CZ-5B rocket stage 2022-085B: reentry forecasts

 (this post is periodically updated when new tracking data become available and have been analyzed)

last updated 30 July 19:05 UT   

My latest forecast is: 30 July, 17:10 UTC +- 15m

The latest CSpOC forecast was:  30 July, 16:49 UTC +- 10m 

The FINAL CSpOC TIP is 16:51 UTC +- 1m, near 3.4 N, 113 E

A possible reentry observation has been made from Kuching (Sarawak, Borneo) near 16:50 UTC 

Click diagram to enlarge

 

On 24 July 2022, China launched a CZ-5B rocket carrying the Wentian module to the Chinese Space Station. The huge CZ-5B core stage, 2022-085B, with a dry mass of 18 tons and a length of 33 meter, is now set for an uncontrolled reentry on July 30.

The diagram above shows the evolution of apogee and perigee altitudes so far.

I am running reentry models in the General Mission Analysis Tool (GMAT) for the CZ-5B stage, that currently point to reentry in the second half of July 30 UTC. At this point in time it is still too early to pinpoint a more precise time or location - and for this reason I do not give geographic coordinates for the nominal reentry point yet.

The map below shows the current risk area, based on the latest forecast and its uncertainty window. Within the uncertainty window, the rocket stage can come down anywhere on the blue line in the map. The yellow circle is the nominal reentry position, i.e. the center of the uncertainty interval, but not necessarily the most likely location.

 

Current risk area. Click map to enlarge

Movement of the spacecraft is from west to east = left to right on the map. Cities between 41.5 N and 41.5 S with 1 million or more inhabitants are shown as yellow dots.

Below is a diagram of the evolution of the reentry forecast so far. Below the diagram is the same data in tabular form, with the most recent forecast at the bottom of the table.

- My latest GMAT based forecast (black dots) is: 30 July, 17:10 UTC +- 15 m

- The last pre-reentry CSpOC TIP forecast (red dots) is: 30 July, 16:49 UTC +- 10 m

- The FINAL CSpOC TIP is 16:51 UTC +- 1 m, near 3.4 N, 113 E

The latter time, with its 1 minute uncertainty, and position are likely based on an infra-red detection of the reentry fireball by a SBIRS Early warning satellite. So it seems my last forecast was about 20 minutes off. It reentered more or less at the start of my uncertainty window.

Below is a map with the final revolution and actual reentry location:

 

click map to enlarge

EXPLANATION OF THE DIAGRAM BELOW:
Each dot is a prediction based on a new orbit release. On the x-axis is the date/time (in decimal days) of the orbit on which the forecast is based. On the y-axis is the predicted reentry time/date resulting from a GMAT model run using  this orbit. These too are given in  decimal days (e.g., "30.5" = "30 July, 12:00 UTC". Note: for dates beyond July 31, "July 32.0" means "August 1, 00:00 UTC" etc.). 

Error bars show the uncertainty in the prediction. Note how the uncertainty window become smaller once we get closer to the reentry.

The black dots are the results of my GMAT model runs. The red dots are predictions by CSpOC, the US Military tracking organization (and "the" authoritive source of orbital tracking data), given for comparison.

click diagrams to enlarge

My reentry modelling in GMAT uses the MSISE90 model atmosphere, current, predicted and past spaceweather, a dry mass of 18000 kg and a drag surface of 62% of the maximum value, which is the best estimate for the average drag surface of a tumbling rocket stage of these dimensions. The depicted uncertainty window is a fixed 20% of the timespan between orbit epoch and the reentry time forecast resulting from the orbit.

 

GMAT model forecasts:

ORBIT DATE/TIME    REENTRY         UNCERTAINTY   REMARKS/Lat Lon
(UTC)              FORECAST (UTC)  INTERVAL

 25-07 11:52:33    31-07 08:28  +-  28.1 h
 25-07 13:01:55    31-07 02:51  +-  26.8 h
 25-07 14:30:57    31-07 02:42  +-  26.4 h
 25-07 17:29:00    31-07 02:45  +-  25.9 h
 25-07 19:29:01    31-07 02:08  +-  25.3 h
 26-07 03:04:47    31-07 02:39  +-  23.9 h
 26-07 11:16:28    31-07 03:40  +-  22.5 h
 26-07 13:11:03    31-07 02:22  +-  21.8 h
 26-07 15:43:05    31-07 02:34  +-  21.4 h
 26-07 18:40:46    31-07 02:44  +-  20.8 h
 26-07 19:12:28    31-07 01:04  +-  20.4 h
 27-07 14:41:30    30-07 21:29  +-  15.8 h
 27-07 15:55:00    30-07 20:57  +-  15.4 h
 27-07 17:18:31    30-07 21:01  +-  15.1 h 
 27-07 18:20:32    30-07 23:39  +-  15.5 h
 28-07 17:05:39    30-07 23:46  +-  10.9 h
 29-07 01:18:22    30-07 21:36  +-   8.9 h
 29-07 08:55:31    30-07 20:12  +-   7.1 h  
 29-07 13:03:52    30-07 19:20  +-   6.1 h   
 29-07 16:34:29    30-07 18:58  +-   5.3 h  
 29-07 18:00:07    30-07 19:00  +-   5.0 h  
 30-07 01:31:37    30-07 20:06  +-   3.7 h 
 30-07 08:22:22    30-07 17:50  +-   1.9 h  
 30-07 09:54:18    30-07 17:29  +-   1.5 h  
 30-07 12:28:44    30-07 17:28  +-   1.0 h 
 30-07 12:58:01    30-07 17:30  +-    54 m  
 30-07 14:17:27    30-07 17:20  +-    37 m   33 N 126 W  
 30-07 15:48:42    30-07 17:09  +-    16 m   40 N 178 E
 30-07 15:57:24    30-07 17:10  +-    15 m   41 N 173 W  latest

 

UPDATE 30 July 17:15 UT:

Footage purportedly shot today from Kuching (Sarawak, Borneo) appears to show the reentry of 2022-085B. It would place reentry near ~16:50 UTC. The footage is here, in a tweet by Nazri Suleiman.
I say 'purported' because for the moment the footage has not yet been verified. But it seems likely it is the reentry indeed.

 

UPDATE 30 July 19:05 UT:

CSpOC gives a final TIP of 16:51 +- 1m UTC near 3.4 N, 113 E, which matches the Kuching sightings well (multiple video's from the Kuching region have since turned up on social media, so it is now quite certain that this was the reentry).

The map below gives the final orbital revolution and location of reentry over Borneo.

 

click map to enlarge

 

Other forecast sources:

CSpOC  (https://www.space-track.org/)

Aerospace Corporation  (https://aerospace.org/reentries/cz-5b-rb-id-53240)

Josep Remis  (https://twitter.com/jremis)

ESA  (https://reentry.esoc.esa.int/reentry) 

EU-SST (https://twitter.com/EU_SST) 

 

Added note on 'Live' satellite tracking websites

BEWARE: contrary to what many people think, purported 'Live' satellite tracking websites such as n2yo.com are NOT showing you satellite locations based on 'live' tracking data!

In reality, they show predictions based on older orbital element sets, that can be hours old actually.

This can be deceptive. They sometimes happily show an object apparently still "on orbit" after it in reality already reentered!