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Why the most detailed photos ever taken of Pluto took so long to reach us

Close-up view of Pluto showing some of the dwarf planet's mountains and nitrogen ice plains, as seen by NASA's New Horizons.
NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

On May 27, NASA posted the most detailed photos of Pluto's surface ever taken, an absolutely stunning look at the dwarf planet's mountains, craters, and nitrogen ice plains. This is likely to be the best Pluto close-up we'll have for a long, long time. Check out the video below:

The images were taken by NASA's New Horizons craft on July 14, 2015, as it flew by Pluto. But they're only being publicized now, 10 months later. And that delay has provoked, uh, consternation from one Fox News anchor:

That's a weirdly phrased tweet, but there were good reasons for the delay. First, Pluto is very, very far away. New Horizons was about 3 billion miles from Earth when these photos were taken. It takes a long time to send those images.

Specifically: It takes about 4.5 hours for a signal from the craft to reach Earth traveling at the speed of light. But that's not the only hurdle. The large distance means the signal that reaches us is extremely faint. NASA has to use three 200-foot-wide radio dishes (one each in Australia, California, and Spain) to pick it up.

As such, information from New Horizons gets transmitted at about 1 to 4 kilobits per second — more than 10 times slower than a 56k modem from the 1990s. (The spacecraft's communicating via crappy interplanetary dial-up, basically.) An image that's 1024 pixels wide can take about 42 minutes to come through.

On top of that, New Horizons is doing more than just sending photos. As Joseph Stromberg explained last year, NASA initially had the craft send back a small set of images in July 2015 so that the public could ooh and aah, but then switched over to transmitting scientific data about Pluto's temperature, atmosphere, interactions with the solar wind (the charged plasma released by the sun), and its five moons.

In September, NASA resumed image-transmitting mode, but still warned that it would take 16 months to relay all the images and data it had collected — due to slow transmission speeds. NASA has been steadily releasing images of Pluto ever since.

Now, these particular photos of Pluto were actually downlinked back in December, and the raw images were posted to the internet about a week thereafter. No one really paid attention then, because they were raw images and hard to interpret. It took some time for NASA to process them and make them prettier and more presentable for public consumption. And that's what they did in last week's press release.

In a follow-up tweet, van Susteren explained she was mostly concerned that budget cuts at NASA might have been responsible for the sluggish photo release. Budget constraints are undoubtedly a real issue for space exploration. NASA's $19.3 billion budget — about 0.49 percent of federal outlays — has come in for a number of cuts and snips in recent years, especially the parts devoted to planetary science.

As David W. Brown wrote for Vox, those particular trims will mean far fewer resources for exploring our solar system in the years to come. Right now, for instance, there are no spacecraft in the pipeline to replace New Horizons, which means these images of Pluto are the best we'll see for decades, maybe longer. "One by one over the next three years," Brown wrote, "as missions end and spacecraft die, the outer planets will again go dark."

But as to why these images took so long, well, that's less a budgetary question and more due to the fact that Pluto is very far away.

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