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光学系统的最小分辨角与口径成反比,集光能力与口径的平方成正比,因此,增大口径对于天文观测及暗弱目标识别至关重要。采用可展开空间望远镜技术建造分块式大口径空间光学望远镜,对空间天文观测等太空探索活动具有重大意义。
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由美国航空航天局牵头研制的詹姆斯·韦伯空间望远镜(James Webb Space Telescope, JWST)作为目前世界上采用空间分块可展开成像技术的唯一工程化项目,受到广泛关注。JWST是工作于日地第二拉格朗日点(L2)附近轨道的低温红外天文望远镜,探测谱段为0.6~28.5 μm,在2 μm波段达到角分辨率0.1″的衍射极限,主要用于研究星系、恒星和行星系统的起源和演化[3-4]。
JWST光学望远镜为三反射镜消像差系统,由主镜、次镜、三镜和精密转向镜等组成[5]。分块式可展开主镜由18块边到边距离约为1.3 m的六边形铍质子镜拼接而成,由一对铰链和每个主镜翼(两侧各一)上四个闩锁组成的主镜展开机构[6]在发射时折叠收拢,入轨后展开锁定,将两侧子镜(每侧三个)机械调整入位。借助波前传感与控制技术[7]完成18块子镜的共焦共相。展开后的主镜等效为口径6.5 m的圆形镜片,集光面积达到25 m2,如图1(a)所示。
图 1 (a) JWST展开后的主镜;(b) JWST在轨展开过程
Figure 1. (a) JWST primary mirror deployed; (b) Deployment sequence of JWST in orbit
JWST次镜展开机构为步进电机驱动的可展开三脚支架型四连杆机构,包含具有两个刚性支柱和一个带有驱动及闩锁机构的铰接支柱。发射时,次镜展开机构折叠固定在望远镜主背板结构上;入轨展开阶段,通过“解锁-展开-锁定”的展开流程,完成次镜部件的高精度展开和可靠支撑。此外,超低热膨胀系数复合材料的支撑连杆具有较高的轻量化率和优异的力热稳定性能,已经顺利通过了发射前次镜展开机构的重力卸载式展开测试[8]。
精密转向镜提供精确的指向和成像稳定度[9]。采用大面积可展开遮阳板[10]与被动制冷相结合的热控方式。JWST入轨后的整个展开过程如图1(b)所示。
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大型紫外/光学/红外巡天望远镜(Large UV/Optical/IR Surveyor, LUVOIR)是一种在概念和设计上与JWST相似的可展开空间天文望远镜[11]。目前,LUVOIR望远镜有两个设计方案,LUVOIR-A是一个同轴的15 m口径分块拼接式望远镜,其主镜由120块边到边尺寸为1.223 m的子镜组成。LUVOIR-B是一个离轴的8 m口径分块拼接式望远镜,其主镜由55块边到边尺寸为0.955 m的子镜组成。图2(a)和图2(b)分别为折叠和展开状态下的LUVOIR-A、LUVOIR-B望远镜。
图 2 (a) LUVOIR-A和(b) LUVOIR-B折叠及展开状态[12]
Figure 2. Stowed and deployed configurations of LUVOIR-A (a) and LUVOIR-B (b)
LUVOIR使用与JWST相同的“翼形折叠”概念[13],将主镜包裹在中央仪器柱周围。LUVOIR-A在主镜的每一侧都有两条铰链线,而由于搭载的火箭整流罩更小,LUVOIR-B每一侧有三条铰链线,使折叠的主镜可以更接近圆柱形,从而可以更有效地利用整流罩空间。
LUVOIR两种方案的次镜展开机构存在较大差异。LUVOIR-A使用与JWST类似的设计,次镜向上折叠并位于主镜后面。而LUVOIR-B因光学系统无遮拦的要求,使用单个桁架结构。三块平板展开并闩锁在一起,形成坚固的三角形横截面梁。
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空间光学高分辨率对地观测已经成为国防安全、地图测绘、资源普查、环保减灾和城市规划等军民用领域获取信息的重要手段。分块式可展开对地观测望远镜主要指分块式可展开主镜望远镜,往往也同时涉及次镜的展开。分块式可展开对地观测望远镜增大了光学系统的焦距和孔径,能有效提高空间分辨率。
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由美国国防部负责开发的分块反射镜望远镜(Segmented Mirror Telescope, SMT)展示了发展大型空间拼接反射镜的关键技术,包括轻量化主动反射镜、展开机构以及波前传感和控制技术[14-15]。SMT采用卡塞格林光学结构,3 m口径主镜由六块1 m口径碳化硅材料六边形子反射镜拼接而成。每块主动子镜均为一种采用平行致动原理的能动混合镜,能够提供校正子镜镜面局部和全局面形的高致动能力。SMT原理样机如图3所示。
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欧洲宇航局提出了高轨光学合成孔径监视成像卫星(High Orbit optical Aperture Synthesis Instrument for Surveillance, HOASIS)项目[16-19],在地球静止轨道以2 m超高分辨率实现每天一次覆盖欧洲的例行调查和对特定区域的应急观测,如图4(a)所示。光学系统采用Korsch型光学合成孔径方案,焦距108 m,视场角0.1°,成像谱段覆盖全色、多光谱、中波红外(Mid-Wave Infrared, MWIR)和长波红外(Long-Wave Infrared, LWIR)。等效口径为7 m的可展开主镜由六块直径为2 m的子镜拼接而成,发射时子镜通过铰链向内折叠,以适配Ariane-5运载火箭,如图4(b)所示。主镜子镜和次镜均包含纳米级五自由度(Degree of Freedom, DOF)调节机构,用于实现子镜展开后主镜和次镜的精确定位。提出了调制传递函数(Modulation Transfer Function, MTF)与信噪比乘积优于4的成像质量要求。
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法国泰雷兹阿莱尼亚宇航公司提出了面向未来对地观测及科学任务的可展开系统主动光学(Active Optics in Deployable Systems, AODS)研究项目[20],如图5所示。该项目旨在评估将主动光学技术应用于对地观测(比如地球静止轨道高分辨率成像)和科学任务(比如类地系外行星成像及表征)所需的大型可展开系统校正的可行性。次镜的展开方案基于带状弹簧展开技术[21-23],具有折叠状态下次镜直接固定在中央主结构上的形式简单、展开状态下相比铰接梁更低的阻塞及卡死风险,以及展开过程平稳可控等优点。与同样是六边形子镜拼接主镜的JWST不同,该项目主镜采用整体对半折叠方式。相比铰接式折叠杆的优势是,支撑次镜的三根直径120 mm带状弹簧可弯曲以适应折叠位置,并且能够在三个方向(piston/tip/tilt)进行主动校正。主镜子镜边到边距离为1.38 m,背部安装有校正系统,确保系统全局波前误差优于38 nm (RMS)。
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荷兰代尔夫特理工大学(TU Delft)可展开空间望远镜(Deployable Space Telescope, DST)旨在大幅降低高分辨率对地观测望远镜的发射成本,以满足更高时间分辨率和更低价格遥感数据的市场需求[24-25]。DST光学系统为斐索型合成孔径环形视场Korsch三反消像差系统,如图6所示。设计轨道高度为500 km,地元分辨率为0.25 m,衍射极限为550 nm,展开后孔径为1.5 m。四块主镜子镜的材料选择为碳化硅,可在最为关键的piston/tip/tilt三个方向致动,通过主镜支撑结构连接到望远镜主框架。次镜展开机构由四个展开臂组成[26]。每个展开臂均通过柔性滚动单元铰链连接至望远镜主体和望远镜最前端的次镜十字框架,展开臂和柔性滚动单元铰链确保了次镜十字框架的稳定性。碳纤维复合材料展开臂主要利用应变能进行展开,具有质量轻、复杂性低、精度高和重复性好,以及优异的热性能等优点。
为了限制热环境变化导致的光学支撑结构变形,同时满足质量和体积要求,设置了可展开遮光罩[27]。可展开遮光罩由可充气臂的支撑结构组成,该支撑结构被隔热多层材料完全包围。可充气臂由铝卡普顿层合薄膜制成,由四个冷气体发生器产生的氮气使该结构膨胀。
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英国天文技术中心提出在3U(1U为10 cm×10 cm×10 cm,下同)立方体卫星上实现高分辨率可展开成像系统HighRes[28],该系统由四瓣拼接主镜构成的卡塞格林望远镜形成等效口径300 mm的可展开望远镜,如图7所示。该系统在全视场内达到衍射极限性能,可在500 km轨道高度上获得0.92 m的全色地元分辨率。主镜子镜的对准和共相根据焦面锐度信息来完成,通过数值仿真进行了验证,表明在压电驱动丝杠电机和电容传感器测量系统之间采用闭环反馈控制手段,可以将反射镜以25 nm的精度驱动到所需共相位置[29-30]。
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麻省理工学院可展开空间相干成像望远镜(The Deployable In-Space Coherent Imaging Telescope, DISCIT)项目旨在开发一种口径为700 mm的可展开稀疏孔径望远镜[31],通过四块子镜的展开以实现700 mm的成像基线,从而在500 km轨道高度上获得0.5 m分辨率的图像,如图8(a)和8(b)所示。DISCIT使用柔性复合材料铰链进行主镜子镜的展开和初步定位[32-34],该铰链可以实现优于10 μm的piston轴向位置重复精度以及优于100 μrad的tip/tilt角度重复性。其次,通过位于每个复合铰链及其主镜子镜之间的三个压电致动器,使用基于图像的闭环校准方法对子镜进行共相。图8(c)和图8(d)分别为折叠及展开状态的铰链。
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德国布伦瑞克工业大学与弗劳恩霍夫协会层和表面技术研究所等提出的超轻型稳健航天器结构光学涂层[35](Optical Coatings for Ultra Lightweight Robust Spacecraft Structures, OCULUS)项目的目标是开发一种高质量的金属化工艺,用于对高精度碳纤维增强塑料(Carbon Fiber Reinforced Plastic, CFRP)结构进行表面改性[36]。该技术可以构建适于空间环境、超轻质量且经济高效的反射镜,并将演示小型空间望远镜概念。提出的OCULUS-Cube验证卫星基于1U立方星平台,采用R-C光学系统[37],400 km轨道高度地元分辨率为1.2 m。超高模量碳纤维主镜设计为四块子镜可展开结构,拼接口径达260 mm。每块子镜由两个压缩弹簧驱动展开,相比扭力弹簧能够将子镜更好地保持居中。子镜tilt通过堆栈压电致动器进行调节。四台压电旋转致动器驱动弹簧臂杆系统以展开次镜,通过调节超高分子量聚乙烯绳索的长度来调整次镜的位姿。图9(a)为零重力环境下展开概念示意图,图9(b)为主镜子镜压缩弹簧驱动机构。
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美国犹他州立大学研制的可展开瓣式望远镜(Deployable Petal Telescope, DPT)[38]采用272 mm焦距的卡塞格林光学系统。为缩小发射体积并提高望远镜成像质量,研制了适于3U立方星平台的可展开四瓣式主镜展开机构和次镜展开机构,如图10所示。主镜的折叠由拔销器这类非爆炸致动器提供锁紧力,展开由机械弹簧通过张紧的绳索传递提供驱动力。子镜的最终定位由子镜和支撑底座之间的半运动学支承控制,机械弹簧力将子镜保持在展开位置,这种被动对准系统降低了对准的成本和复杂性。与主镜机构类似,次镜的展开机构同样由机械弹簧系统提供驱动力,利用阻尼使展开速度维持在较低水平,由运动学定位支承提供高度可重复且准确的定位。可展开次镜能够减小望远镜发射体积,望远镜长度降幅接近50%,最终总长为175 mm。
可展开主镜和次镜的对准重复性测量实验[39]显示能够在长焦距卡塞格林光学配置中支持可见光成像。结合200 mm孔径可展开瓣式望远镜和先进商用组件的概念性光学立方星能够达到1.5 m地元分辨率,信噪比接近70。
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波兰SatRevolution公司联合波兰弗罗茨瓦夫理工大学等机构提出了实时对地观测星座(Real-time Earth-observation Constellation, REC)项目[40-41],旨在建立轻小型、低成本且重访时间短的对地观测纳卫星星座,最终目标是通过在300~350 km的低地球轨道上部署一千多颗立方星ScopeSat,以同时优于1 m的分辨率实现30 min的刷新率。纳卫星折叠状态下的整体尺寸不超过7U,其中2U或3U空间设计为模块化可展开望远镜DeploScope。光学系统采用包括主次镜和三镜等的卡塞格林系统,结合全视场Korsch设计和分块式主镜形成的斐索型合成孔径配置克服了像差和视场狭窄的问题。碳化硅主镜借助伸缩杆的作用力进行展开,子镜在三个轴向的定位调整能力将导致连续的波前校正。通过使用高精度微机电系统致动器对次镜进行姿态调整。图11为折叠及展开状态的主镜。
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光轴方向可展开光学望远镜一般是基于微纳卫星平台设计,目的是沿其光轴展开次镜,以便突破卫星有限的空间对光学系统主次镜间距的限制。事实上,这类以可展开主次镜间连接结构为主的展开机构,其整体质量通常并不轻于传统非展开式刚性结构,但伸缩式展开机构的折叠尺寸明显比传统形式缩小一半以上,显示出较好的空间利用效果。
随着商业航天的蓬勃发展和光学遥感数据的需求增长,光轴方向可展开微纳卫星光学望远镜作为一种展开形式相对简单的技术验证及应用载荷,受到众多大学院所和商业航天公司等机构的高度关注。
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日本遥感与创新太空任务皮卫星(Pico-satellite for Remote-sensing and Innovative Space Missions, PRISM)是公开报道中唯一一个已被证实成功发射的可展开光学卫星。这颗由东京大学牵头研制的8.5 kg遥感卫星于2009年1月发射升空[42],成功进入660 km高度的太阳同步轨道,其主要任务是通过利用超小型卫星实现高分辨率遥感,对具有柔性可展开臂的紧凑型光学系统进行技术演示[43],如图12(a)所示。PRISM是一种孔径为90 mm的折射系统,光学系统采用镀有紫外防护膜的萤石复消色差镜组,焦距为500 mm,地元分辨率为30 m[44]。镜组和可展开臂的总质量仅为2 kg。望远镜从收缩状态到展开状态,可展开臂通过主动控制系统从10 cm伸展到80 cm。可展开臂由柔性材料制成,只需通过内部弹力进行展开,而不需要任何机械致动器。玻璃纤维增强塑料(Glass Fiber Reinforced Polymer, GFRP)框架起到螺旋弹簧的作用[45],当展开结构时,推出透镜及遮光罩,如图12(b)所示。遮光罩起到抑制杂光和一定程度的热防护作用。探测器阵列安装在调焦机构上,以校正由柔性可展开臂引起的对焦误差。
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可折叠多布森空间望远镜(Collapsible Dobson Space Telescope, CDST)是美国航空航天局埃姆斯研究中心提出的小型可展开空间望远镜项目[46],以确定在10 kg级6U纳卫星上使用150~200 mm孔径进行对地观测的可行性,如图13所示。CDST将完全容纳在20 cm×20 cm×10 cm的纳卫星有效载荷包络空间内,采用口径为152.4 mm的整体式主镜,R-C光学系统在完全展开后具有F/8的目标孔径。次镜由五根复合材料矩形杆(盘绕式纵梁)组成的盘绕式伸展臂支撑展开。伸展臂能够提供展开所需的大部分应变能,并在沿纵梁的枢轴点处连接到三个铝环上。超高分子量聚乙烯纤维索通过每个纵梁与铝环铰链接口处的各枢轴点馈入。通过电机驱动线轴来控制展开速度,并通过使用线性弹簧向线轴施加扭矩来将最终张力施加到纤维索上,一旦纵梁的大部分应变能释放,该线性弹簧就会在线轴机构的止动装置中释放[47]。
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英国萨里(Surrey)大学联合萨里卫星技术有限公司等机构正开发一种新型可自动校准的可展开空间望远镜,以满足微小卫星优于1 m地元分辨率的要求[48]。望远镜采用卡塞格林光学系统,通过伸缩式大直径同轴套筒机构将次镜精确、可重复且低冲击地展开750 mm,展开的套筒机构同时充当遮光罩起到抑制杂光的作用,如图14(a)和图14(b)所示。
图 14 (a)折叠状态;(b)展开状态;(c)部件的运动方向
Figure 14. (a) Stowed configuration; (b) Deployed configuration; (c) Movement directions of components
展开机构包括三个同轴的碳纤维套筒,每个套筒的顶部和底部均有法兰,以增加刚度并提供展开机构安装接口。最下部且最窄的套筒安装在与卫星接口的隔板上。发射入轨后,中部和最上部的套筒以及两个碳纤维环,在圆周上相距120°布置的三根丝杠的传动作用以及拉齐成型工艺碳纤维管的导引作用下同时展开。该丝杠由环形齿轮和基座上的单台电机驱动,如图14(c)所示。碳纤维环为多层绝热材料提供安装表面,同时为丝杠的顶部提供支撑[49]。展开的套筒被驱动到几处V型块进行限位,以提高位置重复性。
在套筒和次镜之间设计有三个相同的精细对准机构,基于形状记忆合金的压紧释放机构(Hold Down and Release Mechanism, HDRM)用于确保发射过程中次镜和遮光罩等零件的安全。展开重复性测试显示出展开机构各轴向优于1 mm的较高展开可重复性,并且满足刚度要求,从而能够避免平台微振动引起的图像失真[50]。
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奥克兰(Auckland)大学研发了一种适用于卡塞格林系统空间望远镜(Deployable Optics for CubeSats, DOC)的可展开镜筒[51],如图15(a)所示。镜筒一端安装90 mm口径主镜,另一端支撑次镜。镜筒的三个同轴空心圆筒通过伸缩方式折叠和展开。要求以任一轴向优于0.1 mm的可重复能力将次镜沿着光轴方向展开到距离主镜250 mm的位置。为了保持所需的形状稳定性,主要结构部件由热稳定材料制成,并具有对准和锁定功能。作为展开机构的驱动元件,无需电能输入的弹簧马达驱动穿过镜筒的绳索,且无需机械齿轮,从而避免了空回和微动力学问题。绳索由凯夫拉尔纤维制成,具有高强度、恶劣条件下一般的耐久性和较低的真空出气等优点。图15(b)所示为安装在主镜后面的弹簧马达。在微重力环境下,展开望远镜所需的扭矩极小,仅需克服绳索中的摩擦力和镜筒之间的滑移作用。采用3D打印技术制造了一台1∶1的尼龙材质原理样机,确认了展开机构的整体可行性[52]。
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韩国航空大学提出一种促进卫星小型化的可展开空间望远镜高精度展开机构[53-54]。被动展开机构主要由分别安装主次镜的上下面板、用于连接两个面板的八根定制连杆、用于驱动机构的四个弹簧铰链和用于防止连杆扭曲的八个支撑模块组成[55]。图16所示为展开机构的工作原理。在折叠状态下,弹簧铰链的恢复力被分离装置抑制。当分离装置释放展开时,连杆通过四个弹簧铰链的恢复力展开。
锥形连杆、球形柱塞和闩锁装置能够提高对准精度,减少偏心、倾斜和间隙对准误差。通过理论分析和原理样机制造,设计并制造重力补偿的测量平台,测量了可能在轨道上发生的对准误差。使用由五个基于非接触激光位移传感器的测量平台,对展开机构的对准性能进行了实验研究。
综上,目前国外已发射或在研的可展开空间光学望远镜部分典型项目的基本信息如表1所示。
表 1 国外可展开空间光学望远镜部分典型项目
Table 1. Some typical projects of foreign deployable space optical telescopes
Project Application Country Launch time Working spectrum Aperture/m Spatial resolution Mass/kg Adjustment ability JWST Astrophysics USA 2021 0.6-28.5 μm 6.5 0.1" 6200 Six DOFs + radius of curvature LUVOIR-A Astrophysics USA 2039 0.1-2.5 μm 15 ≤16 milli-arcseconds at 500 nm 27801 Six DOFs positioning LUVOIR-B Astrophysics USA 2039 0.1-2.5 μm 8 ≤16 milli-arcseconds at 500 nm 15132 Six DOFs positioning SMT EO USA — 0.4-0.7 μm 3 — — Six DOFs + face sheet actuation HOASIS EO ESA — 0.45-0.79 μm,
MWIR, LWIR7 2 m@36000 km 8662 Five DOFs AODS EO and Science France — — ~17 — — Piston/tip/tilt TU Delft DST EO Netherlands — 0.45-0.7 μm 1.5 0.25 m@500 km <100 Piston/tip/tilt HighRes EO United Kingdom — Visible 0.3 0.92 m@500 km 8 Piston/tip/tilt DISCIT EO USA — 0.39-0.7 μm 0.7 0.5 m@500 km ~17 Piston/tip/tilt OCULUS EO Germany — — 0.26 1.2 m@400 km — Tilt DPT EO USA — Visible 0.2 1.3 m@500 km — Tilt ScopeSat EO Poland 2023 Visible — <1 m@300-350 km 10 Piston/tip/tilt PRISM EO Japan 2009 Visible 0.09 30 m@660 km 8.5 — CDST EO USA — Visible 0.152 1.2 m@250 km 10 Piston/tip/tilt of the secondary mirror Surrey DST EO USA — Visible 0.3 1 m@500 km <100 Piston/tip/tilt of the secondary mirror Auckland DOC EO New Zealand — Visible 0.09 — — — -
中国科学院长春光学精密机械与物理研究所董吉洪等人[56]提出了主镜展开机构设计思路和设计要点,并给出了4 m口径主镜可展开空间望远镜的设计方案。左玉弟等人[57]针对某光学系统设计了一种基于带状弹簧的新型空间望远镜自展开机构,开展了原理样机展开实验。杨会生等人[58-61]提出了8 m口径可展开合成孔径光学系统方案,主镜由10块直径1.9 m的碳化硅圆形反射镜子镜拼接而成,每块子镜通过六自由度刚体运动致动器进行调节和共相。并对空间甚大口径分体自重组式主镜系统的关键技术进行了研究,建立了定值共相误差影响的分析理论,对主镜共相精度公差进行了合理分配及优化[62]。张龙[63]开展了缩比验证系统的共相调整试验验证,搭建了拼接式主镜卡塞格林系统波前探测实验平台,验证了基于斐索干涉仪共相探测技术的可行性。
北京空间飞行器总体设计部Ni Yanshuo等人[64]设计了一种用于次镜展开的四连杆机构,以满足天基光学遥感系统的高精度在轨展开要求。采用有限元方法对锁紧状态下的整体热变形进行了模拟,分析了四连杆机构在轨道上的重复展开精度。此外,Zhang Shuyang等人[65]基于带有主动锁紧装置的开尔文支承设计了一种高精度展开机构,以满足新型有效载荷在轨展开重复定位精度达到0.005°的要求。并进行了理论分析、仿真分析和原理样机测试。
中国科学院西安光学精密机械研究所李创等人针对可展开空间望远镜技术进行了多项研究。提出了一些不同形式的展开机构、精度调节系统、展开精度测量系统等,主要包括三点六足式带弹簧次镜展开机构[66-67]、盘绕式碳纤维杆次镜自展开结构[68]、基于形状记忆合金的锁紧释放机构[69-70]、基于Stewart平台的次镜六自由度调节机构[71]和基于位置敏感探测器的次镜展开机构对准检测系统[72]等,并开展了原理样机成像试验。
苏州大学王振坤等人[73-74]研究了一种无主动光学系统,可快速精准展开,适用于3U立方星的高分辨率空间相机光学系统,给出了十字形四矩形稀疏孔径光瞳函数和MTF的解析表达式,提出了平均MTF曲线等适用于非圆对称光瞳结构的MTF评价指标,进行了孔径结构形状参数优化和力学仿真分析。
综合来看,国内对于空间光学望远镜的主镜展开进行了一些概念研究、初步设计和样机实验。在分块式可展开对地观测望远镜的主镜展开机构,以及光轴方向可展开微纳卫星光学望远镜涉及到的次镜展开机构和可展开遮光罩等方面进行了设计研究和实验探索,取得了一定的科研成果。但是不难看出,与国外相比,国内在这一领域的起步较晚,发展水平还有差距,实现工程化的成果尚未见报道。
Development and prospects of deployable space optical telescope technology
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摘要: 为了获得更高的角分辨率,空间光学望远镜的口径越来越大,口径超过4 m的空间望远镜将难以突破现有运载火箭整流罩有效包络的限制。另一方面,在研制周期及成本等方面拥有较大优势的微纳光学遥感卫星也对提高空间分辨率和集光面积有广泛的需求,需要在较小的发射体积里容纳下较大的光机系统,以降低发射成本。可展开空间光学望远镜将成为解决发射尺寸受限的可行方式。从大口径空间天文望远镜、分块式可展开对地观测望远镜和光轴方向可展开微纳卫星光学望远镜等方面对国内外可展开空间光学望远镜的研究现状进行了综述。对可展开空间光学望远镜涉及到的一些关键技术和发展趋势进行了阐述和归纳。Abstract: In order to obtain higher angular resolution, the aperture of the space optical telescope is getting larger and larger, and the space telescope with aperture of more than four meters will be difficult to break through the limitation of the effective envelope of the fairing of the existing launch vehicle. On the other hand, the micro-nano optical remote sensing satellite, which has great advantages in terms of development cycle and cost, also has extensive requirements for improving spatial resolution and light gathering area, requiring a smaller launch volume to accommodate a large opto-mechanical system to reduce the launch cost. Deployable space telescopes will be a feasible solution to overcome the limitations of launch size. The research status of deployable space telescopes was reviewed from the aspects of large aperture space astronomical telescopes, segmented mirror deployable telescopes for earth observation and micro-nano satellite optical telescopes deploying along optical axis. Some key technologies and development trends involved in deployable space telescopes were described and summarized.
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图 2 (a) LUVOIR-A和(b) LUVOIR-B折叠及展开状态[12]
Figure 2. Stowed and deployed configurations of LUVOIR-A (a) and LUVOIR-B (b)
表 1 国外可展开空间光学望远镜部分典型项目
Table 1. Some typical projects of foreign deployable space optical telescopes
Project Application Country Launch time Working spectrum Aperture/m Spatial resolution Mass/kg Adjustment ability JWST Astrophysics USA 2021 0.6-28.5 μm 6.5 0.1" 6200 Six DOFs + radius of curvature LUVOIR-A Astrophysics USA 2039 0.1-2.5 μm 15 ≤16 milli-arcseconds at 500 nm 27801 Six DOFs positioning LUVOIR-B Astrophysics USA 2039 0.1-2.5 μm 8 ≤16 milli-arcseconds at 500 nm 15132 Six DOFs positioning SMT EO USA — 0.4-0.7 μm 3 — — Six DOFs + face sheet actuation HOASIS EO ESA — 0.45-0.79 μm,
MWIR, LWIR7 2 m@36000 km 8662 Five DOFs AODS EO and Science France — — ~17 — — Piston/tip/tilt TU Delft DST EO Netherlands — 0.45-0.7 μm 1.5 0.25 m@500 km <100 Piston/tip/tilt HighRes EO United Kingdom — Visible 0.3 0.92 m@500 km 8 Piston/tip/tilt DISCIT EO USA — 0.39-0.7 μm 0.7 0.5 m@500 km ~17 Piston/tip/tilt OCULUS EO Germany — — 0.26 1.2 m@400 km — Tilt DPT EO USA — Visible 0.2 1.3 m@500 km — Tilt ScopeSat EO Poland 2023 Visible — <1 m@300-350 km 10 Piston/tip/tilt PRISM EO Japan 2009 Visible 0.09 30 m@660 km 8.5 — CDST EO USA — Visible 0.152 1.2 m@250 km 10 Piston/tip/tilt of the secondary mirror Surrey DST EO USA — Visible 0.3 1 m@500 km <100 Piston/tip/tilt of the secondary mirror Auckland DOC EO New Zealand — Visible 0.09 — — — -
[1] Lillie C F. Large deployable telescopes for future space observatories [C]//UV/Optical/IR Space Telescopes: Innovative Technologies and Concepts II, 2005, 5899: 58990D. [2] Zhang Xuejun, Fan Yanchao, Bao He, et al. Applications and development of ultra large aperture space optical remote sensor [J]. Optics and Precision Engineering, 2016, 24(11): 2613-2626. (in Chinese) doi: 10.3788/OPE.20162411.2613 [3] Greenhouse M A. The JWST science instrument payload: mission context and status [C]//UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts VI, 2013, 8860: 886004. [4] Sabelhaus P A, Decker J E. An overview of the James Webb Space Telescope (JWST) project [C]//Optical, Infrared, and Millimeter Space Telescopes, 2004, 5487: 550-563. [5] Clampin M. Status of the James Webb space telescope observatory [C]//Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, 2012, 8442: 84422A. [6] Reynolds P, Atkinson C, Gliman L. Design and development of the primary and secondary mirror deployment systems for the cryogenic JWST [C]//37th Aerospace Mechanisms Symposium, 2004: 29-44. [7] Acton D S, Knight J S, Contos A, et al. Wavefront sensing and controls for the James Webb space telescope [C]//Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, 2012, 8442: 84422H. [8] Kimble R A, Bowers C W, McElwain M W, et al. Completion of the JWST spacecraft/sunshield and telescope/instrument elements [C]//American Astronomical Society Meeting, 2020, 235: 372-10. [9] Clampin M. Overview of the James Webb space telescope observatory [C]//UV/Optical/IR Space Telescopes and Instruments: Innovative Technologies and Concepts V, 2011, 8146: 814605. [10] Arenberg J, Flynn J, Cohen A, et al. Status of the JWST sunshield and spacecraft [C]//Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 2016, 9904: 990405. [11] The LUVOIR Team. The LUVOIR mission concept study final report [R]. Washington: National Aeronautics and Space Administration, 2019. [12] Park S, Eisenhower M J, Bolcar M R, et al. LUVOIR thermal architecture overview and enabling technologies for picometer-scale WFE stability [C]//2019 IEEE Aerospace Conference, 2019: 1-13. [13] Hylan J E, Bolcar M R, Crooke J, et al. The large UV/Optical/lnfrared surveyor (LUVOIR): decadal mission concept study update [C]//2019 IEEE Aerospace Conference, 2019: 1-15. [14] Allen M R, Kim J J, Agrawal B N. Correction of an active space telescope mirror using a deformable mirror in a woofer-tweeter configuration [J]. Journal of Astronomical Telescopes, Instruments, and Systems, 2016, 2(2): 029001. doi: 10.1117/1.JATIS.2.2.029001 [15] Watson J J. Correcting surface figure error in imaging satellites using a deformable mirror[D]. Monterey: Naval Postgraduate School, 2013. [16] Mesrine M, Thomas E, Garin S, et al. High resolution earth observation from geostationary orbit by optical aperture synthesys [C]//International Conference on Space Optics, 2006, 10567: 105670B. [17] Aguirre M, Bézy J L. ESA activities related to high resolution imaging from GEO [C]//HR GEO User Consultation Workshop, 2010. [18] Bello U D, Massotti L. ESA studies on HR imaging from geostationary satellites [C]//2nd GEO-HR User Consultation Workshop, 2013. [19] Decourt R. Hoasis: Surveillance à haute résolution depuis l’orbite géostationnaire [EB/OL]. (2013-08-02) [2021-01-01] http://www.futura-sciences.com/magazines/espace/infos/actu/d/astronautique-hoasis-surveillance-haute-resolution-depuis-orbite-geostationnaire-48077/. [20] Behar-Lafenetre S. Active optics in deployable systems for future EO and science missions[R]. Cannes: Thales Alenia Space France SAS, 2020. [21] Marone-Hitz P. Modeling of spatial structures deployed by tape springs: Towards a home-made modeling tool based on rod models with flexible cross sections and asymptotic numerical methods[D]. Marseille: Ecole Centrale Marseille, 2014. [22] Picault E, Bourgeois S, Cochelin B, et al. A new rod model for the folding and deployment of tape springs with highly deformable cross-sections [C]//7th International Conference on Computational Mechanics for Spatial Structures, 2012: 2-83. [23] Picault E, Bourgeois S, Cochelin B, et al. On the folding and deployment of tape springs: A large displacements and large rotations rod model with highly flexible thin-walled cross-sections [C]//53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, 2012: 1956. [24] Dolkens D, Kuiper J M. A deployable telescope for sub-meter resolutions from microsatellite platforms [C]//International Conference on Space Optics, 2014: 10563. [25] Dolkens D, Marrewijk G V, Kuiper H. Active correction system of a deployable telescope for Earth observation [C]//International Conference on Space Optics, 2018, 11180: 111800A. [26] Dolkens D, Kuiper H, Corbacho V V. The deployable telescope: A cutting-edge solution for high spatial and temporal resolved earth observation [J]. Advanced Optical Technologies, 2018, 7(6): 365-376. doi: 10.1515/aot-2018-0043 [27] Arink J W. Thermal-mechanical design of a baffle for the deployable space telescope[D]. Delft: Delft University of Technology, 2019. [28] Schwartz N, Pearson D, Todd S, et al. A segmented deployable primary mirror for earth observation from a CubeSat platform [C]//29th Annual AIAA/USU Conference on Small Satellites, 2016. [29] Schwartz N, Pearson D, Todd S, et al. Laboratory demonstration of an active optics system for high-resolution deployable CubeSat [C]//Small Satellites, System & Services Symposium, 2018. [30] Schwartz N, Brzozowski W, Milanova M, et al. High-resolution deployable CubeSat prototype [C]//Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave, 2020, 11443: 1144331. [31] Silver M J, Echter M A, Reid B M, et al. Precision high strain composite hinges for the deployable in-space coherent imaging telescope [C]//3rd AIAA Spacecraft Structures Conference, 2016: 0969. [32] Silver M, Echter M. Precision high-strain composite hinges for deployable space telescopes [C]//44th Aerospace Mechanisms Symposium, 2018: 417. [33] Echter M A, Silver M J, D'Elia E, et al. Recent developments in precision high strain composite hinges for deployable space telescopes [C]//AIAA Spacecraft Structures Conference, 2018: 0939. [34] Echter M A, Gillmer S R, Silver M J, et al. A multifunctional high strain composite (HSC) hinge for deployable in-space optomechanics [J]. Smart Materials and Structures, 2020, 29(10): 105010. doi: 10.1088/1361-665X/abad4d [35] Stoll E, Mindermann P, Grzesik B, et al. Oculus-Cube – a demonstrator of optical coatings for ultra lightweight robust spacecraft structures [C]//11th IAA Symposium on Small Satellites for Earth Observation, 2017. [36] Grzesik B, Mindermann P, Linke S, et al. Alignment mechanism and system concept of a scalable deployable ultra-lightweight space telescope for a 1U CubeSat demonstrator [C]//68th International Astronautical Congress (IAC), 2017. [37] Grzesik B, Stoll E, De Wit J, et al. Manufacturing and preliminary testing of a scalable deployable ultra-lightweight space telescope[C]//Small Satellites, System & Services Symposium, 2018. [38] Champagne J, Crowther B, Newswander T. Deployable mirror for enhanced imagery suitable for small satellite applications [C]//27th Annual AIAA/USU Conference on Small Satellites, 2013. [39] Champagne J, Hansen S, Newswander T, et al. CubeSat image resolution capabilities with deployable optics and current imaging technology [C]//28th Annual AIAA/USU Conference on Small Satellites, 2014. [40] Łapczyński R. Real-time earth-observation constellation (REC) [C]//ITU Regional Innovation Forum for Europe on Bridging the Digital Innovation Divide, 2018. [41] Graja A, Ćwikła M, Kwapisz P. DeploScope – A modular deployable CubeSat telescope [C]//2018 International Young Scientists and Students Workshop, 2018: 18-24. [42] Tanaka T, Sato Y, Kusakawa Y, et al. The operation results of earth image acquisition using extensible flexible optical telescope of "PRISM" [C]//27th Interlational Symposium on Space Technology and Science, 2009. [43] Sato Y, Kim S K, Kusakawa Y, et al. Extensible flexible optical system for nano-scale remote sensing satellite "PRISM" [C]//Transactions of the Japan Society for Aeronautical and Space Sciences, Space Technology Japan, 2009, 7: Tm_13-18. [44] Inamori T, Shimizu K, Mikawa Y, et al. Attitude stabilization for the nano remote sensing satellite PRISM [J]. Journal of Aerospace Engineering, 2013, 26(3): 594-602. doi: 10.1061/(ASCE)AS.1943-5525.0000170 [45] Komatsu M, Nakasuka S. University of Tokyo nano satellite project "PRISM"[C]//Transactions of the Japan Society for Aeronautical and Space Sciences, Space Technology Japan, 2009, 7: Tf_19-24. [46] Agasid E, Rademacher A, McCullar Ml, et al. Study to determine the feasibility of a earth observing telescope payload for a 6U nano satellite[R]. Moffett Field: Ames Research Center, 2010. [47] Agasid E, Ennico-Smith K, Rademacher A. Collapsible space telescope (CST) for nanosatellite imaging and observation [C]//27th Annual AIAA/USU Conference on Small Satellites, 2013. [48] Gooding D, Richardson G, Haslehurst A, et al. A novel deployable telescope to facilitate a low-cost <1 m GSD video rapid-revisit small satellite constellation [C]//International Conference on Space Optics, 2018: 11180. [49] Shore J, Blows R, Viquerat A, et al. A new generation of deployable optics for Earth observation using small satellites [C]//18th European Space Mechanisms and Tribology Symposium, 2019: 1-8. [50] Shore J, Blows R, Viquerat A, et al. A novel deployable telescope for earth observation [C]//AIAA Scitech 2021 Forum, 2021: 1034. [51] Aglietti G S, Honeth M, Gensemer S, et al. Deployable optics for CubeSats [C]//34th Annual AIAA/USU Conference on Small Satellites, 2020. [52] Yalagach A, Aglietti G, Honeth M, et al. Deployable barrel for a CubeSat’s optical payload [C]//AIAA Scitech 2021 Forum, 2021: 1791. [53] Jeong S, Choi J, Lee D, et al. The establishment of requirement and kinematic analysis of mechanism for deployable optical structure [J]. Journal of the Korean Society for Aeronautical & Space Sciences, 2014, 42(8): 701-706. [54] Choi J, Lee D, Hwang K, et al. A mechanism for a deployable optical structure of a small satellite [J]. International Journal of Precision Engineering and Manufacturing, 2015, 16(12): 2537-2543. doi: 10.1007/s12541-015-0325-5 [55] Choi J, Lee D, Hwang K, et al. Design, fabrication, and evaluation of a passive deployment mechanism for deployable space telescope [J]. Advances in Mechanical Engineering, 2019, 11(5): 1687814019852258. [56] Dong Jihong, Chen Xiaowei. Analysis on design strategies of lager-aperture deployable primary mirror of space telescopes [J]. China Mechanical Engineering, 2012, 23(14): 1667-1670. (in Chinese) [57] Zuo Yudi, Jin Guang, Xie Xiaoguang, et al. Design of the spontaneous deployable mechanism for space telescope based on lenticular tape springs [J]. Infrared and Laser Engineering, 2017, 46(5): 0518002. (in Chinese) doi: 10.3788/IRLA201746.0518002 [58] Yang Huisheng, Zhang Xuejun, Li Zhilai, et al. Study of the impact of co-phasing errors for segmented primary mirror using nonlinear analysis [J]. Optik, 2019, 191: 80-88. doi: 10.1016/j.ijleo.2019.05.104 [59] Yang Huisheng, Zhang Xuejun, Bao He, et al. Influence of random aspheric parameter errors on the wavefront deformation for segmented primary mirror and its correction [J]. Optik, 2020, 200: 163406. doi: 10.1016/j.ijleo.2019.163406 [60] Yang Huisheng, Zhang Xuejun, Li Zhilai, et al. Impact of random segment pose errors for deployable telescope and its tolerance allocation [J]. Optics Communications, 2020, 456: 124549. doi: 10.1016/j.optcom.2019.124549 [61] Yang Huisheng, Zhang Xuejun, Liu Baixu, et al. Large rigid-body displacement parameters extraction of segmented mirror in pose co-phasing adjustment simulation analysis using constrained optimization method [J]. Optik, 2020, 224: 165748. doi: 10.1016/j.ijleo.2020.165748 [62] Yang Huisheng. Research on key technologies of ultra large aperture deployable primary mirror system [D]. Changchun: Changchun Institute of Optics, Fine Mechanics and Physics, 2019. (in Chinese) [63] Zhang Long. Research on optical co-phasing detection technology of segmented telescope [D]. Changchun: Changchun Institute of Optics, Fine Mechanics and Physics, 2020. (in Chinese) [64] Ni Yanshuo, Zhang Shuyang, Liu Dong, et al. A four-bar linkage designed to accurately deploy the secondary mirror of a large space-based optical remote sensing system [C]//2019 IEEE 9th Annual International Conference on CYBER Technology in Automation, Control, and Intelligent Systems (CYBER), 2019: 1073-1078. [65] Zhang Shuyang, Ni Yanshuo, Pan Bo, et al. A high-accuracy deployment mechanism designing based on Kelvin couplings with active locking devices [C]//2019 IEEE 9th Annual International Conference on CYBER Technology in Automation, Control, and Intelligent Systems (CYBER), 2019: 1096-1101. [66] Feng Xuegui, Li Chuang, Ren Guorui. Medium-sized aperture deployable telescope for microsatellite application [C]//International Symposium on Photoelectronic Detection and Imaging, 2011, 8196: 81961V. [67] Li Chuang, Feng Xuegui. Deployment precision measurement modeling of a deployable space telescope based on tape springs [C]//Seventh International Symposium on Precision Engineering Measurements and Instrumentation, 2011, 8321: 83212R. [68] Zhao Chao. Research on self-deployable structure of secondary mirror of space telescope [D]. Xi’an: Xi'an Institute of Optics and Precision Mechanics, 2014. (in Chinese) [69] Zhong Peifeng. Research on the deployment technology to the secondary mirror of the deployable lightweight space telescope [D]. Xi'an: Xi'an Institute of Optics and Precision Mechanics, 2017. (in Chinese) [70] Lei Wang, Li Chuang, Zhong Peifeng, et al. Realization and testing of a deployable space telescope based on tape springs [C]//Pacific Rim Laser Damage, 2017, 10339: 1033920. [71] Zhou Nan. Research on six degrees of freedom adjustment of secondary mirror in space telescopes [D]. Xi'an: Xi'an Institute of Optics and Precision Mechanics, 2015. (in Chinese) [72] Feng Xuegui. Research on the measurement of alignment of the deployable telescope secondary mirror [D]. Xi’an: Xi'an Institute of Optics and Precision Mechanics, 2012. (in Chinese) [73] Wang Zhenkun, Zhao Zhicheng, Liu Li. Optimization of structural parameters of sparse apertures with four rectangular sub-apertures [C]//AOPC 2019: Space Optics, Telescopes, and Instrumentation, 2019, 11341: 1134113. [74] Wang Zhenkun. Design of deployable high-resolution camera for earth observation 3U CubeSat [D]. Suzhou: Soochow University, 2020. (in Chinese) [75] Stahl H P. Design study of 8 meter monolithic mirror UV/optical space telescope [C]//Space Telescopes and Instrumentation, 2008, 7010: 701022. [76] Chonis T S, Gallagher B B, Knight J S, et al. Characterization and calibration of the James Webb space telescope mirror actuators fine stage motion [C]//Space Telescopes and Instrumentation, 2018, 10698: 106983S. [77] Kim J J, Mueller M, Martinez T, et al. Impact of large field angles on the requirements for deformable mirror in imaging satellites [J]. Acta Astronautica, 2018, 145: 44-50. doi: 10.1016/j.actaastro.2018.01.001 [78] Saif B, Chaney D, Greenfield P, et al. Measurement of picometer-scale mirror dynamics [J]. Applied Optics, 2017, 56(23): 6457-6465. doi: 10.1364/AO.56.006457 [79] Tyson R K. Principles of Adaptive Optics[M]. 3rd ed. USA: CRC Press, 2010. [80] Nagashima M, Agrawal B N. Active control of adaptive optics system in a large segmented mirror telescope [J]. International Journal of Systems Science, 2014, 45(2): 159-175. doi: 10.1080/00207721.2012.683835 [81] Liu Tao. An overview of development of foreign large aperture reflection imaging technology on geostationary orbit [J]. Spacecraft Recovery & Remote Sensing, 2016, 37(5): 1-9. (in Chinese) [82] Looysen M W. Combined integral and robust control of the segmented mirror telescope[D]. Monterey: Naval Postgraduate School, 2009. [83] Lake M S, Hachkowski M R. Design of mechanisms for deployable, optical instruments: guidelines for reducing hysteresis[R]. Hampton: Langley Research Center, 2000. [84] Corbacho V V, Kuiper H, Gill E. Review on thermal and mechanical challenges in the development of deployable space optics [J]. Journal of Astronomical Telescopes, Instruments, and Systems, 2020, 6(1): 010902. [85] Yang Shuang, Du Changshuai, Yang Xianwei, et al. Thermal design of space solar telescope [J]. Infrared and Laser Engineering, 2021, 50(4): 20200294. (in Chinese) [86] Jiang Fan, Wu Qingwen, Liu Ju, et al. Thermal design of lightweight space remote sensor integrated with satellite in low earth orbit [J]. Chinese Optics, 2013, 6(2): 237-243. (in Chinese)