At this very moment, NASA’s New Horizons spacecraft is more than 3 billion miles from Earth. To put that into perspective, think about how mind-numbingly far the Sun is from Earth. Then multiply by 32.
That’s how deep in space New Horizons is right now.
Now imagine sending a deluge of data — high resolution photos, measurements of atmosphere and temperature, ultraviolet images, etc. — from that distance at just 600 to 1,200 bits per second, or about 50 to 100 times slower than the speed of a modern cable modem.
“At the data rate we have … it takes over 2 hours to downlink a standard picture from your cell phone! That means we will spend the next 16 months transmitting all the data down to Earth,” Curt Niebur, a NASA program scientist, wrote during a Reddit “Ask Me Anything” thread.
For this very reason, we’re going to have to wait hours, days, even months before we get the best, full-sized, high-resolution images from Pluto.
How the data delay works
New Horizons talks to Earth through a system of four antennas. These allow the spacecraft to transmit raw data, receive commands, send status updates, and deliver tracking information.
But the paltry bandwidth of the antennas means New Horizons has to save data locally until it can beam it to Earth. For that reason, it’s equipped with two solid-state recorders.
Each recorder can collect, compress, sort, and store about 8 gigabytes of data, much in the same way digital cameras store photos to a flash memory card. (Except we’ll never get them back to plug into a computer on Earth.)
New Horizons was scheduled to record an unprecedented amount of measurements and photos with its suite of seven instruments Tuesday morning.
How long it will take to trickle that data back to Earth seems a little uncertain. Although Niebur said it will take 16 months, a NASA press kit states it will take about 9 months.
Either way, we should start to see something tantalising soon.
“Tomorrow [Wednesday] we’ll see images that are 10 times higher resolution” than those taken right before the flyby, said Alan Stern, principle investigator of the New Horizons team, during a live webcast on NASA TV.
For most of the mission, New Horizons will use an 83-inch-wide “high-gain” antenna, which sits on its top deck to communicate with NASA. It takes about four hours and 25 minutes for a radio signal from that antenna to reach New Horizons from Earth, and vice versa. The signals can travel only as fast as the speed of light, and the spacecraft is far enough away that it takes that long to send.
“The one thing I wish we had beefed up on this spacecraft is the antenna to send back the data a little quicker,” Fran Bagel, a New Horizons co-investigator, said during an American Museum of Natural History webcast on Tuesday. “But forget it. It’s too small an object that’s too far away.”
The first images of Pluto might start coming in tonight, but not until NASA first receives a signal confirming the flyby was a success. That signal won’t arrive until around 9 p.m. ET.
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