Carrying names of 440,000 well-wishers, OSIRIS-REx ready for journey to Bennu and back

NASA's OSIRIS-REx, which embarks tomorrow on a journey to asteroid Bennu and back, is a mission of superlatives.

It will be the first time an American spacecraft has returned an asteroid sample to Earth. The sample will be the largest-ever since the Apollo 17 mission in 1972.

The Planetary Society helped give Bennu its name. In 2013, we ran a contest to name the half-kilometer-wide world known as 1999 RQ36, which had been chosen as the target for the OSIRIS-REx mission. More than 8,000 students from around the world submitted entries.

We also collected 440,000 names from well-wishers that wanted to symbolically join the seven-year mission. One copy of those names is stored aboard the spacecraft's sample return capsule, and will plunge back to Earth in 2023. Another copy, aboard OSIRIS-REx itself, will slip into a permanent heliocentric orbit.

"I think people enjoy sending their names in order to be directly involved and to vicariously fly in space," said Bruce Betts, director of science and technology projects for the Planetary Societ. "Not everyone who wants to can fly in space, but everyone's name can."

Full OSIRIS-REx coverage from The Planetary Society

Don't miss our launch preview article by Emily Lakdawalla.

For more pretty pictures, check out our Flickr photo gallery.

How Bennu got its name

The winning asteroid name entry came from 9-year-old Michael Puzio. He's 12 now, and by the time OSIRIS-REx returns its precious soil sample in 2023, Puzio plans to be in college.

"I won't be here," he said recently, speaking to me from his home in North Carolina. "You'll have to call a new number."

Puzio won't be home tomorrow, either. He'll be here at Kennedy Space Center watching the launch, and it won't be his first—he told me he's already seen a SpaceX Falcon 9 rocket blast off from the Cape.

When Puzio heard about the naming contest, he was reading a series of mythological fiction books by the author Rick Riordan. The first thing he did was research the god Osiris, the mission's acronym-enhanced namesake (OSIRIS-REx stands for Origins Spectral Interpretation Resource Identification Security-Regolith Explorer).

According to ancient mythology, Bennu was the manifestation of the god Osiris on Earth, taking the form of a heron—a slender bird. OSIRIS-REx looks particularly bird-like with its solar panels and sample arm deployed; hence, Bennu was a perfect fit.

"Bennu covered so many aspects of the project," said OSIRIS-REx principal investigator Dante Lauretta, speaking with Puzio and Planetary Society senior editor Emily Lakdawalla in 2013. "We were especially impressed with how you compared it to the spacecraft."

Perhaps not surprisingly, Puzio's favorite school subjects include math and science. And while he says the naming contest has certainly piqued his interest in spaceflight, he also continues to have a penchant for naming things after mythological stories. He has a dog named Indy, for Indiana Jones, and another named Set, for the Egyptian god of chaos and destruction.

Riding to orbit

The OSIRIS-REx mission starts with a two-hour launch window that opens at 7:05 p.m. EDT (23:05 UTC) Thursday. Its Atlas V carrier rocket will require just one out of a maximum of five solid rocket boosters, giving it a lopsided look during the initial climb to orbit.

After 12 and a half minutes, the Atlas V will have shed its booster, core stage and payload fairing, and the upper stage and payload will begin a 21-minute coast phase. A second upper stage burn will last 7 minutes, followed by a 15-minute coast.

Then, OSIRIS-REx will be cut loose, pulling away from Earth's gravity well. The ride will be over in less than an hour.

A year later, OSIRIS-REx will swing past Earth again for a final slingshot on to Bennu. It will arrive in August 2018, survey the asteroid for two years and collect a sample weighing up to 2 kilograms as early as July 2020. It is expected to leave in March 2021, but the timeline has some wiggle room.

The return date does not. OSIRIS-REx's precious sample will land in Utah on September 24, 2023. The core spacecraft will sidestep Earth and continue onward into orbit around the sun. NASA could potentially repurpose the spacecraft for extended missions.

The science

Chock full of carbon and almost black in color, asteroid Bennu is a 4.5-billion-year-old time capsule dating back to the dawn of our solar system. It is hoped to contain pristine samples of organic compounds that could shed light on how life arose on Earth.

At Bennu, OSIRIS-REx will use a complex suite of instruments to survey the asteroid. Included on the spacecraft is a laser altimeter, an X-ray imager, a suite of cameras, and visual, infrared and thermal emission spectrometers.

Scientists will be able to create a detailed map of Bennu and characterize its surface composition and temperatures, before choosing a safe but scientifically interesting spot to collect a sample. The sampling arm, TAGSAM, will collect between 60 grams and 2 kilograms of material for return to Earth.

But only a fourth of that material will be analyzed in 2023. Like the Apollo moon rocks, a significant portion will be set aside for future generations to study using yet-to-be-developed techniques and instruments.