Member of Mark Kelly's Crew Tweets on Shooting

Gregory H. Johnson, who is slated to pilot the space shuttle Endeavor when it goes on the STS-134 mission in April, tweeted about the mission, and his commander, Mark Kelly, and his wife, Ariz. shooting victim Congresswoman Gabrielle Giffords.

Johnson thanked his followers for support in the first tweet.

"Thank you all for your support: Gabby, Mark, & our crew. Last week was terrible, horrific. But after one long week, we're in a better place."

In the second tweet, Johnson gave updates on Gabby's condition, referred to his colleague's strength and mentions a proposed back-up plan if Kelly is unable to command the mission.

"Gabby improves daily, Mark is strong, our mission team has already prepared a revised plan and a backup plan if needed. STS134 will succeed."