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Posts Tagged ‘satellites’

Astronomers warn SpaceX Starlink satellites may hinder scientific observation and discovery

28 Aug

SpaceX plans to launch thousands of satellites into space for the firm’s Starlink high-speed satellite internet network. While the Starlink service aims to bring high-speed internet to locations where it is otherwise unavailable or prohibitively expensive, Independent is reporting that hundreds of astronomers have expressed concerns that Starlink’s satellite array will have an impact on astronomy and slow down scientific discoveries.

A report by the Satellite Constellations 1 (SATCON1) workshop stated that constellations of satellites in the night sky are problematic for ground-based observations, including those utilizing optical and infrared technologies. The research underpinning the workshop’s report included input from ‘more than 250 astronomers, satellite operators and dark-sky advocates.’

SATCON1 co-chair Connie Walker from the National Science Foundation’s (NSF) NOIRLab said of the report, ‘Recent technology developments for astronomical research – especially cameras with wide fields of view on large optical-infrared telescopes – are happening at the same time as the rapid deployment of many thousands of low-Earth-orbiting satellites (LEOsats) by companies rolling out new space-based communication technologies.’

Not to scale. Illustration courtesy of NOIRLab / NSF / AURA / P. Marenfeld

The report concludes that large satellite constellations will impact astronomical research and the general human experience of the night sky, although they find that the impact will range from ‘negligible’ to ‘extreme.’ When Starlink’s first 60 communication satellites launched in May 2019, the impact was felt immediately by astronomers and the satellites were ‘brighter than anyone expected.’ It is not fiscally or scientifically feasible to stop utilizing ground-based astronomy.

While the impact of LEOsats may be negative for astronomers, the introduction of communication services to underserved areas is undoubtedly positive for potential users. The SATCON1 workshop is trying to work with satellite operators to find a solution. In the report, there are two main findings. One is that LEOsats ‘disproportionately affect science programs that require twilight observations, such as searches for Earth-threatening asteroids and comets, outer solar system objects, and visible-light counterparts of fleeting gravitational-wave sources.’ The second finding is that there are at least a half dozen ways to reduce the harm caused to astronomy by large satellite constellations.

From the SATCON1 workshop report: ‘A wide-field image (2.3 degrees across) from the Dark Energy Camera on the Víctor M. Blanco 4-m telescope at the Cerro Tololo InterAmerican Observatory, on 18 November 2019. Several Starlink satellites crossed the field of view. Image credit DECam DELVE Survey/CTIO/AURA/NSF.’ For many more visual examples of the impact of Starlink satellites on astronomical observations, read the full SATCON1 technical report.

One of these six ways is to launch fewer or no LEOsats, which is of course an impractical and unlikely solution. More realistically, the workshop found that the impact of LEOsats can be reduced if they are deployed at orbital altitudes no higher than 600 km, satellites are darkened or include sunshades, or are carefully oriented in space to reduce reflections. There may also be ways to reduce the impact of satellite trails with improvements to processing techniques for astronomical images. Further, if satellite owners provide astronomers with accurate orbital information, observers may be able to avoid satellites with their telescopes.

NOIRLab director Patrick McCarthy says of the report’s findings and recommendations that he hopes that they ‘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.’

The next workshop, SATCON2, will aim to tackle the issues of policy and regulation when it meets in early to mid-2021.

Image credit: SpaceX / Starlink

SpaceX plans to launch more than 30,000 Starlink satellites. This represents approximately a doubling of space-based moving objects visible to the naked eye during twilight, according to the SATCON1 report.

Despite there being only about 500 Starlink satellites currently in orbit, the program’s impact has already been felt during significant astronomical events. For example, the comet Neowise made an appearance this summer, something possible only once every 6,800 years, and Starlink satellites disrupted observation for many.

Image credit: SpaceX / Starlink

Thus far, SpaceX has taken steps to reduce the impact of its satellites. The space exploration firm has utilized a twisting technique to make the solar panels on the satellites less reflective. It has also explored painting reflective surfaces black and using sunshades. SpaceX has worked with the American Astronomical Society (AAS), National Radio Astronomy Observatory (NORAF) and the Green Bank Observatory (GBO) in pursuit of a solution to the issue of LEOsat visibility.

SpaceX stated ‘We’ve taken an experimental and iterative approach to reduce the brightness of the Starlink satellites. Orbital brightness is an extremely difficult problem to tackle analytically.’

For astronomers, the SATCON2 workshop cannot come soon enough. Professor Tony Tyson of the University of California, Davis, says that ‘…no combination of mitigations can completely avoid the impacts of satellite trails on the science programs of the coming generation of optical astronomy facilities.’

Articles: Digital Photography Review (dpreview.com)

 
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Elon Musk reveals how SpaceX will address light pollution caused by Starlink satellites

28 Apr

Following the successful launch of its Starlink 6 batch of satellites last week, SpaceX CEO Elon Musk tweeted out a few details about night sky light pollution caused by these low Earth orbit satellites and the company’s plans to address this issue.

According to the tweet, SpaceX is taking ‘some key steps to reduce satellite brightness,’ something that Musk says should make them ‘much less noticeable during orbit raise.’ This change involves adjusting the solar panel angle, according to the tweet, plus there will be a new addition to the satellites starting with the Starlink 9 launch: sunshades.

It’s unclear how drastically these changes will reduce the brightness of its satellites, but the move underscores SpaceX’s efforts to address concerns about light pollution caused by these small satellites.

The Starlink initiative aims to launch thousands of small low-Earth orbit satellites that will beam Internet service to the ground, providing high-speed broadband access in places where it’s unavailable from terrestrial providers, or where only slow and expensive options are available. Musk said in a tweet following the Starlink 6 launch that the company plans to start a private beta of the Starlink service in around three months.

Renewed attention to the issue of light pollution caused by low-Earth orbit satellites was spurred with the launch of NASA’s Satellite Streak Watcher project in early March. In explaining the reason for the initiative, the space agency said that the increasing number of these satellites launched into orbit makes things more difficult for astronomers on the ground.

The light pollution caused by these satellites is also a problem for astrophotographers, causing long streaks of light to appear in long-exposure images. Unlike avoiding light pollution from the ground, it’s not possible to head to a ‘dark sky reserve’ or other similar places to avoid light pollution originating from space.

SpaceX hasn’t been ignoring this problem; back in December 2019, the company said that it was experimenting with a new anti-reflective coating that would make the satellites less bright, though it may potentially result in satellite performance problems by causing thermal issues. Based on Musk’s most recent tweet, it seems the company is turning to sunshades as its solution.

With the Starlink 6 satellite launch last week, SpaceX now has 420 of these small satellites in orbit. The company plans to launch a minimum of 12,000 satellites over the coming months, though the figure may exceed 30,000 in the long run. A public beta of the Starlink service will start in the US and Canada in around six months following the private beta, according to Musk’s tweet. It’s still unclear how much the eventual Starlink Internet service will cost.

Articles: Digital Photography Review (dpreview.com)

 
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NASA is asking the public to use their smartphones to help track light pollution caused by satellites

06 Mar

A newly launched NASA project called Satellite Streak Watcher aims to assess the night sky light pollution caused by low-Earth orbit satellites using images captured by the public. On its SciStarter project page, NASA asks anyone interested in participating to ‘Photographically record satellite streaks across the night sky to monitor this form of sky pollution.’

The space agency explains its concerns related to the satellites, stating, ‘As more satellites are placed into orbit, they will become an increasing problem to astronomers on the ground.’ Participants can use the Heavens-Above website to determine when and where satellites will pass over their local sky; images are uploaded and shared on the project’s website.

The new public science project follows announcements from a number of companies that have launched — or plan to launch — large numbers of small satellites into low-Earth orbit.

The most notable example of this comes from SpaceX, which has spent the past few years working on its Starlink mission. The private space company expects to ultimately launch thousands of small satellites into very-low Earth orbit (VLEO) in order to provide Internet access around the world. As of March 1, 2020, the company has delivered 302 of these satellites into space with plans to launch more throughout the year.

Critics have expressed concerns that Starlink and other projects like it will have a negative impact on the night sky, introducing light pollution that will disrupt astronomy. These satellites also impact astrophotography by adding thin, bright streaks of light to long-exposure images, prompting complaints from photographers who increasingly struggle to deal with light pollution.

DPReview reader Guido Forrier shared the below image in our Astrophotography forum, showing a series of fifteen Starlink satellites flying across the sky in one of his night sky photographs. When we asked what his thoughts on the matter, he said ‘I am surprised and incensed that apart from the already high light pollution, those satellites [have] also come to disturb. [There’s] a lot of rubbish is already flying in space and I see it regularly burning in the atmosphere.’

Photograph by Guido Forrier, shared with permission.

Until now, most efforts to combat light pollution have focused on the ground, not the sky. Light produced by street lamps, billboards, parking lot lights and more is reflected in the night sky, making it hard to see and photograph stars, particularly in regions close to big cities. The problem has spurred the creation of a number of Dark Sky Reserves throughout the world; these are regions of public and private land with ample natural darkness and starkly visible stars.

However, experts have expressed concerns over light pollution that results from satellites launched into low-Earth orbit, as well as more ridiculous future concepts like an artificial moon and space billboards. Because this type of light pollution comes from the sky rather than the planet’s surface, traveling to Dark Sky Reserves won’t help photographers avoid the issue.

According to Astronomy.com, the Starlink satellites are particularly disruptive to the night sky due to their shallow orbit, which is necessary for delivering Internet service to people on Earth. More than 40,000 of these small satellites may eventually be launched under the Starlink mission, and though SpaceX is experimenting with anti-reflective coating on the satellites, it is unclear whether that will be sufficient for reducing the disruption caused by the spacecraft.

MIT Technology Review points out that satellites depend on their reflective nature to help keep them cool; the experimental anti-reflective coating may cause thermal issues for the Starlink satellites. SpaceX applied the coating to the bottom of one of the 60 satellites it launched in December 2019 in order to test its potential impact on performance.

Harvard-Smithsonian Center for Astrophysics astronomer Jonathan McDowell had told Technology Review at the time that while the reflective coating is ‘worth a try,’ he fears it ‘will be offset by the fact that they are moving the constellation to a lower orbit.’

NASA anticipates its Satellite Streak Watcher operating as a long-term project in order to gather data on satellite light pollution over time. The project currently has 136 members and 20 images, which include shots ranging from bright dots on the night sky to several long streaks of light bunched together. Though NASA says citizen scientists can use a basic tripod and most newer smartphones to capture the images, astrophotographers who have more capable camera systems are also welcomed to share their images.

Articles: Digital Photography Review (dpreview.com)

 
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