They began to show up after the Challenger disaster. In 1988, during NASA's first shuttle flight after the accident, a bouquet of roses was delivered to Mission Control in Houston. Seven red ones, plus one white.
There was a note attached -- best wishes and a safe flight from Mark and Terry Shelton and their daughter MacKenzie -- but it didn't say who they were or where they lived. After a bit of hesitation, controllers put the roses in a vase on top of the flight director's control console, a bit of color amid readout screens and flight plan booklets.
Milt Heflin, a veteran flight director, was touched and intrigued. "Frankly, people didn't send things like that to mission control," says NASA's James Hartsfield. Heflin called the florists who had delivered them. They were at first reluctant to give out personal information.
It turned out the Sheltons were just an American family, like yours or mine, from the Dallas suburbs. Mark Shelton, a computer engineer, had been a space buff since childhood. His wife Terry is in the clothing business. MacKenzie, a toddler in 1988, is now 23 and studying to be a special-education teacher.
"I thought it would be nice to remind them the public is out there, and they care," said Mark Shelton in a phone interview. "It's a dangerous job the astronauts have, and so many people are responsible for their lives, and they take it very seriously."
The flowers have kept coming, one bouquet during every shuttle flight. There will always be as many colored roses as there are astronauts on the mission (most shuttles carry seven), plus one white one. Heflin asked why. In memory of the astronauts who gave their lives, said the Sheltons.
This month's mission, STS-119, flown by the shuttle Discovery, was the hundredth since the Sheltons began their quiet tradition, and NASA invited them down to Houston for a ceremony of appreciation.
"I think it means so much because we never asked for it," said Heflin. "We never expected it. We believe it truly represents the sentiment of a large part of the public, as well as a very personal gesture."
(Photo: the bouquet for STS-114 in 2005, the first flight after the Columbia accident. Courtesy NASA.)