Britain's Queen Elizabeth is touring NASA's Goddard Space Flight Center in Maryland, outside of Washington, D.C. as part of her final day of activities in the United States.
The British monarch Tuesday, watched by video link as three astronauts aboard the International Space Station described their work.
During her tour, the queen was to meet with NASA officials and plant a tree at the visitor center.
Later, the queen and her husband, Prince Philip, will visit the National World War II Memorial in Washington. They also are to tour the Children's National Medical Center.
The queen will host a dinner for President Bush and first lady Laura Bush at the British Embassy before returning to London.
On Monday evening, the president and the first lady welcomed Queen Elizabeth II and Prince Philip to a White House dinner.
The queen's visit began last week with a stop in Jamestown, Virginia, to mark the 400th anniversary of England's first American settlement. She and Prince Philip also attended the Kentucky Derby horse race on Saturday.