Daughters of NASA astronaut Alan Shepard, Laura Shepard Churchley, left, Alice Wackermann and Julie Jenkins, right, speak during an unveiling ceremony of two USPS stamps that commemorate and celebrate 50 years of US Spaceflight and the MESSENGER program during an event, Wednesday, May 4, 2011 at the NASA Kennedy Space Center in Cape Canaveral, Fla. One stamp commemorates NASAs Project Mercury, Americas first manned spaceflight program, and NASA astronaut Alan Shepards historic flight on May 5, 1961, aboard spacecraft Freedom 7. The other stamp draws attention to NASAs unmanned MESSENGER mission, a scientific investigation of the planet Mercury. On March 17, 2011, MESSENGER became the first spacecraft to enter into orbit around Mercury.