Search the Community

From wiki. Phase Orbit shells (km) Number of satellites Inclination (degrees) Half size contractual completion time Full size contractual completion time Current completion (23 May 2019) 1 550 1,584 53 March 2024 March 2027 62[43] 1,110 1,600 53.8 0 1,130 400 74 0 1,275 375 81 0 1,325 450 70 0 2 335.9 2,493 42 November 2024 November 2027 0 340.8 2,478 48 0 345.6 2,547 53 0 So, they distinguish 335, 340, and 345 km orbit, and as well 1110 and 1130. They also distinguish 53° and 53.8°, i.e. 0.2° = 12' ~= 12 nm ~= 22 km. So, this gives us a mesh step ~= 5..20 km in their sat pattern. Total area of a sphere of radius: 330 km = 4 * pi * (6370+330)2 ~= 564 mln km2 1330 km = 4 * pi * (6370+1330)2 ~= 745 mln km2 So, 564*106 * ((345+5) - (335-5)) / 7500 = 1.5 mln km3/sat in 340 km orbits. 745*106 * 20 / 4400 = 3.4 mln km3/sat in higher than ISS orbits. A 340 km orbit length = 2 * pi * (6730 + 340) ~= 44 400 km. A 480 km orbit length (ISS) = 2 * pi * (6730 + 480) ~= 45 300 km. So, say, our orbit is ~45 000 km long. Say, our cross-section area is 20 x 20 m ~400 m2 = 4*10-4 km2. (A large sat, a spaceship + upper stage, or else). Total volume of the orbital torus = 45 000 * 4 * 10-4 ~= 18 km3. So, the probability of a sat crossing our way is roughly: ~18 / 1.5*106 ~=1.2 * 10-5, 1 chance per ~80 000 orbital turns in LEO. ~18 / 3*106 ~= 0.6 * 10-5, 1 chance per ~160 000 orbital turns in typical OS 480 km orbit (ISS, Mir), when the sats orbit get significantly decayed. 1 day = 24 / 1.5 = 16 turns. Chances to hit a sat spending in 340 km orbit a day = 1-(1 - 1.2*10-5)16 = 0.0002 = 1:5000 a week = 1-(1 - 0.0002)7 = 0.0014 = 1:700 a month = 1-(1 - 0.0002)30 = 0.006 = 1:160 a year = 1-(1 - 0.006)12 = 0.07 = 1:14 Chances to hit a decaying orbit sat spending in 480 km orbit a year = 1-(1 - 0.6*10-5)16*365 = 0.034 = 1:30 *** Say, a sat lifespan is ~15 years. This means that every year they should deliver ~1/15 of total sats amount = ~800 sats/year. Probably they are going to deorbit the failed sats, so ~800 sats are going to deorbit. But as a launch vehicles are ~0.98 reliable, and the sats to be deorbited are by definition out of service, we can presume that ~20% of sats will stay in orbit as garbage. So, +160 sats every year. Twenty years later there will be ~3000 additional dead sats plus to the initial amount. *** Plus kesslerization of this Say that 15 years long Starlink sat. Say, its cross-section is ~5 m2 (including the solar panel) Its orbital torus volume ~ 45 000 * 5*10-6 ~= 0.2 km3. At 1.5 mln km3/sat around, the probability to hit another Starlink sat is ~ 0.2/1.5*106 ~= 1.3*10-7 per turn. Per year = 1-(1-1.3*10-7)16*365 ~= 0.00076 = 1:1300. So, we can expect ~5..10 Starlink collisions per year. Every collision creates, say, 10 debris, so +several hundred objects per year. Of course, most of them will deorbit, but while deorbiting they can hit a Starlink sat in a lower shell. *** So, if the Starlink had been raised, 30-40 years later there will be no safe orbit below the radiation belts for anything bigger than a Starlink sat.

The first one took several days for us to finally get predictions, and by that time they drifted apart and are obviously a lot less easy to see with naked eye right now. They're still relatively close, at least some parts of the "train". https://heavens-above.com/StarLink.aspx Post your observations here.