Final Built-in Hold Coming Up

Although the countdown will pause at the T-4 minute mark, the team’s work will not. During this 15-minute planned hold, we can expect to hear final readiness polls as NASA Launch Manager Tim Dunn and ULA Launch Conductor Scott Barney verify OSIRIS-REx, the Atlas V rocket and the Eastern Range are ready to proceed.

Why Visit Bennu?

Animation still comparing, from left to right, the asteroid Bennu, the Empire State Building and the Eiffel TowerOSIRIS-REx is headed to Bennu, a roughly spherical asteroid measuring about 1,614 feet (492 meters) in diameter. All asteroids represent remnants of the building blocks of our solar system, so why did scientists decide to send a mission to this one?

Location, location, location. For a sample return mission, accessibility is key. Bennu travels in an Earth-like orbit that varies between .9 and 1.4 astronomical units from the sun (an astronomical unit, or AU, is the average distance between Earth and the sun, about 93 million miles). This puts it within the ideal range of .8 AU to 1.6 AU.

Larger diameter means slower rotation. Smaller asteroids – those measuring less than 650 feet in diameter – tend to rotate faster, ejecting surface materials and making it difficult for a spacecraft to get close enough for a sample. With its larger diameter, Bennu completes its day in just over four hours, slow enough for OSIRIS-REx to approach and do its work.

Carbon-rich composition. Measurements taken from telescopes indicate Bennu is carbon-rich. This is important because primitive asteroids like these may contain volatiles and organic molecules that could trace the origins of life on Earth and the potential for life elsewhere.

Image credit: NASA’s Goddard Space Flight Center Conceptual Image Lab


A Nationwide Effort

OSIRIS-REx mission logoOverall mission management for OSIRIS-REx, including systems engineering as well as safety and mission assurance, is provided by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Dante Lauretta is the mission’s principal investigator at the University of Arizona, and the spacecraft was built by Lockheed Martin Space Systems in Denver.

Launch management is the responsibility of the Launch Services Program, or LSP, at NASA’s John F. Kennedy Space Center in Florida. LSP selects the appropriate launcher for the agency’s science missions, provides oversight as the rocket and spacecraft come together, and conducts the countdown.

“Working alongside our United Launch Alliance colleagues, the engineers and analysts of NASA LSP take great pride in launching OSIRIS-REx,” NASA Launch Manager Tim Dunn said earlier in the week.

OSIRIS-REx is the third mission in NASA’s New Frontiers Program, which is managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington.

View of Space Launch Complex 41

Atlas V on SLC 41 venting gaseous oxygen during tanking for OSIRIS-REx launchIn the image above from NASA TV, viewers can clearly see gaseous oxygen venting away from the Atlas V booster. This is normal and is caused when small amounts of cryogenic liquid oxygen boil off and are vented away.

“All the fueling operations have gone perfectly fine today,” NASA Launch Commentator Mike Curie reported.

The OSIRIS-REx Spacecraft

Solar array illumination test being performed on the OSIRIS-REx spacecraft inside the PHSF.Built by Lockheed Martin Space Systems in Denver, Colorado, the spacecraft measures 10.33 by 8 feet and will be powered in space by two solar panels generating 1,226 watts to 3,000 watts, depending on the distance from the sun. With both of its arrays deployed, the spacecraft extends to 20.25 feet long. Learn more about the spacecraft and its instruments.

OSIRIS-REx is expected to reach Bennu in August 2018, collect a sample from the asteroid in July 2020, depart in March 2021, and return the sample to Earth with a parachute landing in Utah in September 2023.

“We’re following on the heels of successful NASA missions like Stardust. In fact, our return capsule is using the same technology that the Stardust mission did to bring those amazing materials back,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson, referring to the mission that launched in 1999, collected particle samples from comet Wild-2, and returned those particles to Earth in 2006.

The OSIRIS-REx mission includes seven years of spacecraft operations and two years of sample analysis in laboratories on Earth.

“We’ve got great science ahead of us,” Lauretta said Tuesday. “I’m really excited to get to this milestone — to get OSIRIS-REx launched on its journey to Bennu and back.”

Photo credit: NASA/Cory Huston