Cassini to image the Earth tonight | Hacker News Reader

Cassini to image the Earth tonight

saturn.jpl.nasa.gov

102 pointsrowanseymour35 comments

At Saturn's enormous distance, the crescent Earth, with most of North America illuminated by the sun, will span a single pixel and will appear as a pinpoint of light in the depths of space [1, 2]. FYI - The Cassini cameras are 1-megapixel cameras, modes include 1024x1024, 512x512, and 256x256 pixels [3].

I work at an observatory and there was some internal discussion this morning about heading outside to wave. Cool idea, but I don't think you are going to be able to see yourself in the image ;)

Times for anyone in the US to head outside:

  U.S. - Hawaii-Aleutian Stand. Time  Fri 11:27 AM 	11:27 	HAST
  United States - Alaska Daylight     Fri 1:27 PM 	13:27   (24/h) 	AKDT
  U.S. - Pacific Daylight Time 	      Fri 2:27 PM 	14:27 	PDT
  U.S. - Mountain Daylight Time       Fri 3:27 PM 	15:27 	MDT
  U.S. - Central Daylight Time 	      Fri 4:27 PM 	16:27 	CDT
  U.S. - Eastern Daylight Time 	      Fri 5:27 PM 	17:27 	EDT

[1] http://www.cbsnews.com/8301-205_162-57594419/cassini-spacecr...

[2] http://blogs.scientificamerican.com/life-unbounded/2013/06/1...

[3] http://saturn.jpl.nasa.gov/faq/FAQRawImages/#q5

So I've seen some gorgeous images from Cassini, but I could've sworn they're all much higher than 1 megapixel. Do you have any info for how that works?

I would checkout the FAQ page @ http://saturn.jpl.nasa.gov/faq/

I am not sure how the Cassini imagery works, but for something like Hubble Space Telescope (HST), here is what a raw image [1] looks like of M51 [2]. Typically the images you see from HST of M51 [3] will be a compilation of dozens of raw images using colour filters.

[1] http://i.imgur.com/qtQdcBS.jpg

[2] https://en.wikipedia.org/wiki/Whirlpool_Galaxy

[3] https://en.wikipedia.org/wiki/File:Messier51_sRGB.jpg

Thanks :) The links are much appreciated! I have to say, purely from an artistic point of view, there's something a lot more dramatic about the raw images than the final one (at least to my eyes). I think it's a combination of the contrast, and the fact that the object is too big to fit in the frame that gives it a sense of scale.

They mention on the page for this (beautiful!) image:

http://photojournal.jpl.nasa.gov/catalog/PIA08329

that it's a combination of 165 images taken over a period of three hours.

Megapixels aren't everything not matter what the camera companies tell us.

I will be waving. Cuz I'm a dork. But I will actually be waving.

Come to think of it. I might even throw a waving party of some sort. Hold up a sign, have some beer, play some The Blue Danube via Spotify over Airplay.

Shine a spotlight in the direction of Saturn, or build a fire. I wonder how much light you'd need to emit to have a noticeable effect? The Narrow Angle Camera is 1024x1024 I think[1], I have no idea what integration time, so my first guess is that we need to get a major city to riot/burn, or start a forest fire. Hmm, on second thought, maybe I'd better just have a beer and wave like cdevroe.

[1] Based on the properties of this image http://saturn.jpl.nasa.gov/multimedia/images/raw/casJPGFullS...

Not quite the same question, but related - XKCD did a "What If" on whether, if everyone on Earth shone a laser at the Moon, it'd be visible. (TL;DR: No.)

http://what-if.xkcd.com/13/

The team at JPL that built Cassini will be out there too. From the announcement:

"Earth will be just 1.5 pixels wide, with the illuminated part of Earth less than a pixel, so the resulting mosaic will not show any features on Earth. But it's a chance to be part of a special portrait, to contemplate what we look like from interplanetary distances, and to celebrate the longevity of our Cassini spacecraft, which has been successfully orbiting Saturn for nine years."

In 2006 Cassini already took a beautiful image of Saturn with the Earth visible: http://apod.nasa.gov/apod/ap061016.html

I love the romance of this. Even though the earth is only going to be a few pixels, the frame will contain a snapshot of the entire human race.

That's one of my favorite things about the famous Earthrise photo: http://en.wikipedia.org/wiki/Earthrise

The frame contains every living human, and every human who has ever lived - except for three of them.

That's such an overwhelming thought.

Well, assuming the lost cosmonauts conspiracy theory (http://en.wikipedia.org/wiki/Lost_Cosmonauts) is wrong.

> every human who has ever lived

How is that, exactly? Doesn't the picture only contain the light captured at that moment?

The photograph captured the light from the planet where everyone who has ever lived has spent their entire life, except for a small number of astronauts. More accurate, but less spiritual/sentimental sounding.

"The frame contains". Meaning that every dead and then-living human was within the camera's view frustum, except for the three in the spacecraft. Not considering whether they're in the nighttime part of the planet or on the far side away from the camera; just that they're somewhere within the field of view.

Presumably many photos of the Earth from spacecraft have achieved the first part of that criterion, as Cassini's will. But the set of photos of most of the human race minus a few is much smaller: limited to the moon missions, because the shuttle and space station orbit too low to fit the entire Earth in one camera frame.

Assuming perfect accuracy, how many people would it take aiming standard laser pointers at Cassini during the imaging to noticeably impact the resulting image?

Based on XKCD's research (http://what-if.xkcd.com/13/), I am guessing the short version of the answer is, "More than we have."

That's hilarious. However, my question involves impacting the optical imaging system of Cassini which is many, many orders of magnitude easier than overcoming direct illumination from the Sun. The real issue is the matter of beam dispersion rather than having insufficient power, as an astronaut 10 meters away could easily blind Cassini's optical imaging system using a laser pointer.

I'll wave when they send a bigger camera.

I will be waving from WTC (NYC), so hopefully other people will too. 5:27-5:42PM ET. Space programs are awesome!

A bummer, saturn is currently visible here, but will be on the other side of the planet when the time comes.

Isn't Cassini near Saturn? How is it going to image the Earth? Why are we waving?

>How is it going to image the Earth?

The sun is being blocked by saturn itself, so the earth will be visible to the camera. The real purpose is to image the rings. Actual info is here: http://saturn.jpl.nasa.gov/news/waveatsaturn/

> Why are we waving?

To ensure NASA's continued funding/for a bit of innocent amusement. Take your pick.

Right, so it's going to be far from the street-level imaging Google does, as I suspected.

Earth will be a few pixels at best. The pale blue dot photo has basically a single pixel of Earth, though Voyager was farther away than Cassini at the time (past the orbit of Saturn) and its cameras weren't as good.

Casini has a camera that's on the order of one megapixel in black and white. I'd be surprised if earth is more than a few pixels above the noise.

I think the idea is to recreate something like the famous Pale Blue Dot [1] image taken by Voyager 1. Here's a thought from Carl Sagan about that:

From this distant vantage point, the Earth might not seem of any particular interest. But for us, it's different. Consider again that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives.

[1] http://en.wikipedia.org/wiki/Pale_Blue_Dot

which way is saturn at the moment? if it's only imaging for 15 mins, it surely can't see all of us!

I just tried to work that out using a basic app on my phone. My 'calculations' say that Saturn will be to the north east of the moon if you're in the UK? I spent about 3 seconds on this. Can anyone confirm/correct this?

Edit: by north east I mean if you imagine that the moon is on the centre of the map and you look up and to the right from it.

Edit 2: Looks like Saturn will be in the bottom of the constellation Virgo.

ah, so I will be in the field of view, if still too small for the horizontal resolution? cool! thanks :)

Say 'Cheese', guys!

Everyone SMILE! Say cheese!

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