The first mission in NASA's program to take humans back to the Moon has been delayed until spring at the earliest, the US space agency said Wednesday, saying it needed more time to complete safety checks.

The Artemis I launch, initially scheduled for late 2021 and then postponed twice more, will now happen no earlier than April.

"Teams are taking operations a step at a time to ensure the integrated system is ready to safely launch the Artemis I mission. NASA is reviewing launch opportunities in April and May," NASA said in a statement.

Artemis I will be an uncrewed flight test, but will signal the real start of the program, which could eventually see the first woman and the first person of color to step foot on the Moon.

Astronomers will go to great lengths for science. Recently, dozens of astronomers had the misfortune of traveling to one of the most tempting locales in the southwestern U.S.—Las Vegas. But they weren't there for the city's bright lights—they were there to observe the very dim light of a star thousands of light-years away. And what they specifically wanted to see was the light from that star blink out for a few seconds. That lack of light provided the exact data they needed to help them determine the size of Eurybates, one of the Trojan asteroids that will be the focal point of NASA's Lucy mission.

What the scientists were looking for was an occultation. Most people know the most common form of this phenomenon—an eclipse. But occultations can happen with any background star and can be caused by any foreground object. Calculating where these minor occultations of stars by asteroids will occur takes a significant amount of orbital mechanics and processing power. The Earth itself has to be aligned correctly, and the asteroids and stars have to line up just right and be big enough.

A Chinese satellite pulled a defunct navigation satellite out of the way of other satellites on January 22. The satellite, called SJ-21, appeared to operate as a space tug when it grappled onto the navigation satellite from the Chinese CompassG2 network. The operation details didn't come from Chinese authorities but from a report by ExoAnalytic Solutions, a commercial space monitoring company.

Chinese authorities are tight-lipped about the operation, but what can observations tell us about Chinese capabilities?

Earth's geosynchronous orbit is crowded, so on the face of it, having one less piece of space debris is a good thing for all satellite operators. But people can get suspicious when China does something like this.