“嫦娥二號”平動點和小行星探測試驗中的軌道計算

曹建峰

(中國科學(xué)院上海天文臺上海200030)

“嫦娥二號”平動點和小行星探測試驗中的軌道計算

曹建峰?

(中國科學(xué)院上海天文臺上海200030)

論文以CE-2(嫦娥二號)平動點飛行試驗、小行星探測試驗以及YH-1火星探測任務(wù)為背景,對深空探測測定軌技術(shù)開展研究.相關(guān)研究成果直接為小行星圖塔蒂斯探測試驗的拍照成像提供了高精度的軌道支持.針對YH-1火星探測開展了先期的測定軌研究,研究成果雖未能直接應(yīng)用于火星探測任務(wù),但積累的理論知識可服務(wù)于我國后續(xù)深空探測.論文的研究可以概括為以下幾個方面：

(1)回顧統(tǒng)計定軌理論,簡單介紹了時空參考系、動力學(xué)模型、估值方法及考察協(xié)方差理論.

(2)開展深空探測的觀測建模研究.基于理論分析,推導(dǎo)建立測距、多普勒以及VLBI(Very Long Baseline Interferometry)等觀測類型的測量模型.在觀測模型建立過程中對算法進(jìn)行優(yōu)化,在保證計算精度的同時,提高了計算效率.此外,針對嫦娥衛(wèi)星巡航飛行階段自旋穩(wěn)定的特點,建立了測量數(shù)據(jù)的自旋修正模型,既滿足了數(shù)據(jù)修正的需求,亦可實現(xiàn)天線安裝位置的估算.

(3)對CE-2平動點飛行試驗期間積分中心選取的問題進(jìn)行了研究,基于理論推導(dǎo),得出選取地球作為積分中心開展軌道計算更適合的結(jié)論.針對平動點飛行試驗期間的軌道計算,建立了真實力模型下空固坐標(biāo)系與會合坐標(biāo)系的轉(zhuǎn)換關(guān)系;構(gòu)建了對流層延遲修正的平均效應(yīng)模型,實現(xiàn)了CE-2在平動點飛行階段全程2–10 km、在平穩(wěn)飛行階段優(yōu)于5 km的定軌精度,為CE-2平動點飛行試驗提供了精確軌道支持.

(4)對CE-2小行星探測試驗的軌道計算開展了研究,為探測試驗小行星清晰成像提供精確軌道支持.交會前兩次軌道修正僅有13 d間隔,而小行星清晰成像要求軌道精度優(yōu)于15 km.針對控后弧段有限的特點,建立了融合軌控前后測軌數(shù)據(jù)進(jìn)行軌道計算的策略,實現(xiàn)了控后12 d優(yōu)于10 km的定軌精度.

(5)針對早期YH-1火星探測任務(wù)開展了仿真計算,分析了影響定軌精度的主要誤差源和當(dāng)前測控條件下YH-1可能的定軌計算能力,先期的研究工作可為后續(xù)的自主火星探測提供支持.對上海天文臺跟蹤的MEX(Mars Express)測軌數(shù)據(jù)進(jìn)行處理分析,解算的軌道與ESA(European Space Agency)精密軌道偏差百米量級,驗證了深空探測觀測模型、動力學(xué)模型的準(zhǔn)確性以及定軌軟件的能力.

Setting within the context of the flight trial of CE-2(Chang’e 2)around the Sunterrestrial libration point,the asteroid exploration as well as the YH-1 Mars explorationmission,this paper conducted various related studies on orbit determination techniques for deep space exploration.The research results provided high-precision orbit support for the successful photographing of the Toutatis.This paper also carried out preliminary orbit determination studies on YH-1 mission.Although the study findings can not be used directly in the Mars exploration mission,they can still be useful for the future explorations.This thesis is composed of the following five aspects.

(1)Reviewed the statistical orbit determination theory,and gave a description of the spatiotemporal frame of reference,dynamical model issues,methods of estimation,perturbation analysis theory,as well as the algorithms for considering covariance analysis.

(2)Developed the observational model for the deep space exploration.Based on theoretical analysis,the models of ranging,ranging rate,and VLBI(Very Long Baseline Interferometry)are derived.During the modeling process,the algorithm is optimized to improve the computational efficiency without deteriorating the accuracy.In addition,with the spin-stabilized characteristic of CE-2 in its cruise phase taken into consideration,a spin stabilization correction model of the tracking data is constructed,which not only meets the requirement of data correction,but also can estimate the alignment of antenna.

(3)Carried out a study on the selection of integration center for CE-2 libration flight trial.The result shows that the Earth is most suitable for orbital prediction.A precise satellite ephemeris for CE-2’s flight trial is provided.The transformation relation between the spatial- fixed coordinate system and the rotation coordinate system is constructed.An orbital accuracy of 2–10 km in the whole flight process and 5 km for the stable flight phase are achieved based on an overlap comparison.

(4)Provided orbit support for CE-2’s asteroid exploration.Under the circumstances that only 13 days are left between the last two orbit maneuvers before the encounter,and an accuracy of better than 15 km is required for the target photographing,an orbit determination strategy incorporating pre-and post-maneuver tracking data is developed,which achieved an orbit determination accuracy of 10 km,and presented a calibration basis for velocity increment during the maneuver.

(5)Performed YH-1 Mars exploration simulation,and analyzed the major error sources a ff ecting the orbit determination accuracy.The YH-1’s possible orbit determination ability under the current tracking capacity is also studied.These researches can provide support for the subsequent Mars exploration.In addition,the Mars Express tracking data from Shanghai Astronomical Observatory are processed and calculated,and the position discrepancy between the orbit thus obtained and European Space Agency’s orbit is of the order of several hundred meters.This trial tested the accuracy of the observation model,dynamical model,and the ability of orbit determination software for deep space exploration.

Orbit Determination for CE-2 Libration Flight and Asteroid Exploration Trial

CAO Jian-feng
(Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai 200030)

10.15940/j.cnki.0001-5245.2016.01.012 博士學(xué)位論文摘要選登

?2013-07-07獲得博士學(xué)位,導(dǎo)師:上海天文臺胡小工研究員;jfcao@foxmail.com