scholarly journals A study of a two-dimensional scanned lunar image for Advanced Technology Microwave Sounder (ATMS) geometric calibration

2019 ◽  
Vol 12 (9) ◽  
pp. 4983-4992
Author(s):  
Jun Zhou ◽  
Hu Yang
Keyword(s):  
Inflection Point ◽  
Gaussian Function ◽  
Euler Angle ◽  
Advanced Technology ◽  
Two Dimensional ◽  
Geometric Calibration ◽  
Pointing Error ◽  
V Band ◽  
W Band ◽  
Calibration Accuracy

Abstract. The NOAA-20 satellite was successfully launched on 18 November 2017. It carries five key instruments, including the Advanced Technology Microwave Sounder (ATMS). On 31 January 2018, the spacecraft performed a pitch-over maneuver operation, during which two-dimensional lunar scan observations were collected. In this study, a technique has been developed by which the ATMS on-orbit geometric calibration accuracy can be validated based on this lunar scan dataset. The fully calibrated data are fitted to the antenna pattern coordinates via a Gaussian function. The deviation in the center of the fit function from the origin of the frame is taken to be the boresight pointing error of the instrument. This deviation is further transformed to the Euler angle roll and pitch defined in the spacecraft coordinate system. The estimated ATMS boresight pointing Euler angle roll (pitch) is 0.05∘ (0.22∘) at K band, −0.07∘ (0.25∘) at Ka band, 0.02∘ (0.24∘) at V band, -0.07∘ (-0.08∘) at W band, and -0.04∘ (0.02∘) at G band. The results are validated by comparing them with those derived from the coastline inflection point method, showing a good correlation. For the sounding channels where the coastline method is inapplicable, the lunar scan method is still capable of delivering reasonable estimations of their geometric calibration errors.

scholarly journals On Study of Two-Dimensional Lunar Scan for Advanced Technology Microwave Sounder Geometric Calibration

2019 ◽  
Author(s):  
Jun Zhou ◽  
Hu Yang
Keyword(s):  
Inflection Point ◽  
Gaussian Function ◽  
Euler Angle ◽  
Advanced Technology ◽  
Two Dimensional ◽  
Geometric Calibration ◽  
Pointing Error ◽  
V Band ◽  
W Band ◽  
Calibration Accuracy

Abstract. The NOAA-20 satellite was successfully launched on 18 November 2017. It carries five key instruments including Advanced Technology Microwave Sounder (ATMS). On January 31, 2018, the spacecraft performed a pitch-over maneuver operation, during which the two-dimensional lunar scan observations were collected. In this study, a technique has been developed by which the ATMS on-orbit geometric calibration accuracy can be validated based on this lunar scan dataset. The fully calibrated data are fitted in the antenna pattern coordinate by Gaussian function. The deviation of the center of the fit function from the origin of the frame is taken to be the boresight pointing error of the instrument. This deviation is further transformed to the Euler angle roll and pitch defined in spacecraft coordinate system. The estimated ATMS boresight pointing Euler angle roll (pitch) is 0.05°, (0.22°) at K-band, −0.07°, (0.25°) at Ka-band, 0.02°, (0.24°) at V-band, −0.07°, (−0.08°) at W-band, and −0.04°, (0.02°) at G-band. The results are validated by comparing with those derived from the coastline inflection point method. It shows that the Euler angles derived from these two independent methods are consistent very well. For the sounding channels where the coastline method is inapplicable, the lunar scan method is still capable of delivering reasonable estimations of their geometric calibration errors.

HIGH-PRECISION IN-FLIGHT CALIBRATION USING UNKNOWN LANDMARKS

2021 ◽  
Vol 4 ◽  
pp. 117-124
Author(s):  
Alexander Tkachenko ◽  
Keyword(s):  
Good Accuracy ◽  
Star Tracker ◽  
Coordinate Frame ◽  
Geometric Calibration ◽  
The Earth ◽  
Imaging Camera ◽  
Calibration Accuracy ◽  
Combined Algorithm ◽  
Fuzzy State ◽  
Fuzzy State Observer

An in-flight geometric calibration (further — calibration) is interpreted here as a procedure of making more preceise mutual attitude parameters of the onboard imaging camera and the star tracker. The problem of calibration is solved with using of observations of the landmarks from the orbit. In this work, the landmarks are considered as unknown in the sense that they may be identified on the several snapshots, they may be associated with synchronous data of the star tracker and GPS, but their location in the Earth coordinate frame is unknown. While unknown markers are used, it is more complicated to provide high accuracy of calibration than when geo-referenced markers are observed. In such a situation, improvement of the onboard devices and gauges and increasing of their accuracy strenghtens advisability of agreement of attainable accuracy of calculations while in-flight geometric calibration with accessible measurings accuracy. It concerns properly calibration so as geo-referencing of space snaps using results of calibration. In particular, it is important to consider how accuracy of calibration depends on the accuracy of specific measurings and initial data. Actuality of the considered problem is indisputable. Without its solution, attraction of high-accurate measurings is senseless. A main means of investigation is computer simulanion and analysis of its results. The combined algorithm is proposed for the processing of the calibration measuring equations. It consists of two independent parts. The first one belongs to author of this work and is based on photogrammetric condition of collinearity The second part belongs to D.V. Lebedev and is based on photogrammetric condition of coplanarity. The method of state estimation with high convergence characteristics — fuzzy state observer — is used for resolving of measuring equations. The results of above-mentioned calibration are fully fit for the geo-referencing of the unknown ground objects with acceptable accuracy. Computer simulation had demonsrated good accuracy of the proposed method of the in-flight geometric calibration using unknown landmarks in a combination with high-precise characteristics of used technical means. The simulation had shown the calibration accuracy on the level of 5 arc sec and accuracy of the geo-referencing on the level of 10–20 m. It is fully comparable with accuracy when geo-referenced markers are observated.

scholarly journals POINTING ANGLE CALIBRATION OF ZY3-02 SATELLITE LASER ALTIMETER USING TERRAIN MATCHING

2017 ◽  
Vol XLII-1/W1 ◽  
pp. 205-210 ◽  
Author(s):  
G. Li ◽  
X. Tang ◽  
X. Gao ◽  
J. P. Huang ◽  
J. Chen ◽  
...  
Keyword(s):  
Altimetry Data ◽  
Laser Altimetry ◽  
Angle Error ◽  
Laser Altimeter ◽  
Geometric Calibration ◽  
Pointing Error ◽  
The Public ◽  
Ice Cloud ◽  
Laser Data ◽  
Terrain Matching

After GLAS (Geo-science Laser Altimeter System) loaded on the ICESat (Ice Cloud and land Elevation Satellite), satellite laser altimeter attracts more and more attention. ZY3-02 equipped with the Chinese first satellite laser altimeter has been successfully launched on 30<sup>th</sup> May, 2016. The geometric calibration is an important step for the laser data processing and application. The method to calculate the laser pointing angle error based on existed reference terrain data is proposed in this paper. The public version terrain data, such as 90m-SRTM and 30m-AW3D30, can be used to estimate the pointing angle of laser altimeter. The GLAS data with simulated pointing error and actual ZY3-02 laser altimetry data is experimented to validate the algorithm. The conclusion will be useful for the future domestic satellite laser altimeter.

V-band and W-band broad-band, monolithic distributed frequency multipliers

1992 ◽  
Vol 2 (6) ◽  
pp. 253-254 ◽  
Author(s):  
E. Carman ◽  
M. Case ◽  
M. Kamegawa ◽  
R. Yu ◽  
K. Giboney ◽  
...  
Keyword(s):  
Broad Band ◽  
Frequency Multipliers ◽  
V Band ◽  
W Band

scholarly journals System matrix computation for iterative reconstruction algorithms in SPECT based on direct measurements

2011 ◽  
Vol 21 (1) ◽  
pp. 193-202 ◽  
Author(s):  
Damian Borys ◽  
Katarzyna Szczucka-Borys ◽  
Kamil Gorczewski
Keyword(s):  
Point Source ◽  
Iterative Reconstruction ◽  
Gaussian Function ◽  
Detector Response ◽  
Two Dimensional ◽  
Reconstruction Algorithms ◽  
System Matrix ◽  
Matrix Computation ◽  
Direct Measurements ◽  
Matrix Calculation

System matrix computation for iterative reconstruction algorithms in SPECT based on direct measurements A method for system matrix calculation in the case of iterative reconstruction algorithms in SPECT was implemented and tested. Due to a complex mathematical description of the geometry of the detector set-up, we developed a method for system matrix computation that is based on direct measurements of the detector response. In this approach, the influence of the acquisition equipment on the image formation is measured directly. The objective was to obtain the best quality of reconstructed images with respect to specified measures. This is indispensable in order to be able to perform reliable quantitative analysis of SPECT images. It is also especially important in non-hybrid gamma cameras, where not all physical processes that disturb image acquisition can be easily corrected. Two experiments with an 131I point source placed at different distances from the detector plane were performed allowing the detector response to be acquired as a function of the point source distance. An analytical Gaussian function was fitted to the acquired data in both the one- and the two-dimensional case. A cylindrical phantom filled with a water solution of 131I containing a region of "cold" spheres as well as a uniform solution (without any spheres) was used to perform algorithm evaluation. The reconstructed images obtained by using four different of methods system matrix computation were compared with those achieved using reconstruction software implemented in the gamma camera. The contrast of the spheres and uniformity were compared for each reconstruction result and also with the ranges of those values formulated by the AAPM (American Association of Physicists in Medicine). The results show that the implementation of the OSEM (Ordered Subsets Expectation Maximization) algorithm with a one-dimensional fit to the Gaussian CDR (Collimator-Detector Response) function provides the best results in terms of adopted measures. However, the fit of the two-dimensional function also gives satisfactory results. Furthermore, the CDR function has the potential to be applied to a fully 3D OSEM implementation. The lack of the CDR in system matrix calculation results in a very noisy image that cannot be used for diagnostic purposes.

The Application of Building Information Model in the Deepen Design of Prestressed Concrete Structures

2014 ◽  
Vol 716-717 ◽  
pp. 303-306
Author(s):  
Er Wei Guo ◽  
Ying Xin Qian ◽  
Gang Xu ◽  
Jin Dong Gao ◽  
Chen Guang Li
Keyword(s):  
Process Design ◽  
Prestressed Concrete ◽  
Digital Technology ◽  
Concrete Structure ◽  
Concrete Structures ◽  
Advanced Technology ◽  
Two Dimensional ◽  
Building Information Model ◽  
Building Information ◽  
Complete Process

Currently deepen design of prestressed concrete structure exists various problems, them can be solved using BIM building digital technology in the deepen design phase of prestressed concrete structures, such as constant correction of the two-dimensional drawings. BIM technology was advanced technology, the design of prestressed concrete structures, was given by using BIM technology in the complete process; Design process and value of the application of the BIM technology in the prestressed concrete structure were analyzed, Prospects of the BIM technology using in prestressed concrete were discussed.

Development of a Two-Dimensional Turbulent Wake in a Curved Channel With a Positive Streamwise Pressure Gradient

1996 ◽  
Vol 118 (2) ◽  
pp. 292-299 ◽  
Author(s):  
J. John ◽  
M. T. Schobeiri
Keyword(s):  
Pressure Gradient ◽  
Reynolds Stress ◽  
Gaussian Function ◽  
Two Dimensional ◽  
Curved Channel ◽  
Mean Velocity ◽  
Velocity Defect ◽  
Curved Channels ◽  
Stress Components ◽  
Streamwise Pressure Gradient

The development of turbomachinery wake flows is greatly influenced by streamline curvature and streamwise pressure gradient. This paper is part of a comprehensive experimental and theoretical study on the development of the steady and periodic unsteady turbulent wakes in curved channels at different streamwise pressure gradients. This paper reports on the experimental investigation of the two-dimensional wake behind a stationary circular cylinder in a curved channel at positive streamwise pressure gradient. Measurements of mean velocity and Reynolds stress components are carried out using a X-hot-film probe. The measured quantities obtained in probe coordinates are transformed to a curvilinear coordinate system along the wake center line and are presented in similarity coordinates. The results show strong asymmetry in velocity and Reynolds stress components. The Reynolds stress components have higher values at the inner half of the wake than at the outer half of the wake. However, the mean velocity defect profiles in similarity coordinates are almost symmetric and follow the same Gaussian function for the straight wake data. A comparison with the wake development in a curved channel at zero streamwise pressure gradient suggests the decay rate of velocity defect is slower and the growth of wake width is faster for a positive streamwise pressure gradient.

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