Satellite flare

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Flare Simulation.gif
Iridium flare 2008 08 11.jpg
Comet holmes and iridium flare.jpg
  • Top: a simulated animation of a typical Iridium flare
  • Bottom: Both images show a flare of an Iridium satellite. Comet Holmes can be seen in the right image, slightly above the tree branch.

Satellite flare, also known as satellite glint, is a satellite pass visible to the naked eye as a brief, bright "flare". It is caused by the reflection toward the Earth below of sunlight incident on satellite surfaces such as solar panels and antennas (e.g., synthetic aperture radar). Streaks from satellite flare are a form of light pollution that can negatively affect ground-based astronomy, stargazing, and indigenous people. [1] [2] [3] [4]

Contents

Many satellites flare with magnitudes bright enough to see with the unaided eye, i.e. brighter than magnitude +6.5. [5] [6] Smaller magnitude numbers are brighter, so negative magnitudes are brighter than positive magnitudes, i.e. the scale is reverse logarithmic (see apparent magnitude).

The Iridium constellation was one of the first anthropogenic sources of near-space light pollution to draw criticism. Larger satellite constellations, like OneWeb and Starlink, have received increased criticism. [7] [8] [9] Scientific and policy analyses have raised questions about which regulatory bodies hold jurisdiction over human actions that obscure starlight in ways that affect astronomy, [10] [11] [12] stargazers, [13] [14] and indigenous communities. [4] [3] [15]

Controlled satellites

Flaring from reflection of the Sun Iridium animation.gif
Flaring from reflection of the Sun

The time and place of the satellite's flare can be predicted only when the satellite is controlled, and its orientation in space is known. In this case it is possible to predict the exact time of the flare, its place in the sky, the brightness and duration.

Iridium flares

Double flare - Iridium 6 and its replacement, #51, both flare in a 21-second exposure. Iridium 6 & 51.jpg
Double flare - Iridium 6 and its replacement, #51, both flare in a 21-second exposure.
First-generation Iridium satellite. Antennas can be seen in front, and solar panels in the back. Iridium satellite.jpg
First-generation Iridium satellite. Antennas can be seen in front, and solar panels in the back.

The first generation of the Iridium constellation launched a total of 95 telecommunication satellites in low Earth orbit which were known to cause Iridium flares, the brightest flares of all orbiting satellites, starting in 1997. From 2017 to 2019 they were replaced with a new generation that does not produce flares, with the first generation completely deorbited by 27 December 2019. [16] [17]

While the first-generation Iridium satellites were still controlled, their flares could be predicted. [18] These Iridium communication satellites had three polished door-sized antennas, 120° apart and at 40° angles with the main bus. The forward antenna faced the direction the satellite is traveling. Occasionally, an antenna reflects sunlight directly down at Earth, creating a predictable and quickly moving illuminated spot on the surface below of about 10 km (6 mi) diameter. To an observer this looks like a bright flash, or flare in the sky, with a duration of a few seconds.

Ranging up to −9.5 magnitude, some of the flares were so bright that they could be seen in the daytime. This flashing caused some annoyance to astronomers, as the flares occasionally disturbed observations. [19]

As the Iridium constellation consisted of 66 working satellites, Iridium flares were visible quite often (2 to 4 times per night). Flares of brightness −5 magnitude occurred 3 to 4 times per week, and −8 magnitude were visible 3 to 5 times per month for stationary observers.

Flares could also occur from solar panels, but they were not as bright (up to −3.5 magnitude). Such flares lasted about twice as long as those from the main mission antennas (MMA), because the so-called "mirror angle" for the solar panels was twice that for the MMAs. There were also rare cases of flares from MMAs and solar panels, or two MMAs (front and either right or left) of one satellite in a single pass.

The flares were bright enough to be seen at night in big cities where light pollution usually prevents most stellar observation. When not flaring, the satellites were often visible crossing the night sky at a typical magnitude of 6, similar to a dim star.

Mega-constellations

333 seconds-exposure containing 19 or more streaks due to Starlink satellites Starlink Satellites Imaged from CTIO.jpeg
333 seconds-exposure containing 19 or more streaks due to Starlink satellites
Starlink Satellite Trails over Brazil alongside a shooting star - NASA's Astronomy Picture of the Day, 10 December 2019. StarlinkTrails Filter 1080.jpg
Starlink Satellite Trails over Brazil alongside a shooting star - NASA's Astronomy Picture of the Day, 10 December 2019.

Planned low-orbit satellite constellations such as Starlink are a concern for astronomers, stargazers, and indigenous communities because of light pollution. [4] [21] [22] [23]

In February 2020, the Russian Academy of Sciences said it would send a letter to the United Nations complaining that Starlink's satellites will damage "30-40% of astronomical images." [24] [25] [26]

Numerous satellite operators have criticized SpaceX for attempting to overwhelm the FCC with paperwork as a means to gain approval to launch 42,000 satellites, [27] which has raised questions about which aspects of space law pertain to light pollution from satellites. [4]

SpaceX and Elon Musk have asserted in meetings with the National Academy of Sciences [28] and in FCC filings [29] that "SpaceX is committed to reducing satellite brightness to allow enjoyment of the skies and not thwart scientific discovery" [30] and that its objectives are (1) to "make the satellites generally invisible to the naked eye within a week of launch," and (2) to "minimize Starlink's impact on astronomy by darkening satellites so they do not saturate observatory detectors." [30]

Other satellite flares

A COSMO-SkyMed flare COSMO Skymed flare.PNG
A COSMO-SkyMed flare
A MetOp-A flare MetOp-A satellite flare May 26 2019.jpg
A MetOp-A flare

Many other controlled satellites also flare to magnitudes visible to the naked eye, i.e. larger than +6.5. [5]

MetOp-B and C, however, can produce predictable flares up to −5 magnitude (MetOp-A in no longer controlled) . [31] [32] [33] [34] Four COSMO-SkyMed satellites can produce flares up to -3 magnitude, and lasting much longer than the Iridium flares. [35] The Terrasar X and Tandem X also can produce predictable flares up to -3 magnitude.

The International Space Station (ISS) is known to cause bright ISS flares. [36] [37] [38] [39]

Composite image showing 27 minutes of Starlink satellite flares near the constellation Cassiopeia, 4/24/23. Starlink Flares, 53 degree orbital inclination.jpg
Composite image showing 27 minutes of Starlink satellite flares near the constellation Cassiopeia, 4/24/23.

Starlink satellites can flare repeatedly in an isolated area of the sky, typically directly above the sun (below the horizon) as they transit the highest latitude of their orbits. This phenomenon is most obvious when satellites are low over the horizon, and is due to the large number of Starlink satellites that are orbiting the Earth, predominantly at ~53° orbital inclination. [40]

The flares from Starlink have been misidentified as UFOs by airline pilots [41] [42] due to their unusual repetitive nature, which is visually analogous to a car's headlights at night getting brighter (then dimmer) as it rounds a turn.

Uncontrolled satellites

When a satellite goes out of control, it becomes possible to predict only a trajectory of its pass, while it becomes virtually impossible to accurately predict any flaring. These non-operational satellites are also described as "tumbling". This category includes many rotating rocket bodies, some failed Iridium satellites, ALOS satellite (which can produce flashes up to −10 mag), etc. The most important and valuable information about tumbling satellites is the period of flashes. It can vary from 0.5 seconds (rapidly rotating objects) to a minute or more (slowly rotating objects). Other important characteristics are the amplitude of changes in brightness and period of repetition of these changes.[ citation needed ]

Observation

While satellites may be seen by chance, there are websites and mobile apps which provide location-specific information as to when and where in the sky a satellite flare may be seen (for controlled satellites), or trajectory of a tumbling satellite's pass (for uncontrolled satellites) in the sky.

Reflections from satellites and other human space objects are sometimes reported as unidentified flying objects (UFOs), [43] and are often a result of repetitive observations in an isolated area of the sky over a short time period.

See also

Related Research Articles

<span class="mw-page-title-main">Satellite</span> Objects intentionally placed into orbit

A satellite or artificial satellite is an object in space, typically a spacecraft, placed into orbit around a celestial body. Satellites have a variety of uses, including communication relay, weather forecasting, navigation (GPS), broadcasting, scientific research, and Earth observation. Additional military uses are reconnaissance, early warning, signals intelligence and, potentially, weapon delivery. Other satellites include the final rocket stages that place satellites in orbit and formerly useful satellites that later become defunct.

<span class="mw-page-title-main">Satellite constellation</span> Group of artificial satellites working together as a system

A satellite constellation is a group of artificial satellites working together as a system. Unlike a single satellite, a constellation can provide permanent global or near-global coverage, such that at any time everywhere on Earth at least one satellite is visible. Satellites are typically placed in sets of complementary orbital planes and connect to globally distributed ground stations. They may also use inter-satellite communication.

Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection.

<span class="mw-page-title-main">Satellite phone</span> Type of mobile phone

A satellite telephone, satellite phone or satphone is a type of mobile phone that connects to other phones or the telephone network by radio link through satellites orbiting the Earth instead of terrestrial cell sites, as cellphones do. Therefore, they can work in most geographic locations on the Earth's surface, as long as open sky and the line-of-sight between the phone and the satellite are provided. Depending on the architecture of a particular system, coverage may include the entire Earth or only specific regions. Satellite phones provide similar functionality to terrestrial mobile telephones; voice calling, text messaging, and low-bandwidth Internet access are supported through most systems. The advantage of a satellite phone is that it can be used in such regions where local terrestrial communication infrastructures, such as landline and cellular networks, are not available.

<span class="mw-page-title-main">Satellite Internet access</span> Satellite-provided Internet

Satellite Internet access is Internet access provided through communication satellites; if it can sustain high speeds, it is termed satellite broadband. Modern consumer grade satellite Internet service is typically provided to individual users through geostationary satellites that can offer relatively high data speeds, with newer satellites using the Ku band to achieve downstream data speeds up to 506 Mbit/s. In addition, new satellite internet constellations are being developed in low-earth orbit to enable low-latency internet access from space.

<span class="mw-page-title-main">SpaceX</span> American private spacecraft company

Space Exploration Technologies Corporation, commonly referred to as SpaceX, is an American spacecraft manufacturer, launch service provider and satellite communications company headquartered in Hawthorne, California. The company was founded in 2002 by Elon Musk with the goal of reducing space transportation costs and ultimately developing a sustainable colony on Mars. The company currently produces and operates the Falcon 9 and Falcon Heavy rockets along with the Dragon and Starship spacecraft.

<span class="mw-page-title-main">Night sky</span> Appearance of the sky in a clear night

The night sky is the nighttime appearance of celestial objects like stars, planets, and the Moon, which are visible in a clear sky between sunset and sunrise, when the Sun is below the horizon.

<span class="mw-page-title-main">Heavens-Above</span> Website for tracking Earth satellites

Heavens-Above is a non-profit website developed and maintained by Chris Peat as Heavens-Above GmbH. The web site is dedicated to helping people observe and track satellites orbiting the Earth without the need for optical equipment such as binoculars or telescopes. It provides detailed star charts showing the trajectory of the satellites against the background of the stars as seen during a pass. Special attention is paid to the ISS, Starlink satellites, and others. Space Shuttle missions were tracked until the program was retired in July 2011 and Iridium flares were also tracked until the program was retired in May 2018. The website also offers information on currently visible comets, asteroids, planet details, and other miscellaneous information.

<span class="mw-page-title-main">Iridium satellite constellation</span> Satellite constellation providing voice and data coverage

The Iridium satellite constellation provides L band voice and data information coverage to satellite phones, satellite messenger communication devices and integrated transceivers. Iridium Communications owns and operates the constellation, additionally selling equipment and access to its services. It was conceived by Bary Bertiger, Raymond J. Leopold and Ken Peterson in late 1987 and then developed by Motorola on a fixed-price contract from July 29, 1993, to November 1, 1998, when the system became operational and commercially available.

<span class="mw-page-title-main">Starlink</span> SpaceX satellite constellation and internet service

Starlink is a satellite internet constellation operated by Starlink Services, LLC, a wholly-owned subsidiary of American aerospace company SpaceX, providing coverage to over 70 countries. It also aims to provide global mobile broadband.

<span class="mw-page-title-main">Eutelsat OneWeb</span> Global communications company

Eutelsat OneWeb is a subsidiary of Eutelsat Group providing broadband satellite Internet services in low Earth orbit (LEO). The company is headquartered in London, and has offices in Virginia, US and a satellite manufacturing facility in Florida – Airbus OneWeb Satellites – that is a joint venture with Airbus Defence and Space.

<i>Humanity Star</i> Miniaturized passive satellite

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<span class="mw-page-title-main">Paz (satellite)</span> Spanish military Earth observation satellite

Paz is a Spanish Earth observation and reconnaissance satellite launched on 22 February 2018. It is Spain's first spy satellite. The satellite is operated by Hisdesat. Paz was previously referred to as SEOSAR.

A satellite internet constellation is a constellation of artificial satellites providing satellite internet service. In particular, the term has come to refer to a new generation of very large constellations orbiting in low Earth orbit (LEO) to provide low-latency, high bandwidth (broadband) internet service.

<span class="mw-page-title-main">AST SpaceMobile</span> American satellite manufacturer

AST SpaceMobile is a publicly traded satellite designer and manufacturer based in Midland, Texas, United States. The company is building the SpaceMobile satellite constellation, a space-based cellular broadband network that will allow existing, unmodified smartphones to connect to satellites in areas with coverage gaps. Its BlueWalker 3 prototype satellite is the largest commercial communications array in low Earth orbit after its launch in 2022.

<span class="mw-page-title-main">Starlink in the Russo-Ukrainian War</span> Co-operation between Ukraine and Starlink

In February 2022, two days after Russia's full-scale invasion, Ukraine requested American aerospace company SpaceX to activate their Starlink satellite internet service in the country to replace internet and communication networks degraded or destroyed during the war. Starlink has since been used by Ukrainian civilians, government and military. The satellite service has served for humanitarian purposes, as well as defense and attacks on Russian positions.

References

  1. ↑ "SATCON1 Report". 25 August 2020. Archived from the original on 29 November 2020.
  2. ↑ "Media advisory: Press Conference to Unveil Conclusions from Satellite Constellations 1 (SATCON1) Workshop" (Press release). 21 August 2020. Archived from the original on 29 November 2020.
  3. 1 2 Gallozzi, Stefano; Scardia, Marco; Maris, Michele (4 February 2020). "Concerns about ground based astronomical observations: A step to Safeguard the Astronomical Sky". arXiv: 2001.10952 [astro-ph.IM].
  4. 1 2 3 4 Venkatesan, Aparna; Lowenthal, James; Prem, Parvathy; Vidaurri, Monica (2020). "The impact of satellite constellations on space as an ancestral global commons". Nature Astronomy. 4 (11): 1043–1048. Bibcode:2020NatAs...4.1043V. doi: 10.1038/s41550-020-01238-3 . S2CID   228975770.
  5. 1 2 Curtis, Heber Doust (1903) [1901-03-27]. "On the Limits of Unaided Vision". Lick Observatory Bulletin . 2 (38). University of California: 67–69. Bibcode:1903LicOB...2...67C. doi: 10.5479/ADS/bib/1903LicOB.2.67C . PMID   17800603.
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  8. ↑ "Light pollution from satellites will get worse. But how much?". astronomy.com. 14 June 2019. Retrieved 7 November 2019.
  9. ↑ "SpaceX Starlink satellite constellation astronomy light pollution". 29 May 2019. Archived from the original on 29 November 2020.
  10. ↑ Bakos, Gaspar. "Light pollution from Satellites".
  11. ↑ Montgomery, Marc (18 November 2020). "Astronomers vs tech giants in space". Archived from the original on 29 November 2020.
  12. ↑ "SATCON1 Report". 25 August 2020.
  13. ↑ "Why do mega constellations matter to the Dark Sky community" (Press release). 27 December 2019.
  14. ↑ Lawler, Samantha (17 November 2020). "SpaceX's Starlink satellites are about to ruin stargazing for everyone".
  15. ↑ Venkatesan, Aparna; Begay, David; Burgasser, Adam J.; Hawkins, Isabel; Kimura, Ka’iu; Maryboy, Nancy; Peticolas, Laura (6 December 2019). "Towards inclusive practices with indigenous knowledge". Nature Astronomy. 3 (12): 1035–1037. arXiv: 2009.12425 . Bibcode:2019NatAs...3.1035V. doi:10.1038/s41550-019-0953-2. S2CID   212942611.
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  17. ↑ Carter, Jamie (14 November 2017). "Iridium flares to cease by end of 2018". BBC Sky at Night Magazine. Retrieved 26 May 2018.
  18. ↑ Peat, Chris (15 May 2018). "The end of Iridium flares?". Heavens-Above. Munich . Retrieved 2 November 2018.
  19. ↑ "Iridium Flare Satellite Tracker". Apollo Satellite Communications. Retrieved 6 November 2019.
  20. ↑ Filter, Egon (10 December 2019). "NASA's Astronomy Picture of the Day showing Starlink Satellite Trails over Brazil". NASA.
  21. ↑ Hall, Shannon (June 2019). "After SpaceX Starlink Launch, a Fear of Satellites That Outnumber All Visible Stars". The New York Times. Retrieved 3 June 2019.
  22. ↑ "The unexpected brightness of new satellites could ruin the night sky". The Economist. 30 May 2019. Retrieved 3 June 2019.
  23. ↑ "SpaceX's Starlink Could Change The Night Sky Forever, And Astronomers Are Not Happy". Forbes. Retrieved 3 June 2019.
  24. ↑ "RAS will complain to the UN about Elon Musk over the Starlink satellite system". RIA Novosti. 27 February 2020.
  25. ↑ Cole, Brendan (28 February 2020). "Light From Elon Musk's Starlink Satellites Ruins Space Photos, Says Russian Government Agency". Newsweek.
  26. ↑ Tlis, Fatima (3 March 2020). "Russian Academy of Sciences Takes Aim at Musk's SpaceX Satellites". Polygraph Info.
  27. ↑ Hebden, Kerry (18 October 2019). "Companies unite to reject SpaceX satellite plans".
  28. ↑ "Decadal Survey on Astronomy and Astrophysics 2020 (Astro2020): Optical Interference from Satellite Constellations Meeting". National Academy of Science. 27 April 2020.
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  30. 1 2 Musk, Elon (27 April 2020). Starlink: NAS Decadal Panel. National Academy of Sciences.
  31. ↑ "FPAS Reports - DB Query for Metop-A".
  32. ↑ "FPAS Reports - DB Query for Metop-B".
  33. ↑ Wesley (9 April 2014). "MetOp-A satellite flare".
  34. ↑ "Video of Metop-A Flaring". 23 March 2012.
  35. ↑ "FPAS Reports - DB Query for SkyMed 2".
  36. ↑ "Watch International Space Station Flybys All Night Long". Sky & Telescope. 15 May 2019. Retrieved 6 May 2020.
  37. ↑ Dickinson, David (14 May 2019). "The International Space Station Rides High Through the May Sky". Universe Today. Retrieved 6 May 2020.
  38. ↑ Rao, Joe (11 July 2008). "Spot the Space Station". Space.com. Retrieved 6 May 2020.
  39. ↑ "Spot The Station". spotthestation.nasa.gov. Retrieved 6 May 2020.
  40. ↑ warnerjh (24 April 2023). "Starlink Satellites Flaring in Cassiopeia". CatchingTime. Retrieved 3 March 2024.
  41. ↑ "Pilot Shares Videos Of Strange UFO Sightings In Skies Over The US". YouTube. 21 October 2022. Retrieved 21 October 2022.
  42. ↑ "Why "Racetrack" UFOs are mostly Starlink Flares". Metabunk. 15 May 2019. Retrieved 23 October 2022.
  43. ↑ "Is that a UFO?! There's probably an explanation - Human World". EarthSky | Updates on your cosmos and world. 15 December 2020. Retrieved 30 January 2022.
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