Since this is a fluid situation (the planned launch of the next round of Starlink satellites on April 15th has been postponed), we will be publishing new stories as the situation evolves.
We recently published an update to our original story reporting on the effects and aftermath of SpaceX’s first-round launch of 60 Starlink Satellites and the almost immediate effect they had on ground-based astronomy. In this article we continue our discussion and begin with a peer-reviewed article by Jonathan C. McDowell of the Harvard-Smithsonian Center for Astrophysics that will appear in the Astrophysical Journal, now available on Cornell University’s Preprint server here:
The Low Earth Orbit Satellite Population and Impacts of the SpaceX Starlink Constellation
I discuss the current low Earth orbit artificial satellite population and show that the proposed `megaconstellation’ of circa 12,000 Starlink internet satellites would dominate the lower part of Earth orbit, below 600 km, with a latitude-dependent areal number density of between 0.005 and 0.01 objects per square degree at airmass < 2. Such large, low altitude satellites appear visually bright to ground observers, and the initial Starlinks are naked eye objects. I model the expected number of illuminated satellites as a function of latitude, time of year, and time of night and summarize the range of possible consequences for ground-based astronomy. In winter at lower latitudes typical of major observatories, the satellites will not be illuminated for six hours in the middle of the night. However, at low elevations near twilight at intermediate latitudes (45-55 deg, e.g. much of Europe) hundreds of satellites may be visible at once to naked-eye observers at dark sites.
A number of next generation ground-based observatories, comprised of multi-national collaborations with significant national investments from the individual member states will be coming online over the next 18 – 36 months. If Starlink’s rollout proceeds as planned, the fully deployed “Mega Constellation” will pose a direct threat to the planned observing programs and mandates of these new facilities as they come online. In addition to large existing ground-based observatories such as ESO’s VLT (Very Large Telescope) at Paranal, Chile, the twin 10-meter Keck Observatory on the Large Island of Hawaii, the 10.4 meter Gran Telescopio Canarias (Roque de los Muchachos Observatory on the island of La Palma, the Spanish Canary Islands) and Pan-STARRS (Maui Island) among many others, these next gen observatories include:
LSST (Vera C. Rubin Observatory)
GMT (Giant Magellan Telescope)
TMT (Thirty Meter Telescope)
ELT (Extremely Large Telescope)
As recognized by SpaceX (Musk) and quoting from the Sky and Telescope article that links to the above peer-reviewed article, the Vera C. Rubin Observatory (formerly the LSST, the Large Synoptic Survey Telescope) will be most severely impacted:
The Vera C. Rubin Observatory being built in Chile will scan the whole night sky every three days. Astronomers and SpaceX alike recognize it as representing one of the observatories most severely impacted by Starlink.
The issue for Rubin Observatory is that a single too-bright satellites not only streaks across an image, but cross-talk effects between detector segments also create multiple fainter echoes of that trail. A single satellite trail thus ruins not just the pixels within the actual trail but significant portions of the image.
So what is SpaceX’s solution at the moment?
According to the article,
One Potential Solution: The DarkSat
Astronomers have voiced their concerns, and SpaceX is listening. They launched a DarkSat (technically identified as Starlink-1130) on January 6th with an “experimental darkening treatment” to reduce the amount of light it reflects.
According to SpaceX engineer Jessica Anderson in a webcast of the most recent launch:
Preliminary results show a notable reduction
However, observations by Jeremy Tregloan-Reed of the University of Antofagasta, Chile and his colleagues using the 0.6-meter Chakana telescope in northern Chile aren’t as optimistic and have reported their findings in Astronomy and Astrophysical Letters, also available on Cornell University’s Preprint server here:
First observations and magnitude measurement of Starlink’s Darksat
Using images of satellite tracks taken on March 6th, when the satellite had reached its nominal 550-kilometer altitude and oriented its solar panel to the Sun, the astronomers measured a brightness of 7.6 magnitudes. That’s only slightly fainter than another satellite (Starlink-1113), which came in at 6.7 magnitudes.
It should be noted that magnitude 6.0 is historically regarded as the naked-eye visual threshold. Under very dark desert skies, magnitude 6.5 can be achieved by individuals with acute vision with magnitude 7.6 easily achieved by a small pair of binoculars.
It is virtually impossible to overstate the sensitivity and capability of the Vera C. Rubin telescope, a facility that will record the entire sky visible at the location in 5 wavebands every five nights with unprecedented depth and detail.
The ten-year Rubin Observatory Legacy Survey of Space and Time (LSST) will image billions of objects in six colors. This survey, which will cover over half the sky, also records the time evolution of these sources: the first motion picture of our Universe.
The primary instrument consists of an 8.4-meter telescope with a novel, three-mirror design. The Telescope’s compact shape allows it to move quickly from one point in the sky to the next. It will image the sky continuously each night, on an automated cadence, and over the course of the ten-year survey will collect about 800 images of each location in the sky.
The LSST Camera is the largest digital camera ever constructed for the field of astronomy. The size of a small car and weighing more than 3 tons, the 3200-megapixel camera will produce images so large that 1500 high-definition TV screens would be required to view each one.
This is a brief description of only one of the next gen observational facilities that are under direct threat from the fully-deployed Starlink Mega Satellite Constellation. There are very few options, really. Is it possible to fully black-anodize each satellite to the point of invisibility? Probably not, and certainly not to the point where instruments such as the Rubin telescope wouldn’t “see” them. Do we modify the mandate and the already published observing programs and schedules of these observatories when they come online? This wouldn’t suffice to adequately address the magnitude of the problem. SpaceX probably won’t abandon their multi-billion dollar capital investment in R & D; so where do we go from here?
It should also be pointed out, from a purely esthetic viewpoint, the celestial vista from our home planet, the same vista that has inspired countless generations of individuals, astronomers, scientists and poets across the hundreds of millennia since we emerged as the dominant species on the planet, will be forever altered. Even now with only 360 satellites deployed, as seen in the following video, a casual view up towards the evening sky will now be forever marred and spoiled by an alien satellite train not unlike some dystopian scifi movie. It’s truly a shame that Elon Musk, with his obvious genius, hadn’t given this project more forethought, nor even held a modicum of interest in the grand canopy above; I am reminded of Carl Sagan’s Pale Blue Dot and the famous quote by Ralph Waldo Emerson as he beheld the majesty of the unspoiled night sky
“If the stars should appear one night in a thousand years, how would men believe and adore; and preserve for many generations the remembrance of the city of God which had been shown! But every night come out these envoys of beauty, and light the universe with their admonishing smile.”
A related article will follow shortly that will explore the very serious health effects of 5G, its rapid deployment and the ostensible purpose of Starlink to support that rollout. Most notable in this regard is the sharp Oxygen absorption spike at 60.4 Ghz, a frequency located in the now unregulated microwave waveband between 57.05 & 64 GHz, and how that absorption interferes with the hemoglobin and oxygen uptake dynamics in the lungs.
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