The crash of a Chinese Moon-Earth photographer

The last commands to Longjiang-2 were sent during a thunderstorm

You’ve probably seen photos like this one not so long ago:

The Longjiang-2 caught a snapshot of the Moon and Earth during the 2019 total solar eclipse on July 2nd. Photo: Harbin Institute of Technology, Camras, DK5LA

It was taken by the 48 kg heavy Chinese satellite Longjiang-2 that went into a 357 by 13704 kilometer orbit around the Moon in 2018.

But on July 31s the satellite was reduced to a crater on the Moons surface as its Chinese controllers ordered it to do some extreme lithobreaking in the Lunar regolith. The de-orbit maneuver was performed to prevent it from turning into a piece of space debris around the Moon after the mission had concluded.

During the mission, the scientists at Harbin Institute of Technology in China worked together with radio amateurs in Europe to up-link certain commands and receive data from the satellite. Reinhard Kühn from Sörup, Germany, had the task of telling the spacecraft when to take a picture. He did this with a radio antenna he has built in his garden.

Reinhard Kühn in his garden in Sörup, Germany, in front of his antenna. Photo: Sven Geißler.

He’s a retired banker with a passion for setting new records as a radio amateur. He did exactly that, when he, as the first radio amateur ever, communicated with a satellite around the Moon.

“Prior to that, there had only been established contact with satellites in orbit around the Earth at 400 kilometers or geostationary satellites at 36.000 kilometers. This is a record of 400.000 kilometers,” Reinhard Kühn says.

During his work with the Chinese, the retired banker sometimes had to get up in the middle of the night to send signals to Longjiang-2. Especially in the last phase of the mission, the Chinese were running a lot of tests as the satellite moved closer to the Lunar surface and Reinhard had to uplink the commands. He didn’t uplink maneuvering commands, though, only signals that would tell the spacecraft when to take a picture.

A picture of the Moons surface taken in the last phase of Longjiang-2s mission. Photo: Harbin Institute of Technology, Camras, DK5LA

On the 31st of July – the day that would Longjiang-2 crash into the Moon – a thunderstorm had rolled in over Sörup and threatened to strike Reinhards antenna.

At 13:31 UTC Reinhard sent the command that would make Longjiang-2 downlink the last image to be returned from the spacecraft. The image looks like the sun but it is actually an overexposed image of all of us down here on Earth.

Last photo of the Longjiang-2 satellite. Photo: Harbin Institute of Technology, Camras, DK5LA

Lightning struck just 100 meters from Reinhards house so he unplugged all electric cables. But he had to plug them in again at 14:04 UTC in order to send a new command to Longjiang-2. The Chinese had told Reinhard to deliver a command to the spacecraft that would make it downlink another image. The purpose was not to retrieve the image but to spot the exact time when the satellite passed behind the Moon at which point the downlink signal would be broken.

Reinhard sent the command at 14:06. Around a hundred seconds passed and nothing happened. Then Longjiang-2 began transmitting for a few seconds and then it went silent – it had passed behind the Moon at 14:08 UTC. The scientists estimate that it impacted the Lunar surface at 14:20 UTC.

Daniel Estévez, another radio amateur, reports that the final periapsis of Longjiang-2 was -61 kilometers.

“In one way I’m happy to have been responsible for this important task for the Chinese team. On the other hand, my task has now ended with the controlled crash of DSLWP-B (Longjiang-2, red.). I will be missing it,” Reinhard Kühn says.

“Especially the pictures of the eclipse of the 2nd of July have touched me deeply. The are very similar to the pictures from Apollo 11. For me that was a special moment, to have contributed to that. I would never have imagined that. It’s a dream come true for a radio amateur.”

He’s become a big name among radio amateurs and he’s happy to inspire new people to go into the field. Who knows how far ordinary people like Reinhard Kühn will reach in space in the future.

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