— Less than a year after NASA's nine-year, three-billion plus mile New Horizons mission explored Pluto, the U.S. Postal Service dedicated Forever stamps to commemorate the achievement, while releasing a second set of stamps depicting NASA's images of the planets.

The first-day-of-issue dedication ceremony for the "Pluto—Explored!" and "Views of Our Planets" stamps took place before an audience of 500 at the world's largest stamp show, which only occurs in the United States once a decade.

Joining David Williams, USPS chief operating officer and executive vice president, at the May 31, 2016 ceremony in New York City were NASA chief scientist Ellen Stofan; NASA director of planetary science Jim Green; Oceanographer at NASA Goddard Space Flight Center in Greenbelt, MD, Norman Kuring, who created the Earth stamp image; and New Horizons principal investigator, Alan Stern. Honored guests included astronaut John Grunsfeld, NASA's former associate administrator for science, and Alice Bowman, New Horizons mission operations manager.

From left: Dan Durda, Constantine Tsang and Cindy Conrad with the Southwest Research Institute; Alice Bowman, New Horizons mission operations manager; Alan Stern, New Horizons principal investigator; David Williams, USPS chief operating officer and executive VP; Ellen Stofan, NASA's chief scientist; Jim Green, NASA's director of planetary science; Delontae Jenkins, NOAA; Norman Kuring, oceanographer, Goddard Space Flight Center.

Ellen Stofan, NASA's chief scientist.

Ellen Stofan, NASA's chief scientist.

David Williams, USPS chief operating officer and executive vice president.

Jim Green, NASA's director of planetary science.

Norman Kuring, oceanographer, NASA Goddard Space Flight Center, Greenbelt, Maryland.

Alan Stern, New Horizons principal investigator, Southwest Research Institute.

Alan Stern, New Horizons principal investigator, Southwest Research Institute.

Alan Stern, New Horizons principal investigator, Southwest Research Institute.

From left: Dan Durda, Cindy Conrad and Constantine Tsang with the Southwest Research Institute; Alice Bowman, New Horizons mission operations manager; Ellen Stofan, NASA's chief scientist; Alan Stern, New Horizons principal investigator; Jim Green, NASA's director of planetary science; Delontae Jenkins, NOAA; Norman Kuring, oceanographer at the Goddard Space Flight Center.

Views of Our Planets and Pluto—Explored! first-day-of-issue ceremony participants sign autographs at the World Stamp Show at the Jacob K. Javits Convention Center in New York City on May 31, 2016.