On the 24th of September, NASA’s OSIRIS-REx spacecraft will complete its primary mission, delivering nearly 1 kilogram of material from the asteroid Bennu after 7 years in space. This mission is a triumph of engineering, a testament to the power of design and ingenuity – but it is not over yet. After the delivery of the samples to the Utah Test and Training Range, and mission scientists eagerly get their hands on pieces of another world, OSIRIS-REx will take on a new name – OSIRIS-APEX, with its sights set on the formidable asteroid Apophis. Its continuing mission will aim high and set out to assess one of Earth’s biggest threats.
OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) was selected as part of NASA’s New Frontiers program in May 2011, the third mission in this “mid range” class. These missions aim to accomplish more than their smaller scale Discovery class counterparts, but are targeted at lower costs than the larger flagship class. Overall management, engineering and navigation for the mission is provided by NASA’s Goddard Space Flight Center, while the University of Arizona’s Lunar and Planetary Laboratory provides principal science operations. Lockheed Martin Space Systems built the spacecraft and continues to provide mission operations. OSIRIS-REx was launched atop an Atlas V 411 on September 8th, 2016 from Cape Canaveral’s SLC-41, and separated 55 minutes later – sending the intrepid spacecraft towards asteroid Bennu and back.
The asteroid 101955 Bennu, to mission scientists, is a treasure trove of information. Asteroids like Bennu are old and relatively untouched, having undergone little geological change from their time of formation. In particular, Bennu was selected because of the availability of pristine carbonaceous material, a key element in organic molecules necessary for life as well as representative of matter from before the formation of Earth. Organic molecules, such as amino acids, have previously been found in meteorite and comet samples indicating that some ingredients necessary for life can be naturally synthesized in outer space. Samples from Bennu could help paint a picture for how life on Earth came to form, and how the early Solar System produced such suitable conditions. The asteroid was also chosen for its potential to impact Earth, a relatively low 1-1,800 probability.
OSIRIS-REx entered its cruise phase shortly after separation from the launch vehicle following successful solar panel deployment, propulsion system initiation, and establishment of a communication link with Earth. During cruise, the spacecraft was awakened several times to perform system checks and test out its wide variety of instruments and sample return features.
On December 3rd, 2018, NASA announced that OSIRIS-REx had matched the speed and orbit of Bennu at a distance of about 19 km (12 mi), effectively reaching the asteroid. The small nature of Bennu resulted in maneuvers more akin to a rendezvous, rather than an orbital capture. OSIRIS-REx entered orbit around Bennu on December 31st, 2018 at about 1.75 km (1.09 mi) to start its extensive remote mapping and sensing campaign for the selection of a sample site. This is the closest distance that any spacecraft has orbited a celestial object, surpassing the Rosetta mission’s orbit of comet 67P/Churyumov–Gerasimenko at 7 km (4.3 mi). After extensive surveys from orbit, NASA selected the final four candidate sample sites in August 2019, named Nightingale, Kingfisher, Osprey, and Sandpiper. On December 12th, 2019, the agency announced that Nightingale had been selected as the primary sample site with Osprey selected as the backup site.
At 22:13 UTC, on October 20th, 2020, OSIRIS-REx successfully touched-down on Bennu. NASA confirmed via images taken during sampling that the TAGSAM (Touch-And-Go Sample Acquisition Mechanism) sampler had made contact. The spacecraft touched down within 92 cm (36 in) of the target location. Despite initial concerns that the sample mechanism had malfunctioned, as material was seen spilling out of the sample cache, the team managed to stow the material collected and continue with their mission. After an assessment of precisely how much of Bennu the spacecraft had captured, the OSIRIS-REx team prepared the spacecraft for the next phase of the mission – the return cruise to Earth. Initial assessments showed that the team had collected more material than anticipated – validating the design of the TAGSAM mechanism. On April 7th, 2021, OSIRIS-REx completed its final flyover of Bennu and began slowly drifting away from the asteroid. On May 10th, 2021, OSIRIS-REx departed Bennu and began its two-year journey to Earth with the asteroid sample.
On September 24th, 2023, after a 7 year voyage, the OSIRIS-REx return capsule is scheduled to re-enter Earth’s atmosphere and land by parachute at the Air Force’s Utah Test and Training Range, while the spacecraft performs a flyby of the planet. After recovery and initiation of planetary protection protocols, the sample will be curated at NASA’s Astromaterials Research and Exploration Science Directorate (ARES) and at Japan’s Extraterrestrial Sample Curation Center. Asteroid sample material requests will be considered and distributed to organizations worldwide by ARES.
OSIRIS-REx has, for the duration of its mission, remained in remarkable health. Legacy hardware coupled with innovative design has generated a mission ripe for extension. With the sample return capsule planned to be deposited at Earth, mission scientists began to look for ways to continue to use the spacecraft to study elements of our Solar System. On April 25th, 2022, NASA confirmed that the mission would be extended. After dropping off its sample to Earth in 2023, the mission will become OSIRIS-APEX (APophis EXplorer). As its new name suggests, its next target will be the near-Earth asteroid (and potentially hazardous object) 99942 Apophis. Apophis will make an extremely close pass to the Earth on Friday April 13th, 2029. Observations of Apophis will commence on April 8th, 2029 and a few days later, on April 21st, OSIRIS-APEX is planned to rendezvous with the asteroid. This mission extension falls in line with NASA’s recent Planetary Protection objectives, including the Double Asteroid Redirection Test (DART) and NEO Surveyor – missions designed to protect planet Earth from potential threats.
OSIRIS-REx represents an immense feat of human engineering, mastering our species’ ability to voyage to destinations in deep space and back. This mission is unique for many reasons, as not only does it provide space agencies a sample of a geological time capsule, but it helps to assess threats to our planet. OSIRIS-APEX alongside DART, represent humanity’s first steps in protecting our Mother Earth from harm – a crucial step to ensuring our longevity in the solar system.