When landing Apollo 11 in 1969, astronauts looked out the window for distinguishing features that they recognized from maps of the Moon and were able to steer the lander to avoid a disastrous touchdown on top of a rocky area. Now, 50 years later, the process can be automated. Distinguishing features, like known craters, boulders, or other unique surface characteristics, provide insight into surface hazards to help avoid them while landing.
NASA scientists and engineers are maturing technology for navigating and landing on planetary bodies by analyzing images during descent – a process called terrain relative navigation (TRN). This optical navigation technology is included on NASA’s newest Mars rover, Perseverance, which will test TRN when it lands on the Red Planet in 2021, paving the way for future crewed missions to the Moon and beyond. TRN was also being used during NASA’s recent Origins, Spectral Interpretation, Resources Identification, Security, Regolith Explorer (OSIRIS-REx) mission Touch-and-Go (TAG) event to collect samples of the asteroid Bennu in order to better understand the characteristics and movement of asteroids.
Since reaching Bennu in 2018, the OSIRIS-REx spacecraft has mapped and studied its surface, including its topography and lighting conditions, in preparation for TAG. Nightingale crater was chosen from four candidate sites based on its great amount of sampleable material and accessibility for the spacecraft.
Engineers routinely use ground-based optical navigation methods to navigate the OSIRIS-REx spacecraft close to Bennu, where new images taken by the spacecraft are compared to three-dimensional topographic maps. During TAG, OSIRIS-REx performed a similar optical navigation process onboard in real-time, using a TRN system called Natural Feature Tracking. Images were taken of the sample site during TAG descent, compared with onboard topographic maps, and the spacecraft trajectory was readjusted 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 Orbiter (LRO) has acquired images from orbit since 2009. LRO Project Scientist Noah Petro said one challenge to preparing for landed missions is the lack of high-resolution, narrow-angle camera images at every lighting condition for any specific landing site. These images would be useful for automated landing systems, which need the illumination data for a specific time of lunar day. However, NASA has been able to collect high-resolution topographic data using LRO’s Lunar Orbiter Laser Altimeter (LOLA).
“LOLA data, and other topographic data, let us take the shape of the Moon and shine a light on it for any time in the future or past, and with that we can predict what the surface will look like,” Petro said.
Artist concept of Artemis astronaut stepping onto the Moon. Credit: NASA
Using LOLA data, sun angles are overlaid on a three-dimensional elevation map to model shadows of surface features at specific dates and times. NASA scientists know the position and orientation of the Moon and LRO in space, having taken billions of lunar laser measurements. Over time, these measurements are compiled into a grid-map of the lunar surface. Images taken during landing are compared to this master map so that landers that may be used as part of the Artemis program have another tool to safely navigate the lunar terrain.
The lunar surface is like a fingerprint, Petro said, where no two landscapes are identical. Topography can be used to determine a spacecraft’s exact location above the Moon, comparing images like a forensic scientist compares fingerprints from crime scenes to match a known person to an unknown person – or to match a location to where the spacecraft is in its flight.
After landing, TRN can be used on the ground to help astronauts navigate crewed rovers. As part of NASA’s lunar surface sustainability concept, the agency is considering using a habitable mobility platform like an RV as well as a lunar terrain vehicle (LTV) to help crew travel on the lunar surface.
Astronauts can typically travel short distances of a few miles in an unpressurized rover like the LTV so long as they have landmarks to guide them. However, traveling greater distances is much more challenging, not to mention the Sun at the lunar South Pole is always low on the horizon, adding to visibility challenges. Driving across the South Pole would be like driving a car straight east first thing in the morning – the light can be blinding, and landmarks can appear distorted. With TRN, astronauts may be better able to navigate the South Pole despite the lighting conditions, as the computer may better detects hazards.
Speed is the key difference between using TRN to land a spacecraft and using it to navigate a crewed rover. Landing requires capturing and processing images faster, with as short as one second intervals between images. To bridge the gap between images, onboard processors keep the spacecraft on track to safely land.
“When you move slower – such as with rovers or OSIRIS-REx orbiting around the asteroid – you have more time to process the images,” said Carolina Restrepo, an aerospace engineer at NASA Goddard in Maryland working to improve current data products for the lunar surface. “When you are moving very fast – descent and landing – there is no time for this. You need to be taking images and processing them as fast as possible aboard the spacecraft and it needs to be all autonomous.”
Automated TRN solutions can address the needs of human and robotic explorers as they navigate unique locations in our solar system, such as the optical navigation challenges faced by OSIRIS-REx for TAG on Bennu’s rocky surface. Because of missions like LRO, Artemis astronauts can use TRN algorithms and lunar topography data to supplement images of the surface in order to land and safely explore the Moon’s South Pole.
“What we’re trying to do is anticipate the needs of future terrain relative navigation systems by combining existing data types to make sure we can build the highest-resolution maps for key locations along future trajectories and landing sites,” Restrepo said. “In other words, we need high-resolution maps both for scientific purposes as well as for navigation.”
NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
