Thread by @ProfHughLewis

Latest analysis for #Starlink & #OneWeb shows these two constellations accounted for 42% of all close approaches within 5 km predicted by #SOCRATES at the end of August, with Starlink alone accounting for 29%. [1/n]

On average, #SOCRATES predicts that each #Starlink satellite will now experience 1 close approach within 5 km with a non-Starlink object every day, and each #OneWeb satellite will experience 3.4 close approaches with a non-OneWeb object every day. These rates are increasing [2/n]

Here's the same data from [2/n] plotted with respect to the number of satellites in each constellation in orbit, clearly showing #SOCRATES predicts that #OneWeb satellites experience more close approaches (within 5 km) per satellite than the #Starlink satellites [3/n]

Focusing on the #SOCRATES predictions for close approaches with max. collision probability of at least 1E-5, we see that the two constellations accounted for 30% of all such close approaches in August, with #Starlink alone accounting for 20%. [4/n]

We see a rising trend through time in predictions of the average number of such close approaches being experienced by each satellite on a daily basis, with #OneWeb satellites seeing a rate that is now 5 times greater than the #Starlink satellites. at 0.05 per sat per day [5/n]

Here's the equivalent #SOCRATES data showing the average number of conjunctions with max. collision probability of at least 1E-5 per satellite per day [6/n]

Across all of the predicted conjunctions within 5 km for #Starlink just under half (47%) involve a debris object, one-quarter (23%) involve another non-Starlink payload & just over one-fifth (22%) involve another Starlink satellite (likely 'ignored' by the operator) [7/n]

For #OneWeb, the picture is very different. Just under 70% of all the conjunctions involve a non-OneWeb payload with only one-quarter (26%) involving a debris object. [8/n]

Hence the predictions from #SOCRATES suggest that #OneWeb has experienced about 33% more conjunctions with other payloads than #Starlink despite the constellations substantially smaller size. This is likely due to the relatively long orbit raising process through LEO. [9/n]

Taking a snapshot (from a #SOCRATES report generated on 12 September) the close approaches within 5 km involving #Starlink and #OneWeb can be seen clearly, with the #Starlink shells around 550 km & the OneWeb shells around 1200 km dominating. [10/n]

Here's the same #SOCRATES data plotted using a logarithmic y-axis, which distorts but enables a little more clarity at the lower counts. [11/n]

And this is the same data now shown as the proportion of all close approaches at each altitude. #Starlink shells around 350 km & 550 km, and #OneWeb shells between 1100 km & 1200 km become readily apparent, as do close approaches occurring during orbit raising. [12/n]

My thanks to @TSKelso (@CelesTrak) for the #SOCRATES data & support, and to @planet4589 for #Starlink & #OneWeb summary statistics. Hope this thread has been useful! [13/13; fin]