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In a recent science fiction movie there was a space station similar to the ISS, and it had a "proximity alert".

This made me wonder; in the real world, does the real ISS have any capability to automatically detect or sense the proximity of unexpected or un-anticipated objects which reach close proximity with a low relative velocity to the ISS?

Is there any possibility of something like an automatically generated "proximity alert"?

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    $\begingroup$ It's a movie. Movies get lots of things wrong. For example, ignoring the ISS doesn't have any "proximity alerts" to ignore. $\endgroup$ – David Hammen Jun 11 '17 at 1:34
  • $\begingroup$ I've edited your question to make it likely to be better received here. Clearly separate fact from fiction, if you have to mention fiction at all. The question could be asked without any reference to the movie also. And take a little more time to explain or think through exactly what it is you want to ask. It's an interesting question, let's find out if there is an answer here already, or if it's unique. $\endgroup$ – uhoh Jun 11 '17 at 2:03
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    $\begingroup$ I can't state it with certainty, but I'm almost positive the answer is no. Basically everything is done through ground assets. Visiting vehicles make use of retroreflectors on ISS to handle their own proximity operations. The ISS basically is passive and cooperative. $\endgroup$ – Tristan Jun 11 '17 at 2:15
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    $\begingroup$ Thing is you don't care so much about proximity. Once in proximity of the station, it's already too late if objects are travelling at several km/s. You want a good prediction and a broad map of objects. $\endgroup$ – Antzi Jun 11 '17 at 16:37
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    $\begingroup$ Proximity fuzes are really crude devices, made to detect large objects from less than 1 m away. You'd need a high-resolution radar with a range of a few thousand km to have enough time to react. Those are large, heavy, and power-hungry systems. $\endgroup$ – Hobbes Jun 12 '17 at 17:29
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The DOD, JPL, NASA, NOAA, and others do track space debris. The debris the ISS is mainly worried about is microdebris, and others of similar sizes. The companies/organizations listed above do track debris using radar, laser ranging, optical, etc... Most large debris (i.e. R/B, S/C, etc...) are well tracked. The debris sizes around 10 cm^3 or or laptop size are slightly more difficult but are still tracked to some degree of uncertainty. All tracking is done from the ground at ground stations. Some objects can be tracked from other spacecrafts in orbit, but it is usually not the case.

Also most debris locations are around an inclination of 71 to 98 degrees. Currently there is about a week notice before a possible known collision with 10^3 cm to larger objects. The ISS does have features that detect incoming debris or smaller objects.

EDIT: Sources

ISS Debris Detection: http://ieeexplore.ieee.org/document/879836/ and http://www.esa.int/esapub/bulletin/bullet109/chapter16_bul109.pdf

ISS Collision Maneuvers: https://sma.nasa.gov/news/articles/newsitem/2015/11/23/two-more-collision-avoidance-maneuvers-for-the-international-space-station

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    $\begingroup$ Somehow you managed to say all this without mentioning that the tracking happens from the ground. And your final statement ("The ISS does have features that detect incoming debris or smaller objects.") is without basis. $\endgroup$ – called2voyage Jun 12 '17 at 17:18
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    $\begingroup$ @called2voyage, forgot to copy over the other links. And thanks for mentioning that they are tracked from the ground, that is an extremely important detail to not forget! $\endgroup$ – ROB Jun 12 '17 at 17:50
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    $\begingroup$ The IEEE paper is from before Kibo launched. I cannot find any reference of the LCDE on Kibo. I can't find mention of on-board detection in the ESA article. Can you point it out to me? $\endgroup$ – called2voyage Jun 12 '17 at 17:57
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    $\begingroup$ the ISS "feature that detects incoming debris" is an experimental one-time use of the laser communications experiment, not an operational system. $\endgroup$ – Hobbes Jun 12 '17 at 18:07
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    $\begingroup$ @called2voyage Not only without basis, flatly incorrect. All debris tracking is done with ground assets. The linked articles were experiments and proofs of concept, none of which have ever been incorporated into the vehicle. $\endgroup$ – Tristan Jul 14 '17 at 16:41

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