Chinese astronauts successfully performed the country's first tandem spacewalk on Sunday, working for seven hours on the outside of the new Tiangong station in orbit around Earth.

Tiangong's construction is a major step in China's ambitious space programme, which has seen the nation land a rover on Mars and send probes to the Moon.

Three astronauts blasted off last month to become the station's first crew, where they are to remain for three months in China's longest crewed mission to date.

On Sunday morning, two of them exited the station for around seven hours of work in the first spacewalk at Tiangong, the China Manned Space Agency said.

Researchers from the National Time Service Center (NTSC) of the Chinese Academy of Sciences have proposed a new method to realize absolute calibration of multi-mode satellite navigation receiver delay.

The new method can be applied to fields like navigation positioning, satellite timing, and time transfer, increasing user positioning and timing accuracy.

The calibration of global navigation satellite system (GNSS) receiver delay poses a technology difficulty in the field of satellite navigation. The widely used relative calibration method can only obtain the delay difference between a tested receiver and a reference receiver.

However, fields like GNSS time offset monitoring, satellite timing technology and satellite-ground time synchronization need absolute calibration.

NTSC researchers used satellite simulator hardware and high-speed oscilloscope to completely calibrate all kinds of GNSS receiver delay, with the calibration accuracy better than 1.5ns(1σ).

An atomic clock provided reference frequency for all equipment. Testing Time-to-Code (TtC) by the oscilloscope was used to calibrate the simulator delay, and the channel delay could be calculated by the pseudorange, 1and PPS output delay measured by a time interval counter.

This image taken with the NASA/ESA Hubble Space Telescope depicts the open star cluster NGC 330, which lies around 180,000 light-years away inside the Small Magellanic Cloud. The cluster—which is in the constellation Tucana (the Toucan)—contains a multitude of stars, many of which are scattered across this striking image.

Because star clusters form from a single primordial cloud of gas and dust, all the stars they contain are roughly the same age. This makes them useful natural laboratories for astronomers to learn how stars form and evolve. This image uses observations from Hubble's Wide Field Camera 3 and incorporates data from two very different astronomical investigations. The first aimed to understand why stars in star clusters appear to evolve differently from stars elsewhere, a peculiarity first observed with Hubble. The second aimed to determine how large stars can be before they become doomed to end their lives in cataclysmic supernova explosions.

Hubble images show us something new about the universe.

NASA's newest six-wheeled robot on Mars, the Perseverance rover, is beginning an epic journey across a crater floor seeking signs of ancient life. That means the rover team is deeply engaged with planning navigation routes, drafting instructions to be beamed up, even donning special 3D glasses to help map their course.

But increasingly, the rover will take charge of the drive by itself, using a powerful auto-navigation system. Called AutoNav, this enhanced system makes 3D maps of the terrain ahead, identifies hazards, and plans a route around any obstacles without additional direction from controllers back on Earth.

"We have a capability called 'thinking while driving,'" said Vandi Verma, a senior engineer, rover planner, and driver at NASA's Jet Propulsion Laboratory in Southern California.