Mr. Cabbage said it was too early to say how Mark Kelly’s scheduled Endeavour mission would be affected. The Kelly brothers were to have been the first twins to be in space together when Endeavour visited the space station, but the launching of Endeavour has slipped to April, a month after Scott Kelly’s scheduled return to Earth.

Ms. Giffords and Mark Kelly, 46, married in November 2007. In Congress, Ms. Giffords has played a major role in NASA policy. Until the Republicans assumed control of the House of Representatives last week, she was chairwoman of the Space and Aeronautics Subcommittee of the House Committee on Science.

As the Obama administration sought last year to end NASA’s Constellation program to send astronauts to the moon, Ms. Giffords was critical of the shift, arguing that the program should be modified, not canceled. In September, she voted against an authorization bill that laid out the blueprint for NASA for the next three years.

She said the bill, which passed and was signed into law by President Obama, “forces NASA to build a rocket that doesn’t meet its needs, with a budget that’s not adequate to do the job and on a schedule that NASA’s own analysis says is unrealistic.”

“As a longtime supporter of NASA, Representative Giffords not only has made lasting contributions to our country, but is a strong advocate for the nation’s space program and a member of the NASA family,” Maj. Gen. Charles F. Bolden Jr., the NASA administrator, said in a statement. “We at NASA mourn this tragedy and our thoughts and prayers go out to Congresswoman Giffords, her husband, Mark Kelly, their family, and the families and friends of all who perished or were injured in this terrible tragedy.”