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  1. 去年
    2017-07-26 02:38:06

    所以如何解释头疼……

  2. 2017-07-25 00:57:02

    他们说看手机电脑时间长了以后会有头疼、眼睛干等症状,是因为电磁波的缘故
    然后我解释不是电磁波blabla,然后他们问:那怎么解释这些症状?为什么看书的时候没有头疼眼干的症状?
    so如何解释?百度了一下好多回答电磁波的(我是不是不应该百度)

  3. 3年前
    2015-07-24 20:19:18

    Power/电源

    【Flying with anRTG/带着RTG(放射性同位素热电式发电机)旅行】

    【How hot is the RTG? Sensors attached to the outsideof the RTG case before launch pegged the case temperature at about 245 C(nearly 475 F). When New Horizons reaches Pluto, engineers estimate thetemperature will have dropped to around 208 C (406 F) – thanks to a combinationof distance from the Sun and fuel decay.】
    【一台RTG设备有多热呢?临发射时,贴在RTG箱外表的传感器报告了245℃的数据。当新视野号到达冥王星时,工程师们估计其温度将下降到约208℃,由于远离太阳和燃料衰变的共同作用。】

    【The RTG is not hot enough to produce visible light,but it does emit infrared (or thermal) radiation.】
    【RTG还没有热到发出可见光的程度;不过红外辐射或者说热辐射还是有的。】

    【At launch the fuel produced almost 4,000 watts ofthermal power; of that, New Horizons used about 25 watts of the waste heat towarm the spacecraft. Electrical power output of the RTG was about 245 watts.Some of that electrical power (about 120 watts) is also reused after poweringcomponents to help heat the spacecraft. The rest of the RTG heat and any extraelectrical power are radiated into space.】
    【发射时的燃料产生了4千瓦的热功率,其中新视野号使用了25瓦用来保温。RTG的输出功率为245瓦。一部分(120瓦)功率在为电器经手后被重新利用起来维持温度,另外的一部分就辐射耗散到宇宙空间了。】

    【Many scientific instruments work better when theyare cold; that’s one reason why they are located on the opposite side of thespacecraft from the RTG. New Horizons also has a heat shield around the base ofthe RTG to avoid a direct line of sight from the instruments to the RTG. Thesedesign features help avoid any interference from the RTG with scientificmeasurements.】
    【许多科学仪器在温度较低时工作得更好;这也是它们排布在RTG对侧的原因之一。新视野号在RTG的基部有热屏蔽措施以避免仪器直接“看到”RTG。这些设计特征有助于避免RTG对科学测量的干扰。】

    New Horizons'electrical power comes from a single radioisotope thermoelectric generator(RTG). The RTG provides power through the natural radioactive decay ofplutonium dioxide fuel, which creates a huge amount of heat. Unlike fission orfusion nuclear reactions, the RTG simply harnesses the heat produced and turnsit into electricity.
    新视野号的电力源自一台放射性同位素热电式发电机(RTG)。RTG通过钚材料的放射性衰变释放功率,同时产生大量的热。不像裂变或聚变反应,RTG只是简单地将产生的热量转化为电能。

    The New HorizonsRTG, provided by the U.S. Department of Energy, carries approximately 11kilograms (24 pounds) of plutonium dioxide. Onboard systems manage thespacecraft’s power consumption so it doesn’t exceed the steady output from theRTG, which has decreased by about 3.5 watts per year since launch.
    新视野号的RTH由美国能源部提供,携带11千克/24磅的二氧化钚。星务系统控制探测器的功耗使其小于发电机的稳态输出,后者每年大约减少3.5瓦。

    Typical of RTG-basedsystems, as on past outer-planet missions, New Horizons does not have a batteryfor storing power.
    作为使用RTG电源系统的样板,就像从前的行星际探测一样,新视野号未携带蓄电池。

    At the start of themission, the RTG supplied approximately 245 watts (at 30 volts of directcurrent) – the spacecraft’s shunt regulator unit maintains a steady input fromthe RTG and dissipates power the spacecraft cannot use at a given time. By July2015 (when New Horizons flies past Pluto) that supply will have decreased toabout 200 watts at the same voltage, so New Horizons will ease the strain onits limited power source by cycling science instruments during the encounter.
    在任务启动之初,RTG输出的功率约为245瓦(30V,直流电)——飞船的并联稳压单元接受来自RTG的稳定输电,同时存储一时半会儿不会使用的电能。到了2015年7月(新视野号掠过冥王星时),输出功率在同样的电压将下降到200瓦,所以新视野号会用这样的办法缓解供电紧张的问题,即在交会期间安排科学仪器轮流工作。

    The spacecraft’sfully redundant Power Distribution Unit (PDU) – with 96 connectors and morethan 3,200 wires – efficiently moves power through the spacecraft’s vitalsystems and science instruments.
    飞船全部包含冗余的电源分配单元(PDU)——包含96连接器和超过3200条电线——高效地将电力输送到探测器重要的系统和科学仪器中。

  4. 2015-07-24 20:18:35

    Guidanceand Control/导航与控制

    New Horizons must beoriented precisely to collect data with its scientific instruments, communicatewith Earth, or maneuver through space.
    新视野号必须准确定向地使用它的科学仪器收集资料、与地球通讯、抑或在太空机动。

    Attitudedetermination – knowing which direction New Horizons is facing – is performedusing star-tracking cameras, Inertial Measurement Units (containingsophisticated gyroscopes and accelerometers that measure rotation andhorizontal/vertical motion), and digital Sun sensors. Attitude control for thespacecraft – whether in a steady, three-axis pointing mode or in aspin-stabilized mode – is accomplished using thrusters.
    姿态确定——即知道新视野号的空间指向——通过恒星跟踪摄像机、惯性导航单元(IMU)和数字太阳敏感器来操作。惯性导航单元包含能测量转动和水平/竖直平动的复杂陀螺仪和加速度计。对航天器的姿态控制——不论三轴定向模式还是自旋稳定模式——使用推进器实现。

    The IMUs and startrackers provide constant positional information to the spacecraft’s Guidanceand Control processor, which like the Command and Data Handling processor is a12-MHz Mongoose V. New Horizons carries two copies of each of these units for redundancy.The star-tracking cameras store a map of about 3,000 stars; 10 times per secondone of the cameras snaps a wide-angle picture of space, compares the locationsof the stars to its onboard map, and calculates the spacecraft’s orientation.The IMU feeds motion information 100 times a second. If data shows New Horizonsis outside a predetermined position, small hydrazine thrusters will fire tore-orient the spacecraft. The Sun sensors back up the star trackers; they wouldfind and point New Horizons toward the Sun (with Earth nearby) if the othersensors couldn’t find home in an emergency.
    IMU和星敏感器提供恒定的位置信息给探测器的导航与控制处理器,命令和数据处理器是一块12MHz猫鼬-V处理器承担的。新视野号携带了两套处理设备以提供冗余。恒星跟踪相机存储着涵盖大约3000颗恒星的星图;一台相机每秒拍摄十张广角相片,将恒星的位置与板载星图比较,并计算探测器的指向。IMU每秒能提供100组运动数据。如果数据显示新视野号误入歧途,小巧的肼推进器会点火以使探测器归位。太阳敏感器为恒星跟踪相机提供备份;如果其他的敏感器在紧急情况下全部失效,太阳敏感器会寻找太阳(地球就在其旁边)并使新视野号指向它

    Operators usethrusters to maneuver the spacecraft, which has no internal reaction wheels.Its smaller thrusters are used for fine pointing; thrustersthat are approximately five times more powerful are used during the trajectorycourse maneuvers that guide New Horizons toward its targets. NewHorizons spins – typically at 5 revolutions per minute (RPM) – duringtrajectory-correction maneuvers and long radio contacts with Earth, and whileit “hibernated” during long cruise periods. Operators steady and point thespacecraft during science observations and instrument-system checkouts.

    操作人员使用推进器操纵探测器,后者是没有安装反作用飞轮的。小型的推进器被用来精确指向;(用于定向时)推进器的工作能力是使新视野号执行飞向冥王星的弹道航向机动时的五倍。新视野号在轨道修正机动中与遥远的地球联络、或者在漫长的巡航中休眠时,通常以每分钟5转(5rpm)的速度自转。在科学观测和仪器——系统检修时,操作人员对探测器实施稳定/定向操作。

  5. 2015-07-24 20:16:37

    Structure/结构
    -image-
    New Horizons' primarystructure includes an aluminum central cylinder that supports the spacecraftbody panels, supports the interface between the spacecraft and its radioisotopethermoelectric generator (RTG) power source, and houses the propellant tank. Italso served as the payload adapter fitting that connected the spacecraft to thelaunch vehicle.
    新视野号的主要结构包括一个支撑星体面板、支撑航天器外表面与内部放射性同位素热电机分隔面、同时安置推进器贮箱的铝制中柱。中柱同时可作为有效载荷适配器配件,连接运载火箭和探测器。
    -image-
    Keeping mass down,the panels surrounding the central cylinder feature an aluminum honeycomb corewith ultra-thin aluminum face sheets (about as thick as two pieces of paper).To keep it perfectly balanced for spinning operations, the spacecraft was weighedand then balanced with additional weights just before mounting on the launchvehicle.
    为了减轻重量,环绕中柱的面板是用超薄铝面板(大约像两张纸那样薄)制作的铝蜂窝芯制作的。为了让探测器在旋转操作中保持完美的平衡,探测器在临发射前进行了配重和平衡。

    Not all balanceweights are built – or even worth – the same!
    并非所有的配重块都是同一个长相、同一个逼格!
    (译者注:新视野号的配重块中包括一枚佛罗里达州的25美分硬币)

    Commandand Data Handling/指令和数据处理
    -image-
    The command and datahandling system – a radiation-hardened 12 megahertz Mongoose V processor guidedby intricate flight software – is the spacecraft’s “brain.” The processordistributes operating commands to each subsystem, collects and processes instrumentdata, and sequences information sent back to Earth. It also runs the advanced“autonomy” algorithms that allow the spacecraft to check the status of eachsystem and, if necessary, correct any problems, switch to backup systems orcontact operators on Earth for help.
    指令和数据处理系统——一款搭载复杂飞行软件的抗辐射Mongoose-V处理器——是探测器的大脑。处理器分配操作指令给各分系统,采集和处理仪器数据,将这些信息排定序传回地球。同时处理器上运行着高级的“自主”算法,允许航天器检查各个系统的现状,甚至在必要时尝试修复、切换到备份系统或与地球联络寻求解决方案。

    For data storage, NewHorizons carries two low-power solid-state recorders (one backup) that can holdup to 8 gigabytes each. The main processor collects, compresses, reformats,sorts and stores science and housekeeping (telemetry) data on the recorder –similar to a flash memory card for a digital camera – for transmission to Earththrough the telecommunications subsystem.
    在数据存储方面。新视野号搭载了两块低功率固态存储设备(其一为备份),每块能提供最高8GB的数据容量。主处理器采集、压缩、转码、排序和存储科学和管理(遥测)数据——就像一台数码相机的存储卡一样——并通过通讯子系统传回地球。

    The Command and DataHandling system is housed in an Integrated Electronics Module that alsocontains a vital guidance computer, the communication system and part of theREX instrument.
    指令和数据处理系统被安放在一个集成电子模块上,模块也包含重要的导航计算机,包含通讯系统和REX元件的一部分。

  6. 2015-07-24 20:13:15

    Under a range oflightning and viewing angles, New Horizons also captured the clearest imagesever of the tenuous Jovian ring system. In them, scientists spotted clumps ofdebris that may indicate a recent impact inside the rings, or some more exoticphenomenon; movies made from New Horizons images also offer an unprecedentedlook at ring dynamics, with the tiny inner moons Metis and Adrastea shepherdingthe materials around the rings. A search for smallermoons inside the rings – and possible new sources of the dusty material – foundno bodies wider than a kilometer.
    在一个光度和角度合适的视角下,新视野号拍摄了木星黯淡环系最清晰的照片。在照片中,科学家们注意到成团的碎片可能表明环最近受到影响、或发生了一些更奇特的现象。新视野号照片制作的视频,提供了前所未有的动力学图景,微小而靠内的卫星梅蒂斯和另一颗卫星阿德剌斯忒亚在驱动着成环材料的运动。对于环内小卫星——也许是成环碎屑的最新来源——的研究表明,环内物质的直径没有超过一公里的。

    The mission’sinvestigations of Jupiter’s four largest moons focused on Io, the closest toJupiter and whose active volcanoes blast tons of material into the Jovianmagnetosphere (and beyond). New Horizons spied 11 different volcanic plumes ofvarying size, three of which were seen for the first time and one – aspectacular 200-mile-high eruption rising above the volcano Tvashtar – thatoffered an unprecedented opportunity to trace the structure and motion of theplume as it condensed at high altitude and fell back to the moon’s surface. Inaddition, New Horizons spotted the infrared glow from at least 36 Io volcanoes,and measured lava temperatures up to 1,900 degrees Fahrenheit, similar to manyterrestrial volcanoes.
    任务对四颗伽利略卫星的 科研工作聚焦在伊娥上;伊娥是四颗卫星中距离木星最近的,它表面活跃的火山将成吨的物质喷发到木星的磁气圈中,甚至更远的地方。新视野号码观测了11个大小各异的火山羽,其中的三个是此次首见;特瓦史塔火山升腾而起200英里高的壮观火山云,当火山云在高空凝结并落回卫星表面时,对追踪火山羽的运动与组成提供了前所未有的机会。此外,新视野号从伊娥表面至少36个火山观测到红外闪光,经测量,火山熔岩的温度高达1900华氏度,这个数字接近于诸多地球火山。

    New Horizons’ globalmap of Io’s surface backs the moon’s status as the solar system’s most activebody, showing more than 20 geological changes since the Galileo Jupiter orbiterprovided the last close-up look in 2001. The remote imagers also kept watch onIo in the darkness of Jupiter’s shadow, noting mysterious glowing gas cloudsabove dozens of volcanoes. Scientists suspect that this gas helps to resupplyIo’s atmosphere.
    新视野号对伊娥表面的地图绘制揭示了这颗卫星是太阳系最活跃的天体——自上一次伽利略卫星在2001年拍摄特写以后,伊娥表面已经产生了20多处地质变化。当伊娥处于木星的影子中时,探测器依然保持观测,并注意到数十个火山上神秘而炽热的气体云。

    New Horizons' flightdown Jupiter's magnetotail gave it an unprecedented look at the vast regiondominated by the planet's strong magnetic field. Looking specifically at thefluxes of charged particles that flow hundreds of millions of miles beyond thegiant planet, the New Horizons particle detectors saw evidence that tons ofmaterial from Io’s volcanoes move down the tail in large, dense, slow-movingblobs. By analyzing the observed variations in particle fluxes over a widerange of energies and scales, New Horizons scientists are exploring how thevolcanic gases from Io are ionized, trapped and energized by Jupiter's magneticfield, then ultimately ejected from the system.
    新视野号穿越木星磁尾的过程,给了人们对这一被木星强大磁场主宰的区域前所未有的认识。在着重观察从巨大行星上飞出数亿英里的带电粒子流的连续变化时,新视野号的粒子探测器发现了证据,表明伊娥的火山喷发出的成吨物质在以巨大、密集、慢速斑点的形式向磁尾移动。通过在很宽很广的范围内对变化的粒子流展开分析,新视野号的科研人员正在探索伊娥的火山气体是如何在木星磁场中是如何被电离、捕获、获得能量并最终逸出木星系的。

  7. 2015-07-24 20:09:41

    Beyond Pluto: Kuiper Belt Possibilities/飞越冥王星:科伊珀带的可能性
    -image-
    New Horizons has thecapability to fly beyond the Pluto system and explore additional Kuiper BeltObjects. New Horizons carries extra hydrazine fuel for a KBO flyby; itscommunications system is designed to work from far beyond Pluto and itsscientific instruments can work in light levels even lower than the dimsunlight at Pluto.
    新视野号有飞越冥王星系并探索其他科伊珀带天体的能力。新视野号携带了额外的肼燃料以执行对科伊珀带天体的飞越。探测器的通信系统经过精心设计,能在比冥王星更远的地方使用,而科学仪器能够在比冥王星更晦暗的条件下开展工作。

    So the New Horizonsteam had to undertake a dedicated search for small KBOs the spacecraft couldreach. In the early 2000s, no such KBOs had even been discovered. The NationalAcademy of Sciences directed New Horizons to fly by small KBOs about 20 to 50 kilometers(about 12 to 30 miles) across, which are more likely to be primitive bodies,less well-formed than planets like Pluto.
    Read more about thediscovery of the prospective, post-Pluto New Horizons targets.
    所以新视野号的团队需要承担对探测器肯能到达之处渺小科伊珀带天体的专门研究。在2000年代早期,没有这样的科伊珀带天体被发现。国家科学院指导新视野号飞掠直径20~50公里/12~30英里的科伊珀带天体,这些天体比冥王星更蛮荒、更渺小。

    In 2014, using theHubble Space Telescope, New Horizons science team members discovered three KBOs– all in the range of 20-55 kilometers across, and all with possible flybydates in late 2018 or in 2019 — a billion miles beyond Pluto.
    在2014年,新视野号团队使用哈勃太空望远镜找到了三个科伊珀带天体,它们的直径范围在20~55公里内,而且都有望在2018年稍晚时候或2019年被新视野号掠过——它们比冥王星还要远10亿英里。
    -image-
    In summer 2015,after the Pluto flyby, the New Horizons team will work with NASA to choose thebest candidate among the three. In fall 2015, operators will fire the enginesaboard New Horizons – at the optimal time to minimize the fuel required toreach the selected target – to begin the journey.
    在2015年夏天,飞越冥王星以后,新视野号的团队会与NASA一起从三个天体中选择最好的候选者。在2015年秋季,操作人员将会启动新视野号探测器上的引擎——在燃料消耗量最小的时机——开始探测选定目标的征程。

    All NASA missionsthat seek to do more exploration beyond their primary objectives submit aproposal to NASA to fund an extended mission. The proposal to exploreadditional KBOs will be due in 2016; it will be evaluated by an independentteam of experts to gauge its merit: the team will evaluate the health of thespacecraft and its instrument payload, the value of the science New Horizonscan do at a KBO, the cost of the flight to and the exploration of the targetKBO, and more. If it recommends funding and NASA approves, the New HorizonsExtended Mission would begin in 2017, allowing the team to plan and test theencounter (which would take place one-two years later) and to continue tooperate New Horizons.
    所有想要超越主要目标、做出更多探索的NASA任务都要向NASA提出建议对拓展任务拨付款项。对科伊珀带天体开展探索的建议预定在2016年做出;会有一个评估任务价值的独立的专家组做出评价——专家组会评估航天器和有效载荷的健康情况,评估新视野号探索科伊珀带天体的价值,评估新视野号探索目标天体的花销以及更多的事项。如果能得到拨款和NASA的首肯,新视野号拓展任务会在2017年开始,以允许团队计划和测试一两年后的交会,继续地对新视野号实施操纵。

  8. 2015-07-24 19:58:34

    《Mission Timeline/任务时间线》

    Launch/发射
    -image-
    Launch: January 19,2006
    发射时间:2006年1月19日
    Launch Vehicle:Atlas V 551 first stage; Centaur second stage; STAR 48B solid rocket thirdstage
    运载火箭:第一级:“宇宙神”-5 551型;第二级:半人马座;第三级:Star 48B固体火箭发动机
    Location: CapeCanaveral Air Force Station, Florida
    发射地点:佛罗里达州卡纳维尔角空军基地
    Trajectory: To Plutovia Jupiter Gravity Assist
    运行轨道:借助木星引力加速至冥王星

    The Voyage/旅程
    -image-
    Early Cruise: Thefirst 13 months included spacecraft and instrument checkouts, instrumentcalibrations, small trajectory correction maneuvers and rehearsals for theJupiter encounter. New Horizons passed the orbit of Mars on April 7, 2006; italso tracked a small asteroid, later named "APL", in June 2006.
    早期巡航:前13个月的任务包括航天器仪器检测,仪器校准,小幅度轨道修正机动和排演与木星的交会。新视野号于2006年4月7日越过火星轨道。探测器也追踪了一颗小行星,这颗小行星于2006年6月被命名为APL(约翰·霍普金斯大学应用物理实验室)。

    Jupiter Encounter:Closest approach occurred February 28, 2007. Moving about 51,000 miles per hour(about 23 kilometers per second), New Horizons flew about 3 to 4 times closerto Jupiter than the Cassini spacecraft, coming within 1.4 million miles (2.3 millionkilometers) of the large planet.
    与木星交会:最接近时刻在2007年2月28日。探测器的速度高达51000迈/23公里每秒,掠过木星的距离不超过140英里/230公里是卡西尼号探测器的1/3到1/4。

    InterplanetaryCruise: Activities during the approximately 8-year cruise to Pluto includedannual spacecraft and instrument checkouts, trajectory corrections, instrumentcalibrations and Pluto encounter rehearsals.
    行星际巡航:在前往冥王星的8年旅程中探测器的人物包括年度检修、轨道校正、仪器校准和交会排演。

    During the cruise,New Horizons also crossed the orbits of Saturn (June 8, 2008), Uranus (March18, 2011) and Neptune (August 25, 2014).
    在巡航期间,新视野号先后越过了土星(2008年6月8日)、天王星(2011年3月18日)和海王星(2014年8月25日)的轨道。

  9. 2015-07-24 18:58:25

    Closing In/接近

    【Science at Jupiter】
    【Science opportunities at Jupiter included meteorology, aurora studies, magnetospheric sampling, dust sampling and surface mapping, compositional mapping and atmospheric studies of Jupiter's large moons.】

    【在木星的探测】
    【在木星的科研机会涵盖气象科学、极光研究、磁层采样、粉尘采样、表面地图绘制、组合地图绘制和木星大卫星的大气研究等领域。】

    The cameras on New Horizons will take data on Pluto and its moons months before the spacecraft arrives. Pluto and Charon will first appear as unresolved bright dots, but the planet and its moons appear larger as the encounter date approaches. Three months from the closest approach - when Pluto is about 65 million miles (105 million kilometers) away - the cameras on the spacecraft can make the first maps. For those three months, the mission team will take pictures and spectra measurements.
    在抵达冥王星的数月前,探测器携带的相机开始采集冥王星和众冥卫的数据。在照片上,冥王星和卡戎起初只是无法分解的亮点,但随着交会日期的临近,冥王星和卫星们将逐渐揭开它们的面纱。在交会前的三个月,当冥王星还有6500万英里/1.05亿公里远的时候,探测器便能够拍摄第一张照片了。在接下来的三个月里,任务组会着手拍摄照片并开展光谱测量。

    Pluto and Charon each rotate once every 6.4 Earth days. For the last two Pluto days before encounter (11 to 12 Earth days), the team will compile maps and gather spectra measurements of Pluto and Charon every half-day. The team can then compare these maps to check changes over a Pluto day, at a scale of about 30 miles (48 kilometers), as might be caused by new snow or other weather.
    冥王星和卡戎每6.4(地球)日绕转一圈。在交会前的两冥王星日(11到12地球日),任务组每半天会编辑冥王星和卡戎的地图,收集它们的光谱测量数据。任务组接下来会比对这些比例尺大约能达到30英里级别的地图,并致力于利用地图检测一个冥王星日里的变化——这些变化可能是由新的降雪或其他天气现象引起的。

  10. 2015-07-24 18:53:27

    《Mission Design/任务设计》
    -image-
    A direct airplaneflight might be the quickest way across the country, but the fastest route toPluto requires a trip past Jupiter. The giant planet's gravity can actually"slingshot" a spacecraft toward the outer solar system.
    要跨越广袤的国土,最快捷的方式也许是一条笔直的飞机航线。然而要前往冥王星,最快的路线则要包含一段木星之旅。这一巨行星的重力足以将航天器“弹射”到太阳系的外层。

    There are tworeasons why the New Horizons science team wants to reach Pluto and Charon assoon as possible. The first has to do with Pluto's atmosphere: Since 1989,Pluto has been moving farther from the Sun, getting less heat every year. AsPluto gets colder scientists expect its atmosphere will "freeze out,"so the team wants to arrive while there is a chance to study a thickeratmosphere.
    有两条原因支撑着新视野号的科研团队尽快地探测冥王星和卡戎。其一关乎冥王星的大气层——自1989年以来,冥王星开始远离太阳(从近日点向远日点运行),获得的热量逐年减少。科学家们相信,随着冥王星逐渐变冷,它的大气层会“冻结”,故而团队希望在探测器到达时能够赶上探测冥王星稀薄大气的机会。

    The second reason isto map as much of Pluto and Charon as possible. On Earth, the North Pole andother areas above the Arctic Circle have half a year of night and half a yearof daylight. In the same way, parts of Pluto or Charon never see the Sun for decadesat a time. The longer we wait, the more of Pluto and Charon are shadowed in along "arctic night," impeding the spacecraft's ability to takepictures of the entire surface in reflected sunlight.
    第二个原因是为了尽可能广地绘制冥王星和卡戎的地图。在地球上,北极点和北极地区会经历半年更替的极昼极夜。出于相同的原因,冥王星和卡戎的也会有一部分隐藏在黑暗中数十(地球)年之久。我们等待的时间越长,冥王星和卡戎被漫长极夜吞没的地方也越多,这将严重妨害探测器拍摄全星照片(冥王和冥卫不发光,只反射微弱的太阳光)的能力。

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