Upon landing at Apollo 11 in 1969, astronauts looked out a window to distinguish features they recognized from a map of the Moon and were able to control a lander to avoid a carpet collision. dire atop a rocky area. Now, 50 years later, this process can be automated. Distinguishing features, like craters, known rocks or other unique surface features, provide insight into surface hazards to help avoid them upon landing.
NASA Scientists and engineers are perfecting the technology of navigating and landing on planetary celestial bodies by analyzing images during landing – a process known as topographic relativity (TRN) navigation. . This optical navigation technology is included above Mars The rover, Perseverance, will test TRN as it lands on the Red Planet in 2021, paving the way for crew missions to the Moon and beyond. TRN has also been used in NASA Recent Origins, Spectral Interpretation, Resource Identification, Confidentiality, Regolith Explorer (OSIRIS-REx) Touch-and-Go events (TAG) missions to collect samples of asteroid Bennu to better understand the asteroid’s characteristics and motion.
Since arriving in Bennu in 2018, the OSIRIS-REx spacecraft has mapped and studied its surface, including topography and lighting conditions, in preparation for the TAG. Nightingale Crater was chosen from four candidate locations based on the large amount of sampled material and the accessibility for spacecraft.
On October 20, the OSIRIS-REx spacecraft successfully navigated to the surface of the asteroid Bennu and collected a sample. Image provider: NASA Goddard Space Flight Center / Science Imaging Studio
Engineers regularly use ground-based optical navigation methods to navigate the OSIRIS-REx spacecraft closer to Bennu, where new images taken by the spacecraft are compared to a three-dimensional topographic map . During TAG time, OSIRIS-REx has performed the same optical navigation on board in real time, using a TRN system called Natural Feature Tracking. Image captured of the sample site during the lowering of the TAG, compared with the on-board topographic map and the spacecraft’s trajectory adjusted to target the landing site. Optical navigation could also be used in the future to minimize the risks associated with landing in other unfamiliar environments in our solar system.
NASA’s lunar reconnaissance (LRO) orbiter has been in orbit since 2009. LRO Project scientist Noah Petro said a challenge to preparation for landing missions. is the lack of high-resolution, narrow-angle camera images in any lighting conditions for any particular landing site. . These images will be useful for automated landing systems, which need lighting data for a specific time of lunar day. However, NASA was able to collect high-resolution topographic data using the LRO’s Lunar Orbital Laser Altimeter (LOLA).
“LOLA and other topographic data, allowing us to determine the shape of the Moon and light it at any time in the future or past, and thus we can predict the what the face will be like, ”said Petro.
Using LOLA data, solar angles are overlaid on a three-dimensional elevation map to create a shadow modeling of surface features at specific dates and times. NASA scientists know the position and orientation of the Moon and LRO in space, after making billions of lunar laser measurements. Over time, these measurements were aggregated into a grid map of the Moon’s surface. The images taken during the landing were compared to this main map so that the landers could be used as part of the program Artemis had another tool for safely navigating the lunar terrain.
Petro says that the surface of the Moon is like a fingerprint where no two landscapes are exactly the same. The terrain can be used to determine the exact location of a spacecraft above the Moon, comparing images like a forensic scientist comparing fingerprints from a crime scene to match a person is known to an unknown person – or to match a position to where the spacecraft is flying.
After landing, TRN can be used on the ground to help astronauts navigate aircraft with crew. As part of NASA’s concept of sustainability on the lunar surface, the agency is looking at using a habitable mobile platform such as a RV as well as a lunar off-road vehicle (LTV) to help with its the crew moves on the surface of the moon.
Astronauts can typically travel short distances of a few miles in an unpressurized rover like the LTV as long as they have the place to guide them. However, traveling longer distances will be much more difficult, not to mention that the Sun at the South Pole of the Moon is always low on the horizon, adding to the challenges of vision. Driving through Antarctica is like driving a car straight east in the morning – lights can be blinding and landmarks can be distorted. With TRN, the astronauts can better navigate Antarctica regardless of the lighting conditions, as the computer can better detect hazards.
Speed is the main difference between using a TRN to land a spaceship and using it to navigate an aircraft with crew. Landing requires faster image capture and processing, with distances between images just one second. To bridge the gap between images, the on-board processor keeps the spacecraft on track for a safe landing.
Carolina Restrepo, an aerospace engineer at NASA Goddard in Maryland, said: “When you move more slowly – like with a roller coaster or OSIRIS-REx orbiting asteroids – you have more time to image processing”. surface. “When you’re moving really fast – getting down and landing – there’s no time for this. You need to take pictures and process them as quickly as possible on the spaceship and it needs to be on your own. “
Automated TRN solutions can address the needs of humans and explorers as they navigate unique locations in our solar system, such as the optical navigation challenges that OSIRIS-REx Face TAG on Bennu’s rock surface. Due to missions like the LRO, Artemis astronauts are able to use the TRN algorithm and lunar topographic data to add surface images to safely land and explore the Moon’s Antarctic.
“What we are trying to do is predict the need for relative topographic navigation systems in the future by incorporating existing data types to ensure we can build a map of degree. Highest resolution for key positions along the trajectory and future landing sites, ”Restrepo said. “In other words, we need high resolution maps for both scientific and navigation purposes.”