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This answer includes the following information:

During the great geomagnetic storm of 13-14 March 1989, tracking of thousands of space objects was lost and it took North American Defense Command (NORAD) many days to reacquire them in their new, lower, faster orbits. One LEO satellite lost over 30 kilometers of altitude, and hence significant lifetime, during this storm.

source: Space Weather Prediction Center Topic Paper: Satellites and Space Weather - NOAA SWPC


Question: Which LEO satellite lost over 30 km of altitude in the geomagnetic storm of 13-14 March 1989?

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    $\begingroup$ It is always fascinating what kind of questions you come up with :D $\endgroup$ – Polygnome Apr 12 '18 at 7:51
  • $\begingroup$ @Polygnome this traces all the way back to Uwe's comment! I just followed up. $\endgroup$ – uhoh Apr 12 '18 at 7:56
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This appears to be an error that has propagated from paper to paper over the years. Examining the original paper cited by all these other authors, "Effects of the March 1989 Solar Activity" by Allen et al. shows us that the actual altitude loss was 3 miles (not 30 km) and the satellite in question was "the aging NASA satellite SMM" aka Solar Maximum Mission, (which incidentally had already been repaired by a Space Shuttle crew in 1984).

The linked pdf of the original paper is not searchable, but you can find the satellite effects described about the middle of the left-hand column on page 4 of the pdf (page 1488 of the document).

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  • $\begingroup$ Very nice find! it seems the "space lore" grew in notability over time. I've made a plot in the other answer... any thoughts? $\endgroup$ – uhoh Apr 12 '18 at 0:40
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    $\begingroup$ I wonder if this story has had a detour in Scandinavia. We are metric, and we have a metric "mil" that is 10km (So, 1 mil ~= 6 miles) No idea how widespread the "metric mil" is. $\endgroup$ – Stig Hemmer Apr 16 '18 at 8:50
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After reading @OrganicMarble's answer and the link there as well, I looked at the TLEs for the Solar Maximum Mission in 1989 (1980-014A, 11703) and while the altitude loss in March does not seem to be in any way dramatic overall, there is in fact a drop in the average altitude at the time.

enter image description here

I've propagated the TLEs for one complete orbit starting at the epoch of each TLE and plotted maximum and minimum values, and for the second plot also included the time-averaged altitude (averaged over one orbit, at epoch). At about day 73 there is indeed a sudden drop in altitude, although it seems more like only a 1 kilometer "brick wall".

The loss in altitude is not the problem as much as the fact that even a tiny but unexpected change in altitude will change the period, and so the object will move faster and will not appear where it is expected. This advance in phasing is probably a better way to think about the cause of the sudden loss of tracking, rather than the altitude itself.

A drop of 1 km will shorten a 5595 second period by about 1.2 seconds. At a velocity of 7.65 km/s, a 1 kilometer drop in altitude advances the satellite by about 6.1 km per hour, or 145 kilometers per day. So it won't be anywhere near where it is expected the next time one looks for it.

enter image description here

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    $\begingroup$ You gotta love the mixing of metric/imperial units in one sentence from that paragraph from the paper. $\endgroup$ – Organic Marble Apr 12 '18 at 0:44
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    $\begingroup$ @OrganicMarble updated plot, I found a drop, though not as dramatic as first "hoped for". $\endgroup$ – uhoh Apr 12 '18 at 1:00
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    $\begingroup$ Nice job with the plots. $\endgroup$ – Organic Marble Apr 12 '18 at 1:10
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    $\begingroup$ @Uwe I've used Skyfield which contains a standard SGP4 propagator. Similar scripts that I've posted here and here show how to use it. Since this answer just plots what comes out from running Skyfield (I don't really calculate anything myself here) I didn't post the script in the answer. However here it is: pastebin.com/pR6xt6qg $\endgroup$ – uhoh Apr 12 '18 at 14:20
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    $\begingroup$ @OrganicMarble The sentence quotes two different sources and I guess the author thought their readership would be familiar enough with the units that conversion was unnecessary. $\endgroup$ – David Richerby Apr 13 '18 at 14:46

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