽  
Measurement Range ◽  
Hydraulic Pressure ◽  
Discharge Process ◽  
Pressure Sensitivity ◽  
Diaphragm Thickness ◽  
Order Of Magnitude

We demonstrate a silica diaphragm-based fiber tip Fabry–Perot interferometer (FPI) for high-pressure (40 MPa) sensing. By using a fiber tip polishing technique, the thickness of the silica diaphragm could be precisely controlled and the pressure sensitivity of the fabricated FPI sensor was enhanced significantly by reducing the diaphragm thickness; however, the relationship between the pressure sensitivity and diaphragm thickness is not linear. A high sensitivity of −1.436 nm/MPa and a linearity of 0.99124 in hydraulic pressure range of 0 to 40 MPa were demonstrated for a sensor with a diaphragm thickness of 4.63 μm. The achieved sensitivity was about one order of magnitude higher than the previous results reported on similar fiber tip FPI sensors in the same pressure measurement range. Sensors with a thinner silica diaphragm (i.e., 4.01 and 2.09 μm) rendered further increased hydraulic pressure sensitivity, but yield a significant nonlinear response. Two geometric models and a finite element method (FEM) were carried out to explain the nonlinear response. The simulation results indicated the formation of cambered internal silica surface during the arc discharge process in the fiber tip FPI sensor fabrication.

Differential Surface Plasmon Resonance Sensor for the Detection of Chemicals and Biochemicals

2013 ◽  
Vol 543 ◽  
pp. 310-313 ◽  
Author(s):  
Carmelo Fallauto ◽  
Guido Perrone ◽  
Alberto Vallan
Keyword(s):  
Surface Plasmon Resonance ◽  
Surface Plasmon ◽  
Plasmon Resonance ◽  
High Sensitivity ◽  
Practical Implementation ◽  
Resonance Sensor ◽  
Order Of Magnitude ◽  
Long Term Monitoring ◽  
Term Monitoring

Surface plasmon resonance is one the most common optical sensing techniques for the detection of chemicals and biochemicals, although still mainly confined to lab applications. Typically, these sensors are made by a thin gold layer deposited on a glass prism or on an optical fiber similar to those used in telecom applications. Key advantages of this technique are the possibility to specifically detect different chemicals through functionalization of the metal surface and the high sensitivity, although the latter may turn into a weakness in long term monitoring applications due to cross-sensitivity to parasitic effects. To overcome this limitation the paper proposes a novel sensor implementation with a cascaded double sensing area, particularly suited for long term monitoring of pollutant since one sensing area is actually used to detect the desired molecules, while the other for compensating drifts due to fluctuations, misalignments and temperature variations. The paper addresses mainly the prism-based implementation, but the proposed configuration is suited also for an all-fiber approach. Examples of practical implementation of the proposed techniques are given, evidencing an accuracy improvement of more than an order of magnitude.

scholarly journals Planar Block Adjustment for China’s Land Regions with LuoJia1-01 Nighttime Light Imagery

2019 ◽  
Vol 11 (18) ◽  
pp. 2097 ◽  
Author(s):  
Xin Li ◽  
Taoyang Wang ◽  
Guo Zhang ◽  
Boyang Jiang ◽  
Peng Jia ◽  
...  
Keyword(s):  
Root Mean Square Error ◽  
Mean Square Error ◽  
Root Mean Square ◽  
High Sensitivity ◽  
Experimental Results ◽  
Mean Square ◽  
Ground Control Points ◽  
Nighttime Light Data ◽  
Nighttime Light ◽  
Nighttime Light Imagery

The Luojia1-01 satellite provides high-resolution, high-sensitivity nighttime light data at a resolution of 130 m. To effectively use the Luojia1-01 nighttime light data for global applications, the problems of relative and absolute positioning accuracy should be solved. This paper proposes a high accuracy regional geometric processing method of nighttime light imagery. We utilized a nighttime light image matching algorithm to obtain tie points, which are used in the planar block adjustment with ground control points. Then, orthorectification of all images is implemented. Finally, we obtain the nighttime light map of China by mosaicking all the nighttime light orthoimages. According to the experimental results for 275 Luojia1-01 images, the root mean square error of the tie points is 0.983 pixels and the root mean square error of independent checkpoints is 195.491 m (less than 1.5 pixels) after the planar block adjustment. The experimental results prove the validity and feasibility of the proposed method.

scholarly journals Characterization and correction of stray light in TROPOMI-SWIR

2018 ◽  
Vol 11 (7) ◽  
pp. 4493-4507 ◽  
Author(s):  
Paul J. J. Tol ◽  
Tim A. van Kempen ◽  
Richard M. van Hees ◽  
Matthijs Krijger ◽  
Sidney Cadot ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Light Signal ◽  
Stray Light ◽  
Main Reflection ◽  
Data Processor ◽  
Point Light ◽  
Shortwave Infrared ◽  
Operational Data ◽  
Ground Calibration

Abstract. The shortwave infrared (SWIR) spectrometer module of the Tropospheric Monitoring Instrument (TROPOMI), on board the ESA Copernicus Sentinel-5 Precursor satellite, is used to measure atmospheric CO and methane columns. For this purpose, calibrated radiance measurements are needed that are minimally contaminated by instrumental stray light. Therefore, a method has been developed and applied in an on-ground calibration campaign to characterize stray light in detail using a monochromatic quasi-point light source. The dynamic range of the signal was extended to more than 7 orders of magnitude by performing measurements with different exposure times, saturating detector pixels at the longer exposure times. Analysis of the stray light indicates about 4.4 % of the detected light is correctable stray light. An algorithm was then devised and implemented in the operational data processor to correct in-flight SWIR observations in near-real time, based on Van Cittert deconvolution. The stray light is approximated by a far-field kernel independent of position and wavelength and an additional kernel representing the main reflection. Applying this correction significantly reduces the stray-light signal, for example in a simulated dark forest scene close to bright clouds by a factor of about 10. Simulations indicate that this reduces the stray-light error sufficiently for accurate gas-column retrievals. In addition, the instrument contains five SWIR diode lasers that enable long-term, in-flight monitoring of the stray-light distribution.

scholarly journals Fast radio bursts to be detected with the Square Kilometre Array

2020 ◽  
Vol 497 (4) ◽  
pp. 4107-4116 ◽  
Author(s):  
Tetsuya Hashimoto ◽  
Tomotsugu Goto ◽  
Alvina Y L On ◽  
Ting-Yi Lu ◽  
Daryl Joe D Santos ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Mass Density ◽  
Formation Rate ◽  
High Sensitivity ◽  
High Angular Resolution ◽  
Radio Bursts ◽  
Square Kilometre Array ◽  
Luminosity Functions ◽  
Radio Signals ◽  
Order Of Magnitude

ABSTRACT Fast radio bursts (FRBs) are mysterious extragalactic radio signals. Revealing their origin is one of the central foci in modern astronomy. Previous studies suggest that occurrence rates of non-repeating and repeating FRBs could be controlled by the cosmic stellar-mass density (CSMD) and cosmic star formation-rate density (CSFRD), respectively. The Square Kilometre Array (SKA) is one of the best future instruments to address this subject due to its high sensitivity and high-angular resolution. Here, we predict the number of FRBs to be detected with the SKA. In contrast to previous predictions, we estimate the detections of non-repeating and repeating FRBs separately, based on latest observational constraints on their physical properties including the spectral indices, FRB luminosity functions, and their redshift evolutions. We consider two cases of redshift evolution of FRB luminosity functions following either the CSMD or CSFRD. At $z$ ≳ 2, $z$ ≳ 6, and $z$ ≳ 10, non-repeating FRBs will be detected with the SKA at a rate of ∼104, ∼102, and ∼10 (sky−1 d−1), respectively, if their luminosity function follows the CSMD evolution. At $z$ ≳ 1, $z$ ≳ 2, and $z$ ≳ 4, sources of repeating FRBs will be detected at a rate of ∼103, ∼102, and ≲10 (sky−1 d−1), respectively, assuming that the redshift evolution of their luminosity function is scaled with the CSFRD. These numbers could change by about one order of magnitude depending on the assumptions on the CSMD and CSFRD. In all cases, abundant FRBs will be detected by the SKA, which will further constrain the luminosity functions and number density evolutions.

scholarly journals Nd3+-Doped BiVO4 luminescent nanothermometers of high sensitivity

2019 ◽  
Vol 55 (50) ◽  
pp. 7147-7150 ◽  
Author(s):  
Pascal M. Gschwend ◽  
Fabian H. L. Starsich ◽  
Robert C. Keitel ◽  
Sotiris E. Pratsinis
Keyword(s):  
High Sensitivity ◽  
Spectral Lines ◽  
Careful Selection ◽  
Order Of Magnitude ◽  
Selection Of

The sensitivity of neodymium-based nanothermometers can be increased by an order of magnitude through careful selection of spectral lines.

scholarly journals A Novel High-Sensitivity Rapid-Acquisition Single-Photon Cardiac Imaging Camera

2009 ◽  
Vol 50 (4) ◽  
pp. 635-643 ◽  
Author(s):  
S. S. Gambhir ◽  
D. S. Berman ◽  
J. Ziffer ◽  
M. Nagler ◽  
M. Sandler ◽  
...  
Keyword(s):  
Cardiac Imaging ◽  
Single Photon ◽  
High Sensitivity ◽  
Rapid Acquisition ◽  
Imaging Camera

Dielectric Barrier Discharge Detection System Based on PMT

2012 ◽  
Vol 220-223 ◽  
pp. 2057-2063
Author(s):  
Ding Qu Zhang ◽  
Rui Min Chen ◽  
Yong Xiao ◽  
Wei Ming Sun ◽  
Jia Hu ◽  
...  
Keyword(s):  
Dielectric Barrier Discharge ◽  
Barrier Discharge ◽  
Detection System ◽  
High Sensitivity ◽  
Fast Response ◽  
Light Signal ◽  
Photoelectric Conversion ◽  
Dielectric Barrier ◽  
Interference Signals ◽  
Discharge Detection

This paper puts forward a dielectric barrier discharge detection system using PMT for photoelectric element. According to faint light signal characteristics and testing purpose of dielectric barrier discharge, this system is designed, including three parts: optical fiber transmission, photoelectric conversion and signal processing circuit. This paper introduces design and ideas of the system framework and presents circuit design parameter. Results in atmospheric pressure of dielectric barrier discharge detection experiment show that the system has high sensitivity, fast response, can effectively distinguish discharge and interference signals, gather more signals in different areas.

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