Physics 20A - Tracy Vuong
Who Owns the Near-earth Orbits & Night Sky?
What Are Mega-Constellations?
Background Information
- Networked satellites launched by operators and companies in the satellite industry
- Low earth-orbit (LEO) satellite constellations
- Orbit the planet at altitudes up to 2,000 km
- Have been seen to pose a threat to our grounded view of the night sky
What Mega-constellation Initiatives Have We Seen So Far?
Existing Mega-constellations
- Starlink from SpaceX - led by Elon Musk
- Amazon's Project Kuiper
- OneWeb
- SATNET (the Atlantic Packet Satellite Network)
- Virgin Orbit
Progress In Satellite Networks
SpaceX's Starlink
Satellite
Amazon's Satellite Test Sequence
The Issue at Hand
What Is The Issue?
- Near-earth space is becoming more democratized and potentially exploited by private satellite operators
- Increased access to the night sky may pose threats to the integrity of astronomical observations
- Data collected by astronomers studying space from a grounded view has been compromised by visible streaks of light (reflected by orbiting satellites)
A digital diagram of a LEO mega-constellation (SpaceNews)
Visuals of LEO Mega-constellation
A captured "photobomb" caused by a Starlink satellite (Forbes)
What Groups Are Affected?
- Professionals in astronomy-related fields
- Skywatchers
- Amateur astronomers
- LEO satellites prevent many astronomers from observing faint visuals in the sky with even the largest telescopes
- Individuals using narrow-field instruments to study the night sky - a relatively less affected group
- Individuals using wide-field telescopes may find much less success in making astronomical observations
- Most likely to lose a significant percentage of captured images due to satellite interference
- Observations taking place around sunset and sunrise may achieve the least success
- These are times when networked satellites may be the most visible and disruptive
Groups/Studies Affected By Networked Constellations
Controversy
Over Mega-constellations
- Not all astronomers and satellite operators see eye-to-eye about this particular topic
- There is still debate over ways to mitigate the effect that these mega-constellations have on astronomical observations
Why Is This An Issue?
The Astronomer's Argument
An Astronomer's Perspective
- Disadvantages of LEO satellite networks
- Launching an excess number of satellites results in congestion of Earth's exosphere -- further reducing grounded visibility of objects in space
- Streaks of light from reflected sunlight often interfere with observations that are necessary for astronomical studies - unnecessary light pollution
- Increasingly limits viewings of dark skies (on Earth) that are free of light pollution
- Some believe that the only way to resolve the disruption of mega-constellations is to completely eliminate satellite networks
- Rebuttals to solutions suggested by the public:
- Unable to discard all affected pixels of an image - image-cleaning software is not always capable of restoring visual data that is lost
- Unable to refrain from doing observations when light pollution is apparent - pollution is more visible closer to sunset and sunrise, coincides with the peak times for astronomers to make ground observations
- “astronomers have put forth a series of major recommendation guidelines for satellite providers to follow...2 takeaways for optical astronomy
1) satellites at low altitude are better than satellites at high altitude with 550-600 km as the highest recommended figure
2) and satellites should be below magnitude +7 at that altitude, limited to about ~30% of the brightness limit that our naked eye can perceive" (Forbes).
Opposing Arguments
- Advantages of LEO satellite networks
- A more affordable alternative to launching individual satellites
- Furthers global connectivity - "As 5G internet has successfully arrived in different countries, the need for better connectivity lures big brands like SpaceX and Amazon to enter the sphere of satellite mega-constellations and make the most out of this technology" (https://www.analyticssteps.com/blogs/what-satellite-mega-constellation-advantages-and-disadvantages).
- Advocates of mega-constellations emphasize the ability to reduce disruptions of satellites through altitude adjustment
- Satellites orbiting at a higher altitude will make less of an impact on nighttime observations
- Limits the vulnerability of select programs and astronomical tools
- People's increasing reliability on the Internet calls for the establishment of stronger networks supported by mega-constellations
How Can We Resolve This Issue?
Possible Solutions
- Some (but not all) groups of astronomers and operators have communicated in order to reach some form of middle ground
- Efforts been made by some operating companies towards modifying the structure and design of these satellites
Efforts to Mitigate the Effect of LEO Satellites
DarkSat
- SpaceX painted dark coatings onto the satellites in order to limit visibility and reflectivity in the night sky
- January 2020 - the effectiveness of this alternative design was observed during a test run
- The addition of this coating resulted in solar energy absorption and heat generation
- Radiated even more in the infrared and would further disrupt infrared observations
- Also still visible in data collection
- Concluded that DarkSats were not the best solution
VisorSat
- Garnered relatively greater success than the DarkSat
- Employs visors along with orientation roll to reduce the reflection of sunlight
- Observed to be approximately 1-2 magnitudes dimmer than original SpaceX satellites
Efforts to Mitigate the Effect of LEO Satellites [cont.]
Nanosatellites
- Aims to launch a new generation of improved satellites in hopes of reducing the adverse effects of using standard satellites
- "Virgin Orbit successfully deployed ten small, cube-shaped satellites in mid-January. They are “nanosatellites”, because their size doesn’t exceed 1m20 by 1m20 by 1m20 and their weight less than 20kg – 10 times less than a Starlink satellite," (Telescope Live)
- Virgin Orbit nanosatellites were designed to support broadband internet as well, their smaller structures minimize reflectivity and lowers the chances of it distorting views of the night sky
The Future of Virgin Orbit Satellites
- "The company aims to deliver 1,024 nanosatellites to Low Earth Orbit by 2026, with early customers including agricultural and energy businesses in the US, Poland and abroad," (Our Vision - Virgin Orbit).
- Note: How can we be sure that their efforts to reduce light pollution (through modifying satellite size) are enough to counterbalance the impact of launching this many satellites?
Satellite Constellations 2 Workshop
- A workshop/gathering used to discuss the looming issue of launching satellites close to Earth
- Used to address possible ramifications of allowing operators in the satellite industry to have unregulated access to the skies
- Reports acknowledged that the sky "must be considered part of the environment, and the current [U.S.] National Environmental Policy Act (NEPA) exemption for the satellite constellation industry must end," (Space.com)
- Suggests that specific and immediate action must be taken to ensure preservation of the sky
- Called for advancements in satellite tracking
- Helps with taking precautions to prevent unwarranted interference of LEO objects
- Members mostly agreed upon recommendations for further communication between private space companies and astronomers affected by satellites
Why Should This Be a Topic of Interest?
Significance
- Private space companies expect to launch an unusually high quantity of individual satellites within the upcoming years/decades
- Issues caused by satellites may be quickly exacerbated if not properly addressed or regulated
- What we need from astronomers
and operators in the satellite
industry is an increased
willingness to cooperate
and discuss how to
effectively modify
existing satellite
networks
What Other Adverse Effects Can Mega-constellations Have on Earth?
- Other relevant issues have warranted further concerns about the ramifications of establishing networked satellites
- Other Space Contamination
- Launching LEO satellites at an exponential rate may lead to a greater likelihood of orbital collisions happening
- More collisions will result in a greater number of space debris, which may also obstruct an astronomer's view of objects in space
- Compromised Ozone Layer
- Satellite material can react chemically and possibly alter stratosphere composition
- Weakened ozone layer can make us physically vulnerable to UV radiation
Projected Growth of Mega-constellations
Projected Growth of Mega-constellations
- Operators in the satellite industry already have plans to boost their launch rate for the sake of increased global connectivity
- SpaceX has already launched more than 650 satellites out of the projected 12,000 Starlink satellites
- "We’ll continue to innovate on the production side to minimize costs, while also scaling up our launch rate to an unprecedented frequency," (Vision For the Future - Virgin Orbit).
- Numbers of individual satellites have increased rapidly over recent years, putting astronomical studies at greater risk
- Project growth calls for a greater urgency for private space companies to consider the global impact mega-constellations can have on humans and the environment
Sites Used
- https://www.space.com/spacex-starlink-satellite-megaconstellation-launch-photos.html
- https://www.universetoday.com/149700/astronomers-confirm-that-darksat-is-about-half-as-bright-as-an-unpainted-starlink/
- https://www.space.com/spacex-starlink-satellites-astronomers-visibility-response.html
- https://www.darksky.org/why-do-mega-constellations-matter-to-the-dark-sky-community/
- https://telescope.live/blog/darksat-visorsat-and-cubesat
- https://www.nature.com/articles/s41598-021-89909-7
- https://www.nature.com/articles/d41586-020-02480-5
- https://www.space.com/megaconstellations-could-destroy-astronomy-no-easy-fix
- https://www.analyticssteps.com/blogs/what-satellite-mega-constellation-advantages-and-disadvantages
- https://www.space.com/starlink-satellite-reentry-ozone-depletion-atmosphere
- https://virginorbit.com/vision/
Image Sources
- https://www.space.com/spacex-starlink-satellite-megaconstellation-launch-photos.html
- https://www.universetoday.com/149700/astronomers-confirm-that-darksat-is-about-half-as-bright-as-an-unpainted-starlink/
- https://www.space.com/spacex-starlink-satellites-astronomers-visibility-response.html
- https://www.darksky.org/why-do-mega-constellations-matter-to-the-dark-sky-community/
- https://telescope.live/blog/darksat-visorsat-and-cubesat
- https://www.mushroomnetworks.com/blog/spacexs-starlink-satellite-internet-service-review/
- https://noirlab.edu/public/images/ann21021a/