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SpaceX satellites' effect on night sky can't be eliminated, astronomers say – Ars Technica

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Enlarge / Artist’s impression of low-Earth orbit satellites like those launched by SpaceX and OneWeb.

Broadband satellites being launched by SpaceX and other companies will inevitably have a negative impact on astronomers’ ability to observe the night sky, according to a new report by astronomers. There are no mitigation strategies that can completely eliminate the satellites’ impact on astronomical observations—other than not launching satellites at all—but the report includes recommendations for how satellite operators can minimize disruption and how observatories can adjust to the changes.

The report released this week is titled, “Impact of Satellite Constellations on Optical Astronomy and Recommendations Toward Mitigations.” The report resulted from the recent Satellite Constellations 1 (SATCON1) workshop, which was organized jointly by the National Science Foundation’s NOIRLab and the American Astronomical Society (AAS). SpaceX engineers participated in the online workshop, but the report was written by members of the SATCON1 Scientific Organizing Committee and represents their consensus views. The committee members hail from NOIRLab, AAS, the Lowell and Steward observatories in Arizona, the Rubin Observatory in Chile, the University of Michigan, UC-Davis, Smith College, and the Association of Universities for Research in Astronomy (AURA).

The report said:

Changes are required at both ends: constellation operators and observatories. SpaceX has shown that operators can reduce reflected sunlight through satellite body orientation, Sun shielding, and surface darkening. A joint effort to obtain higher-accuracy public data on predicted locations of individual satellites (or ephemerides) could enable some pointing avoidance and mid-exposure shuttering during satellite passage. Observatories will need to adopt more dynamic scheduling and observation management as the number of constellation satellites increases, though even these measures will be ineffective for many science programs.

SpaceX has so far launched over 600 satellites and OneWeb has launched 74. Both companies plan to eventually launch tens of thousands of satellites into low-Earth orbits and provide broadband to areas that lack fast wired service. Amazon is also planning to launch thousands of satellites. Because of their low-Earth orbits (LEO), the satellites will provide lower latency than traditional satellite networks.

Musk predicted no impact

SpaceX CEO Elon Musk said in March that he is “confident that we will not cause any impact whatsoever in astronomical discoveries.” He said the satellites are visible immediately after launching because “they’re tumbling a little bit” and essentially “blink” or “reflect in ways that is not the case when they’re on orbit.” Once satellites stabilize and raise their orbits, they shouldn’t cause problems for astronomers, Musk claimed.

But it’s been over a year since SpaceX began launching broadband satellites, and astronomers have now “accumulated enough observations of constellation satellites like those being launched by SpaceX and OneWeb and run computer simulations of their likely impact to begin to understand the magnitude and complexity of the problem,” the SATCON1 report said.

Enlarge / A wide-field image (2.2 degrees across) from the Dark Energy Camera on the Víctor M. Blanco 4-m telescope at the Cerro Tololo InterAmerican Observatory, taken on November 18, 2019. Several Starlink satellites crossed the field of view.

“If the 100,000 or more LEOsats proposed by many companies and many governments are deployed, no combination of mitigations can fully avoid the impacts of the satellite trails on the science programs of current and planned ground-based optical-NIR [near-infrared] astronomy facilities,” the report said. “Astronomers are just beginning to understand the full range of impacts on the discipline. Astrophotography, amateur astronomy, and the human experience of the stars and the Milky Way are already affected.”

Report authors said they “performed simulations of representative LEOsat constellations” in order to reach their conclusions. Recommendations for minimizing harms to astronomy “are based on work by and collaboration between astronomers and SpaceX,” but these are “intended for a broad audience, and especially the satellite constellation industry as a whole,” the report said.

Altitude is important

The satellites’ impact on astronomy will be affected by their altitude. Satellites orbiting at altitudes below 600km (like those being launched by SpaceX) are not as harmful to observations as those orbiting above 600km (like those launched by OneWeb). Amazon’s plan calls for altitudes of 590km, 610km, and 630km.

“LEOsat constellations below 600km are visible for a few hours per night around astronomical twilight from observatories at middle latitudes, but they are in Earth’s shadow and invisible for several hours per night around local solar midnight, with some satellites visible during the transitions. This visibility pattern causes these constellations to most heavily impact twilight observers,” the report said.

With sub-600km satellites being closer to the Earth’s surface, they are “brighter than the same satellites would be at higher orbital altitudes” and “more likely to exceed the unaided-eye brightness threshold if operators fail to design with this criterion in mind,” the report said. However, satellites “above 600km are an even greater concern to astronomers because they include all the impacts mentioned above, but can also be illuminated all night long. Full-night illumination causes these high-altitude constellations to impact a larger set of astronomical programs.”

Satellite constellations will be brightest “near the horizon and during twilight,” disproportionately impacting “searches for near-Earth objects (NEOs), distant Solar System objects and optical counterparts of fleeting gravitational wave sources,” the report said, adding:

Depending on constellation design, LEO satellites can also be visible deep into the night, broadening the impact to encompass all astronomical programs. We find that the worst-case constellation designs prove extremely impactful to the most severely affected science programs. For the less affected programs, the impact ranges from negligible to significant, requiring novel software and hardware efforts in an attempt to avoid satellites and remove trails from images.

Satellite constellations like OneWeb’s, with orbits of 1,200km, “present particularly serious challenges; they will be visible all night during summer and significant fractions of the night during winter, fall, and spring, and will have negative impacts on nearly all observational programs,” the report said. (OneWeb, which is going through a bankruptcy and sale, is also using medium-Earth orbits of 8,500km.)

So far, SpaceX has permission to launch nearly 12,000 satellites, OneWeb has approval for 2,000, and Amazon has approval for 3,236. SpaceX has applied to the Federal Communications Commission for another 30,000 satellites and OneWeb has applied for another 47,844.

Action plan

The report listed these methods of minimizing the impact on astronomy:

  1. Launch fewer or no LEOsat constellations. This is the only option identified that can achieve zero impact.
  2. Deploy satellites at orbital altitudes no higher than ~600 km.
  3. Darken satellites by lowering their albedo, shading reflected sunlight, or some combination thereof.
  4. Control each satellite’s attitude in orbit so that it reflects less sunlight to Earth.
  5. Remove or mask satellite trails and their effects in images.
  6. Avoid satellite trails with the use of accurate ephemerides [that provide data about a satellite’s position relative to Earth].

Satellite operators should also “make their best effort to avoid specular reflection (flares) in the direction of observatories.”

The report’s recommendations for observatories focus heavily on development of new software. Observatories should support “development of a software application available to the general astronomy community to identify, model, subtract, and mask satellite trails in images on the basis of user-supplied parameters,” the report said. They should also support development of observation-planning software for “the general astronomy community that predicts the time and projection of satellite transits through an image, given celestial position, time of night, exposure length, and field of view, based on the public database of ephemerides.”

Researchers also provided recommendations for work that observatories and satellite providers can do together, such as “an immediate coordinated effort for optical observations of LEOsat constellation members, to characterize both slowly and rapidly varying reflectivity and the effectiveness of experimental mitigations.”

There’s optimism about the ongoing collaboration. “I hope that the collegiality and spirit of partnership between astronomers and commercial satellite operators will expand to include more members of both communities and that it will continue to prove useful and productive,” NOIRLab director Patrick McCarthy said in a press release. “I also hope that the findings and recommendations in the SATCON1 report will serve as guidelines for observatories and satellite operators alike as we work towards a more detailed understanding of the impacts and mitigations and we learn to share the sky, one of nature’s priceless treasures.”

We’ve provided a summary of the report here, but if you want much more detail on the group’s findings and recommendations, you can check out the report and the lengthy appendices directly.

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The body of a Ugandan Olympic athlete who was set on fire by her partner is received by family

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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.

Kenya’s high rates of violence against women have prompted marches by ordinary citizens in towns and cities this year.

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.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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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.”

The Canadian Press. All rights reserved.

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B.C. sets up a panel on bear deaths, will review conservation officer training

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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.

The Canadian Press. All rights reserved.

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