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Mir Re-entry


Tyneside, UK
2018 Jul 17
Tuesday, Day 198

Maintained by:










Russia's Announcement

During 2001 November, Russia announced its plans to take the Mir complex out of orbit around 2001 February 28. It stated that the plan involved two Progress supply vessels (Progress M-43, which was already docked with Mir, and the yet-to-be launched Progress M1-5) and the Progress engines being used to perform a de-orbit manoeuvre.

2001 January 11, a refined date for re-entry was published of March 6, approximately one week later than in the earlier announcement. Mid January 2001, Russia provided a little more information in the form of the aiming point for the major fragments to hit the ocean.

The main part of the following analysis was published on this page 2000 November 20 and relates to a de-orbit event late-February. It contains additional notes based on March 6.

Calculations

The starting point is the de-orbiting of Progress M1-3 on 2000 November 1 after it left the International Space Station. Retrofire was at 07:05 UTC, south of the Aral Sea and re-entry occurred about 35 minutes later over the southern Pacific Ocean.<

Looking at Mir's ground track on the same day shows that it could have followed a similar re-entry trajectory by firing its engine at 14:25 UTC for an entry into the atmosphere at 15:00.

A combination of the Earth's rotation and precession of Mir's orbit means that as time goes by, Mir comes around a little earlier each day. For the same re-entry track, the retrofire time on 16 November, for example, was around 08:25 UTC. The time for a complete rotation of Mir's orbit plane around the Earth's polar axis, to bring events back to about the same time of day, is a few hours short of 60 days.

The time difference between 2000 November 1 and 2001 February 28 is 119 days or exactly two rotations of the orbit plane. In other words, similar events and alignments occur at the same time of day so the re-entry times are pretty much identical on the two dates.

Retrofire

The actual time of the retrofire on the day will be controlled by a number of factors including Mir's position around its orbit, variation in the rate of precession and the precise location chosen for the entry into the atmosphere. Yuri Koptev, head of the Russian Space Agency has clarified the last of these points by stating that Mir will re-enter between 1,500 and 2,000 kilometres to the east of Australia.

Koptev's information allows the position of the planned ground track to be estimated. It lies around 40 degrees to the west of the one computed for a retrofire at 14:25, and moves the time about 165 minutes later to approximately 17:10 UTC (for February 28), soon after Mir enters the Earth's shadow for the last time.

Re-entry

A re-entry on February 28 will occur at approximately 17:45 UTC, above the southern Pacific - 05:45 local time the following day. This will be about one hour before local sunrise.

Whatever the date, as long as Mir hits the "Koptev Corridor", the position will be 26 degrees South, 172 degrees East, just south of Fiji. A potential observer will need to be located within about 500 kilometres of the event.

The amount of debris that will survive, and its spread, is unpredictable but the trajectory is such that it misses any major land masses. Yuri Koptev estimates that the potential trail of debris will be 200 kilometres wide and will extend some 8,000 kilometres along the ground track from the entry point - taking it towards South America but falling short of the continent itself.

Ground Track

Target Ground Track

The map shows the target ground track, based on the information in Yuri Koptev's statement. Manoeuvring engines aboard the Progress spacecraft that will be used to initiate re-entry will be used in the days prior to the event to place the ground track within the "Koptev Corridor" off Australia.

Times are shown for the originally-announced February dates and for the new date in March. A March 6 re-entry means that visual observation of Mir from the ground (for orbit measurement) will be possible around the time of retro-fire and the re-entry itself will take place in the dark, which will mean that the space station can be observed visually in its final fiery moments.

In Summary (times are approximate but accurate to within about 20 minutes):

Date Retrofire Re-entry
2001 Feb 2717:35 UTC
20:35 Local Time
18:10 UTC
06:10 Local Time
2001 Feb 2817:10 UTC
20:10 Local Time
17:45 UTC
05:45 Local Time
2001 Mar 614:40 UTC
17:40 Local Time
15:15 UTC
03:15 Local Time
Copyright © Robert Christy, all rights reserved
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