This summer season, the OSIRIS-REx spacecraft will undertake NASA’s first-ever try to the touch the floor of an asteroid, gather a pattern of it, and safely again away. However since arriving at asteroid Bennu over a yr in the past, the mission group has been tackling an surprising problem: the way to accomplish this feat at an asteroid whose floor is blanketed in building-sized boulders.
Utilizing these hazardous boulders as signposts, the mission group developed a brand new precision navigation technique to beat the problem.
In late August, the OSIRIS-REx spacecraft will navigate to asteroid Bennu’s floor for its first pattern assortment try. To do that, it would use an onboard picture software program referred to as Pure Function Monitoring (NFT) — a type of optical navigation that’s fully autonomous.
Credit: NASA’s Goddard Area Flight Heart/Scientific Visualization Studio
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The OSIRIS-REx group had initially deliberate to make use of a LIDAR system to navigate to Bennu’s floor through the Contact-And-Go (TAG) pattern assortment occasion. LIDAR is just like radar, but it surely makes use of laser pulses relatively than radio waves to measure distance. The OSIRIS-REx Steering, Navigation, and Management (GNC) LIDAR is designed to navigate the spacecraft to a comparatively hazard-free floor. The mission had initially envisioned a landing website 164 ft (50 meters) in diameter, however the largest protected areas on Bennu are a lot smaller. The largest website is simply 52 ft (16 m) extensive, or roughly 10% of the protected space envisioned. The group realized that they wanted a extra exact navigation approach that might enable the spacecraft to precisely goal very small websites whereas dodging potential hazards.
Within the face of this problem, the OSIRIS-REx group switched to a brand new navigation technique known as Pure Function Monitoring (NFT). NFT gives extra intensive navigation capabilities than LIDAR, and is essential for executing what the group is looking “Bullseye TAG,” which delivers the spacecraft to the a lot smaller sampling space. As an optical navigation approach, it requires the creation of a high-resolution picture catalog onboard the spacecraft.
Earlier this yr, the spacecraft made reconnaissance passes over the mission’s major and backup pattern assortment websites, designated Nightingale and Osprey, flying as shut as zero.four miles (625 m) over the floor. Throughout these flyovers, the spacecraft collected photos from totally different angles and lighting situations to finish the NFT picture catalog. The group makes use of this catalog to establish boulders and craters distinctive to the pattern website area, and can add this info to the spacecraft earlier than the pattern assortment occasion. NFT autonomously guides the spacecraft to Bennu’s floor by evaluating the onboard picture catalog with the real-time navigation photos taken throughout descent. Because the spacecraft descends to the floor, NFT updates its predicted level of contact relying on the spacecraft’s place in relation to the landmarks.
In the course of the pattern assortment occasion, Pure Function Monitoring (NFT) will information NASA’s OSIRIS-REx spacecraft to asteroid Bennu’s floor. The spacecraft takes real-time photos of the asteroid’s floor options because it descends, after which compares these photos with an onboard picture catalog. The spacecraft then makes use of these geographical markers to orient itself and precisely goal the landing website.
Credit: NASA/Goddard/College of Arizona
On the bottom, group members created “hazard maps” for each the Nightingale and Osprey websites to doc the entire floor options that might doubtlessly hurt the spacecraft, like massive rocks or steep slopes. The group used the picture catalog at the side of knowledge from the OSIRIS-REx Laser Altimeter (OLA) to create 3D maps that intently mannequin Bennu’s topography. As a part of NFT, these maps doc boulder heights and crater depths, and information the spacecraft away from potential hazards whereas concentrating on a really small website. Throughout descent, if the spacecraft predicts it would contact unsafe terrain, it would autonomously wave-off and again away from the floor. Nonetheless, if it sees that the realm is freed from hazards, it would proceed to descend and try to gather a pattern.
NFT shall be utilized in April to navigate the spacecraft throughout its first pattern assortment rehearsal. The operations group carried out preliminary testing through the Orbital B mission section in late 2019, and the outcomes demonstrated that NFT works in real-life situations as designed. NFT may also be used for navigation through the second rehearsal deliberate for June.
OSIRIS-REx’s first pattern assortment try is scheduled for late August. The spacecraft will depart Bennu in 2021 and is scheduled to ship the pattern to Earth in September 2023.
NASA’s Goddard Area Flight Heart in Greenbelt, Maryland, gives total mission administration, methods engineering, and the security and mission assurance for OSIRIS-REx. Dante Lauretta of the College of Arizona, Tucson, is the principal investigator, and the College of Arizona additionally leads the science group and the mission’s science commentary planning and knowledge processing. Lockheed Martin Area in Denver constructed the spacecraft and gives flight operations. Goddard and KinetX Aerospace are accountable for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program, which is managed by NASA’s Marshall Area Flight Heart in Huntsville, Alabama, for the company’s Science Mission Directorate in Washington.
For extra info on NASA’s OSIRIS-REx mission, go to:
by Brittany Enos
College of Arizona
Final Up to date: March 9, 2020
Editor: Karl Hille