偏振滤光增强白昼测星信噪比效能分析

doi:10.11947/j.AGCS.2024.20230416

摘要/Abstract

摘要：

目前的天文大地测量只能在夜间可见光波段观测恒星等自然天体实现定位定向，尚未实现全天时测量，因此研究白昼测星技术具有重要的意义。为增强白昼测星信噪比，本文通过构建偏振滤光信噪比增强模型，分析了采用偏振滤光方法的测星信噪比增强效能。首先，分析了大气偏振态的表征模型，并以瑞利散射模型为基础构建了偏振滤光模型；然后，推导了白昼测星信噪比增强模型，并对信噪比增强效能及影响因素进行了分析；最后，搭建室外试验平台，验证了偏振滤光增强白昼测星实际效能。试验结果表明，在900~1700 nm的近红外波段，基于瑞利散射模型构建的滤光模型准确度较好，其中77%的点位偏振角误差小于5°,100%的点位偏振角误差优于12°，可满足实用偏振滤光模型的精度需求；通过对Arcturus、Kochab等6颗恒星观测表明，不同观测方位恒星信噪比可提升22%~109%，与信噪比增强模型基本一致；在全天域采用偏振滤光方法进行白昼测星具有重要应用价值，当全天域最大偏振度为0.65时，偏振度均值可达0.34，对应测星信噪比可提升约51.5%。

关键词: 天文大地测量, 全天时, 白昼测星, 大气偏振, 偏振滤光

Abstract:

Now, astronomical geodesy can only observe the celestial bodies in the visible band at night, and has not yet achieved all-time measurement. Therefore, studying daytime star measurement technology is very meaningful. In order to enhance the signal-to-noise ratio(SNR) of star measurement in daytime, this paper constructs a polarization filtering SNR enhancement model and analyzes the effectiveness of using polarization filtering method for star measurement SNR enhancement. Firstly, the characterization model of atmospheric polarization state is analyzed, and then a polarization filtering model is put forward based on the Rayleigh scattering model. Then, an enhancement model for improving the SNR is derived, and the SNR enhancement efficiency and influencing factors are analyzed. Finally, two outdoor experimental platforms were built to verify the effectiveness of the model. The experimental results show that in the band of 900~1700 nm, the filtering model constructed based on the Rayleigh scattering model has high accuracy, with 77% of the point polarization angle errors being smaller than 5° and 100% smaller than 12°, which can meet the accuracy requirements for the practical polarization filter model. Through observations of 6 stars, including Arcturus and Kochab, it was shown that the SNR of stars with different observation orientations can be improved by 22%~109%, which is consistent with the SNR enhancement model. The use of polarization filtering method for daytime star measurement in the entire sky has important application value. When the maximum polarization degree of the entire sky is 0.65, the average polarization degree can reach 0.34, and the corresponding star measurement SNR can be improved by about 51.5%.

Key words: astronomical geodesy, all-day measurement, daytime star measurement, atmospheric polarization, polarization filtering

中图分类号:

P228.7

勾万祥, 李崇辉, 詹银虎, 杨原, 郑勇. 偏振滤光增强白昼测星信噪比效能分析[J]. 测绘学报, 2024, 53(8): 1574-1585.

Wanxiang GOU, Chonghui LI, Yinhu ZHAN, Yuan YANG, Yong ZHENG. Efficiency analysis of polarizing filter enhanced signal to noise ratio for daytime star measurement[J]. Acta Geodaetica et Cartographica Sinica, 2024, 53(8): 1574-1585.

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太阳高度角/(°)	信噪比增强值(SNE)
太阳高度角/(°)	≤30%	30%~60%	60%~90%	90%~120%	120%~150%	150%~180%	≥180%
0	19.6	13.6	8.9	7.7	7.7	8.6	33.9
30	23.9	17.2	16.6	9.8	7.5	6.7	18.3
60	44.6	15.0	9.0	6.6	5.5	5.1	14.2
90	49.6	13.0	8.0	6.1	5.0	4.7	13.5

滤光模型误差Δω/(°)	偏振度p
滤光模型误差Δω/(°)	0.1	0.3	0.5	0.7	0.9
0	11%	43%	100%	233%	900%
10	10%	39%	89%	192%	548%
30	5%	18%	33%	54%	82%
50	－2%	－5%	－8%	－11%	－14%
70	－7%	－19%	－28%	－35%	－41%
90	－9%	－23%	－33%	－41%	－47%

高度角		方位角
高度角		0°	30°	60°	90°	120°	150°	180°	210°	240°	270°	300°	330°
20°	AOP	－32°	－24°	－22°	－25°	20°	14°	22°	31°	47°	70°	－70°	－45°
20°	DOP	0.64	0.38	0.25	0.12	0.04	0.23	0.65	0.60	0.38	0.21	0.21	0.47
40°	AOP	－30°	－17°	5°	23°	－43°	－2°	17°	36°	57°	80°	－73°	－57°
40°	DOP	0.57	0.36	0.22	0.10	0.04	0.17	0.35	0.47	0.40	0.35	0.38	0.47
60°	AOP	－28°	－11°	15°	56°	－57°	－18°	7°	32°	54°	83°	－67°	－50°
60°	DOP	0.46	0.27	0.22	0.09	0.08	0.17	0.36	0.55	0.64	0.57	0.59	0.60
80°	AOP	－22°	2°	39°	64°	－69°	－38°	－7°	21°	55°	81°	－76°	－51°
80°	DOP	0.33	0.25	0.17	0.17	0.16	0.34	0.33	0.38	0.46	0.44	0.43	0.47

高度角		方位角
高度角		0°	30°	60°	90°	120°	150°	180°	210°	240°	270°	300°	330°
20°	AOP	－3°	－3°	－5°	4°	－5°	－3°	0°	1°	1°	－4°	0°	－1°
20°	DOP	－0.01	－0.09	0.08	0.10	0.01	0.03	0.14	－0.04	－0.04	－0.04	－0.05	0.02
40°	AOP	3°	－1°	4°	－10°	－4°	1°	2°	5°	6°	5°	4°	－5°
40°	DOP	－0.06	－0.05	0.06	0.07	0.02	0.03	－0.04	－0.15	－0.22	－0.18	－0.15	－0.15
60°	AOP	3°	－4°	－6°	－4°	11°	8°	4°	5°	3°	8°	12°	4°
60°	DOP	－0.06	－0.08	0.03	－0.01	－0.01	0.01	0.04	0.06	0.03	－0.08	－0.06	－0.02
80°	AOP	3°	－2°	4°	－4°	9°	6°	5°	4°	10°	8°	4°	2°
80°	DOP	－0.06	－0.08	－0.10	－0.06	－0.07	0.08	0.02	0.01	0.03	－0.02	－0.03	0.03

恒星	观测方位(A_S，h_S)	原灰度均值(16 bit)	滤光后灰度均值(16 bit)	曝光时间Δt/ms	曝光延长Δt_p/ms
Arcturus	(81°，22°)	45 686	44 647	15	55
Kochab	(19°，36°)	46 816	40 016	10	40
Antares	(292°，68°)	51 972	53 109	5	12
Rigil Kent	(217°，46°)	41 938	47 438	5	14
Enif	(47°，29°)	42 049	43 752	20	62
Atria	(201°，51°)	43 266	45 507	20	70