LightSail 2 reentry prediction
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.
Starting from 2022-09-02, the predictions actually include three different simulations with the purpose of defining a confidence interval for the reentry date.
The indices contained in the Archived Forecast files are compared with the measured values ("BEGIN OBSERVED"/"END OBSERVED" block of the "Legacy starting 1957 Oct 01" file in the "Space Weather Data" section). Then two confidence intervals are calculated for each day; one for F107measured / F107predicted and the other for Appredicted - Apmeasured. Since those errors are very far from being normally distributed, a distribution-free confidence interval formula needs to be used.
The paper "Non-parametric detection of meaningless distances in high dimensional data" by Ata Kabán gives the formula 17, which is used in the simulations to calculate the confidence interval for the errors for each day beyond the last available measured values. All those confidence intervals are used to calculate, day by day, the lower and upper bounds of the F107 and Ap indices.
The graphs show three sets of plots: blue trajectories are obtained using the upper bound of the confidence interval (higher air density and earlier reentry), the azure trajectories are obtained using the lower bound and the orange trajectories are obtained using the average errors, which are usually slightly less than 1 for the F107 index (on average the NASA's long range forecast is very good).
It should be considered that the two extreme limits are reached only if NASA's long range forecast is always biased to the lower or upper limit throughout the propagation, which is extremely unlikely. To avoid this unlikely scenario, the lower confidence bound (only the lower bound) used for propagation is modulated between the mean and the calculated lower bound. Empirical validation of this method was done by extensive simulations on reentered objects and the result was satisfactory.
Simulation date: 2022-11-17
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date (averaged the TLEs of each set) @ % nominal confidence level (the actual confidence level is 1% to 2% higher):
upper bound of the solar indices
most probable solar indices
modulated lower bound of the solar indices
Best fit average ballistic coefficient: 0.77 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2022 Nov 17 12:40 UTC, "nov2022f10_prd.txt" updated 09 November 2022
High precision ITRF93 frame: created 2022-11-16T17:07:02 by NAIF/JPL
Gravity model: SGG-UGM-2 truncated to degree and order 15
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 plots no longer show the mean radius vector (or semi-major axis), they show the instantaneous radius vector. The popup label shows the terrestrial time, the radius vector (km) and the inertial speed (m/s).
Simulation date: 2022-11-16
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date (averaged the TLEs of each set) @ % nominal confidence level (the actual confidence level is 1% to 2% higher):
upper bound of the solar indices
most probable solar indices
modulated lower bound of the solar indices
Best fit average ballistic coefficient: 0.77 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2022 Nov 16 09:40 UTC, "oct2022f10_prd.txt" updated 04 October 2022
High precision ITRF93 frame: created 2022-11-15T17:07:03 by NAIF/JPL
Gravity model: SGG-UGM-2 truncated to degree and order 15
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 plots no longer show the mean radius vector (or semi-major axis), they show the instantaneous radius vector. The popup label shows the terrestrial time, the radius vector (km) and the inertial speed (m/s).
Simulation date: 2022-11-15
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date (averaged the TLEs of each set) @ % nominal confidence level (the actual confidence level is 1% to 2% higher):
upper bound of the solar indices
most probable solar indices
modulated lower bound of the solar indices
Best fit average ballistic coefficient: 0.71 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2022 Nov 15 12:40 UTC, "oct2022f10_prd.txt" updated 04 October 2022
High precision ITRF93 frame: created 2022-11-14T17:07:02 by NAIF/JPL
Gravity model: SGG-UGM-2 truncated to degree and order 15
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 plots no longer show the mean radius vector (or semi-major axis), they show the instantaneous radius vector. The popup label shows the terrestrial time, the radius vector (km) and the inertial speed (m/s).
Simulation date: 2022-11-14
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date (averaged the TLEs of each set) @ % nominal confidence level (the actual confidence level is 1% to 2% higher):
upper bound of the solar indices
most probable solar indices
modulated lower bound of the solar indices
Best fit average ballistic coefficient: 0.57 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2022 Nov 14 15:40 UTC, "oct2022f10_prd.txt" updated 04 October 2022
High precision ITRF93 frame: created 2022-11-13T17:07:03 by NAIF/JPL
Gravity model: SGG-UGM-2 truncated to degree and order 15
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 plots no longer show the mean radius vector (or semi-major axis), they show the instantaneous radius vector. The popup label shows the terrestrial time, the radius vector (km) and the inertial speed (m/s).
Simulation date: 2022-11-12
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date (averaged the TLEs of each set) @ % nominal confidence level (the actual confidence level is 1% to 2% higher):
upper bound of the solar indices
most probable solar indices
modulated lower bound of the solar indices
Best fit average ballistic coefficient: 0.58 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2022 Nov 12 12:40 UTC, "oct2022f10_prd.txt" updated 04 October 2022
High precision ITRF93 frame: created 2022-11-11T17:07:03 by NAIF/JPL
Gravity model: SGG-UGM-2 truncated to degree and order 15
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 plots no longer show the mean radius vector (or semi-major axis), they show the instantaneous radius vector. The popup label shows the terrestrial time, the radius vector (km) and the inertial speed (m/s).
Simulation date: 2022-11-07
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date (averaged the TLEs of each set) @ % nominal confidence level (the actual confidence level is 1% to 2% higher):
upper bound of the solar indices
most probable solar indices
modulated lower bound of the solar indices
Best fit average ballistic coefficient: 0.63 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2022 Nov 07 12:40 UTC, "oct2022f10_prd.txt" updated 04 October 2022
High precision ITRF93 frame: created 2022-11-06T17:07:02 by NAIF/JPL
Gravity model: SGG-UGM-2 truncated to degree and order 15
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 plots no longer show the mean radius vector (or semi-major axis), they show the instantaneous radius vector. The popup label shows the terrestrial time, the radius vector (km) and the inertial speed (m/s).
Simulation date: 2022-11-01
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date (averaged the TLEs of each set) @ % nominal confidence level (the actual confidence level is 1% to 2% higher):
upper bound of the solar indices
most probable solar indices
modulated lower bound of the solar indices
Best fit average ballistic coefficient: 0.63 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2022 Nov 01 12:40 UTC, "oct2022f10_prd.txt" updated 04 October 2022
High precision ITRF93 frame: created 2022-10-31T17:07:03 by NAIF/JPL
Gravity model: SGG-UGM-2 truncated to degree and order 15
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 plots no longer show the mean radius vector (or semi-major axis), they show the instantaneous radius vector. The popup label shows the terrestrial time, the radius vector (km) and the inertial speed (m/s).
Simulation date: 2022-10-14
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date (averaged the TLEs of each set) @ % nominal confidence level (the actual confidence level is 1% to 2% higher):
upper bound of the solar indices
most probable solar indices
modulated lower bound of the solar indices
Best fit average ballistic coefficient: 0.79 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2022 Oct 14 06:41 UTC, "oct2022f10_prd.txt" updated 04 October 2022
High precision ITRF93 frame: created 2022-10-13T17:07:02 by NAIF/JPL
Gravity model: SGG-UGM-2 truncated to degree and order 15
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 plots no longer show the mean radius vector (or semi-major axis), they show the instantaneous radius vector. The popup label shows the terrestrial time, the radius vector (km) and the inertial speed (m/s).
Simulation date: 2022-09-02
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date (averaged the TLEs of each set) @ % nominal confidence level (the actual confidence level is 1% to 2% higher):
upper bound of the solar indices
most probable solar indices
lower bound of the solar indices
Best fit average ballistic coefficient: 0.69 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2022 Sep 02 15:40 UTC, "aug2022f10_prd.txt" updated 09 August 2022
High precision ITRF93 frame: created 2022-09-01T17:07:02 by NAIF/JPL
Gravity model: SGG-UGM-2 truncated to degree and order 15
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 plots no longer show the mean radius vector (or semi-major axis), they show the instantaneous radius vector. The popup label shows the terrestrial time, the radius vector (km) and the inertial speed (m/s).
Simulation date: 2022-08-16
There are two predictions. The first was made using the same procedure used for the other predictions, while the second uses the "SW-All.txt" data file for past and future solar indices (it does not use the NASA data file).
The graphs show 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 initial state of the satellite has been calculated using the following TLEs: .
Best fit average ballistic coefficient: 0.64 kg/m2
Gravity model: SGG-UGM-2 truncated to degree and order 15
High precision ITRF93 frame: created 2022-08-15T17:07:02 by NAIF/JPL
Solar indices: "SW-All.txt" updated 2022 Aug 16 12:40:00.00, "aug2022f10_prd.txt" updated 09 August 2022
Reentry date: 2022-11-28 (averaged the 10 TLEs)
Solar indices: "SW-All.txt" updated 2022 Aug 16 12:40:00.00
Reentry date: 2023-01-18 (averaged the 10 TLEs)
Simulation date: 2022-06-10
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date: 2022-11-13 (averaged the 10 TLEs)
Best fit average ballistic coefficient: 0.58 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2022 Jun 10 12:40:00.00 UTC, "jun2022f10_prd.txt" updated 07 June 2022
Gravity model: SGG-UGM-2 truncated to degree and order 15
High precision ITRF93 frame: created 2022-06-09T17:07:02 by NAIF/JPL
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).
Simulation date: 2022-04-13
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date: 2022-11-09 (averaged the 10 TLEs)
Best fit average ballistic coefficient: 0.49 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2022 Apr 11 12:40:00.00 UTC, "apr2022f10_prd.txt" updated 11 April 2022
Gravity model: SGG-UGM-2 truncated to degree and order 15
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).
Simulation date: 2021-10-23
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date: 2023-01-15 (averaged the 10 TLEs)
Best fit average ballistic coefficient: 0.67 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2021 Oct 23 12:40:00.00 UTC, "oct2021f10_prd.txt" updated 08 October 2021
Gravity model: SGG-UGM-2 truncated to degree and order 15
According to the site LightSail 2 - Mission Control, the spacecraft is currently in the "Solar Sailing" attitude control mode which means that "The spacecraft is attempting to raise its orbit using the solar sail. To do this, it must make two 90-degree turns each orbit. When flying towards the Sun, the sail orients itself edge-on, effectively turning off the thrust. When flying away from the Sun, the sail turns broadside to the Sun's rays and gets a slight push." (see the page "See the Latest Data from LightSail 2 on Our New Mission Control Dashboard").
That is probably the reason why the spacecraft is at a higher altitude than the one obtained from the previous simulation.
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).
Simulation date: 2021-04-05
The initial state of the satellite has been calculated using the following TLEs: .
Reentry date: 2022-07-14.7 (averaged the 5 TLEs)
Best fit average ballistic coefficient: 0.56 kg/m2
NRLMSISE-00 data files: "SW-All.txt" updated 2021 Apr 05 12:45:16 UTC, "mar2021f10_prd.txt" updated 12 March 2021
Gravity model: SGG-UGM-1 truncated to degree and order 15
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).