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If any spacecraft has remained at station-keeping with respect to the ISS for 12 hours or more, how far from the station did the craft remain?

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    $\begingroup$ The case of failed docking of Soyuz MS-14 may fit for the question. It was in the orbit near ISS for 3 days between failed docking attempt and successful attempt. Wikipedia states "the spacecraft backed away to a safe distance from the ISS". I couldn't find elsewhere on the web though what that distance was. $\endgroup$
    – Sergiy Lenzion
    Commented Jan 21, 2020 at 5:59
  • $\begingroup$ Why wouldn't spacecraft that were near the ISS for 11 hours be interesting? Why wouldn't spacecraft that were near the ISS and did so without necessarily needing to do proper, explicit station-keeping be interesting? I'm just curious why your question is so constrained, and I admire how you did all of that in a single sentence. Ever-so-slightly related: What is the “ISS's Keep Out Sphere” and what is its radius? $\endgroup$
    – uhoh
    Commented Jan 21, 2020 at 7:18
  • $\begingroup$ For MS-14, various sources state that immediately after the first failed docking attempt the spacecraft was commanded to move away from ISS to "the safe distance of" (here sources vary) a) 279, b) 280 or c) approximately 300 meters, whilst the decision was being made how to deal with the situation. There's no further reports whether this distance was changed after decision was made to postpone docking for few days. Some sources state "According to calculations, during the [next] day the ship will remain at a safe distance from the station" $\endgroup$
    – Sergiy Lenzion
    Commented Jan 21, 2020 at 10:07
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    $\begingroup$ @LeoS that looks like a good answer. There may be other instances but that doesn't detract from your research. $\endgroup$
    – Carl Witthoft
    Commented Jan 21, 2020 at 16:03
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    $\begingroup$ @uhoh I'm writing a novel. In one scene a spacecraft needs to be in station keeping to a space station. I want to have a ballpark figure of what is a reasonable distance for station keeping. $\endgroup$
    – Bob516
    Commented Jan 21, 2020 at 16:36

2 Answers 2

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The case of failed docking of Soyuz MS-14 may fit to constraints of the question. It was in orbit near ISS for 3 days between failed docking attempt and successful attempt. The linked above Wikipedia article states

the spacecraft backed away to a safe distance from the ISS

Further research resulted in locating few news articles mentioning that immediately after the first failed docking attempt the spacecraft was commanded to move away from ISS to "the safe distance of" (here sources vary)

meters,

whilst the decision was being made how to deal with the situation.

There's no further reports whether this distance was changed after decision was made to postpone docking for few days.

Some articles 4а, 4b (in Russian) state that it was calculated that the spacecraft will stay at a safe distance:

По расчетам баллистиков, в течение дня корабль будет находиться на безопасном расстоянии от станции...

According to calculations performed by "ballistic personnel" [sic] [perhaps meaning the personnel of "ballistic and navigation support service of Roscosmos' TsUP (MCC)], for the [next] day the ship will [remain to] be at a safe distance from the station

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The first Orbital Cygnus mission that eventually docked with the ISS experienced GPS issues during its initial berthing procedure. The Cygnus aborted the berthing and retreated to a safe-ish distance from the ISS while Orbital engineers devised a software fix, initially planned for a two day delay. But then NASA asked Orbital for an even longer delay due to the upcoming arrival of Soyuz TMA-10M. Cygnus Orb-D1 berthed with the ISS a week after it initially arrived. In the interim, it retreated well behind the ISS, by a distance of up to 2400 km.

The tenth SpaceX Dragon mission that eventually docked with the ISS initially experienced a data error in its navigation system. The Dragon aborted its initial inberthing procedure and similarly retreated to a safe-ish distance. It then went into a racetrack pseudo-orbit about the ISS while SpaceX engineers devised a fix. This pseudo-orbit was much closer than was the Cygnus Orb-D1 retreat, about 7 km x 4 km, keeping the vehicle well outside of the 4x2x2 km approach ellipsoid. SpaceX CRS-10 berthed with the ISS a couple of days later.

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