In-orbit geometric imaging simulation based on ray-tracing for long-linear-array and whisk-broom thermal infrared imager

Xiao-Yan LI; Zhuo-Yue HU; Lin-Yi JIANG; Fan-Sheng CHEN

doi:10.11972/j.issn.1001-9014.2022.01.014

Journal of Infrared and Millimeter Waves, Volume. 41, Issue 1, 2021337(2022)

In-orbit geometric imaging simulation based on ray-tracing for long-linear-array and whisk-broom thermal infrared imager

Xiao-Yan LI^1,2,3, Zhuo-Yue HU^2,3, Lin-Yi JIANG^2,3,4, and Fan-Sheng CHEN^1,2,3、*

Author Affiliations

¹Hangzhou Institute for Advanced Study，University of Chinese Academy of Sciences，Hangzhou 310024，China

²Key Laboratory of Intelligent Infrared Perception，Chinese Academy of Sciences，Shanghai 200083，China

³CAS Key Laboratory of Infrared System Detection and Imaging Technology，Shanghai Institute of Technical Physics，Chinese Academy of Sciences，Shanghai 200083，China

⁴University of Chinese Academy of Sciences，Beijing 100049，China

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Figures & Tables(10)

Fig. 1. Diagrams of spliced detector，optical path and in-orbit imaging（a）diagram of in-orbit imaging，（b）diagram of optical path，（c）diagram of spliced detector

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Fig. 2. Flowchart of on-orbit geometric imaging simulation of TIRI

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Fig. 3. Referencing data（a）upsampled AwiFS images with 30 m resolution，（b）30 m ASTER GDEM，（c）30 m Landsat8 orthoimage

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Fig. 4. The simulation image and GCPs matching results（a）the simulation images of two scan periods，（b）GCPs matching results of the simulation image and reference image

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Fig. 5. Distribution comparison of geometric positioning errors of simulation images：（a）positioning errors in X before calibration，（b）positioning errors in Y before calibration，（c）positioning errors in Z before calibration，（d）positioning errors in X after calibration，（e）positioning errors in Y after calibration，（f）positioning errors in Z after calibration

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Fig. 6. Distribution comparison of planar geometric positioning errors of simulation images：（a）planar positioning errors before calibration，（b）planar positioning errors after calibration

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Table 1. Orbit parameters of SDGSAT-1 and specifications of LLAWB TIRI

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Table 1. Orbit parameters of SDGSAT-1 and specifications of LLAWB TIRI

SDGSAT-1		TIRI
Items	Design indexes	Items	Design indexes
Orbit type	Sun-synchronous	Swath	300 km
Orbit	505 km	Resolution	30 m
Local time of descending node	09：30	Bands	8-10.5 μm 10.3-11.3 μm 11.5-12.5 μm
Orbit period	94.7 mins	Pixel size	30 μm
Inclination	97.4°	Scan period	7.48 s
Eccentricity	0.0	Field of view（FOV）along-track/ cross-track	7.0°/≥ 33.1°
Revisit interval	~10.5 days	F#	1.94
Life	>3 years	Focal length	505×（1±5%）mm

Table 2. In-orbit geometric imaging simulation based on ray tracing for LLAWB TIRI

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Table 2. In-orbit geometric imaging simulation based on ray tracing for LLAWB TIRI

Input：Sensor model，Referencing DOM & DEM，simulated attitudes and ephemeris，GCPs

Output：Simulating images

1. Construct the rigorous positioning model：

${[X, Y, Z]}^{T} = g ({(i, j, 1)}^{T})$

2. Ray-tracing-based intersection calculation and gray-value projection：

Initial simulating image： $I_{i n i t i a l} (x, y)$

3. Geometric calibration of the rigorous positioning medel：

${[X, Y, Z]}^{T} = g_{c a l i b r a t e d} ({(i, j, 1)}^{T})$

4. Repeat step 2 until convergence

Final simulating image： $I_{f i n a l} (x, y)$

Table 3. Simulating ephemeris and attitudes of SDGSAT-1 minisatellite in J2000

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Table 3. Simulating ephemeris and attitudes of SDGSAT-1 minisatellite in J2000

Time（UTCG）	X（Km）	Y（Km）	Z（Km）	Vx （km/sec）	Vy （km/sec）	Vz （km/sec）	Yaw（°）	Pitch（°）	Roll（°）
02：44：00.000	-2 033.847 02	-5 244.471 93	3 967.558 30	-2.702 40	-3.595 56	-6.138 05	111.822	17.186	-127.108
02：44：00.100	-2 034.116 79	-5 244.831 03	3 966.945 27	-2.702 15	-3.594 92	-6.138 54	111.820	17.188	-127.102
02：44：00.200	-2 034.386 53	-5 245.190 06	3 966.332 19	-2.701 90	-3.594 28	-6.139 02	111.818	17.190	-127.096
$⋮$	$⋮$	$⋮$	$⋮$	$⋮$	$⋮$	$⋮$	$⋮$	$⋮$	$⋮$
02：44：15.800	-2 076.161 07	-5 300.413 66	3 870.104 48	-2.662 76	-3.493 89	-6.213 63	111.531	17.555	-126.135
02：44：15.900	-2 076.426 88	-5 300.762 60	3 869.483 90	-2.662 50	-3.493 24	-6.214 10	111.529	17.557	-126.129
02：44：16.000	-2 076.692 67	-5 301.111 48	3 868.863 27	-2.662 25	-3.492 60	-6.214 57	111.528	17.559	-126.123

Table 4. Geometric positioning accuracy comparison of simulation images before and after calibration

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Table 4. Geometric positioning accuracy comparison of simulation images before and after calibration

Items	Positioning error before calibration				Positioning error after calibration
Items	X（m）	Y（m）	Z（m）	XY-plane（m）	X（m）	Y（m）	Z（m）	XY-plane（m）
Maximum	656.543	567.579	821.984	784.353	186.959	293.231	231.615	473.753
Minimum	0.115	17.808	43.964	34.601	0.051	17.808	0.069	2.782
Mean	216.651	245.243	261.516	350.416	34.234	49.563	31.511	63.875
Median	257.013	247.215	241.014	349.778	30.270	49.283	29.533	61.733
RMSE	153.061	47.074	78.831	181.837	34.145	40.471	30.366	39.876

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Xiao-Yan LI, Zhuo-Yue HU, Lin-Yi JIANG, Fan-Sheng CHEN. In-orbit geometric imaging simulation based on ray-tracing for long-linear-array and whisk-broom thermal infrared imager[J]. Journal of Infrared and Millimeter Waves, 2022, 41(1): 2021337

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Paper Information

Category: Research Articles

Received: Oct. 20, 2021

Accepted: --

Published Online: Apr. 18, 2022

The Author Email: Fan-Sheng CHEN (cfs@mail.sitp.ac.cn)

DOI:10.11972/j.issn.1001-9014.2022.01.014

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