What Earth satellite remained in orbit the longest before reentering?

Question

@BillGray's excellent answer in September 2018 mentions that the Soviet magnetospheric research satellite 1977-093A (NORAD 10370) was expected to reenter the atmosphere in 2019 due to effects including the Kozai mechanism.

Is this currently the artificial Earth satellite that survived the longest before then reentering the Earth's atmosphere (40+ years) or has one stayed in orbit longer, then reentered?

I'm asking primarily about payloads (satellites) but discarded rocket bodies (R/B) or other objects of note will receive honorable mentions.

Are you asking which object stayed in orbit the longest (which would include still orbiting satellites), or is re-entry necessary? — Polygnome, Dec 28 '19 at 00:35
@Polygnome Yes, it's the not-as-easily answered question of the object "that survived the longest before then reentering the Earth's atmosphere". Reentry is required. If you can think of a way to improve the wording please feel free to edit, thanks! — uhoh, Dec 28 '19 at 00:37

score 5 · Answer 1 · edited Jun 17 '20 at 08:54

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My bet would be on needles of the Project West Ford experiment, launched 9 May 1963.

a ring of 480,000,000 copper dipole antennas (needles which were 1.78 centimetres long [...] was placed in orbit to facilitate global radio communication.

Fifty years later, in 2013, some of the dipoles which had not deployed correctly still remained in clumps, contributing a small amount of the orbital debris tracked by NASA’s Orbital Debris Program Office. Their numbers have been diminishing over time as they occasionally re-enter. As of May 2019, 40 clumps of needles were still known to be in orbit

In other words, they keep reentering. The larger clumps are observable. The smaller ones - not. We may be seeing a reentry every couple of days or weeks. That would be around 56 years by now and the number will grow as more of the needles reenter.

edited Jun 17 '20 at 08:54

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answered Dec 28 '19 at 11:48

SF.

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Those turned out to be the answer to What is the largest number of identical satellites launched together? as well as Highest number of satellites launched on a single rocket (similar but not identical questions) so they might as well be the answer this one as well! If only there was a reentry that has a timestamp on it, we could be sure. If I understand correctly the individual needles have long since reentered, right? – uhoh Dec 28 '19 at 13:49
If it's just the clumps with the high mass/area (low BSTAR) that remain, then perhaps there's a notable clump reentry with a date associated – uhoh Dec 28 '19 at 13:53
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"Needles" is a little misleading: their diameter is just 17 microns, at the lower bound for human hairs (says Wikipedia). The total mass of 480 million copper "needles" seemed implausible, but at just 40 micrograms each that's just 20kg of sparkly dust. – Tom Goodfellow Dec 28 '19 at 20:18
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I'd seriously doubt the clumps are firmly bound in any way - I'd bet even minor perturbations make them lose needles now and then, and then these needles will reenter soon after. – SF. Dec 28 '19 at 21:06

What Earth satellite remained in orbit the longest before reentering?

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