The air density (the most significant unknown in determining the reentry date) is calculated by means of NRLMSISE-00 atmosphere model along with two data files for the current and predicted solar and geomagnetic indices. Please, see here for the current value and short range prediction of the solar and geomagnetic indices and here for the long range prediction.
The Marshall Solar Cycle Forecast site gives the best estimate value of the F10.7 and Ap indices along with an approximate ±2 sigma interval. The following simulation uses the +2 sigma values (95th percentile) to predict the earliest possible reentry date with "high confidence" (a reentry before that date is very unlikely). That lower bound only takes into account the uncertainty of air density and ignore the TLEs uncertainty, but this is perfectly valid, as the TLEs uncertainty is completely negligible compared to the uncertainty of the air density.
Simulation date: 2020-06-06
The initial state of the satellite has been calculated using the following TLEs: .
NRLMSISE-00 data files: "SW-All.txt" updated 2020 Jun 06 06:45:16 UTC, "may2020f10_prd.txt" updated 11 May 2020 Gravity model: SGG-UGM-1 truncated to degree and order 15 Reentry date: 2024-02-28 (averaged the 10 TLEs) Earliest reentry: 2022-10-24 (averaged the last 5 TLEs) Best fit average ballistic coefficient: 81 kg/m2
The graph shows the predicted minimum, mean and maximum radius vector scaled to a reference sphere with radius of 6371 km (just to show an approximate altitude), but when the instantaneous radius vector drops below 125 km, the blue plot no longer shows the mean radius vector (or semi-major axis), it shows the instantaneous radius vector. The popup label shows the terrestrial time, the radius vector (km) and the inertial speed (m/s).
The next graph is obtained for an high solar activity (95th percentile of the indices).
Here's the thermal stress prediction.
The graph shows the dynamic pressure and the airspeed during reentry.
This last graph shows the deceleration and the time taken to go from 90 km down to 10 km.
