开始翻译“新地平线”号官方网站的Science部分

跨越地平线

part1

Science Overview
新地平线号发射于2006年1月。它将于2007年2月接近木星展开科学研究并且借助木星引力推动在2015年7月到达冥王星和她的卫星，卡戎。那时，作为一个长期的任务，太空船将至少在离开海王星轨道之外10亿英里的科伊伯带这一广大的地区来研究这些迷你的冰雪世界。发射一艘太空船进行这次漫长的旅途将会帮助我们回答一系列这些星体的基本问题，诸如表面特性、地质、大气和内部结构.(感谢夜空翻译)

New Horizons launched in January 2006. It will swing past Jupiter for a gravity boost and scientific studies in February 2007, and reach Pluto and its moon, Charon, in July 2015. Then, as part of an extended mission, the spacecraft would head deeper into the Kuiper Belt to study one or more of the icy mini-worlds in that vast region, at least a billion miles beyond Neptune's orbit. Sending a spacecraft on this long journey will help us answer basic questions about the surface properties, geology, interior makeup and atmospheres on these bodies.

Highest Priority
A special panel of the National Academy of Sciences that was formed to advise NASA on a planetary science strategy for the next 10 years (the so-called "Decadal Survey") ranked the exploration of Kuiper Belt Objects, including Pluto, as its highest scientific priority. The New Horizons mission is NASA's way to implement that recommendation.



The Third Region

Generally, New Horizons seeks to understand where Pluto and Charon "fit in" with the other objects in the solar system. We currently classify the planets into groups. Earth, Mars, Venus and Mercury are the "terrestrial" planets, which are mostly rocky objects. In contrast, the "gas giant" planets, which include Jupiter, Saturn, Uranus and Neptune, are dominated by thick, molecular hydrogen atmospheres.

Pluto and Charon belong to a third category that could be called "ice dwarfs." They have solid surfaces but, unlike the terrestrial planets, a significant portion of their mass is icy material (such as frozen water, carbon dioxide, molecular nitrogen, methane and carbon monoxide).


Kuiper Belt Kings

Pluto and Charon are also widely considered to be among the largest objects in the Kuiper Belt, a vast reservoir of icy objects located just outside of Neptune's orbit and extending out to about 50 astronomical units from the Sun. The Kuiper Belt is thought to be the source of most short-period comets - those with orbits shorter than 200 years - so scientists really want to compare the composition and surface properties of Pluto and Charon to those of cometary nuclei.

Pluto and Charon are truly part of the current "frontier" in planetary science. No spacecraft has ever explored them, yet they promise to tell us much about the origins and outskirts of our solar system.

[ 本帖最后由 跨越地平线 于 2006-3-7 12:45 PM 编辑 ]

跨越地平线

Data Collection New Horizons is on a one-way journey to the Kuiper Belt and beyond. Unlike some missions that return back to the Earth, New Horizons sends back all of its data using a radio transmitter and its 83-inch (2.1-meter) diameter radio antenna. It receives commands over this link, and returns both science data and information on the spacecraft's temperature, health, and power.

Sending Commands to the Spacecraft

All commands sent to the New Horizons spacecraft must first pass a rigorous development and review process to ensure the safety of the spacecraft. The science team will work closely with the instrument mission operations and spacecraft teams to develop the commands that trigger New Horizons' scientific activity. After the command sequences are tested on the ground, they will be sent by the New Horizons Mission Operations Center at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, to NASA's Deep Space Network (DSN), which is operated and managed by the Jet Propulsion Laboratory.


Spacecraft Pointing

Usually, New Horizons must be oriented in a particular direction to take data with its scientific instruments. For example, its various telescopes must be accurately pointed at a specific target (such as a location on the surface of Pluto). New Horizons has an advanced guidance and control (G&C) system for determining its orientation. An inertial measurement unit (IMU), which is a sophisticated gyroscope, provides relatively coarse positional information and keep the spacecraft stable. Star tracker cameras employing charge coupled devices (CCDs) image the sky, and the positions of the detected stars are used to acurately determine the orientation of the spacecraft. The star tracker feeds star-position information to the G&C computer, which compares the observed position to the commanded position. If the difference is outside some predetermined tolerance, small hydrazine thrusters will fire to re-orient the spacecraft to the desired position.

The thrusters provide the only mechanism for maneuvering the New Horizons spacecraft, and the amount of hydrazine thruster fuel will be carefully watched to ensure that the mission's scientific objectives are fullfilled. Besides the small thrusters that are used to fine-point the spacecraft, thrusters that are approximately five times more powerful will be used during trajectory correction maneuvers (TCMs) that keep New Horizons on the proper path to its targets.


Science Instruments

New Horizons carries seven scientific instruments, which will collect several types of data. (The instrument names and main functions are described in the science payload section of the Web site.) As an instrument makes an observation, data will be transferred to a solid state recorder (similar to a flash memory card for a digital camera), where they are compressed (if necessary), reformatted and transmitted to Earth through the spacecraft's radio telecommunications system.


The Data Rate Challenge

A major challenge for the New Horizons mission will be the relatively low "downlink" rate at which data can be transmitted to Earth, especially when you compare it to rates now common for high-speed Internet surfers.

During the Jupiter flyby in February 2007, New Horizons will send data home at about 38 kilobits per second (kbps), which is slightly slower than the transmission speed for most computer modems. The situation gets even more challenging when New Horizons reaches Pluto, where the downlink rate falls to about 300-600 bits per second. At 300 bps, mission operators would need nearly 12 hours to downlink a single image from New Horizons' long-range imager, and nearly 40 days of continuous downlink to gather the entire 10 gigabits (or so) of data during the Pluto-Charon encounter.

Since NASA's Deep Space Network has to track other missions besides New Horizons, the team plans to produce compressed "browse" data - using an average compression ratio of about 20 - that will be sent back to Earth within 10 days of Pluto closest approach. At that compression rate some of the original data will be lost. However, New Horizons scientists will examine the browse data carefully and set priorities for downlinking "losslessly compressed" data that doesn't lose any original content. Some of the browse data will good enough for immediate public release, so everyone can share in the excitement of the flyby. Initial analyses of the so-called losslessly compressed data should appear in peer-reviewed scientific journals with a year after the Pluto-Charon flyby.


New Horizons Mission Operations Center

Data received on Earth through the Deep Space Network will be sent to the New Horizons Mission Operations Center at APL, where data will be "unpacked" and stored. The mission operations and instrument teams will scour the engineering data for performance trend information, while science data will be copied to the Science Operations Center at the Southwest Research Institute in Boulder, Colorado. At the Science Ops Center, data will pass through "pipeline" software that converts the data from instrumental units to scientific units, based on calibration data obtained for each instrument. Both the raw and calibrated data files will be formatted for New Horizons science team members to analyze. Within nine months of receipt, both the raw and calibrated data, along with various ancillary files (such as documents describing the pipeline process or the instruments) will be archived for use by the general scientific community at the Small Bodies Node of NASA's Planetary Data System.

跨越地平线

Science FAQs

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What kind of life could there be on Pluto?
The surface of Pluto is extremely cold, roughly 40 degrees above absolute zero (minus 387° Fahrenheit or minus 233° Celsius), so it seems unlikely that life could exist there. At such cold temperatures, water, which is vital for life as we know it, is essentially rock-like. Pluto's interior is warmer, however, and some think there could even be an ocean deep inside.

Life as we know it requires three things:

Water
Biogenic elements such as carbon, phosphorus and sulfur, in addition to the oxygen and hydrogen in water
A source of energy (light, heat, chemical potential) that a living organism can use
Pluto's surface is far too cold for liquid water, but its interior is probably warm and maintained that way by the slow decay of naturally occurring elements such as uranium, potassium-40 and thorium.

Enough heat is released that a water ocean may exist between the rocky core of Pluto and its thick outer layer of ice. Planetary scientists have long thought that icy satellites might possess oceanic layers underneath their surface ice layers. The discovery by the Galileo orbiter that Europa, Callisto and possibly Ganymede possess interior oceans greatly increases our expectation that Pluto also possesses an ocean. Pluto's ocean is also likely to contain biogenic elements in a solution, especially if it is in contact with an organic-rich layer.

Where Pluto probably does not pass astrobiological muster is in the matter of sufficient energy to power life. Pluto's ocean would be dark and cold - near-freezing. Even if in contact with a rock core, it is almost certainly true that this modest core is today insufficiently hot to be volcanically active or even to drive circulations. So it is difficult to argue for a deep biosphere on Pluto today. On the other hand, it is also true that Pluto's rock core was much hotter and probably active in the geological past, so it is not utter lunacy to speculate that some form of primitive, microbial life may have evolved long ago and just might have once plied the "Styxian seas" of Pluto.


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What is the scientific motivation to send a spacecraft to Pluto?

A special panel of the National Academy of Sciences that was formed to advise NASA on a planetary science strategy for the next 10 years (the so-called "Decadal Survey") ranked the exploration of Kuiper Belt Objects, including Pluto, as its highest scientific priority. The New Horizons mission is NASA's way to implement that recommendation.

The key scientific objectives of the New Horizons mission are:

Characterize the global geology and morphology of Pluto and Charon - What do Pluto and Charon look like close up?
Map the surface composition of Pluto and Charon - What are Pluto and Charon made of, and how are those materials distributed over the surface of each object?
Characterize the neutral atmosphere of Pluto and its escape rate - Why does Pluto have an atmosphere and how long will it last?
Generally, New Horizons seeks to understand where Pluto and Charon "fit in" with the other objects in the solar system. We currently classify the planets into groups. Earth, Mars, Venus and Mercury are the "terrestrial" planets, which are mostly rocky objects. In contrast, the "gas giant" planets, which include Jupiter, Saturn, Uranus and Neptune, are dominated by thick, molecular hydrogen atmospheres. Pluto and Charon belong to a third category that could be called "ice dwarfs." They have solid surfaces but, unlike the terrestrial planets, a significant portion of their mass is icy material (such as frozen water, carbon dioxide, molecular nitrogen, methane and carbon monoxide).

Pluto and Charon are also widely considered to be among the largest objects in the Kuiper Belt, a vast reservoir of icy objects located just outside of Neptune's orbit and extending out to about 50 astronomical units from the Sun. The Kuiper Belt is thought to be the source of most short-period comets - those with orbits shorter than 200 years - so scientists really want to compare the composition and surface properties of Pluto and Charon to those of cometary nuclei.

Pluto and Charon are truly part of the current "frontier" in planetary science. No spacecraft has ever explored them, yet they promise to tell us much about the origins and outskirts of our solar system.


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How does New Horizons plan to measure Pluto's atmosphere?
The New Horizons mission has a plan for measuring Pluto's atmosphere. After flying by Pluto, the New Horizons spacecraft enters the planet's shadow. As the spacecraft moves into Pluto's shadow, sunlight must pass through the planet's atmosphere before reaching the spacecraft. Absorption of sunlight by Pluto's atmosphere is detected as characteristic "dips" in the ultraviolet part of the spectrum of light measured by New Horizons' Alice instrument. This technique is a very powerful method for measuring even trace amounts of atmospheric gas.

In addition, radio waves sent from Earth to New Horizons will bend as they pass through Pluto's atmosphere. The amount of bending of the radio waves is detected by the New Horizons Radio Science Experiment (called REX) and is related to both the average molecular mass and the temperature of the atmosphere.

Together, these ultraviolet and radio "occultation experiments" provide powerful probes of Pluto's tenuous atmosphere.


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Are there other interesting objects in the solar system near Pluto?
Charon, of course! There may be other objects in the Pluto-Charon system, but they haven't yet been found. However, the current limits are not very restrictive objects about 60 miles (100 kilometers) wide could be found. In fact, the New Horizons team hopes to improve the search so that objects in the gravitational stability zone of Pluto-Charon as small as 3 to 6 miles (about 5 to 10 kilometers) could be detected.


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Will Pluto's atmosphere "freeze out" by the time the spacecraft arrives?
Pluto is currently moving away from the Sun, having reached its closest approach distance in 1989. Generally, the closer an object is to the Sun, the warmer it should be and the more rapidly its surface ice should sublime into space. The sublimation of ices on the surface of Pluto is responsible for its tenuous atmosphere. As Pluto moves away from the Sun it will get colder and, eventually, its atmosphere will almost completely condense back onto the surface.

The actual situation is a bit more complicated than the simple illustration discussed above. Because of "thermal lag," the time of Pluto's closest approach to the Sun in 1989 was probably not when its surface temperature was greatest, just as the temperature on Earth is hottest at mid-afternoon rather than noon. In the case of Pluto, the latest observations reveal that the atmosphere has thickened during the past decade. But this trend will definitely reverse as Pluto continues moving away from the Sun. Scientists don't know exactly when the condensation will start to dominate sublimation - which is why they want to get to Pluto as soon as possible!


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Can New Horizons go to recently discovered Kuiper Belt Objects Quaoar and Sedna?
Unfortunately, New Horizons can't reach either object. Quaoar is located far away from the trajectory of any spacecraft that travels toward Pluto during the next several decades. The outer solar system is a big place with a lot of volume! New Horizons is just our first attempt to probe this region, but scientists are sure Quaoar and Sedna will be high on the list of candidate targets as they contemplate other missions to explore the outer solar system during the next several decades.


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How do astronomers know about the composition and other characteristics of Pluto's surface?
In the 1970s technological advances in telescopes and other instruments brought tiny, faint Pluto within range for Earth-bound observers. In 1975, using the technique of light analysis called spectroscopy, astronomers Dale Cruikshank, David Morrison and Carl Pilcher measured a portion of Pluto's infrared spectrum using one of the then-largest telescopes on Earth.

They aimed the 4-meter Mayall Telescope and its powerful spectrometer (located at Kitt Peak National Observatory in Arizona) at Pluto and recorded the signature, or spectral fingerprint, of frozen methane. This discovery gave the first indication that Pluto's surface is icy rather than rocky, and opened a new era of investigations of the realm of small icy objects in the outer solar system that continues today. Working with other colleagues, Cruikshank (now a New Horizons team member) later discovered the frozen nitrogen and carbon monoxide, as well as evidence for the colored organic chemicals that make up Pluto's surface.

From our understanding of the properties of the ices of Pluto, we know that some of them slowly evaporate from the surface and enter the atmosphere as gases, much in the way that ice cubes evaporate in the freezer of the refrigerator. Ices of carbon monoxide and methane have also been detected on Pluto's surface using telescope measurements of reflected sunlight (at near infrared wavelengths). Scientists therefore believe that the atmosphere also contains trace amounts of carbon monoxide and methane gases supplied by sublimation of their ices.

Thus, even frigid, distant and tiny Pluto is a dynamic world where the processes of nature continuously change the surface and the atmosphere, creating an alien and exotic world that beckons us from Earth to visit, explore and learn.

跨越地平线

Glossary
Astronomical Unit (AU) is the average distance between Earth and the Sun, about 93 million miles or 149 million kilometers.

Cometary plasma is gas that has escaped from a comet (or Pluto) and become ionized by ultraviolet sunlight.

Density is the amount of mass per unit volume of matter, and is usually given as grams per cubic centimeter or kilograms per cubic meter. Water at room temperature has a density of 1 g/cm 3, (or 1000 kg/m 3), rocks are about 3 g/cm 3, and iron has a density of 7.9 g/cm 3. For convenience you can say "Pluto has a density of about 2," meaning it is about twice as dense as water.

Differentiation occurs when a dense material (such as rock) sinks into the middle of a planet and leaves a lighter material (such as ice) on the outer layer. Differentiation generally requires that the interior of the object become warm enough to melt and allow materials to separate — a bit like chocolate chips moving to the bottom of a tub of melting ice cream.

Eccentricity is the departure of an elliptical orbit from a circle. A circle has an eccentricity of 0; a very elongated orbit has an eccentricity approaching 1. The eccentricity of Pluto's orbit has the largest value of all the planets (0.248).

The Ecliptic is the plane of the Earth's orbit. Most of the planetary orbits are close to this plane. Pluto's orbit is inclined at an angle of 17.14 degrees to the ecliptic plane - the largest deviation of any planet.

Frost occurs when a minority constituent condenses out from an atmosphere, such as water on freezing out of the Earth's atmosphere or (probably) methane on Pluto. For both Earth and Pluto the main constituent is molecular nitrogen (N 2). When the atmosphere itself condenses, as in N 2 on Pluto, it forms ice, not frost. The difference is significant, both from the surface (very different surface textures result from the two processes) and from the atmosphere, where frost formation is limited by the ability of the minority species to move through the majority component, while condensation of ice is only limited by the ability of the atmosphere to cool.

Infrared is the part of the electromagnetic spectrum next to visible light. Wavelengths of infrared light are longer than those of visible light.

The Ionosphere is the region in a planet's upper atmosphere of a planet where sunlight ionizes gases.

Jupiter Family Comets have orbits that are strongly influenced by Jupiter's gravity and usually take less than 20 years to make a single trip around the Sun.

The Kuiper Belt is a disk of thousands of icy objects (known as KBOs) outside Neptune's orbit, between about 30 to 50 astronomical units (AU) from the Sun.

The Magnetosphere is the region where a planet's magnetic field or ionosphere shields the planet from the solar wind.

An Occultation occurs when an object moves behind another object. In a stellar occultation, for example, a star moves behind a planetary object.

Most comets come from the Oort Cloud, a roughly spherical-shaped region between 10,000 and 100,000 astronomical units (AU) from the Sun, and typically have orbital periods of about a million years.

Photochemistry is when sunlight stimulates a chemical reaction, such as changing methane into more complex hydrocarbon molecules.

A Photomosaic combines separate images covering neighboring or nearby regions into a single image.

Pick-up ions are newly charged particles in the outer regions of an atmosphere; once they become ionized they are usually "picked up" and carried away in the solar wind.

Proto-Triton was the object that later became Triton, before it was captured by the planet Neptune.

Radiolysis occurs when energetic particles (such as those from the Sun or cosmic rays from beyond the solar system) bombard a planetary object and break up molecules in the top layers of the surface. When the molecules rejoin they often form larger molecules. Thus, under the influence of radiolysis, the simplest hydrocarbon such as methane can be turned into complex organic materials.

Reflectivity - the fraction of light that is reflected, rather than absorbed - is an important property of a planet's surface. Reflectivity factors into surface temperatures; high reflectivity (such as white) means little absorption of sunlight and a cooler surface, similar to the advantages of wearing white clothes in summer. Conversely, a very dark surface absorbs lots of sunlight and warms up.

Refraction is the bending of light due to a gradient in density, such as the bending of light around the limb of a planet's atmosphere.

There are many forms of Resonance between planetary objects, but the simplest is when one object orbits the Sun (or a satellite orbits a planet) in exact proportion to another object's orbit. For example, Pluto orbits the Sun twice for every 3 times Neptune orbits, putting them in a 2:3 resonance.

Most of the objects in the solar system spin and orbit the Sun in the same direction —counter-clockwise looking down on the solar system from above. Retrograde objects have suffered collisions that caused them to spin or orbit in the opposite direction.

Solar Wind is the streams of charged particles that speed from the Sun into space.

Spectroscopy is the study of light coming from an object by examining the intensity at different wavelengths - and a very powerful tool for investigating the composition of surfaces and atmospheres.

Sublimation is the transformation of a solid into a gas. You see it on Earth with theatrical fog machines.

Terrestrial Planets are also known as the "rocky" planets; they include Mercury, Venus, Earth and Mars.

卢平α

单词好象不难,
但愧于文笔实在不行啊~~

如果需要大家一起翻译的话,不如直接安排一下任务,
一人翻,一人校.这样会有效率些,
但好象可行性不太强啊.

翻译了第一小段,感觉还挺怪的~~

科学总览
行星探索是NASA历史上始终努力的方向及主要焦点.(??)新地平线号第一个探测了冥王星及Charon这一双星系统,也就是我们太阳系中最后访问的行星.它帮助我们了解太阳系的前沿信息.其接下来的使命是访问海王星以外的科伊伯带中一个或更多星体.

[ 本帖最后由 卢平α 于 2006-3-5 04:35 PM 编辑 ]

跨越地平线

原帖由 卢平α 于 2006-3-5 04:33 PM 发表
单词好象不难,
但愧于文笔实在不行啊~~

如果需要大家一起翻译的话,不如直接安排一下任务,
一人翻,一人校.这样会有效率些,
但好象可行性不太强啊.

翻译了第一小段,感觉还挺怪的~~

科学总览
行星探索是 ...

很好，十分积极，奖励4分！可以看看English Translation 版块规定
对了那个“（？？）”是什么？

夜猫子

卢平α 翻译得挺好！读起来很顺口，虽然我不懂英文。

夜空

翻译得挺好啊，不错。

夜空

New Horizons launched in January 2006. It will swing past Jupiter for a gravity boost and scientific studies in February 2007, and reach Pluto and its moon, Charon, in July 2015. Then, as part of an extended mission, the spacecraft would head deeper into the Kuiper Belt to study one or more of the icy mini-worlds in that vast region, at least a billion miles beyond Neptune's orbit. Sending a spacecraft on this long journey will help us answer basic questions about the surface properties, geology, interior makeup and atmospheres on these bodies

新地平线号发射于2006年1月。它将于2007年2月接近木星展开科学研究并且借助木星引力推动在2015年7月到达冥王星和她的卫星，卡戎。那时，作为一个长期的任务，太空船将至少在离开海王星轨道之外10亿英里的科伊伯带这一广大的地区来研究这些迷你的冰雪世界。发射一艘太空船进行这次漫长的旅途将会帮助我们回答一系列这些星体的基本问题，诸如表面特性、地质、大气和内部结构.

[ 本帖最后由 夜空 于 2006-3-7 02:35 PM 编辑 ]

夜空

翻译得不太好，感觉不是很对，欢迎大家来指出错误。

跨越地平线

原帖由 夜空 于 2006-3-6 11:08 PM 发表
翻译得不太好，感觉不是很对，欢迎大家来指出错误。

"太空船将更深入至少在海王星轨道之外10亿英里的科伊伯带“这句话，有点不顺口，应该是”太空船将至少在离开海王星轨道之外10亿英里的科伊伯带“。

加5分:)

卢平α

原帖由 跨越地平线 于 2006-3-6 12:51 PM 发表

对了那个“（？？）”是什么？

是觉得绕口的地方~~

夜空

重要性

一个由国家科学研究院组成的座谈小组，目的是专门为国家航空局提供意见和建议，建议美国宇航局在以后的十年的行星探测(所谓 "十年调查")作一个科伊伯带天体的探测排名，包括冥王星，作为它最高的科学优先权。新地平线号的使命便是美国宇航局实施那个推荐的方式。


第三个地区

通常, 新地平线号寻求了解冥王星和卡戎以其它对象在太阳系中的合适位置。 我们当前把行星分几类。 地球、火星、金星和水星是类地行星, 主要成分是岩石。 相反, "气体巨人" 行星, 包括木星, 土星, 天王星和海王星, 是厚实分子氢大气主宰的气体行星。

冥王星和卡戎属于第三类，可以叫做“冰侏儒”。他们有坚实表面但不同于类地行星, 他们大部份都是冰冷的物质(譬如冰, 二氧化碳、氮气分子、甲烷和一氧化碳) 。


科伊伯带之王

冥王星和卡戎一直以来被认为是科伊伯带最大的天体,在海王星轨道之外一直延伸到大约50天文单位处，隐藏着数量众多的冰冷的天体。科伊伯带还有很多短周期的彗星----它们的轨道周期都少于200年- 所以科学家们都想比较冥王星和卡戎与那些彗星彗核的组成和表面特性。

Pluto 和Charon 真正地作为当前横行科学的"边境的" 部分。 航天器曾经未探索他们, 他们许诺告诉我们关于我们的太阳系起源和太阳系边境的环境。

还是那句话，有什么错漏的还请各位指正啊。

[ 本帖最后由 夜空 于 2006-3-23 01:38 PM 编辑 ]

跨越地平线

很好，Pluto 和Charon的意思分别是“冥王星”和“冥卫一”

nagunaruka龙

各位的英语水平都不错啊。。这么好的帖子 多些人关注吖