Astronomers admit new satellite constellations “are not a threat” to Hubble
In a June 5, 2023 press release from the Space Telescope Science Institute (STScI) that operates both the Hubble and Webb space telescopes, astronomers admitted that the increased number of orbiting satellites from SpaceX and OneWeb have had little impact on Hubble’s observations, and even that impact has been reduced by new software tools.
Stark applied the new tool, based on the image analysis technique known as the Radon Transform, to identify satellite trails across Hubble’s camera with the widest field of view, the Advanced Camera for Surveys (ACS). In 2002 the satellite streaks were present in five percent of ACS exposures, with many of those too faint to discern easily. This rose to ten percent by 2022, although the typical brightness of the detected trails remained unchanged.
…”To date, these satellite trails have not had a significant impact on research with Hubble,” said Tom Brown, Head of STScI’s Hubble Mission Office. “The cosmic rays that strike the telescope’s detectors are a bigger nuisance.”
Radiation from space hits the ACS electronic detectors on every exposure, leaving streaks. These are easy to identify from exposure to exposure. The same holds true for artificial satellites. “The average width I measured for satellites was 5 to 10 pixels. The ACS’ widest view is 4,000 pixels across, so a typical trail will affect less than 0.5% of a single exposure. So not only can we flag them, but they don’t impact the majority of pixels in individual Hubble images. Even as the number of satellites increases, our tools for cleaning the pictures will still be relevant,” said Stark. [emphasis mine]
In other words, the claims by many astronomers that the increase in satellites is a threat to astronomy have been exaggerated. The new satellites might have a greater impact on ground-based telescopes, but based on these numbers (which would be comparable if not better for the giant 8-meter-plus big telescopes on Earth), that impact should be as easily mitigated.
I am gob-smacked that STScI issued this press release, since it undercuts the entire political narrative of the astronomical community that demands these new satellite constellations be either regulated, limited, or even banned, because otherwise all astronomy will be impossible. Based on the information presented here, none of those regulations are justified, at all, and that narrative is an utter lie.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
In a June 5, 2023 press release from the Space Telescope Science Institute (STScI) that operates both the Hubble and Webb space telescopes, astronomers admitted that the increased number of orbiting satellites from SpaceX and OneWeb have had little impact on Hubble’s observations, and even that impact has been reduced by new software tools.
Stark applied the new tool, based on the image analysis technique known as the Radon Transform, to identify satellite trails across Hubble’s camera with the widest field of view, the Advanced Camera for Surveys (ACS). In 2002 the satellite streaks were present in five percent of ACS exposures, with many of those too faint to discern easily. This rose to ten percent by 2022, although the typical brightness of the detected trails remained unchanged.
…”To date, these satellite trails have not had a significant impact on research with Hubble,” said Tom Brown, Head of STScI’s Hubble Mission Office. “The cosmic rays that strike the telescope’s detectors are a bigger nuisance.”
Radiation from space hits the ACS electronic detectors on every exposure, leaving streaks. These are easy to identify from exposure to exposure. The same holds true for artificial satellites. “The average width I measured for satellites was 5 to 10 pixels. The ACS’ widest view is 4,000 pixels across, so a typical trail will affect less than 0.5% of a single exposure. So not only can we flag them, but they don’t impact the majority of pixels in individual Hubble images. Even as the number of satellites increases, our tools for cleaning the pictures will still be relevant,” said Stark. [emphasis mine]
In other words, the claims by many astronomers that the increase in satellites is a threat to astronomy have been exaggerated. The new satellites might have a greater impact on ground-based telescopes, but based on these numbers (which would be comparable if not better for the giant 8-meter-plus big telescopes on Earth), that impact should be as easily mitigated.
I am gob-smacked that STScI issued this press release, since it undercuts the entire political narrative of the astronomical community that demands these new satellite constellations be either regulated, limited, or even banned, because otherwise all astronomy will be impossible. Based on the information presented here, none of those regulations are justified, at all, and that narrative is an utter lie.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
I’m an amateur astrophotographer. I’ve had long exposure photos ruined by satellites decades before SpaceX existed. However, low earth orbit satellites are generally only a problem either shortly after sunset or shortly before sunrise. It’s only during these hours that these satellites are exposed to sunlight. They are in the earth’s shadow if they are overheard during the other hours of the night. ISS is only about 200 miles up (around the same altitude as Hubble), which is a very low altitude compared to the radius of the earth. If you’ve watched ISS after sunset, you can often see it disappear as it passes into the earth’s shadow. Most astronomers aren’t taking high quality pictures immediately after sunset because the air isn’t steady, and the telescope is usually cooling down rapidly which causes tube currents and unsteady images.
Jason Lewis: Fascinating. Based on what you write, the claims of the astronomy community are even more bogus than I imagined.
Here was a sat designed to produce flares
https://en.m.wikipedia.org/wiki/Humanity_Star
No big outcry
If there is a threat to astronomy, I agree that it is not the light streaks, the flares, seen at dawn and dusk, a time when scientific observations would be sub-optimal anyway.
But if there is a threat it is during the shorter defined astronomical period of darkness, and it is from the actual obscuring of targets by satellite bodies themselves. I believe the impact of this could be difficult to detect, because while the data gathered could be modified, no visual indication of the modification within the data would necessarily occur.
A natural reaction would be to say that average sized satellites would be incredibly unlikely to interfere with observations. That may true or not, but it is inevitably true that with the advent of super-heavy-lift launchers, the frequency of very large satellites will increase.
A few weeks back, I tried to ask another astrophotographer a few questions that I thought relevant:
https://behindtheblack.com/behind-the-black/points-of-information/april-20-2023-quick-space-links/#comment-1409631
However, he apparently does not read this site often enough to have seen my questions.
Jason Lewis,
Would you be able to answer them? Some seem to be already answered by your comment, above:
1) Don’t these Starlink satellites shine and spoil the photographs only shortly after sunset and shortly before sunrise? The sun does not shine on them once the satellites are in Earth’s umbra. Doesn’t this give several hours of Starlink-free viewing and photography? When I go satellite watching, I am limited to observations at these times when the satellites are not yet in Earth’s umbra.
2) Aren’t the times that these satellites are not yet in Earth’s umbra mostly times when it is not yet dark enough to do good time-lapse photography? Since doing this astrophotography requires long exposure times, don’t your photographs begin toward the east, where the satellites are already in the umbra, so that as your camera moves toward the west, the satellites will already be in the umbra when your camera gets there? When I go satellite watching, I observe that the satellites first lose their visibility toward the east, then this loss of visibility drifts westward as the evening wears on. In the morning, I imagine, visibility should return toward the east before it does in the west, but when the Sun is about to rise, isn’t it better to not start photographing long exposure times?
3) Don’t large numbers of satellites already pass through your field of view during these same times that Starlink satellites interfere with your viewing? Even before Starlink, when I went satellite watching, I observed many satellites that have yet to enter Earth’s umbra. A quarter century ago, there was the phenomenon with the Iridium satellites when they would occasionally shine brightly during these times as one of their solar arrays briefly would be angled just right with the sun to reflect the light onto parts of the Earth, where viewers could see them as temporary, very bright lights in the sky. It was called an Iridium flare. They looked like flashes in the sky, and photographed as bright streaks. Do they still do this, or are the next generation Iridium satellites doing something different with their solar arrays?
4) Don’t airplanes already fly at night and spoil your photography and viewing with their flashing lights? Don’t these airplanes fly all night long rather than only near sunset and sunrise? They do in my area. Airliners, cargo planes, military aircraft, and the occasional nighttime private plane. Despite being inside Earth’s umbra, when passive objects would not be lit up, these airplanes are actively lit with “see and be seen” navigation lighting. Don’t these planes spoil your photography even after Starlink and the other satellites enter the Earth’s umbra and are no longer visible? When I go satellite watching, I see all kinds of airplanes in the sky during the times that the satellites are visible, before they enter the Earth’s umbra.
5) How do you photograph areas of the sky in which geostationary satellites would interfere with the photographs. These satellites only spend about 2% of their time inside Earth’s umbra (a greater percent of each orbit within a few weeks of the equinoxes, and no time spent in the umbra for several weeks on either side of the solstices).
6) Why are the Starlink satellites singled out? Each year, literally hundreds of other small satellites are taken to low Earth orbit, yet these others are not the subject of complaints for spoiling photography of the stars. Neither are OneWeb satellites. Will the Kuiper constellation likewise not be the subject of complaints?
Edward,
#1: I agree. My understanding is that Starlink is purposely in low orbit in order to reduce transmission delays. I just looked up Starlink’s altitude is about 340 miles, while ISS is 254 miles. Hubble is 332 miles. Geosynchronous orbits are 22,236 miles.
#2: Correct. The air isn’t very steady right after sunset and telescope is cooling down. Most amateur astrophotographers will be polar aligning during this time, anyway.
In the olden days when I started astrophotography with film, we’d take very long exposures that could be up to 2 hours. You’d hope that you don’t get any gusts of wind or someone walking near your scope which could ruin your photo. With modern digital cameras, you typically make several short exposures of 5-10 minutes which are stacked. You can simply throw out any bad ones.
I remember the Iridium flares. They were amazing!
Airplanes are definitely a nuisance, and they can spoil an image at any time of the night.
I’m not aware of any geosynchronous satellites spoiling any of my photos, but I’ve had an occasional unexplained streak which I usually attributed to an airplane. They typically have an oscillating intensity across the image, and there has been some debate as to whether it could be a rotating satellite. Do satellite rotate? It would be like it would make it difficult to aim an antenna that way. I recently saw someone on Twitter who purposely imaged some geosynchronous satellites. They are pretty fair out there at 22K miles to they weren’t very bright.
Go to ISS tracker to find times and dates when the ISS will be over your location. They will always been near sunrise or sunset. I’m sure that you can find a Hubble tracker which is a little closer to Starlink’s altitude, but it won’t make much difference.
https://spotthestation.nasa.gov/
Jason Lewis,
Thank you for the answers. Many were informative. Stacking shorter photos to eliminate stray airplanes, satellites, or passing people is something is new to me, but then, I don’t do much photography of any kind, much less astronomical objects.
“I’m not aware of any geosynchronous satellites spoiling any of my photos, but I’ve had an occasional unexplained streak which I usually attributed to an airplane. They typically have an oscillating intensity across the image, and there has been some debate as to whether it could be a rotating satellite. Do satellite rotate? It would be like it would make it difficult to aim an antenna that way. I recently saw someone on Twitter who purposely imaged some geosynchronous satellites. They are pretty fair out there at 22K miles to they weren’t very bright.”
I would expect that passing airplanes would have red flashing lights, an attempt to be seen by other aircraft, so if your unexplained streaks have little red pearls, then those may be planes.
Spin stabilization is not as common for satellites as it used to be, and for those satellites the antennas are either designed to account for the spin or are mounted on de-spun platforms on the satellite. All the geostationary Earth orbit (GEO) satellites that I know of are three-axis stabilized, pointing to the Earth at all times. Dead satellites and spent upper stages tend to tumble, which may account for the oscillating intensities.
I once went to an overnight astronomy viewing party on top of a short mountain, and one of the guys had his telescope pointed to something that was on the far side of the GEO orbit. Every once in a while a string of white dots would cross the field of view. These were geostationary satellites.*
GEO satellites are also located at specific longitudinal locations. The broadcast frequencies that they use determine how far apart they must be from other satellites that use the same frequencies, sometimes 1 degree, sometimes 2-1/2 degrees, so at 1/2 degree increments (as you know, about the width of the Moon) you may find half a dozen-ish of these satellites fairly close together. My recollection is that 1/2 degree is two minutes.
________________
* For readers unfamiliar, the geostationary satellites still orbit the Earth, which is why they do not fall down to the ground. This means that they appear stationary to we observers on Earth, but they still move relative to the background stars. Our satellite TV antennas can hold one position and continuously listen to a satellite. From our point of view, or reference frame, the stars move around the Earth, just like the Sun and the Moon, and the GEO satellites are stationary (geo = Earth, stationary = not moving relative to a viewer on that Earth).
For astronomical viewing, many powerful telescopes are counterspun relative to the Earth’s rotation, which is the purpose of those domed observatories, so that as we view the stars, they remain stationary in the eyepiece. However, that means that the GEO satellites appear to move across the eyepiece as we view our stars. It is all a matter of reference frame and whether or not it is moving. We live on a rotating reference frame. Don’t get dizzy thinking about it, you may fall from your chair.
Just to clarify: digital astrophotographers would stack short images even if there weren’t any satellites or airplanes. They are typically limited in exposure time due to saturation of the pixels.