NASA’s OSIRIS-REx asteroid mission to launch Thursday
CAPE CANAVERAL, Fla. — United Launch Alliance (ULA) is all set to launch NASA’s Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) atop the company’s Atlas V 411 rocket. The spacecraft will be sent to asteroid Bennu and spend a couple years there before descending to the surface of the small body to collect up to 4.4 pounds (2 kilograms) of samples. The probe will bring those samples back to Earth by September of 2023.
The launch window is currently set for 7:05 p.m. EDT (23:05 GMT) Thursday, Sept. 8, from Cape Canaveral Air Force Station’s Space Launch Complex 41 (SLC-41) in Florida. The ULA team has a two hour launch window to get OSIRIS-REx into space with a liftoff time available every five minutes.
Sunset will occur at 7:35 p.m. EDT (23:35 GMT), which should provide viewers the opportunity to see some fairly dramatic colors as the sunset illuminates the rocket’s plume as it travels skyward.
Weather conditions for the launch are about typical for central Florida in September. The 45th Weather Squadron has predicted a 30 percent chance of unacceptable during the roughly two-hour long Sept. 8 launch window with the primary concern being cumulus and anvil clouds.
Should weather not cooperate, the Eastern Range has reserved an additional two days to attempt to get the mission underway. Each day, the start of the window begins five minutes later than the day before. However, weather conditions are not expected to change much through the end of the week.
Ultimately, OSIRIS-REx must be launched and sent toward Bennu before Oct. 12. Failure to do so will mean the team will miss this year’s launch window. Should that happen, the launch will be delayed for a whole year.
The Atlas V launch vehicle completed a “wet” launch dress rehearsal (a practice launch countdown with propellants on board) back on Aug 25. Now enclosed within its 13-foot (four-meter) diameter payload fairing, OSIRIS-REx has completed communications system testing and is ready to fly.
The mission is the latest and, to date, the most ambitious asteroid mission ever assembled. After an orbit around the Sun, which will include a gravity-assist maneuver around Earth, OSIRIS-REx should catch up with Bennu in 2018 and go into orbit around the rocky body. There it will survey the asteroid for more than a year. During that time, it is planned to have the probe map the surface, identify the material composition of its surface materials, and identify the best place or places for collecting samples.
In 2020, the asteroid’s minuscule gravity should enable OSIRIS-REx to make a gradual descent toward the surface. Once it gets within 11 feet (3.4 meters) or so of the asteroid, a sampling device called the Touch and Go Sample Acquisition Mechanism (TAGSAM) will reach out to the surface and use a blast of pressurized gas to force nearby regolith into the Sample Return Capsule. This touch-and-go maneuver could be done up to three times.
With its samples safely on board, OSIRIS-REx will return to Bennu orbit until the time is right to return to Earth (in 2021). The entire spacecraft will return to Earth’s vicinity by September of 2023, at which point the Sample Return Capsule will separate from the spacecraft and reenter the Earth’s atmosphere, using atmospheric braking and two parachutes to return safely to the surface.
The key objectives of OSIRIS-REx are spelled out in its rather lengthy acronym: it will investigate the asteroid’s structure and composition to determine its origins; study the surface over a range of visible, infrared, and x-ray spectra; identify potentially useful resources; study asteroid behavior with an eye toward planetary security; and collect samples of the asteroid’s regolith for study back on Earth.
Building on previous missions
OSIRIS-REx is ambitious due to its complexity, mission length, level of surface analysis, and quantity of samples it is designed to return. Previous NASA missions – including Galileo (1991), the Near Earth Asteroid Rendezvous (NEAR) (2000), Deep Space 1 (1999-2001), and DAWN (2011-Present) – have orbited or flown by asteroids and captured data using cameras and spectrometers. Japan’s Hayabusa spacecraft was the first spacecraft to return samples from an asteroid (Itokawa in 2010).
The OSIRIS-REx mission is a major step forward in asteroid exploration in that its instruments include three cameras, a laser altimeter, an infrared spectrometer, a visual-infrared spectrometer, and an x-ray spectrometer. In addition to this array of instruments, the spacecraft will be returning up to 4.4 pounds (2 kilograms) of surface samples.
Video courtesy of The University of Arizona
Bart Leahy is a freelance technical writer living in Orlando, Florida. Leahy's diverse career has included work for The Walt Disney Company, NASA, the Department of Defense, Nissan, a number of commercial space companies, small businesses, nonprofits, as well as the Science Cheerleaders.