CCD漂移扫描系统的建立及在同步卫星观测中的应用
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摘要
研制成功基于S1C077相机的外部同步触发装置，使S1C077相机具有适用于天文观测的CCD漂移扫描(drift scan)功能。为解决通常利用满帧(Full Frame)CCD漂移扫描模式观测带来的诸多问题，通过程序实现了短帧(Part Frame)CCD漂移扫描模式。利用短帧CCD漂移扫描模式和凝视模式交替观测恒星和地球同步卫星，获得参考恒星和地球同步卫星良好的圆星像。讨论了利用此设备观测地球同步卫星观测方案的制定和实施。
针对该设备获得的地球同步卫星的观测资料，独立编制了数据处理软件的初级版本，该软件主要包括以下功能：漂移扫描恒星FTS图像中星像的自动化检测、参考星的匹配与证认、CCD成像模型参数的归算、星等模型参数归算以及最终得到地球同步卫星的光学位置(站心平位置)和视星等。该软件选用UCAC2为参考星表。
利用上海天文台的20cm马克苏托夫望远镜和25cm牛顿—卡塞格林望远镜已经对几十颗地球同步卫星进行了观测。基于该软件对一些实测资料进行了处理，得到了目标的光学位置和视星等。光学定位结果的内部精度约为0.5角秒。详细分析了主要的误差来源，分别是由参考星决定的局部参考架的误差约0.15角秒，目标量度坐标误差约为0.45角秒。当台站观测条件好、望远镜光学性能佳时，地球同步卫星的光学定位精度将会大大提高，理论上可以与该望远镜的恒星定位精度相当。
根据对小天区地球同步卫星搜索的试验性研究，通过对搜索过程和比对结果的分析，提出了新的搜索方案。新搜索方案的出发点是“具有“8”字运动的有倾角的地球同步卫星总是会在24小时内两次穿过赤道”。对新搜索方案的搜索效率和实施优点做了详细的分析和讨论。
通常观测地球同步卫星时采用跟踪卫星的凝视模式观测，针对观测资料中出现的拖长恒星星像的特点，利用平均几何中心法定恒星星像的中心。通过与重心法定拖长星像中心结果的比较，认为确定拖长星像的重心，平均几何中心法要远优于重心法。另外在确定曝光过度星像中心时，平均几何中心法也能够获得精度很高的结果。
Based on camera S1C077, having success with developing special exteriorsynchronizer in order to achieve CCD drift scan mode which can apply to astronomyobservation more advantageously. To avoid many questions with full frame CCDdrift scan mode, part frame CCD drift scan mode was achieved by software. In orderto obtain good circular images of reference stars and GSS (Geo Stationary Satellites),part frame CCD drift scan mode and stare mode were carried out by turns. Makingand implementing observation plan for GSS were discussed also.
The elementary version of special software for data reduction was finished byourselves. This special software was called SHAO_GSS_Positioning. The mainfunctions of this software includes detecting stars in FTS file automatically,matching and identifying reference stars automatically, obtaining parameters ofsuitable plate model and magnitude mode of CCD automatically and finally gettingthe optical coordinates and visual magnitudes of GSS. By the way, UCAC2 is used tobe the catalogue of reference stars.
More than fifty GSS were observed by this system and their coordinates andmagnitudes were computed by SHAO_GSS_Positioning. The total internal errors ofoptical positioning results was about 0.5as. There were two main part of error source,the local reference system which was about 0.15as and the measurement coordinates of objects which were about 0.45as. The better observation condition the station isand the better optical performance the telescope is, The higher precision-position forGSS will be obtained.
According to the observing process and the matching result of the previous testwhich purpose was surveying GSS in one small sky area, a new survey plan wasmade. The main principle of the new survey plan is always having telescope point tothe equator in order to avoid missing the objects which will pass by the area ofequator. The advantages and efficiency of the new survey plan were analyseddetailedly also.
Usually, GSS objects are observed with stare mode so that images of referencestars will be stretched because of the relative movement between telescope and stars.Therefore, a new centering method, that is MGC (mean-geometric-centering), wasapplied to compute centers of stars. MGC is more precise than moment forcomputing centers of stretched stars images. In fact, MGC is more suitable forsaturated stats images also.
针对该设备获得的地球同步卫星的观测资料，独立编制了数据处理软件的初级版本，该软件主要包括以下功能：漂移扫描恒星FTS图像中星像的自动化检测、参考星的匹配与证认、CCD成像模型参数的归算、星等模型参数归算以及最终得到地球同步卫星的光学位置(站心平位置)和视星等。该软件选用UCAC2为参考星表。
利用上海天文台的20cm马克苏托夫望远镜和25cm牛顿—卡塞格林望远镜已经对几十颗地球同步卫星进行了观测。基于该软件对一些实测资料进行了处理，得到了目标的光学位置和视星等。光学定位结果的内部精度约为0.5角秒。详细分析了主要的误差来源，分别是由参考星决定的局部参考架的误差约0.15角秒，目标量度坐标误差约为0.45角秒。当台站观测条件好、望远镜光学性能佳时，地球同步卫星的光学定位精度将会大大提高，理论上可以与该望远镜的恒星定位精度相当。
根据对小天区地球同步卫星搜索的试验性研究，通过对搜索过程和比对结果的分析，提出了新的搜索方案。新搜索方案的出发点是“具有“8”字运动的有倾角的地球同步卫星总是会在24小时内两次穿过赤道”。对新搜索方案的搜索效率和实施优点做了详细的分析和讨论。
通常观测地球同步卫星时采用跟踪卫星的凝视模式观测，针对观测资料中出现的拖长恒星星像的特点，利用平均几何中心法定恒星星像的中心。通过与重心法定拖长星像中心结果的比较，认为确定拖长星像的重心，平均几何中心法要远优于重心法。另外在确定曝光过度星像中心时，平均几何中心法也能够获得精度很高的结果。
Based on camera S1C077, having success with developing special exteriorsynchronizer in order to achieve CCD drift scan mode which can apply to astronomyobservation more advantageously. To avoid many questions with full frame CCDdrift scan mode, part frame CCD drift scan mode was achieved by software. In orderto obtain good circular images of reference stars and GSS (Geo Stationary Satellites),part frame CCD drift scan mode and stare mode were carried out by turns. Makingand implementing observation plan for GSS were discussed also.
The elementary version of special software for data reduction was finished byourselves. This special software was called SHAO_GSS_Positioning. The mainfunctions of this software includes detecting stars in FTS file automatically,matching and identifying reference stars automatically, obtaining parameters ofsuitable plate model and magnitude mode of CCD automatically and finally gettingthe optical coordinates and visual magnitudes of GSS. By the way, UCAC2 is used tobe the catalogue of reference stars.
More than fifty GSS were observed by this system and their coordinates andmagnitudes were computed by SHAO_GSS_Positioning. The total internal errors ofoptical positioning results was about 0.5as. There were two main part of error source,the local reference system which was about 0.15as and the measurement coordinates of objects which were about 0.45as. The better observation condition the station isand the better optical performance the telescope is, The higher precision-position forGSS will be obtained.
According to the observing process and the matching result of the previous testwhich purpose was surveying GSS in one small sky area, a new survey plan wasmade. The main principle of the new survey plan is always having telescope point tothe equator in order to avoid missing the objects which will pass by the area ofequator. The advantages and efficiency of the new survey plan were analyseddetailedly also.
Usually, GSS objects are observed with stare mode so that images of referencestars will be stretched because of the relative movement between telescope and stars.Therefore, a new centering method, that is MGC (mean-geometric-centering), wasapplied to compute centers of stars. MGC is more precise than moment forcomputing centers of stretched stars images. In fact, MGC is more suitable forsaturated stats images also.
引文
[1] D. W. Evans, M. J. Irwin, and L. Helmer . A&A, 2002,347:348
[2] http://www.driftscan.com/#uebersicht, 2003
[3] D. W. Evans, M. J. Irwin, and L. Helmer . A&A, 2002,347:348
[4] Belizon. F, Muinos. J. L, Vallejo. M et al. AdeLA Publications Series, 2003,1:61-63
[5] B. Viateau, Y. Requieme, J. F. Le Campion et al. A&A, 1999,134:173-186
[6] http://www.nofs.navy.mil/about_NOFS/telescopes/fastt. html, 1999, 3
[7] Ronald C. Stone, David G. Monet, Alice K. B et al. AJ, 2003, 126:2060-2065
[8] Ronald C. Stone. AJ, 1998, 506:93-96
[9] Garcia. L. A, Salas. B. E, Gomez. F et al. Information Bulletin on Variable Stars, 2003, No. 5455,1.
[10] http://www.mao.nikolaev.ua/
[11] Pinigin. G. I, Kovalchuk. A. N, Protsyuk. Y. I et al. Astronomische Gesellschaft Abstract Series, 2001, 18:23
[12] C. N. Sabbey, P. Coppi, and A. Oemler. PASP, 1998, 110:1067-1068
[13] C. Baltay, J. A. Snyder, P. Andrews et al. PASP, 2002,114:780-794
[14] http://www.cida.ve/des_quest.html 2000,11
[15] Tom Nicinski. ASP Conf. Ser. 1996, 101:424
[16] http://www.sdss.org/background/telescope. html
[17] D. W. Evans, M. J. Irwin, and L. Helmer . A&A, 2002,347:348
[18] Rabinowitz. D, Baltay. C, Emmet. W et al. American Astronomical Society Meeting, 2003, No. 38, 12
[19] Elliott P. Horch, Zoran Ninkov, Robert ff. Slawson. AJ, 1997, 114:5
[20] http://www.bao.ac.cn/kjz/top10/2002/p17.htm
[21] http://www.pmo.ac.cn/tushu/zttxdetail.asp?newsid=456 2004-11-19
[22] Brad K. Gibson, Paul Hickson. MNRAS, 1992,258:543-551
[23] 王庆有，孙学珠．CCD应用技术．天津大学出版社，1993：2-5
[24] 吴建文，姚永强．单片机与嵌入式系统应用，2002，12期
[25] Kavachuk A. private communication, 2004-11-10
[26] Ugeen E. private communication, 2006-12-03
[27] Ronald C. Stone,, Jeffrey R. Pier,, &David G. Monet. AJ, 1999, 118:2488-2502
[28] Tang, Z.H., Wang, S.H., &Jim W.J. 2002, AJ, 123: 125
[29] 刘学富．观测天体物理学．北京：北京师范大学出版社，1996．12
[30] Trujillo. C, AJ, 1998,115:1680
[31] 赵铭．天体测量学导论．北京：中国科技出版社
[32] Ronald C. Stone. 1989, AJ, Vol. 97, p. 1227.
[33] L.H. Auer, W.F. van Atena, 1978 AJ, Vol. 83, p. 531
[34] Hog E. et al. 1999, A&Ap, Vol. 357, p. 367
[2] http://www.driftscan.com/#uebersicht, 2003
[3] D. W. Evans, M. J. Irwin, and L. Helmer . A&A, 2002,347:348
[4] Belizon. F, Muinos. J. L, Vallejo. M et al. AdeLA Publications Series, 2003,1:61-63
[5] B. Viateau, Y. Requieme, J. F. Le Campion et al. A&A, 1999,134:173-186
[6] http://www.nofs.navy.mil/about_NOFS/telescopes/fastt. html, 1999, 3
[7] Ronald C. Stone, David G. Monet, Alice K. B et al. AJ, 2003, 126:2060-2065
[8] Ronald C. Stone. AJ, 1998, 506:93-96
[9] Garcia. L. A, Salas. B. E, Gomez. F et al. Information Bulletin on Variable Stars, 2003, No. 5455,1.
[10] http://www.mao.nikolaev.ua/
[11] Pinigin. G. I, Kovalchuk. A. N, Protsyuk. Y. I et al. Astronomische Gesellschaft Abstract Series, 2001, 18:23
[12] C. N. Sabbey, P. Coppi, and A. Oemler. PASP, 1998, 110:1067-1068
[13] C. Baltay, J. A. Snyder, P. Andrews et al. PASP, 2002,114:780-794
[14] http://www.cida.ve/des_quest.html 2000,11
[15] Tom Nicinski. ASP Conf. Ser. 1996, 101:424
[16] http://www.sdss.org/background/telescope. html
[17] D. W. Evans, M. J. Irwin, and L. Helmer . A&A, 2002,347:348
[18] Rabinowitz. D, Baltay. C, Emmet. W et al. American Astronomical Society Meeting, 2003, No. 38, 12
[19] Elliott P. Horch, Zoran Ninkov, Robert ff. Slawson. AJ, 1997, 114:5
[20] http://www.bao.ac.cn/kjz/top10/2002/p17.htm
[21] http://www.pmo.ac.cn/tushu/zttxdetail.asp?newsid=456 2004-11-19
[22] Brad K. Gibson, Paul Hickson. MNRAS, 1992,258:543-551
[23] 王庆有，孙学珠．CCD应用技术．天津大学出版社，1993：2-5
[24] 吴建文，姚永强．单片机与嵌入式系统应用，2002，12期
[25] Kavachuk A. private communication, 2004-11-10
[26] Ugeen E. private communication, 2006-12-03
[27] Ronald C. Stone,, Jeffrey R. Pier,, &David G. Monet. AJ, 1999, 118:2488-2502
[28] Tang, Z.H., Wang, S.H., &Jim W.J. 2002, AJ, 123: 125
[29] 刘学富．观测天体物理学．北京：北京师范大学出版社，1996．12
[30] Trujillo. C, AJ, 1998,115:1680
[31] 赵铭．天体测量学导论．北京：中国科技出版社
[32] Ronald C. Stone. 1989, AJ, Vol. 97, p. 1227.
[33] L.H. Auer, W.F. van Atena, 1978 AJ, Vol. 83, p. 531
[34] Hog E. et al. 1999, A&Ap, Vol. 357, p. 367
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