Astronomy

How do satellites impede current telescopes?

How do satellites impede current telescopes?



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As we send up more and more satellites, it stands to reason that our view of the universe becomes more and more obscured. I would certainly expect for example that a large telescope such as the LSST would be able to see the International Space Station, and since the ISS is not transparent, it wouldn't be able to observe the patch of the sky beyond it.

How do current telescopes currently deal with satellites obstructing their view? Do they simply not observe where the satellite is? If we send up more and more satellites, does it mean that telescopes will have to focus on narrower and narrower fields of view to avoid the swarm?


Satellites, even in geostationary orbits, move with respect to the background stars and make "trails" on telescopic images that are tracked at the sidereal rate.

Removal of these can be as straightforward as taking the median of a set of exposures.

What I mean by this, is that in a sequence of exposures, the satellite trail will pollute different pixels in each exposure. Therefore if you take a sequence of exposures, tracked to keep stellar positions identical, then take the pixel-by-pixel median of the sequence of frames, the presence of the satellite will be removed. i.e. Each x,y pixel in your stacked image is formed by taking the median of the values of that pixel (scaled by the exposure time if necessary) in each image. It is essentially the same procedure by which cosmic ray strikes are removed.


Satellites already cause problems for telescopes, but not by obstructing their view. Actually the light reflected from satellites is a bigger problem, and for observations of radio waves, their communications are the really big problem.

In terms of reflected light, you might remember the controversy around the "Humanity Star" being too bright. The same applies to starlink, which this image shows really well:

Credit: CTIO/NOIRLab/NSF/AURA/DECam DELVE Survey

Radio wave observations are important because they allow astronomers to look the furthest back in time towards the big bang, when everything was strongly red-shifted. They are also used for measuring pulsars, and for SETI. Satellites only use discrete frequencies for communications (broadened by doppler shifting) but there are already so many communications, and signal strength is so much stronger than what we receive from distant galaxies that removing the noise is a topic of active research. Due to the long wavelengths, radio wave antennae have to be quite large, so these telescopes are usually earth based - there are not many radio wave telescopes "above" LEO orbit which would give us an untainted view.

While researching this, I read that variations in the brightness of a star are important for detecting exoplanets, and satellites blocking that light momentarily could disturb the measurement. I would have expected that the timescales for the satellite and the planet to be blocking the light would be different enough that you could filter that out - but it would be an additional noise source for what is already a very sensitive measurement.


As satellites proliferate, telescopes go dark

For millennia, humans have peered into the night sky hoping to divine their place in the universe. Telescopes and other technologies allowed them to look ever deeper. Now that age-old custom is running up against a very modern threat: satellites.

More than 3,300 operational satellites are currently in orbit, according to the Union of Concerned Scientists. As global demand for broadband and other services soars, that number could exceed 100,000 in the years ahead. This has scientists worried: Satellites reflect sunlight, causing bright trails across the night sky, which in turn can impede crucial observations or corrupt astronomical data.

Without government action, the rise of satellite constellations could soon make ground-based telescopes all but unusable — affecting everything from the study of the stars to the search for dangerous near-Earth objects.

Astronomers have long had a fraught relationship with technology. Tensions date to the 19th-century gas lamp. Cheap lights improved public safety, enabled factories to keep longer hours and allowed for the emergence of nightlife. But by the mid-1800s, big cities were so well lit (and so polluted) that astronomers were losing sight of the dimmest stars. In response, they tended to decamp for remoter pastures. When the countryside lit up, too, they pushed out to the world’s last dark places, such as the remote deserts of northern Chile.

Even those outposts weren’t entirely free from interference, and researchers had to learn to filter out (for example) radio and television signals. But bigger telescopes and better technology still allowed them to scan the cosmos effectively.

In 1997, Motorola Solutions Inc. made that task more difficult when it launched the first of dozens of communication satellites in a constellation around the Earth. Now operated by Iridium Communications Inc., the array provides global voice and data coverage. But its powerful transmitters also interfere with the bands of radio spectrum allocated (under international agreement) to scientific instruments like telescopes.

That interference is growing worse every year, as more and more satellites come online. SpaceX has already launched more than 1,300 satellites for its broadband network, called Starlink, and has been authorized to send up nearly 12,000 in total. OneWeb plans to have some 7,000 in orbit in the next few years, while Amazon.com Inc. wants to launch 3,236. Meanwhile, China is preparing for two constellations with a combined 12,992 satellites.

Last year, dozens of researchers from around the world met virtually to study the risks these launches pose. Results are being presented this week at the Committee on the Peaceful Uses of Outer Space at the United Nations. Their conclusions are grim: “The situation for astronomy is reaching a point of no return from continuous interference with observations and loss of science.” Up to 40% of the images collected by wide-field telescopes could be rendered unusable, they found. Surveys of moving objects, including the International Asteroid Warning Network, could also be in jeopardy, while radio-telescope operators will find it increasingly hard to point at the sky without finding a satellite in their path.

Fortunately, SpaceX and OneWeb have publicly recognized these dangers. SpaceX, in particular, is working with astronomers to darken its satellites so that they have less impact on observatories. But even if both companies devise reasonable solutions, there’s no assurance that their competitors (public and private) will do the same.

Does it matter? From a cultural standpoint, it would be tragic if the ancient pursuit of studying the night sky were degraded to such an extent. On a more practical level, astronomy has played a huge role in advancing human welfare and boosting technologies from navigation to communication. Are future discoveries worth jeopardizing for the sake of global broadband?

With some reasonable precautions, that should be a false choice. As a start, bodies such as the U.N. should be raising the alarm and studying possible solutions to this problem. Existing agreements for divvying up radio frequencies could be a starting point for new talks on mitigating satellite risks. Governments should also create satellite-licensing agreements that require companies to protect essential scientific efforts. And operators should follow SpaceX’s lead in reaching out to scientists and incorporating their needs into technology designs.

There’s no going back to the dark nights of our ancestors. But with some foresight, policy makers should be able to ensure clearer skies into the future.

Adam Minter is a Bloomberg Opinion columnist.

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Contents

Satellites in use today include the XMM-Newton observatory (low to mid energy X-rays 0.1-15 keV) and the INTEGRAL satellite (high energy X-rays 15-60 keV). Both were launched by the European Space Agency. NASA has launched the Swift and Chandra observatories. One of the instruments on Swift is the Swift X-Ray Telescope (XRT).

The GOES 14 spacecraft carries on board a Solar X-ray Imager to monitor the Sun's X-rays for the early detection of solar flares, coronal mass ejections, and other phenomena that impact the geospace environment. [1] It was launched into orbit on June 27, 2009, at 22:51 GMT from Space Launch Complex 37B at the Cape Canaveral Air Force Station.

On January 30, 2009, the Russian Federal Space Agency successfully launched the Koronas-Foton which carries several experiments to detect X-rays, including the TESIS telescope/spectrometer FIAN with SphinX soft X-ray spectrophotometer.

ISRO launched the multi-wavelength space observatory Astrosat in 2015. One of the unique features of ASTROSAT mission is that it enables the simultaneous multi-wavelength observations of various astronomical objects with a single satellite. ASTROSAT observes universe in the optical, Ultraviolet, low and high energy X-ray regions of the electromagnetic spectrum, whereas most other scientific satellites are capable of observing a narrow range of wavelength band.

The Italian Space Agency (ASI) gamma-ray observatory satellite Astro-rivelatore Gamma ad Imagini Leggero (AGILE) has on board the Super-AGILE 15-45 keV hard X-ray detector. It was launched on April 23, 2007, by the Indian PSLV-C8. [2]

The Hard X-ray Modulation Telescope (HXMT) is a Chinese X-ray space observatory, launched on June 15, 2017 to observe black holes, neutron stars, active galactic nuclei and other phenomena based on their X-ray and gamma-ray emissions. [3]

The 'Lobster-Eye X-ray Satellite' was launched on 25 July 2020 by CNSA. it is the first in-orbit telescope to utilize the Lobster-Eye imaging technology of ultra-large field of view imaging to search for dark matter signals in the x-ray energy range. [4]

A soft X-ray solar imaging telescope is on board the GOES-13 weather satellite launched using a Delta IV from Cape Canaveral LC37B on May 24, 2006. [5] However, there have been no GOES 13 SXI images since December 2006.

Although the Suzaku X-ray spectrometer (the first micro-calorimeter in space) failed on August 8, 2005, after launch on July 10, 2005, the X-ray Imaging Spectrometer (XIS) and Hard X-ray Detector (HXD) are still functioning.

The Russian-German Spektr-RG carries the eROSITA telescope array as well as the ART-XC telescope. It was launched by Roscosmos on 13 July 2019 from Baikonur and began collecting data in October 2019.

The Solar Orbiter (SOLO) will approach to 62 solar radii to view the solar atmosphere with high spatial resolution in visible, XUV, and X-rays. The nominally 6 yr mission will be from an elliptical orbit around the Sun with perihelion as low as 0.28 AU and with increasing inclination (using gravity assists from Venus) up to more than 30° with respect to the solar equator. The Orbiter will deliver images and data from the polar regions and the side of the Sun not visible from Earth. [6] It launched in February 2020.

Past observatories include SMART-1, which contained an X-ray telescope for mapping lunar X-ray fluorescence, ROSAT, the Einstein Observatory (the first fully imaging X-ray telescope), the ASCA observatory, EXOSAT, and BeppoSAX. Uhuru was the first satellite launched specifically for the purpose of X-ray astronomy. Copernicus which carried an X-ray detector built by University College London's Mullard Space Science Laboratory made extensive X-ray observations. ANS could measure X-ray photons in the energy range 2 to 30 keV. Ariel 5 was dedicated to observing the sky in the X-ray band. HEAO-1 scanned the X-ray sky over 0.2 keV - 10 MeV. Hakucho was Japan's first X-ray astronomy satellite. ISRO's IRS-P3 launched in 1996 with the Indian X-ray Astronomy Experiment (IXAE) on board which aimed to study the time variability and spectral characteristics of cosmic X-ray sources and for detection of transient X-ray sources. IXAE instruments consisted of three identical pointed mode proportional counters (PPCs) operated in the energy range 2-20 keV, FOV of 2° x 2° and effective area of 1200 cm2, and an X-ray sky monitor (XSM) operating in the energy range 2-10 keV.

Array of low-energy X-ray imaging sensors Edit

The Array of Low Energy X-ray Imaging Sensors (ALEXIS) featured curved mirrors whose multilayer coatings reflect and focus low-energy X-rays or extreme ultraviolet light the way optical telescopes focus visible light. The launch of ALEXIS was provided by the United States Air Force Space Test Program on a Pegasus Booster on April 25, 1993. The spacing of the molybdenum (Mo) and silicon (Si) layers on each telescope's mirror is the primary determinant of the telescope's photon energy response function. ALEXIS operated for 12 yr.

OSO-3 Edit

The third Orbiting Solar Observatory (OSO 3) was launched on March 8, 1967, into a nearly circular orbit of mean altitude 550 km, inclined at 33° to the equatorial plane, deactivated on June 28, 1968, followed by reentry on April 4, 1982. Its XRT consisted of a continuously spinning wheel (1.7 s period) in which the hard X-ray experiment was mounted with a radial view. The XRT assembly was a single thin NaI(Tl) scintillation crystal plus phototube enclosed in a howitzer-shaped CsI(Tl) anti-coincidence shield. The energy resolution was 45% at 30 keV. The instrument operated from 7.7 to 210 keV with 6 channels. OSO-3 obtained extensive observations of solar flares, the diffuse component of cosmic X-rays, and the observation of a single flare episode from Scorpius X-1, the first observation of an extrasolar X-ray source by an observatory satellite. Among the extrasolar X-ray sources OSO 3 observed were UV Ceti, YZ Canis Minoris, EV Lacertae and AD Leonis, yielding upper soft X-ray detection limits on flares from these sources. [7]

ESRO 2B (Iris) Edit

ESRO 2B (Iris) was the first successful ESRO satellite launch. Iris was launched on May 17, 1968, had an elliptical orbit with (initially) apogee 1086 km, perigee 326 km, and inclination 97.2°, with an orbital period of 98.9 minutes. The satellite carried seven instruments to detect high energy cosmic rays, determine the total flux of solar X-rays, and measure trapped radiation, Van Allen belt protons and cosmic ray protons. Of special significance for X-ray astronomy were two X-ray instruments: one designed to detect wavelengths 1-20 Å (0.1-2 nm) (consisting of proportional counters with varying window thickness) and one designed to detect wavelengths 44-60 Å (4.4-6.0 nm) (consisting of proportional counters with thin Mylar windows). [8]

Wavelength dispersive X-ray spectroscopy (WDS) is a method used to count the number of X-rays of a specific wavelength diffracted by a crystal. WDS only counts X-rays of a single wavelength or wavelength band. In order to interpret the data, the expected elemental wavelength peak locations need to be known. For the ESRO-2B WDS X-ray instruments, calculations of the expected solar spectrum had to be performed and were compared to peaks detected by rocket measurements. [9]

  • The SOLar RADiation satellite program (SOLRAD) was conceived in the late 1950s to study the Sun's effects on Earth, particularly during periods of heightened solar activity. [10]Solrad 1 is launched on June 22, 1960, aboard a Thor Able from Cape Canaveral at 1:54 a.m. EDT. [11] As the world's first orbiting astronomical observatory, Solrad 1 determined that radio fade-outs were caused by solar X-ray emissions. [10]
  • The first in a series of 8 successfully launched Orbiting Solar Observatories (OSO 1, launched on March 7, 1963) had as its primary mission to measure solar electromagnetic radiation in the UV, X-ray, and gamma-ray regions.
  • OGO 1, the first of the Orbiting Geophysical Observatories (OGOs), was successfully launched from Cape Kennedy on September 5, 1964, and placed into an initial orbit of 281 × 149,385 km at 31° inclination. A secondary objective was to detect gamma-ray bursts from the Sun in the energy range 80 keV - 1 MeV. The experiment consisted of 3 CsI crystals surrounded by a plastic anti-coincidence shield. Once every 18.5 seconds, integral intensity measurements were made in each of 16 energy channels which were equally spaced over the 0.08-1 MeV range. OGO 1 was completely terminated on November 1, 1971. Although the satellite did not achieve its goals due to electrical interference and secular degradation, searching back through the data after the discovery of cosmic gamma-ray bursts by the Vela satellites revealed the detection of one or more such events in the OGO 1 data.
  • Solar X-ray bursts were observed by OSO 2 and an effort was made to map the entire celestial sphere for direction and intensity of X-radiation.
  • The first USA satellite which detected cosmic X-rays was the third Orbiting Solar Observatory, or OSO-3, launched on March 8, 1967. It was intended primarily to observe the Sun, which it did very well during its 2-year lifetime, but it also detected a flaring episode from the source Sco X-1 and measured the diffuse cosmic X-ray background.
  • The fourth successful Orbiting Solar Observatory, OSO 4, was launched on October 18, 1967. The objectives of the OSO 4 satellite were to perform solar physics experiments above the atmosphere and to measure the direction and intensity over the entire celestial sphere in UV, X, and gamma radiation. The OSO 4 platform consisted of a sail section (which pointed 2 instruments continuously toward the Sun) and a wheel section which spun about an axis perpendicular to the pointing direction of the sail (which contained 7 experiments). The spacecraft performed normally until a second tape recorder failed in May 1968. OSO 4 was put into a "standby" mode in November 1969. It could be turned on only for recording special events in real-time. One such event occurred on March 7, 1970, during a solar eclipse. The spacecraft became totally inoperable on December 7, 1971.
  • OGO 5 was launched on March 4, 1968. The satellite, primarily devoted to Earth observation, was in a highly elliptical initial orbit with a 272 km perigee and a 148,228 km apogee. The orbital inclination was 31.1°. The satellite took 3796 minutes to complete one orbit. The Energetic Radiations from Solar Flares experiment was operational from March 1968 - June 1971. Primarily devoted to solar observations, it detected at least 11 cosmic X-ray bursts in time coincidence with gamma-ray bursts seen by other instruments. The detector was a 0.5 cm thick NaI(Tl) crystal with a 9.5 cm 2 area. Data were accumulated into energy ranges of: 9.6-19.2, 19.2-32, 32-48, 48-64, 64-80, 80-104, 104-128, and > 128 keV. The data were sampled for 1.15 seconds once every 2.3 seconds. was launched April 19, 1968 and contained an X-ray experiment. Orbit characteristics: 261 × 426 km, at an inclination of 48.5°. The orbital period was
  • The Vela satellites 5A and 5B, launched on May 23, 1969, are responsible for significant discoveries of gamma-ray bursts and astronomical X-ray sources including V 0332+53.
  • Like the previous Vela 5 satellites, the Vela 6 nuclear test detection satellites were part of a program run jointly by the Advanced Research Projects of the U. S. Department of Defense and the U. S. Atomic Energy Commission, managed by the U. S. Air Force. The twin spacecraft, Vela 6A and 6B, were launched on April 8, 1970. Data from the Vela 6 satellites were used to look for correlations between gamma-ray bursts and X-ray events. At least 2 good candidates were found, GB720514 and GB740723. The X-ray detectors failed on Vela 6A on March 12, 1972, and on Vela 6B on January 27, 1972. was launched by the USSR into Earth orbit on June 24, 1971, and recovered July 6, 1971. The orbit characteristics: apogee/perigee/inclination 208 km, 271 km, and 51.8°, respectively. It was a military satellite on which X-ray astronomy experiments had been added. There was a scintillation spectrometer sensitive to X-rays >30 keV, with a 2° × 17° field of view. In addition, there was an X-ray telescope which operated in the range 2-30 keV. Cosmos 428 detected several X-ray sources which were correlated to already identified Uhuru point sources.
  • Following on the success of Uhuru (SAS 1), NASA launched the Second Small Astronomy Satellite SAS 2. It was launched from the San Marco platform off the coast of Kenya, Africa, into a nearly equatorial orbit.
    was put in a nearly circular polar sun-synchronous orbit, with apogee 545 km, perigee 533 km, and inclination 97.6°. It was ESRO's first 3-axis stabilized satellite, with one axis pointing to the Sun to within ±5°. The optical axis was maintained perpendicular to the solar pointing axis and to the orbital plane. It scanned the entire celestial sphere every 6 months, with a great circle being scanned every satellite revolution. After about 2 months of operation, both of the satellite's tape recorders failed. A network of ground stations was put together so that real-time telemetry from the satellite was recorded for about 60% of the time. After 6 months in orbit, the satellite entered a period of regular eclipses as the satellite passed behind the Earth—cutting off sunlight to the solar panels. The satellite was put into hibernation for 4 months, until the eclipse period passed, after which systems were turned back on and another 6 months of observations were made. TD-1A was primarily a UV mission however it carried both a cosmic X-ray and a gamma-ray detector. TD-1A reentered on January 9, 1980.
  • To continue the intensive X-ray investigation of the Sun and the cosmic X-ray background, OSO 7 was launched on September 29, 1971. OSO 7 made the first observation of solar gamma-ray line emission, due to electron/positron annihilation at 511 keV, from a solar flare in April 1972.
  • To conduct experiments in X-ray astronomy and solar physics among others the Indian Space Research Organization (ISRO) built Aryabhata. It was launched by the Soviet Union on April 19, 1975, from Kapustin Yar. A power failure halted experiments after 4 days in orbit.
  • The third US Small Astronomy Satellite (SAS-3) was launched on May 7, 1975, with 3 major scientific objectives: 1) determine bright X-ray source locations to an accuracy of 15 arcseconds 2) study selected sources over the energy range 0.1-55 keV and 3) continuously search the sky for X-ray novae, flares, and other transient phenomena. It was a spinning satellite with pointing capability. SAS 3 was the first to discover X-rays from a highly magnetic WD binary system, AM Her, discovered X-rays from Algol and HZ 43, and surveyed the soft X-ray background (0.1-0.28 keV).
  • Orbiting Solar Observatory (OSO 8) was launched on June 21, 1975. While OSO 8's primary objective was to observe the Sun, four instruments were dedicated to observations of other celestial X-ray sources brighter than a few milliCrab. A sensitivity of 0.001 of the Crab nebula source (= 1 "mCrab"). OSO 8 ceased operations on October 1, 1978.
    (launched on June 17, 1977) was part of the Soviet Union's Intercosmos program.
  • Bhaskara was the second Indian Space Research Organization (ISRO) satellite. It was launched on June 7, 1979, with a modified SS-5 Skean IRBM plus upper stage from Kapustin Yar in the Soviet Union. A secondary objective was to conduct X-ray astronomy investigations. Bhaskara 2 was launched on November 20, 1981, from Kapustin Yar like its predecessor also in size, mass and design may have conducted X-ray astronomy investigations.
  • On March 23, 1983, at 12:45:06 UTC, the Astron spacecraft is launched into an orbit around the Earth with an apogee of 185,000 km allowing it to make observations with an onboard X-rayspectroscope outside the Earth's umbra and radiation belt. Observations of Hercules X-1 are made from 1983 to 1987 in both the prolonged low state ("off" state) and "high on" state. [14]
  • The Global Geospace Science (GGS) Polar Satellite was a NASA science spacecraft launched at 06:23:59.997 EST on February 24, 1996, aboard a McDonnell DouglasDelta II 7925-10 rocket from launch pad 2W at Vandenberg Air Force Base in Lompoc, California, to observe the Earth's polar magnetosphere. Polar is in a highly elliptical orbit, at an 86° inclination with an orbital period of
  • A later satellite of the Intercosmos series, Intercosmos 26, (launched on March 2, 1994) as part of the Coronas-I international project may have conducted X-ray studies of the Sun. , formerly known as Astro-H, was a Japanese satellite which attempted to re-fly the microcalorimeter that failed on the Suzaku mission, along with hard-X-ray and soft-gamma instruments. It launched successfully on February 17, 2016. However, spacecraft controllers lost communications with Hitomi on March 26, and declared the spacecraft lost April 28.

ATHENA Edit

Advanced Telescope for High Energy Astrophysics was selected in 2013 as a second large mission of the Cosmic Vision programme. [16] It will be one hundred times more sensitive than the best of existing X-ray telescopes. [17]

Astro-H2 Edit

In July 2016 there were discussions between JAXA and NASA on launching a satellite to replace the Hitomi telescope lost in 2016. [18] [19] Astro-H2, also known as XRISM, is set to launch in 2022. [20]

International X-ray Observatory Edit

International X-ray Observatory (IXO) was a cancelled observatory. A result of the merging of NASA's Constellation-X and ESA/JAXA's XEUS mission concepts, it was planned to feature a single large X-ray mirror with a 3 m 2 collecting area and 5" angular resolution, and a suite of instrumentation, including a wide field imaging detector, a hard X-ray imaging detector, a high-spectral-resolution imaging spectrometer (calorimeter), a grating spectrometer, a high timing resolution spectrometer, and a polarimeter.

Constellation-X Edit

Constellation-X was early proposal that was superseded by IXO. It was to provide high resolution X-ray spectroscopy to probe matter as it falls into a black hole, as well as probe the nature of dark matter and dark energy by observing the formation of clusters of galaxies.


An Uncertain Future for the Night Skies

As recently as a hundred years ago, the Milky Way was visible from outside most cities. As electric lighting became cheaper and more common, light pollution made it impossible to see features of our galaxy from all but the most remote locations, which today are home to the largest telescopes. The advent of inexpensive LEDs in the past two decades has made bluer street lamps and household lighting more common, leading to further reductions in sky visibility hundreds of miles from major metropolitan areas. And now, the dark skies are being illuminated from above. Since May of 2019, SpaceX has launched more than 770 Starlink satellites at a rate of roughly 60 per month, and these are some of the brightest satellites in orbit. Over the next 5-10 years, we may experience a 30-fold increase in the number of satellites like those of Starlink. If these plans come to fruition, it’s possible there will be more satellites visible by eye than stars, and our view of the night sky will be changed across the world.

So what is the plan with these satellites, what should we expect to happen, and when? Is there a cause for concern for ground-based astronomy, and what might researchers and the private industry do to mitigate problems? Here we hope to provide concise, fact-based answers to these types of questions.

Figure 1: Starlink satellites have been found in images taken by observatories across the world like the one above. This image, showing a fleet of Starlink satellites passing overhead, comes from Cerro Tololo, Chile, the home of more than a dozen professional telescopes. Credit: NSF’s National Optical-Infrared Astronomy Research Laboratory / CTIO / AURA / DELVE.

What exactly is happening, and why?

Across the next decade, numerous private industry companies (including SpaceX , Kuiper Systems by Amazon, Samsung , and Boeing ) each plan to launch between several hundred and several thousand satellites into “low Earth orbits” (LEO). Satellites in LEO orbit at an altitude of less than

1000km. Though there are currently some 11,000 artificial satellites in LEO, the majority of these objects are small debris orbiting at altitudes greater than 600km. Starlink satellites, on the other hand, make up the majority of large objects (> 100kg) orbiting below 600km. Because of their low orbits and their sizes, most of these satellites are bright enough to be seen by the naked eye. Each set of satellites will form “megaconstellations,” harmonized groups of satellites working together to accomplish the same goal. There are a number of motivations for placing several thousand satellites into LEO, but the majority of these companies seek to provide high-speed, low-latency internet across the world. At LEO, satellites circle the Earth about once every 90 minutes, meaning they have little time to communicate with facilities on the ground. Only a megaconstellation of satellites can provide consistent and uniform communication to populated areas across the Earth.

These types of services accomplish many goals. On the one hand, services like these may be the only means for some rural areas to obtain quality internet access. Indeed, according to the FCC , tens of millions of Americans are without access to broadband internet, and in 2017, the UN reported that the majority of the world lacked access to broadband (most notably in Africa and Asia). The communication business is also lucrative. According to SpaceX CEO Elon Musk, “ Total internet connectivity revenue in the world is on the order of a trillion dollars, and we think maybe we can access about 3 percent of that, or maybe 5 percent. ” At the moment, it is not clear how expensive these services will be, though the claim is that they will be competitive with current internet providers.

To date, SpaceX is leading the race to populate LEO with satellites, having successfully launched several hundred. Future scheduled launch dates include the end of September and October. The company plans to offer service to the Northern U.S. and Canada by the end of 2020, expanding across the world in 2021. Furthermore, there is no end in sight, as the FCC has approved 1 million Starlink ground stations for communication, and more than 700,000 Americans are subscribed to Starlink’s web-updates .

What’s the worry?

Satellites in LEO are nothing new, but their impact on astronomy depends on how bright they are. Starlink satellites now make up the majority of LEO satellites, as shown in Figure 2, and all of those that have been launched to date are visible by eye (between 3rd and 7th magnitude, and as bright as 1st magnitude immediately upon launch). Depending on a location’s latitude, time of year, and time of night, several hundred LEO satellites may be overhead at once, potentially visible by eye. Any object this bright is easily detected by even moderate telescopes with the shortest exposure times: images of the night sky, like Figure 1, may soon become filled with LEO satellites.

Figure 2: Number of objects orbiting Earth at altitudes between 200 and 600 km as a function of time. The majority of large objects (right) are visible by eye. In teal, the contribution of Starlink is shown. Since the creation of this figure,

400 more Starlink satellites have been launched, and these are now the most numerous large satellites at these altitudes. Credit: Fig. 3 of McDowell et al. (2020).

Fortunately, mitigating the effects of LEO satellites is a priority for the forerunner in this space-race, SpaceX. Musk has previously claimed “[We are] confident that we will not cause any effect whatsoever in astronomical discoveries. Zero. That’s my prediction. We’ll take corrective action if [the impact] is above zero.” However, achieving this admirable goal will require successful strategies that darken the current satellite design dramatically, as current Starlink satellites are already bright enough to disrupt basic observations. Two methods under consideration are meant to darken the Starlink satellites and are currently being tested. The first includes darkening the satellite to reduce reflectivity (DarkSat), while the second option includes a sun-shade to reduce illumination of reflective components (VisorSat). A prototype of the former has already been launched, but astronomers have determined it to be only a factor of 2 fainter than the original Starlink satellites . The DarkSat is just barely too faint to be seen by eye but is still easily bright enough to disrupt observations. To address these concerns and collaborate on methods for further mitigation, both the American Astronomical Society and International Astronomical Union have established working groups which actively communicate with SpaceX. This is still a work in progress, though both sides have expressed optimism. You can follow their updates here .

Case Study: Vera Rubin Observatory

The area of astronomy most systematically affected by the presence of numerous LEO satellites will be survey-type missions from the ground which repeatedly image large areas of the sky. The foremost example of this type of work is the Legacy Survey of Space and Time (LSST) to be carried out by the Vera Rubin Observatory. Each night for ten years, astronomers will use the Rubin Observatory’s incredible camera (with a ten square degree field of view!) to take 1000 images of the entire sky visible from Cerro Pachón in Chile. A single 30-second exposure with this camera reveals objects 20 million times fainter than can be seen by the human eye, i.e., 20 million times fainter than LEO satellites like Starlink.

Recently, a team of astronomers investigated the potential impacts of LEO megaconstellations on the science goals of LSST . In this work, the team considers modifying the LSST observation scheduling algorithm to avoid LEO satellites, simulates the effects of satellite trails on the science camera, reports on observations of current Starlink satellites, and discusses further challenges in need of consideration. Figure 3 shows the expected streaks across the sky that a megaconstellation of 48,000 satellites would produce above Chile in 10 minutes. Below are the main takeaways of their analysis, assuming the satellites are as bright as Starlink has been so far.

  • The time of year with most impact from LEO satellites is the Chilean summer, where between 10-20% (midnight) and 40-90% (twilight) of observations will contain a satellite trail. In the winter, virtually no LEO satellites will be visible at midnight from Chile. The prevalence of Starlink satellites at twilight will pose serious challenges for programs that must observe during those hours due to the availability of their target.
  • Regular Starlink satellites are confirmed to be roughly

5 mags bright in the Sloan g-filter, plenty bright to be seen by eye. DarkSat is measured to be roughly half as bright (

500km, and all must be fainter than 7th magnitude or

The team concludes there are numerous problems posed by LEO satellites for LSST’s mission, though the many can be alleviated if the satellites are faint enough (> 7th mag). The authors write, “The science community may have to do some amount of extra work to reach the promise of using LSST to discover the unexpected. There may be cost and schedule impacts, and the presence of LEOsats may require LSST to run for longer than ten years to achieve all science goals.”

Figure 3: Predicted sky map above Rubin Observatory illustrating the number of satellite trails by a megaconstellation of 48,000 LEO satellites. This prediction is for a randomly chosen date (Oct. 11, 2022), just after twilight. An incredible amount of trails are created in only 10 minutes of the simulation. The dark spot is caused by Earth’s own shadow. Credit: Fig. 3 Tyson et al. (2020).

It is perhaps not much longer a clear night sky will be filled with stars and the inner planets rather than human-engineered satellites. For better or for worse, the future of the night sky seems destined to change. There are no guarantees that other companies will attempt to darken their satellites in the way SpaceX has, and it is not clear how many LEO satellites may eventually be functioning at one time.

However, advancements in astronomy have not come in spite of technological advances, they’ve been made because of them. Light pollution has already rendered most observatories in the American Northeast obsolete, but today we use remote observing to connect to state-of-the-art observatories across the globe, as will be the case with the Rubin Observatory. Furthermore, technological advances have made surveys such as the LSST, unimaginable decades ago, a real possibility today. Seeing through the atmosphere has always been a resolution-limiting feature, so space agencies like NASA and ESA have launched telescopes into orbit and are following up with the next generation of space-based observatories, including the James Webb Space Telescope , the Nancy Grace Roman Space Telescope , and Euclid , to name a few.

The future of the night skies is uncertain but the future of astronomy is not: the new challenges posed by Starlink and other megaconstillations will require collaboration and innovation to overcome, but ultimately will not impede astronomers’ quest to study the cosmos.


How do communications satellites work?

What do they do?

Communications satellites are "space mirrors" that can help us bounce radio, TV, Internet data, and other kinds of information from one side of Earth to the other.

Uplinks and downlinks

If you want to send something like a TV broadcast from one side of Earth to the other, there are three stages involved. First, there's the uplink , where data is beamed up to the satellite from a ground station on Earth. Next, the satellite processes the data using a number of onboard transponders (radio receivers, amplifiers, and transmitters). These boost the incoming signals and change their frequency, so incoming signals don't get confused with outgoing ones. Different transponders in the same satellite are used to handle different TV stations carried on different frequencies. Finally, there's the downlink , where data is sent back down to another ground station elsewhere on Earth. Although there's usually just a single uplink, there may be millions of downlinks, for example, if many people are receiving the same satellite TV signal at once. While a communications satellite might relay a signal between one sender and receiver (fired up into space and back down again, with one uplink and one downlink), satellite broadcasts typically involve one or more uplinks (for one or more TV channels) and multiple downlinks (to ground stations or individual satellite TV subscribers).

Artwork: Communications satellites bounce signals from one side of Earth to the other, a bit like giant mirrors in space. A ground-based satellite transmitter dish (red) beams a signal to the satellite's receiving dish (yellow). The satellite boosts the signal and sends it back down to Earth from its transmitter dish (red) to a receiving dish somewhere else on Earth (yellow). Since the whole process happens using radio waves, which travel at the speed of light, a "satellite relay" of this kind usually takes no more than a few seconds, at most. The various transmitters and receivers on the satellite and on Earth are examples of antennas.

Satellites are like any other vehicle inasmuch as they have two main parts: the generic vehicle itself and the specific thing it carries (the payload) to do its unique job. The "vehicle" part of a satellite is called the bus, and it includes the outer case, the solar panels and batteries that provide power, telemetry (a remote-controlled system that sends monitoring data from the satellite to Earth and operational commands back in the other direction), rocket thrusters to keep it in position, and reflective materials or other systems ("heat pipes") to protect it from solar radiation and dissipate heat. The payload might include transponders for a communications satellite, computers and atomic clocks to generate time signals for a navigation satellite, cameras and computers to images back to digital data for a photographic satellite, and so on.

What's inside a satellite?

Artwork: Communications satellite. From US Patent: #3,559,919: Active communication satellite, courtesy of US Patent and Trademark Office.

These are amazingly complex and expensive machines with tons of electronic bits and pieces jammed into them, but let's not get too bogged down in the details: the basic idea is very simple. In this outside view of a typical satellite, from a patent filed in 1968 by German engineer Hans Sass (US Patent: #3,559,919: Active communication satellite), you can see all the main bits and it's easy to figure out what they do.

I've left the original numbers on the diagram and I won't bother to label them all, since some are obvious and some are duplicates of others. The most interesting bits are the fold-out solar panels that power the satellite, the sending and receiving antennas that collect signals coming up from Earth and send them back down, and the motors and engines that keep the satellite in exactly the right position at all times:

4 : Large parabolic dish antenna for sending/receiving signals. (Orange)

5 : Small parabolic dish antenna for sending/receiving signals. (Orange)

6 : Lower solar "battery" of four solar panels. (Red)

7 : Upper solar "battery" of four more solar panels. (Red)

8 : Supports fold out the lower solar panels once the satellite is in orbit. (Gray-brown)

9 : Supports fold out the upper solar panels. (Gray-brown)

10 : Main satellite rocket motor. (Light blue)

11, 12, 15, 17 : Small control engines keep the satellite in its precision position, spin, and orbit. (Green)

Photography, imaging, and scientific surveying

Photo: Satellite photography helps scientists understand our changing planet. This image shows the Columbia Glacier in Alaska. By comparing it with earlier images taken from the same viewpoint, we can measure the rate at which climate change is taking place. Picture by Lauren Dauphin using Landsat data from the US Geological Survey. Image courtesy of NASA Earth Observatory.

Not so many years ago, newspapers used to run scare stories about spy satellites high in space that could read newspapers over your shoulder. These days, we all have access to satellite photos, albeit not quite that detailed: they're built into search engines like Google and Bing, and they feature routinely on the news (giving us an instant visual impression of things like disappearing rainforests or tsunami destruction) and weather forecasts. Scientific satellites work in a similar way to photographic ones but, instead of capturing simple visual images, systematically gather other kinds of data over vast areas of the globe.

There have been many interesting scientific satellite missions over the last few decades. NASA's TOPEX/Poseidon and Jason satellites, for example, have routinely measured sea levels since the early 1990s. SeaWiFS (active until 2010) scanned the color of the ocean to measure plankton and nutritional activity in the sea. As its name suggests, a weather satellite called TRMM (Tropical Rainfall Measuring Mission) monitored rain near the equator from 1997 through 2015. As of 2016, NASA listed 25 ongoing satellite missions on its website, including CALIPSO (which studies how clouds and aerosols interact) Nimbus (a long-running scientific study of weather and climate using satellite data) and, the longest-running and perhaps best known scientific satellites of all-time, Landsat, a series of eight satellites that have been continuously mapping and monitoring changes in land use across Earth since 1972.

Photo: NASA's Jason-3 satellite, launched in January 2016, is part of a long-running project to monitor the height of Earth's ocean surface, producing invaluable data for studying our planet's climate. Its main instrument is a very sophisticated radar altimeter. Artist's impression courtesy of NASA JPL.

Navigation

Finally, most of us with GPS-enabled cellphones and "sat-nav" devices in our cars are familiar with the way satellites act like sky compasses you'll find GPS, Glonass, and similar systems discussed in much more detail in our article about satellite navigation.


How Space-X satellites will destroy astronomy

Sorry, no hyperbole or overreaction here. Just my opinion based on current evidence. Overwhelming majority of us here on these forums think this will be detrimental.

Your dismissive attitude and belief in the superiority of your opinion does not change the facts.

the overwhelming majority of folks on CN have determined that their lives are ruined by satellites being too numerous, eh? Aside from the fact that you could not possibly know this, it’s hard NOT to think my opinion on the matter is superior to being of the opinion that the night sky will be ruined and no longer inspiring if there are more satellites up there.

but as a practical matter, what is to be done? I’m sure a far larger minority of astronomers are affected adversely by light pollution, yet - and here’s the thing - it’s here and getting worse all the time, astronomers and their needs notwithstanding. So are you thinking that THIS TIME we can do anything about it? Or are you already working on your ad in Astromart selling all your gear?

i don’t do AP, but there are AP people in this very thread that don’t think this will be an insurmountable issue. Maybe they have a point?

#52 Tony Flanders

I'm sorry, but I think you are really over reacting. It won’t “ruin” the sky for everyone. Not even close. These kinds of hyperbole don’t help.

Time will tell. Only a minuscule fraction of the proposed fleets are in orbit now.

In the grand scheme of things, the problems that satellites cause for professional telescopes, in particular the forthcoming Large Synoptic Survey Telescope, and the risks of orbital collisions, debris from failed launches, and so on seem like much more important issues than anything that might happen to amateur astrophotographers.

How to balance all of those against the naive view of the night sky of a herdsman in East Africa, who unlike most folks in the industrialized world will actually see all those satellites, but benefit from them not at all, is more imponderable.

#53 Astrojedi

the overwhelming majority of folks on CN have determined that their lives are ruined by satellites being too numerous, eh? Aside from the fact that you could not possibly know this, it’s hard NOT to think my opinion on the matter is superior to being of the opinion that the night sky will be ruined and no longer inspiring if there are more satellites up there.

but as a practical matter, what is to be done? I’m sure a far larger minority of astronomers are affected adversely by light pollution, yet - and here’s the thing - it’s here and getting worse all the time, astronomers and their needs notwithstanding. So are you thinking that THIS TIME we can do anything about it? Or are you already working on your ad in Astromart selling all your gear?

i don’t do AP, but there are AP people in this very thread that don’t think this will be an insurmountable issue. Maybe they have a point?

We are all entitled to our opinions. Its fine if you believe otherwise and you have made your opinion clear earlier in the thread. But attacking others who don't share your opinion by calling their view hyperbole is not helpful.

Also I did not speak to / address any of these additional points you mention above in my original post. Yes, LP is getting worse - can I control it, no I can't, but the fact is it is getting worse. Will 40K+ satellites in the sky be detrimental to this hobby I love so much - yes, it will be, can I stop it, unlikely. I don't have all the solutions although I wish I did.

#54 Andrekp

Time will tell. Only a minuscule fraction of the proposed fleets are in orbit now.

In the grand scheme of things, the problems that satellites cause for professional telescopes, in particular the forthcoming Large Synoptic Survey Telescope, and the risks of orbital collisions, debris from failed launches, and so on seem like much more important issues than anything that might happen to amateur astrophotographers.

How to balance all of those against the naive view of the night sky of a herdsman in East Africa, who unlike most folks in the industrialized world will actually see all those satellites, but benefit from them not at all, is more imponderable.

well, as we both know, the sky 40 years ago was infinitely better In most places for observing and AP than it is today. LP is much, much worse now. This is fact and we can probably all agree and mourne.

however, we can probably ALSO agree that astronomers are doing more amazing things now, especially in AP, that were ever done 40 years ago. The point being, it is a mistake to view the future under the rubric of the present.

so I suspect that as the issue gets worse, other things, just as before, will get better, if not as compensation, at least as offset. And I suspect Astrojedi will not be telling everyone in 40 years how Astronomy was irrevocably ruined for everyone.

#55 Andrekp

We are all entitled to our opinions. Its fine if you believe otherwise and you have made your opinion clear earlier in the thread. But attacking others who don't share your opinion by calling their view hyperbole is not helpful.

Also I did not speak to / address any of these additional points you mention above in my original post. Yes, LP is getting worse - can I control it, no I can't, but the fact is it is getting worse. Will 40K+ satellites in the sky be detrimental to this hobby I love so much - yes, it will be, can I stop it, unlikely. I don't have all the solutions although I wish I did.

With due respect, having a different opinion is not an attack on you. Nor is thinking that one’s own opinion is better than another’s in some way. It is how opinions work and why we express them. It’s the give and take of the Marketplace of Ideas. I do think you are exaggerating, and I’m sorry if you think it is wrong to express that opinion. You are obviously quite free to have a different opinion and express it.

#56 Astrojedi

well, as we both know, the sky 40 years ago was infinitely better In most places for observing and AP than it is today. LP is much, much worse now. This is fact and we can probably all agree and mourne.

however, we can probably ALSO agree that astronomers are doing more amazing things now, especially in AP, that were ever done 40 years ago. The point being, it is a mistake to view the future under the rubric of the present.

so I suspect that as the issue gets worse, other things, just as before, will get better, if not as compensation, at least as offset. And I suspect Astrojedi will not be telling everyone in 40 years how Astronomy was irrevocably ruined for everyone.

Don't create strawmans and attack them and don't twist what I have said. I was not talking about astronomy in general. I was specifically referring to the experience of being under a dark sky. You seem to be a person who cannot tolerate opinions that don't agree with yours.

Also no, you cannot compensate for dark skies. For visual observing I still have to drive 1 hour to access dark skies. Even for imaging I just cannot match the SNR I get from a dark site. For my asteroid and exoplanet research my limiting magnitude from my backyard is much poorer than dark skies. There is a reason professional observatories are still built in the middle of nowhere.

Technology cannot solve everything. But what is more frightening is that even in dark skies we will not be able to escape this junk.

#57 Astrojedi

With due respect, having a different opinion is not an attack on you. Nor is thinking that one’s own opinion is better than another’s in some way. It is how opinions work and why we express them. It’s the give and take of the Marketplace of Ideas. I do think you are exaggerating, and I’m sorry if you think it is wrong to express that opinion. You are obviously quite free to have a different opinion and express it.

You already expressed your opinion earlier in the thread. Not sure why you felt the need to respond to my post and attack it. People reading the thread can read your opinion as well as mine and make up their own mind as to whether I am exaggerating.

And if you do want to debate and change my mind present some real concrete evidence and I will consider it. I can change my mind if I see compelling and large body of evidence. But just calling my view hyperbole will not persuade me in any way. So it makes me question what are you trying to achieve with your response.

#58 Andrekp

I’m dropping it now, as I have no idea what is going on here.

#59 LDW47

Its not just "a handful of guys trying to take pretty pictures". The skies will be ruined for all.

Looking up at a dark sky is a life experience that everyone should have. The first time I looked up in truly dark skies as a youngster and saw a blazing Milky Way it forever changed how I viewed myself and our place here and it peaked a lifelong curiosity and desire for learning. Almost everyone I know who has experienced really dark skies has had a similar visceral experience even if they did not end up becoming serious amateur astronomers.

Our urban skies have already been ruined by LP to such an extent that when people in LA see the Milky Way they call 911. These satellites will likely ruin what dark skies are left for the rest of us. It saddens me to think that my grandchildren may never get the opportunity to have a truly visceral / transformative experience that I had.

Or maybe your grandchildren will, how do know ? And I’ll ask once again what is your solution to this issue ??

#60 LDW47

You already expressed your opinion earlier in the thread. Not sure why you felt the need to respond to my post and attack it. People reading the thread can read your opinion as well as mine and make up their own mind as to whether I am exaggerating.

And if you do want to debate and change my mind present some real concrete evidence and I will consider it. I can change my mind if I see compelling and large body of evidence. But just calling my view hyperbole will not persuade me in any way. So it makes me question what are you trying to achieve with your response.

Back and forth thoughts are not always how it works on this site especially if the majority thinks differently, thats been seen many times but thats OK its how life works ! PS: You said it right !

#61 LDW47

I read that as a low blow to an honest poster !

#62 LDW47

You already expressed your opinion earlier in the thread. Not sure why you felt the need to respond to my post and attack it. People reading the thread can read your opinion as well as mine and make up their own mind as to whether I am exaggerating.

And if you do want to debate and change my mind present some real concrete evidence and I will consider it. I can change my mind if I see compelling and large body of evidence. But just calling my view hyperbole will not persuade me in any way. So it makes me question what are you trying to achieve with your response.

You sure haven’t changed many minds to your way of thinking either, many that haven’t witnessed what is being said, being pushed ! I would say it is hyperbole or exaggeration or whatever you want to call it ! What and who exactly do you think we skilled observers are that scan the nite skize every chance we get and have not witnessed these multitudinous numbers of bright trains, brighter than the stars themselves, of small satellites and have never witnessed this awe inspiring happening(s) ?? Opinions can go both ways ! Clear trainless skiys ! PS: I’m sure as h*l* in trouble again. lol !

#63 LDW47

In response to post 55 ! Every time some one expresses some thing that goes against another opinion in a different direction its called an attack ! I would honestly like to know why and I am sure many others would to, I mean aren’t we all brotherly members wanting the same thing ie to enjoy astronomy ? Clear brotherly skiys !

#64 Astrojedi

Disagreeing with someone’s opinion is one thing but calling someone’s opinion hyperbole and accusing them of exaggerating is not exactly what I would call expressing a different opinion. Why not say “ I disagree and here is why. “. I would welcome that debate.

#65 LDW47

Disagreeing with someone’s opinion is one thing but calling someone’s opinion hyperbole and accusing them of exaggerating is not exactly what I would call expressing a different opinion. Why not say “ I disagree and here is why. “. I would welcome that debate.

In the eyes of those that scan the skies every chance they get, under many varying conditions, as I expressed in my post it is just that or similar ! Please understand, in plain language, many have not witnessed this dastardly phenomena of which you speak. And once again, the one time I saw about 4 go whizzing by after each other in my telescope, it was over in an instant, they were a lot fainter than the stars and they were very small pin points of lite ! Thats my proof which differs from others and I have yet to see yours and all the other great experts ! And the world didn’t end, lol !

Edited by LDW47, 05 August 2020 - 09:36 PM.

#66 Astrojedi

My comments are not about today.. it is a few years from now when there are 40,000+ of these these satellites are in space and this is just American companies. Wait till Chinese, Russian, European and Indian Govt/companies start putting up their own networks (and they will for national security concerns, they same reason China is putting up their own GPS network and US is fighting China on 5G tech). You will need to find new orbits as well. If anyone thinks this will end with SpaceX they are fooling themselves. The other players may not be as accommodating as Musk on making them less reflective. I always hope I am wrong. We will see in a few years.

Edited by Astrojedi, 05 August 2020 - 09:51 PM.

#67 LDW47

My comments are not about today.. it is a few years from now when there are 40,000+ of these these satellites are in space and this is just American companies. Wait till Chinese, Russian, European and Indian Govt/companies start putting up their own networks (and they will for national security concerns, they same reason China is putting up their own GPS network and US is fighting China on 5G tech). You will need to find new orbits as well. If anyone thinks this will end with SpaceX they are fooling themselves. The other players may not be as accommodating as Musk on making them less reflective. I always hope I am wrong. We will see in a few years.

Until it happens (if) lets just keep looking up, its all we can do if it grows the way you speculate !

#68 spereira

OK, folks, I sense an increase in temperature in this topic.

Let's all just take a deep breath. Everyone is entitled to their opinion, and all are welcome to post their opinion in a civil fashion here. Let's please refrain from any remarks that may appear to be aimed at the person rather than the opinion.

If we cannot keep the discussion/disagreements civil, then we all know what ends up happening .

#69 OldSkyEyes

Do we actually know how many will be visible, angular speed and how bright they will be from one point on earth after they have all been deployed?

Angular speed range: 0.5 - 1 degree / sec.

Meaning 1 satellite will be in my frame for less than 1 sec usually at mag 7, that's good news.

Assuming multiple satellites aren't burning in the same track in my sensor.

A few lines are still very easily mathematically removed during stacking. (since not present on all frames on the same place)

How many of them do we see at the same time?

If we spread them evenly over earth then:

From zenith to horizon we see this angle of the sphere: Cos x = 6400 / (6400+550)

Satellite sphere surface we see = 2 * pi * 6950² * (1 - Cos x)
Total surface satellite sphere = 4 * pi * 6950²

or we can see (1 - 6400/ 6950) / 2 = 4 % at any give moment

If I calculated that correctly
4% of 40000 is still 1600 satellites in view all the time, that is a lot I hope I made a calculation mistake.

For a moon frame: you can fit about 40 000 frames in the sky so the chance of a satellite in your view at any time is about 1600 / 40 000 or 4 %. the more to zenith the lower the chance a satellite is there.

Meaning you have to delete about 4% fast frames due to starlink. (assuming you detect mag 7)

A photo of the milky way, that may be a problem, on the bright side they aren't standing still so the effect on the sensor may be limited, does anybody know if the satellite path stays the same on the background or is it staying the same from our point of view??

Will make a big difference if a nebula moves behind it or if that path stays the same.

Maybe SpaceX can launch one 20 inch telescope in the sky for every 50 starlink satellites and make it easy available like compensation for the extra trouble they created. (everyone can dream right)

Also one more thing due to the low orbit they aren't all catching sun light during the night.

Edited by OldSkyEyes, 07 August 2020 - 06:15 AM.

#70 LDW47

Do we actually know how many will be visible, angular speed and how bright they will be from one point on earth after they have all been deployed?

Some 'guessing/info':

<. snip. >

Great post, a different perspective and great news, it all hits the nail right on the head ! Hopefully some of the fretting will dissipate into black outer space ?

#71 viewer

Glad I have solar to fall back on. At least the satellites will not be ruining that, or?

Edited by viewer, 07 August 2020 - 05:21 PM.

#72 JohnnyLingo

Wow, just finished crunching through this "heated debate", and it seems more like a debate about what actually a debate is.. Too bad..

Please, folks, do both this forum and yourselves a favor and read up on a topic before posting your beliefs as if they were facts (if the cap fits..).

To facilitate the latter, I already posted a link above (post 27) and so did others and here is yet another one for your convenience:

One important fact: SpaceX satellites on station (= final operational orbit) will be invisible to the naked eye under the darkest skies. I am sure astrophotographers will find their tricks to mitigate an increased number of satellites on their photographs. If LSST and similar surveys are not ruined by satellites (and they won't be), then casual night sky photographers will also have the means to deal with this "problem".

Finally, I used apostrophes in the above sentence because I think the real problem affecting astronomy (hobby and professional alike) is ground-based light pollution. And this problem is so bad that most people do not even know what they miss. I had been actually making a living from astronomical research for several years when I saw a completely clear, moonless Bortle 1 sky for the first time in my life, with the bulge hanging from the zenith and at that moment, I almost cried. Because until then, I only had an idea in my mind about how it looked, but when I saw it, I realized that I actually had no idea.. Starlink will not take away that view from people who head out to dark sites. In contrast, light pollution already took that away from most of the planet's population who don't have a chance to glimpse that view even once in their entire lifetime.


Telescopes and astronomy

2. Allow you to see where all the planets are etc. This would be good in my main thread (check my signature, at the bottom of all my posts) because then you would know what direction to fly in etc. They should move around in the corresponding to the galaxy map etc.

IsoMS

Member

There should be a way to craft a telescope for looking at the stars and planets. So. You know how in ther mars sky, you can see a tiny blot of blue and green, the overworld. (and a galaxy)

So looking through telescopes should

2. Allow you to see where all the planets are etc. This would be good in my main thread (check my signature, at the bottom of all my posts) because then you would know what direction to fly in etc. They should move around in the corresponding to the galaxy map etc.

MasterOanarchY

Moderator

Ezer'Arch

Administrator

Astrology. so we're introducing horoscopes into Galacticraft to predict future? I think he wanted to mean astronomy.

Wolfboyft

Member

Wolfboyft

Member

. you're thinking of Aztec (or mayan, whatever) fortune telling with the planets. I mean just looking at planets through telescopes. Basically, doing what people do with their telescopes nowadays.

And no, astronomy is planets and stars' physics and the universe etc. Astrology is star-gazing and telescopes.

Ezer'Arch

Administrator

Astronomy is a science to study the celestial bodies (planets, moons, starts, their physics, positions etc). You can do it with a Hubble-like telescope or with a simple 4" optical telescope in your backyard.
Astrology is a divination based on the position of celestial bodies.

Anyway, I understood your idea. You want to create an instrument through which we "visualize" the planets in the sky since it's impossible to see them on Overworld by normal ways. It's cool but I don't see many applications for it (unless it were required that you steer the rocket and travel in the space, I saw the topic in your sig). The only thing I'd want to know about other planets is whether it's daytime or nighttime there. I hate to land with a Party of Brainless Stupidity waiting for me on ground.

He thought you want a telescope to see the actual terrain of a planet from the other or chunks far away on the Overworld.

If it's about some kind of advanced and powerful telescope that could show me from the Overworld the physics of a planet, like atmosphere, minerals, temperature, gravity, local time. it could be very useful. Then we are talking.

Wolfboyft

Member

Astronomy is a science to study the celestial bodies (planets, moons, starts, their physics, positions etc). You can do it with a Hubble-like telescope or with a simple 4" optical telescope in your backyard.
Astrology is a divination based on the position of celestial bodies.

Anyway, I understood your idea. You want to create an instrument through which we "visualize" the planets in the sky since it's impossible to see them on Overworld by normal ways. It's cool but I don't see many applications for it (unless it were required that you steer the rocket and travel in the space, I saw the topic in your sig). The only thing I'd want to know about other planets is whether it's daytime or nighttime there. I hate to land with a Party of Brainless Stupidity waiting for me on ground.


He thought you want a telescope to see the actual terrain of a planet from the other or chunks far away on the Overworld.

If it's about some kind of advanced and powerful telescope that could show me from the Overworld the physics of a planet, like atmosphere, minerals, temperature, gravity, local time. it could be very useful. Then we are talking.

Oh. So. I think that a level 1 telescope shows the planet's icon, and shadowing for day and night time,

and a level 2 telescope, it has a lot further zoom, and just like sensor goggles, k switches modes to advanced or not advanced. Not advanced is just like level 1. Advanced, shows the terrain. Minimap style, blocks would be impossible. But we have to remember that minecraft planets are infinite dimensions, so that would ruin the idea of terrain-view. Unless there was some sort of update that made the dimensions planets or whatever.

Ezer'Arch

Administrator

Well, I don't know about yours, but my telescope is ready.

IsoMS

Member

Well, I don't know about yours, but my telescope is ready.

Mrcrayfish's furniture mod?

Ezer'Arch

Administrator

IsoMS

Member

Wolfboyft

Member

Wolfboyft

Member

Well, I don't know about yours, but my telescope is ready.

Dex Luther

Member

. you're thinking of Aztec (or mayan, whatever) fortune telling with the planets. I mean just looking at planets through telescopes. Basically, doing what people do with their telescopes nowadays.

And no, astronomy is planets and stars' physics and the universe etc. Astrology is star-gazing and telescopes.

No. Astrology is like the fortune cookies in Chinese restaurants. They think they can predict that today is your lucky day based on where and how stars and planets were lined up when you were born. It's complete fiction and nonsense. All the way down to the fact that the Zodiac has 13 symbols, but astrologists and horoscope writers decided they liked the number 12 better and completely ignore the 13th sign.

Astronomy is a natural science that is the study of celestial objects (such as moons, planets, stars, nebulae, and galaxies), the physics, chemistry, mathematics, and evolution of such objects, and phenomena that originate outside the atmosphere of Earth, including supernovae explosions, gamma ray bursts, and cosmic background radiation. A related but distinct subject, cosmology, is concerned with studying the universe as a whole.[1]

Astronomy is one of the oldest sciences. Prehistoric cultures left behind astronomical artifacts such as the Egyptian monuments and Nubian monuments, and early civilizations such as the Babylonians, Greeks, Chinese, Indians, Iranians and Maya performed methodical observations of the night sky. However, the invention of the telescope was required before astronomy was able to develop into a modern science. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, and the making of calendars, but professional astronomy is nowadays often considered to be synonymous with astrophysics.[2]

Oh. So. I think that a level 1 telescope shows the planet's icon, and shadowing for day and night time,

and a level 2 telescope, it has a lot further zoom, and just like sensor goggles, k switches modes to advanced or not advanced. Not advanced is just like level 1. Advanced, shows the terrain. Minimap style, blocks would be impossible. But we have to remember that minecraft planets are infinite dimensions, so that would ruin the idea of terrain-view. Unless there was some sort of update that made the dimensions planets or whatever.

Not EVERYTHING in the mod needs multiple tiers. I think it would be fine to just create one telescope, and have it do whatever it's going to do right out of the box.

To keep it from betting overly complicated (and probably hell for server resources), I think the player activating the telescope should get a GUI. The GUI would list different areas of interest. When the player selects one of the items, the moon or mars for instance, the player could then refine their view using co-ordinates. Once set the player would click a button and have to wait a few ticks (to simulate how most real telescopes images don't instantly appear). A "Collecting light" message could appear. During this wait the mod would send an invisible player type entity to the appropriate place and take a maybe 4 chunk by 4 chunk screenshot of the area from above. This image would then be displayed for the player.

If the player has a mod like Computer Craft installed, they could then print, save, or display the image on Computer craft monitors. Printing the image would let the player hang it on the wall like a painting.

You'd be able to see your base or tell a friend to check it out and even be able to see someone walking around, but the screenshot would make it easier and less of a burden on server resources.


The U.S. has long been the leading power in space. But there’s a new kid on the block, isn’t there? How much of a threat is China?

I have mixed feelings about this because we had the chance to invite China to be part of the International Space Station. But we said, “No, China, you’re not going to join because of human rights violations.” Rather than removing China, though, it just re-doubled China’s effort to become a space-faring nation. And that’s exactly what they did. They have launch bases and satellites they launched the Shenzhou-5 spacecraft, becoming the third nation after Russia and the U.S. to launch a human being into space in their own rocket. They did an exercise where, from an Earth-based launch, they sent a missile that destroyed one of their satellites. It would be an act of war if they destroyed one of ours! So they destroyed one of their own. That’s not an act of war but it’s certainly a display of power, of capability.

There are people who are worried about China. I’m not as worried. We are so co-mingled with our economies and trade that I just don’t see them becoming a military adversary. At all. There could be some tensions here and there as there always are, but I’m not an expert.


How do satellites impede current telescopes? - Astronomy

My question: How do probes (like Voyager 1) navigate through space, the asteroid belt and around planets without colliding with something?

I realize space is a vast place, but with the velocity everything has and the lag on communication how is it possible to avoid a rock (any size would be disastrous)? I assume most all rocks are too dark and cold to be visual. Do probes use radar for guidance? If so, what power source is used that doesn't drain?

All unmanned space probes are steered from the ground. As you say, there's a lot of room in space, and it's not like there are any bumps in the road. We keep very close track of the spacecraft's position and velocity, and given those, we can predict very precisely where it is going, so running into large objects is not a problem. Generally, the trajectory of the spacecraft is planned out years in advance, and so "steering" it just a matter of commanding it to do the proper rocket burns at the proper times, and making tiny adjustments. And in fact, exactly the same thing happens in missions crewed by humans, except instead of commanding the onboard computer to do it, you just ask the pilot nicely.

We can track asteroids down to 50 km or so in size, and objects down to 1 cm in size in low Earth orbit. Of course, smaller, undetectable rocks are more numerous. However, even in the asteroid belt, they are spread out over such a large area that the likelihood of a collision with a rock large enough to end the mission is very, very small, and we must simply accept it as one of the risks of spaceflight.

Spacecraft are often hit by micrometeorites up to the size of a grain of sand. A few hits like this are considered just normal wear-and-tear. Another common source of trouble are hits by cosmic rays, which are high-energy radiation. These can cause small bugs in the on-board software, or, more rarely, damage electronics.

However, the must common reason for losing a mission is a component failure or human error. Spacecraft are lost when their engines blow up (like CONTOUR, which failed to phone home after a scheduled burn, and was later found along its planned orbit--in three pieces), when humans send them the wrong commands (like Mars Observer, where JPL thought that a subcontractor was giving them burns in metric units, and actually they were sending them in imperial units), or when a key system fails (like the landing system on Mars Polar Observer or the bad wiring in the oxygen tanks on Apollo 13). Space missions are extremely complicated, and the mission can be doomed by a tiny flaw in an any critical system, either in the design or from damage during launch or exposure to the temperature extremes and vacuum spacecraft must weather.

Often, spacecraft fail without any indication what went wrong. They just stop radioing back to Earth. Was there a problem with the software? Did a cosmic ray cripple the computer? Did a critical bit of hardware fail? Was it hit by a meteorite?

We can calculate the risk from the meteorite hits, and it is pretty low. Human mistakes and engineering failures, though, are much more unpredictable.

Page last updated on June 25, 2015.

About the Author

Britt Scharringhausen

Britt studies the rings of Saturn. She got her PhD from Cornell in 2006 and is now a Professor at Beloit College in Wisconson.


Apr 20, 2021

Updated Spacecraft Position and History Files Available

The updated files include the addition of the SC_VELOCITY column. This column contains a vector with the spacecraft velocity in meters per second (in the same coordinate frame as SC_POSITION) at the start of the interval to aid pulsar timing and other precise applications that require the full state vector. The files improve the calculation of the spacecraft geodetic latitude and altitude. The geodetic calculation now uses the exact Ferrari's solution rather than the approximation that was done previously. The changes in latitude are less than 0.04 degrees. The changes in altitude are from 0 to 6 km. In both cases, the difference is minimum at the equator and maximum at the latitude extremes. The files also use the latest the IGRF model, a standard mathematical description of the Earth's main magnetic field. The previous IGRF expired at the end if 2019. The 2020 and 2021 spacecraft files have been reprocessed to use the IGRF-13 model. Both the 30-second and 1-second files have been updated. The FSSC's data server now returns the new files. The weekly and mission long files have been updated on the FSSC's FTP site.