Enlarge / A Long March 5 rocket, the largest launch vehicle in China's inventory, put a secret Chinese military satellite into orbit on Friday.
China's largest rocket apparently wasn't big enough to launch the country's newest spy satellite, so engineers modernized the rocket.
The Long March 5 launch vehicle flew with a payload fairing about 20 feet (6.2 meters) higher than its usual nose cone as it launched with a Chinese military spy satellite on Friday. This made the Long March 5 the highest rocket China has ever flown, at a height of about 200 feet.
Adding to the intrigue, the Chinese government claimed that the spacecraft aboard the Long March 5 rocket, named Yaogan-41, was a high-altitude optical remote sensing satellite. These types of surveillance satellites typically fly much closer to Earth to obtain the clearest images possible of an opponent's forces and strategically important locations.
That could mean a few things. First, assuming China's official description is correct, the satellite could be heading toward a location in geosynchronous orbit, a position that would give any near-Earth sensor a continuous view of a third of the Earth's surface. In this orbit, the spacecraft would orbit the Earth once every 24 hours, synchronizing its movement with the rotation of the planet.
Since this mission was launched with China's most powerful rocket and the longer payload fairing, the Yaogan-41 spacecraft is likely to be quite large. The U.S. military's space tracking network spotted the Yaogan-41 satellite in an elliptical or oval shape shortly after launch on Friday. Yaogan-41's trajectory ranges from an altitude of about 121 miles (195 kilometers) to 22,254 miles (35,815 kilometers), according to publicly available tracking data.
This is a standard orbit for spacecraft going into geosynchronous orbit. It is likely that the Yaogan-41 satellite will maneuver into this more circular orbit in the coming weeks, where it will maintain an altitude of 22,236 miles (35,786 kilometers) and possibly move into an orbit closer to the equator.
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Staring down from space
In an official statement, China's state news agency Xinhua claimed that Yaogan-41 would be used for civilian purposes such as land surveying and agricultural monitoring. In reality, China uses the name Yaogan as a blanket name for most of its military satellites.
U.S. military officials will closely monitor where Yaogan-41 lands. If, as analysts expect, Yaogan-41 achieves a geosynchronous orbit over the Indian Ocean or the Pacific Ocean, Yaogan-41 would have a constant view of China, Taiwan and neighboring countries.
From such a high altitude, Yaogan-41's optical image sensor will not have the sharp view of a satellite closer to Earth. But it's easy to imagine the benefits of all-day coverage, even at lower resolution, without the Chinese military having to wait hours for a follow-up flight over a potential target from another satellite in low Earth orbit.
In August, China sent a synthetic aperture radar surveillance satellite into geosynchronous orbit using a Long March 7 medium-sized rocket. This spacecraft can achieve a resolution of 20 meters (66 feet) at the Earth's surface with its radar instrument, which can capture images day and night in all weather conditions.
Optical payloads, like those on Yaogan-41, are limited to daytime observations over cloud-free regions. China launched a smaller optical remote sensing satellite into geosynchronous orbit in 2015, ostensibly for civilian purposes.
Although Chinese officials did not disclose Yaogan-41's exact capabilities, it would almost certainly be capable of continuously tracking U.S. Navy and allied ships across a wide swath of the Indo-Pacific. Aside from using the larger payload fairing, the Long March 5 rocket that launched Yaogan-41 can carry about 31,000 pounds (14 tons) of payload mass into orbit, which it reached during Friday's launch.
This suggests that China could have equipped Yaogan-41 with a large telescope to look down from space. In particular, China recognized Yaogan-41's purpose as an optical imaging satellite. China's government doesn't always do this. Perhaps this is a signal to US officials.