Some random scribbles on Starlink

Home Forums Imaging Project idea Some random scribbles on Starlink

#581889
Jim Verner
Participant

djswan2002,  I too would welcome an in-depth study into the impact of Starlink et al as it’s something that I certainly find concerning.

I’ve done a little digging around the internet and what I’ve found doesn’t look too good, I’ve tried to summarise my thoughts here as best as possible. This is by no means a study into Starlink, at best it’s a few random scribbles on the back of an envelope by someone who considers himself as a mere star gazer and no mathematician and certainly not an astronomer, but it’s food for thought, even if it may not stand up to scrutiny.

The number of proposed satellites

Starlink    42,000     (12,000 approved, paperwork submitted to International Telecommunication Union for 30,000 more)

Amazon     3,000

OneWeb      650     (possibly increasing to 2000)

TelSat LEO    300

Hongyun       320     (altitude 1,100km)

 

Total        46,270  New Satellites

 

Others who have proposed constellations but so far have no planed launches

Boeing        1,400

Samsung    4,600

 

The total number of new satellites then stands at a whopping 46,270 up to a possible 53,620 in the next decade. That is in addition to nearly 2,000 current operational satellites and 20,000 bits of space debris of which around 1500 are 100kg or above.

So what impact is this likely to have?

** Note Xilman pointed out a pretty dumb mistake I made when doing the following calculations, he quite correctly pointed out that I should have used steradians to work out the total number of square degrees, doing so gives a total of 41,253 not  the erroneous figure of 129600 (now removed) that I initially came up with. The corrected maths follows  **

So, to calculate the total square degrees that would be 360 / (2 x pi) = 57.3 (there abouts) and then (4 x pi) x 57.3^ = 41253 square degrees. (always the same value for any size of sphere).

That would then give us a concentration of  46,270 satellites divided across 41,270 square degrees 

  46,270 / 41,253 = 1.12 satellites per one square degree

So, if the moon covers an area of 0.2 square degrees (if memory serves me correctly) that equates roughly to one satellite for each area of the sky equal to five times the area of the moon based on the lower number of satellites or 1.38 satellites in the same area if using the higher number of 57,120. That seems quite a lot to me!

Starlink / Space x have said they will look at measures to reduce the albedo of their satellites, this may help, however some are suggesting that the solar panel cannot be altered and it’s the most reflective part. Additionally a few have mentioned on various forums that the combined effect of so many objects in or close to near earth orbits is going to cause a not insignificant occultation issue for DSO observations in particular asteroid hunting using the blink comparison technique.

I’ve only really concentrated on the increase in numbers of objects in NEO , there is of course other issues like the amount of RF these satellites will emit and the impact of the satellite to satellite links, which I recall reading somewhere were going to be done optically (is that some sort of laser or IR link perhaps), nor have I went into detail on the size of the satellites, indeed, information on the physical size of the satellites seems very sparse, an estimate made by one person on reddit puts the size at around 1.1m x 2.4m for the satellite body not including the solar panel. Cees Bassa from the Netherlands Institute for Radio Astronomy, calculated that up to 140 of the starlink mega constellation satellites could be visible at any one time if all the planned satellites launch (Forbes.com article).

Another article from Space.com highlights the brightness of these new satellites –  

[Patrick Seitzer, an astronomy professor emeritus at the University of Michigan, said Wednesday (Jan. 8) during a special news conference at the 235th meeting of the American Astronomical Society (AAS) called “Astronomy Confronts Satellite Constellations.” 

“We knew these tens of thousands[-strong] megaconstellations were coming, but based on the sizes and shapes of things currently in orbit, I thought maybe 8th or 9 magnitude,” Seitzer added. “We were not expecting 2nd or 3rd magnitude in the parking orbits, and we were certainly not expecting 4th to 5th magnitudes in the [operational] orbits.”]

 

In conclusion, will this amount to a change in astronomy as we know it? – Personally I’d say yes, but I’m not 100% sure, it may even render backyard astrophotography almost impossible, however there are many that say otherwise and even those who say it will have an impact on astronomy seem to be taking a wait and see approach. Again, speaking personally, I find the ‘wait and see’ approach as frankly bazar. Are we going to be in a position ten or twelve years from now when the astronomical community look up and say, ‘we can now say for certain this is having a big impact on us, would you mind taking your $30 billion per year earning satellites down please so we can do astronomy again?’ I can imagine the answer to that question would be short and to the point.

Smoking probably isn’t bad for you….

Nah, CFC’s couldn’t be damaging the ozone layer….

Dumping millions of tons of plastic every year is fine, it’s not an issue….

Putting tens of thousands of satellites in orbit around our planet is not going to be a problem………

Err, Houston…. We may have a problem!