Depiction of the three telescope system described in the paper. Credit: Paul McKee, Hoang Nguyen, Michael W. Kudenov, John A. Christian
One of the hardest things for many people to conceptualize when talking about how fast something is going is that they must ask, “Compared to what?” All motion only makes sense from a frame of reference, and many spacecraft traveling in the depths of the void lack any regular reference from which to understand how fast they’re going.
There have been several different techniques to try to solve this problem, but one of the ones that have been in development the longest is StarNAV—a way to navigate in space using only the stars.
Several projects named “StarNAV” seem to be ongoing at various stages of development, including a NASA Institute for Advanced Concepts grant for some researchers on the East Coast of the US and a small start-up company based on technology out of UC Irvine. In this case, we’ll look at the work done by the researchers, particularly a paper they released last year detailing some progress toward a prototype.
The technology developed by Paul McKee of Rensselaer Polytechnic Institute, Hoang Nguyen and Michael Kudenov of North Carolina State, and John Christian of Georgia Tech is based on a specific feature of stars known as stellar aberration. As defined in the Special Theory of Relativity, stellar aberration occurs when the velocity of an observer changes the apparent distance between it and a star.
This technique has been used before; however, it has had wide error bands when calculating a spacecraft’s instantaneous velocity. Typically, existing solutions would use a large telescope to measure a property known as an “inter-star angle” between two stars in a relatively narrow field of view precisely. If it is precise enough, some pretty complex math can produce a spacecraft’s velocity from only one inter-star angle.
Getting a measurement that is precise enough is the tricky part. To accurately detect the position of an individual star in an inter-star pair, many telescopes have to have a narrow field of view (FOV). That narrow FOV means that only one star can be tracked per telescope, which requires a second telescope and a complicated metrology system to track the relative alignment of these telescopes.
[embedded content]Fraser discusses some of the difficulties of navigating in space.
The NIAC researchers came up with a method of using slightly less precise inter-star angle measurements but multiple measurements, and once again using fancy math to calculate an accurate velocity measurement without the complicated tracking systems.
The system described in the Acta Astronautica paper consists of three different telescopes offset from each other at known angles, each observing a different pair of stars. With these three slightly less precise measurements, an algorithm can still calculate an average stellar aberration and, therefore, a reasonable estimate of spacecraft velocity.
If there wasn’t enough math in this process already, the authors decided to prove the accuracy of their system by running some experiments using every mathematician’s favorite random test algorithm—a Monte Carlo simulation.
While they did find some confounding factors that must be dealt with in a calibration process, the simulation proved that, in theory, at least, the system would work with an accuracy compared to the best narrow FOV solutions currently available and would be much cheaper and easier to operate.
In a final proof of concept, the researchers also modeled how big such a system would be. They fit it into a 3U CubeSat chassis—measuring about 10cm x 30cm x 10cm. And because of the modularity of CubeSats designs, it might be possible to attach any such module onto another chassis as part of a fully-fledged mission.
That hasn’t happened yet, though, and it doesn’t appear that a complete prototype of this system has been built yet. Though, as mentioned above, there is a start-up looking to commercialize very similar technology, though mainly for Earth-based navigation as an alternative to GPS—they have several military contracts, who would be looking for ways to continue navigation if GPS happens to be knocked out of commission by enemy action.
As more and more spacecraft start venturing into deep space, improving how they calculate their velocity will become an ever-increasing problem. StarNAV seems well placed to do so—it just needs a bit more of a push into the prototyping stage to get there.
More information:
Paul McKee et al, StarNAV with a wide field-of-view optical sensor, Acta Astronautica (2022). DOI: 10.1016/j.actaastro.2022.04.027
Citation:
Lost in space? Just use relativity (2023, December 26)
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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.
