I simulated with Orbiter the Tiangong-1 reentry. The result fairly agrees with a standalone specially crafted simulation.
Since the radius vector and the orbital speed seem to have a “strange” shape, I created the attached graph to better understand how the orbit is changing.
I used 133 TLEs downloaded from celestrak.com. For each TLE, I calculate the satellite's position and speed by mean of the SGP4 propagator. I collect those values starting from 2 orbits before the TLE epoch to 2 orbits after the TLE epoch with a step of 0.5 s.
The graph shows the min, the average and the max values obtained for each TLE (there are 4 orbits for 1 TLE which is 1 point, since there are 133 TLEs, each plot consists of 133 points).
We see that the Tiangong-1 is currently loosing 128 m/day and that it accelerates of about 73 mm/s/day; nothing strange here.
What seems strange to me is that the shape of both the speed min and speed max plots don’t follow the sinusoidal shape of the distance, the upper part of the plot is flat.
Please, could somebody explain why?
Since the radius vector and the orbital speed seem to have a “strange” shape, I created the attached graph to better understand how the orbit is changing.
I used 133 TLEs downloaded from celestrak.com. For each TLE, I calculate the satellite's position and speed by mean of the SGP4 propagator. I collect those values starting from 2 orbits before the TLE epoch to 2 orbits after the TLE epoch with a step of 0.5 s.
The graph shows the min, the average and the max values obtained for each TLE (there are 4 orbits for 1 TLE which is 1 point, since there are 133 TLEs, each plot consists of 133 points).
We see that the Tiangong-1 is currently loosing 128 m/day and that it accelerates of about 73 mm/s/day; nothing strange here.
What seems strange to me is that the shape of both the speed min and speed max plots don’t follow the sinusoidal shape of the distance, the upper part of the plot is flat.
Please, could somebody explain why?
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