Even assuming that Voyager still had the power to do this, that the cameras hadn’t been switched off leaving the entire instrument boom at the temperature of liquid helium, and that even the software for sending images hadn’t been removed from the flight computers (and the ground computers and software retired and scrapped)… why, exactly, would you want to do this?
Do you think that, looking back towards the sun, Voyager would see something like this?
Well, I hate to break it to you, but that’s not how the solar system actually works.
Space, as I’ve mentioned before on Quora, is big. Really big. And more importantly, it’s empty. Really empty.
Voyager did turn around and take a “Family Portrait” of the solar system. It looks like this:
Over on the left in the middle of the “arc” of pictures, is a bright star. That’s the Sun. In the image to the left of that is the Earth, and Venus. Mercury and Mars were lost in the glare of the sun. The entire inner Solar System — Mercury, Venus, Earth, Mars and the Sun — are contained in those two 800×800 pixel squares.
图片“弧”中间的左上方有一颗明亮的星星。 那是太阳。 在左边的图像中是地球和金星。 水星和火星在阳光的照耀下没法看到。 整个内太阳系-水星，金星，地球，火星和太阳-只包含在这两个800×800像素的正方形中。
To put that in perspective, were the sun the size of a basketball, that area would be the size of a football field, with Mars skirting the end zones. (Or the end lines on a soccer field, for those who prefer European football.) And even at that scale, Earth would be just about a millimeter across. Imagine standing a mile away from the football field and trying to find a single BB lit only by the light blasting from a carbon arc-lamp in the middle of the field. Like I said, Space is Big.
准确来说，如果太阳大小等于篮球大小，那么内太阳系就是足球场的大小，而火星会绕过边界区域。 （或者，对于喜欢欧洲足球的人来说，是足球场上的终点线。）即使在这样的规模下，地球也只有约一毫米宽。 想象一下，站在距离棒球场一英里远的地方，您要找到一个这个棒球场上的一个棒球（指地球和火星这类行星），而这个棒球场仅由场中央的碳弧光灯照亮（指太阳）。 就像我说的，空间很大。
Yet when they turned the Narrow Angle Camera (think “Zoom lens”) on where the Earth should be, they managed to catch a photo of it, despite the glare of the Sun.
To Paraphrase Carl Sagan, the Earth, the planet where every scrap of history you’ve ever heard of, every man, woman, and child you’ve ever met, every war, every accomplishment, every disaster, every triumph, every living thing… is a single, pale blue dot, caught in a ray of sunshine.
如Carl Sagan所说的那样，地球，这星球上的每一个历史遗迹，您遇到的每个男人，女人和孩子，每一次战争，每一次成就，每一次灾难，每一次胜利，每一个生物 ……是一个浅蓝色的单点，成为一束阳光的一部分。
(NASA – The Pale Blue Dot photograph)
See it? On the right? In the orange-ish beam of sunlight?
One Pixel. (Technically, Earth was only 0.12 pixels wide at that distance.)
That’s you. That’s me. That’s the whole Earth. Lost in vast sea of darkness, balanced on a sunbeam.
Jupiter, the King of the Planets, is four pixels across.
Saturn with it’s vast rings, is six pixels wide, and is halfway across the panorama, though even with how brightly Saturn reflects the Sun’s light, it cannot be seen on the Wide Angle panorama.
Uranus, still closer to voyager, is a blue streak (the camera couldn’t be held steady for the 15 second exposure it took to get a picture) that covers about 12 pixels.
And Neptune, at the far right edge, and closest to Voyager when the picture was taken, is lost in a field of stars, a mere four pixels wide, and that mostly from motion smearing as well.
(By NASA – Public Domain, File:Voyager Portrait Family diagram.jpg)
It took nearly two hours to take this panorama of 60 photos. It took another 10 hours to transmit them from the edge of the Solar System back to Earth. Most of the frames (39) were taken with the Wide Angle Camera, but each planet was imaged with the Narrow Angle Camera, three times each, with different filters over the black and white camera to produce a color image (21 frames).
The image of the sun was taken with the darkest filter (Methane absorption band) and only for 1/125th of a second. The Wide Angle Camera panorama was taken with one second exposures. The Narrow Angle Camera images were taken with up to 15 second exposures just to get the planets to show up.
Voyager 1 was 6 billion kilometers (4 billion miles) from Earth when it took this picture on Valentine’s Day of 1990.
The entire panorama is only about 4000 pixels wide.
Every year, Voyager 1 travels another 3.6(ish) AUs further away. That’s about another half a billion kilometers. In the 27 years since Voyager took this photo, it has gotten to three times the distance – 141 AUs, 21 billion kilometers, or 13 Billion miles. That means the entire picture would be 9 times smaller now (inverse square law). Meaning the whole Solar System (not counting the Kuiper Belt and the Oort Cloud) would now take up about 440 pixels of one picture.
每年，旅行者1号又要行驶3.6（ish）个AU（astronomy unit，天文单位）。 大约又是十亿公里。 自Voyager拍摄这张照片以来的27年中，它的距离已达到之前距离的三倍-141个AU，210亿公里或130亿英里。 这意味着整个图片现在将缩小9倍（平方反比）。 这意味着整个太阳系（不包括柯伊伯带和奥尔特云）现在将占据一张图片的约440像素。
Which means, your panorama of the Solar System, which would be totally swamped by the light of the sun (still several orders of magnitude brighter than anything else in the sky) would look like this:
Or, to put it in perspective, here’s the same 800×800 Voyager-sized image with the original “Family Portrait” overlaid to scale. Even Jupiter and Saturn are lost in the glare of the Sun, and Uranus and Neptune (despite them being slightly brighter pixels here) would be far too small and dim to see.
The real fact is, the “Family Portrait” taken by Voyager 1 was really right at the limit of the instruments, and any further pictures would just have been of the sun getting dimmer and dimmer. So there’s really no point in spending what’s left of Voyager’s extremely limited power budget on taking pictures out where it’s dark, and there’s nothing to see anyway.
Which is, of course, why the “Family Portrait” was the last set of images taken by either of the Voyager spacecraft before the cameras and their heaters were switched off to preserve power for the other instruments that were still doing real science.
So, the reason there were no more panoramas taken was that there was no reason to take any more of them. Carl Sagan convinced them to take the Family Portrait, and it is still a great object lesson in both how small we are as a people, and how vast space is. We are a curious species, and this should just whet our appetite to venture further and explore more.
因此，不再拍摄全景图的原因是没有必要了。 卡尔·萨根（Carl Sagan）说服他们拍摄了全家福，这仍然是能让我们认识到人类有多渺小，太空有多宽广的一节好课。我们只是好奇的物种，为了满足我们永远满足不了的好奇心，我们将继续探索更深更远。
“The surface of the Earth is the shore of the cosmic ocean. On this shore, we’ve learned most of what we know. Recently, we’ve waded a little way out, maybe ankle-deep, and the water seems inviting.” — Carl Sagan, Cosmos.