Replacement of Iridium 9 by Iridium 84

Iridium 9 was replaced in the operational constellation, after some cosiderable delay, by Iridium 84:

Iridium 9 was lowered from its position in plane 5 to an "engineering orbit" on 14 September 2000.
See Iridium 9 manoeuvre - on the way down? at

By 20 September 2000, it had been confirmed that this did not necessarily represent the start of a de-orbit.
See Iridium 9 is not deorbiting at

On 11 October 2000, the orbit started to be lowered even further.
See Iridium 9 orbit alteration at

On 15 October 2000, it was confirmed that Iridium 9 *was* now being deliberately de-orbited, but that this did *not* represent a first step in de-orbiting the whole constellation.
See Iridium 9 de-orbit is NOT the beginning of the end at

On October 17, the character of the orbit adjustment changed, evidently with the aim of reducing the perigee as much as possible. See Descent of Iridium 9 (#24838) at
The aim of reducing the perigee to 250km was not achieved. Presumably the fuel supply ran out.

By 2 November 2000, Iridium 9 had been observed to be tumbling out of control.
See CoSaTrak Observations at

(Iridium 9 (24838, 1997-030C) eventually decayed on 11 March 2003.
See Iridium 09 decayed at

The replacement of Iridium 9 was evidently delayed pending the confirmation of the handover of the Iridium system to new owners, even though there were two spare satellites in the relevant plane.

However, at the Iridium Satellite LLC press conference call on 12 December 2000
(see, it was stated that "Right now we have had one failure in 23 months and that's been de-orbited, out of the orbit. Beginning tomorrow, we will drift one of the spares up into that slot. That's been the only failure in 23 months and that's one that was identified quite a long time ago."

However, it was actually several weeks before the replacement was put into place:

As of 5 January 2001, Iridium 84 appeared to be in process of being raised to fill the gap.
See Iridium 84 being raised at

However, no element sets for Iridium 84 were released by the Orbital Information Group (OIG) for a long time.
See the discussion threads
Has OIG "lost" Iridium 84 ? starting at and
iridium 84 mislaid? starting at

After a break of 13 days, the next element set released for Iridium 84, on 18 January 2001, showed it on station.
See the discussion thread iridium 84 now on station starting at

Note: until the manouver of 05 January 2001, Iridium 84 appears to have had its orbit adjusted only very occasionally, for instance on 22 September 2000 when its orbit was raised.
See Iridium 84 manouver at

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