The astronauts of Space Shuttle mission STS-131 are delighted by the response to their extra-terrestrial Twitter messages, they said Monday.

In space for 16 days, the crew included NASA astronaut Clay Anderson (@Astro_Clay) and Japanese astronaut Naoko Yamazaki (@Astro_Naoko) who kept tens of thousands of followers on the ground updated with the progress of the mission.

"I think it's a very effective way, a very quick way, a very easy way for crew members to relate to people on the ground to tell them the excitement and the spectacular views that we have," said Anderson at a Tokyo news conference. "It's a great way to communicate the wonder of spaceflight."

Anderson's messages included snippets about his time in space that managed to cram his enthusiasm for the mission in 140 characters or less.

"Day 8 in orbit about the Earth! Beautiful views to relax to, after a 7 hour & 26 minute EVA! Whew! What a vehicle!," he wrote on April 13.

But they almost didn't make it online. A malfunctioning dish antenna on Space Shuttle Discovery meant Anderson wasn't able to transmit the messages from the Shuttle itself and had to wait until it docked with the International Space Station. From their he was able to use the space station's communications equipment.

"I sent it to some people on the ground who then did the tweeting for me from Houston," he said.

It was just over a year ago, on May 12, 2009, that the first message was posted to Twitter from space. Astronaut Mike Massimino (@Astro_Mike) sent a tweet from Space Shuttle Atlantis. He's become the most-followed astronaut on the micro-blogging site with almost 1.3 million people subscribed to his Twitter feed.

Japanese astronaut Naoko Yamazaki said she valued Twitter for the feedback it brought her from followers on the ground.

"I got feedback from the readers," she said. "I hope this communication will be more advancing in the future so that space will get more familiar to us."

She became the second Japanese astronaut to use Twitter in space, following in the footsteps of Soichi Noguchi (@Astro_Soichi), who built up a following of several hundred thousand people by tweeting out photographs he had taken from the ISS, sometimes snapped to order after requests from followers. Noguchi recently returned to Earth on June 2.

Martyn Williams covers Japan and general technology breaking news for The IDG News Service. Follow Martyn on Twitter at @martyn_williams. Martyn's e-mail address is martyn_williams@idg.com

Copyright 2010 IDG. All Rights Reserved.