「作為行星科學家 我不知道還能怎麼形容冥王星：它又大又圓有數千英裡寬」新視野號太空任務 首席研究員Alan•Stern
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2015年7月4日
On July 4, 2015,
美國家航空航天局一艘名為「新視野」的太空船
a NASA spacecraft called New Horizons
距離地球五十億公裡
was 5 billion kilometers away from Earth.
在它突然失去聯繫時
It was only 10 days away from Pluto,
已經飛行了九年半的時間
after flying for 9.5 years,
距冥王星只有10天的路程
when it suddenly dropped out of contact.
但是我們稍微回顧一下
But let’s back up a little.
截至1989年
As of 1989,
人類已經成功地將飛船送到了
mankind had successfully sent craft to
太陽系中 除冥王星之外每個已知的行星上
every known planet in the solar system except one—Pluto.
你可能聽說過 天文學家們並不認為冥王星
You may have heard that astronomersdon’t consider Pluto
及其伴星屬於行星類
or its brethren to be planets.
然而 絕大多數行星科學家仍這樣認為
However, most planetary scientists still do,
這就是我們此處用「行星」一詞的原因
which is why we’re usingthat terminology here.
我們從地球上了解到的冥王星的知識有限
There’s a limited amountwe can learn about Pluto from Earth
因為它離我們太遠了
because it’s so far from us.
然而 冥王星是一個科學界的金礦
Pluto, however, is a scientific goldmine.
它位於一個叫做柯伊伯帶的區域
It’s located in a region called the Kuiper Belt,
那裡有許多小行星
home to many small planets,
有成千上萬的古代冰冷天體
hundreds of thousands of ancient icy objects,
還有數萬億的彗星
and trillions of comets.
這個神秘的區域存在
This mysterious region holds clues to the formation
太陽系形成的線索
of our solar system,
它很長很長 遙不可及
and it was long,tantalizingly beyond our reach.
直到新視野號的出現
Until New Horizons.
它的任務是探索冥王星
Its objectives: explore Pluto,
收集儘可能多的科學數據
collect as much scientificdata as possible,
把它傳送回地球
transmit it back to Earth,
然後再近一步探索柯伊伯帶
then explore farther out in the Kuiper Belt.
為實現這一目標新視野號團隊為他們的飛船配備了
To achieve this, the New Horizons teamoutfitted their craft
七種最先進的科學儀器
with seven state-of-the-artscientific instruments.
其中包括Ralph：一套功能強大的攝像機
Those included Ralph, a set of cameras
可以從數萬公裡外拍攝到曼哈頓
powerful enough to capture features the size of city blocks in Manhattan
城市街區的大小及特點
from tens of thousands of kilometers away.
還有REX：用無線電波
And REX, designed to use radio waves
測量冥王星的大氣壓和溫度
to measure Pluto’s atmospheric pressureand temperature.
所有太空船上的設備都必須
All of the onboard equipment had
製造得既可靠又輕便
to be built to be both reliable and lightweight
因為新視野號還有一項額外的挑戰：
because New Horizons had anadditional challenge;
它必須以最快的速度到達目的地
it had to reach its target as fast as possible.
為什麼呢？
Why?
大約在2020年 冥王星會在其軌道上運行到一處
Around 2020, Pluto will reacha point in its orbit
大氣可能會凝結的地方
where its atmosphere could freeze.
並且由於中軸的傾斜度
And due to the tilt of its axis,
冥王星表面每年都會有越來越多的部分籠罩在黑暗中
more and more of Pluto’s surface is shrouded in darkness every year.
每248個地球年冥王星才能完成一次完整的軌道運行
Pluto completes a full orbit once every 248 Earth years,
所以下次訪問的最佳機會 會經歷漫長的等待
so it would be a long wait for the next prime opportunity to visit.
為看到新視野號是如何及時趕到冥王星的
To see how New Horizons got to Pluto in time,
我們直接跳到發射的部分
let’s jump to its launch.
它的三個火箭傳送階段 將新視野號的速度加快到
Its three rocket stages acceleratedNew Horizons to such great speeds
僅用9小時就越過40萬公裡飛到月球
that it crossed the 400,000 kilometers to the moon in just nine hours.
大約一年後 這艘飛船到達了木星
About a year later,the craft reached Jupiter
並得到了引力輔助
and got what’s called a gravity assist.
就是說 它要飛到離這個氣體巨星足夠近的地方
That’s where it flies close enough to the gas giant
去獲取引力彈弓效應
to receive a gravitational slingshot effect.
之後 新視野號以每小時約50,000公裡的速度飛行
New Horizons was then flyingat around 50,000 kilometers per hour,
並以同樣的速度飛行八年
as it would for the next eight years
穿越無盡的深淵到達冥王星
to cross the remaining gulf to Pluto.
以如此驚人的速度飛行
Going at such an astonishing speed
意味著放慢速度進入軌道或著陸
meant that slowing down to get into orbit or land
是不可能的
would』ve been impossible.
這就是為什麼說 新視野號執行的是一次飛越任務
That’s why New Horizons was on a flyby mission,
它只有一次機會掃過
where it would get just one chance to screen
冥王星並進行觀測
by Pluto and make its observations.
這次飛行必須完全自動化
The flyby would have to be fully automated,
因為在那種距離 任何從地球發出的引導信號
since at that distance, any signalsto guide it from Earth
都需要四個半小時才能到達
would take 4.5 hours to reach it.
因此 該團隊為飛船的計算機
So the team loaded the ship’s computer
裝載了一系列數千條指令
with a series of thousands of commands,
稱之為核心裝載
called the core load,
那些指令會在飛船距冥王星六天半的距離時開始執行
that would begin to execute when the craft was 6.5 days from Pluto.
可是 當新視野號離它只有十天的距離時
But when New Horizonswas just ten days out,
災難幾乎降臨
disaster almost struck.
地面控制失去了與太空船的聯繫
Ground control lost contact with the spacecraft.
歷經令人幾近崩潰的兩小時後
After two nerve-wracking hours,
新視野號重新上線
New Horizons came back online.
但任務控制人員發現其主計算機已重新啟動
but mission control discoveredthat its main computer had rebooted,
丟失了整個核心裝載和其他關鍵數據
losing the entire core load and other critical data.
沒有它們 飛船會很快閃過冥王星
Without that, it would soon whizz by Pluto
這項任務就會無功而返
with virtually nothing to show for the mission.
任務的運營經理Alice Bowman
Alice Bowman, the mission’s Operations Manager,
帶領團隊連續工作72小時未合眼
led a team for 72 sleepless hoursto get the instructions
及時將指令加載回新視野號
loaded back into New Horizons in time.
沒有絲毫犯錯的餘地
Without room for a single error,
她和她的團隊使飛船重新恢復了正常
she and her team pulled it off,
新視野號開始拍攝並播放令人驚嘆的圖片
and New Horizons began takingand broadcasting breathtaking images.
這些觀測結果呈現了一個令人愉悅的多樣化世界
Those observations have revealeda delightfully varied world,
有地面霧 高海拔霧霾
with ground fogs, high altitude hazes,
可能存在的雲 峽谷
possible clouds, canyons,
高聳的山脈 斷層 隕石坑
towering mountains, faults, craters,
極地冰河地帶 冰川 明顯的沙丘地
polar caps, glaciers, apparent dune fields,
疑似的冰火山
suspected ice volcanoes,
還有過去留下的液體流動的證據等等
evidence for past flowing liquids, and more.
其中一個最令人興奮的發現是
One of the most exciting discoveries
1000公裡寬的史波尼克冰川
is the 1000-kilometre-wide Sputnik Planitia glacier.
它主要由緩慢攪動的冷凍氮氣組成
Sputnik Planitia is mainly composedof slowly churning frozen nitrogen,
以前我們在太陽系從未見過類似的東西
and we』ve never seen anythinglike it in our solar system.
冥王星的探索取得了巨大成功
The exploration of Pluto was a great success,
但新視野號的任務還沒結束
but New Horizons isn’t done yet.
2019年1月1日
On January 1, 2019,
它會打破自己探索最遠天體的記錄
it』ll break its own record forfurthest explored object
去探測柯伊伯帶中 一個叫2014 MU69的天體
when it visits a Kuiper Belt Object called 2014 MU69,
它正在比冥王星更遠的十億公裡處圍繞著太陽運行
which is orbiting the sun another billion kilometers farther away than Pluto.
全世界都在屏住呼吸看看它會在那裡發現什麼
The world is holding its breath to see what it』ll find there.
本節課的作者Alan Stern博士
The author of this lesson, Dr. Alan Stern
是一位行星科學家和新視野號任務的領導者
is a planetary scientist and leader of the New Horizons mission.
他工作了二十多年
He worked for over twenty years
帶領著一個數百人的團隊
leading a team of hundreds
去完成這項令人難以置信的勘探任務
to accomplish this incredible act of exploration.
想了解完整的故事
For the full story,
我們強烈推薦Alan的著作：
we highly recommend Alan’s book,
《追逐新視野號—-首次探索冥王星的艱辛歷程》
Chasing New Horizons — The Epic First Mission to Pluto.
此書與行星科學家David Grinspoon合著
co-authored with planetary scientist, David Grinspoon.