Arizonans can rightfully be proud of our home-grown NASA mission named OSIRIS REx. The University of Arizona is a major player in this mission to collect a sample of the asteroid Bennu and return it to Earth. About 500 people at UA have worked on the mission, including about 200 students and the mission’s Principle Investigator Dante Lauretta.
Conceived at UA’s Lunar and Planetary Laboratory over 20 years ago, the OSIRIS REx mission is set to achieve its primary goal this month, when on Oct. 20, it will attempt to collect at least 60 grams of regolith from the near-earth asteroid. The collection will be accomplished by an innovative device known as the Touch and Go Sample Acquisition Mechanism or “TAGSAM” designed and built by Lockheed Martin.
A collection head the size of a car air filter will be extended below the spacecraft by an 11-foot articulated arm. The spacecraft will approach the 500-meter asteroid at walking speed, and the head will touch down at a site called “Nightingale” for about 15 seconds. Contact will be detected by accelero-meters and a pogo stick-like spring will absorb the impact. A five-second blast of pressurized nitrogen will fluidize the surface and draw particles up to about an inch in size through a simple one-way valve and into the collection head. The operation will be documented by a suite of cameras designed and built at LPL. Velcro-like loops of stainless steel around the base of the head will pick up millimeter sized particles. The spacecraft will then back away from the asteroid to a safe distance and will spin in place to measure the weight of the sample. The arm will then fold to point the collector toward another LPL designed camera called SAMCAM to further document the sample size and condition.
If a sufficient sample has been collected, the arm will retract and deposit the collection head into a sample return capsule. SAMCAM will witness the stowage, and once the arm is separated, the capsule will be closed creating a hermetically sealed chamber. Team members hope to collect up to two kilograms of material, but 60 grams will allow completion of the mission’s objectives. OSIRIS REx will remain at asteroid Bennu until its departure next spring. After a two-year return flight to Earth, the sample return capsule will be detached, enter the Earth’s atmosphere and land at the Utah Test and Training Range on Sept. 24, 2023, where it will be retrieved and brought to NASA Houston.
OSIRIS REx arrived at Bennu in December 2018 and conducted a yearlong study of the asteroid with selection of a sample site as a prime objective. The sample site was selected by a scoring process that assigned values related to the safety of the spacecraft, the sample ability of the surface material and the science value of the site. The Nightingale site, near the asteroid’s north pole, is by far the best site and provides the greatest chance of a successful sampling operation.
If this month’s sample maneuver fails for any reason, a second attempt, probably at the backup site named Osprey on Bennu’s equator, will happen in December. The spacecraft has enough nitrogen for three attempts.
The mission has a number of objectives. First, by collecting a sample of this very primitive remnant of the formation of our solar system, scientists hope to learn more about the origin of planets. It is possible that objects like Bennu brought the water to build our oceans and perhaps was the source of the organic materials that anchor the chemistry of life.
Second, the mission will use a sophisticated array of instruments to analyze the asteroid’s composition with an eye toward identifying valuable resources that can be useful here on Earth or as a source of rocket fuel for future exploration. Think gas stations in space.
And finally, to learn as much as we can about how to protect the Earth from impact by an asteroid. Bennu currently is the most hazardous object known, having about a 1 in 3,000 chance of impacting Earth in the 2100’s. What we learn today may be essential to a future asteroid deflection mission, and might literally save the Earth!
About 25% of the sample will be studied in the first few years after retrieval, and 75% will be archived for future study by scientists not yet born. A small portion of the sample will be exchanged for a sample of another asteroid, Ryugu, which is the target of Japan’s JAXA mission Hayabassa 2. The two missions have been cooperating since their inception.
If all goes well, the sample returned by OSIRIS REx will be the largest sample return since the Apollo missions. For information about the mission, you can visit https://www.asteroidmission.org/