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Have there ever been significant changes in the altitude of the ISS?

By significant, I mean changes greater than about 40 km, thus by far exceeding the periodic reboosts.

If there haven't been, then why not?

Would the ISS technically be able to change its altitude and be able to surive at other altitudes?

user
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Zaibis
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  • Except for the initial launches and assembly, you mean? – John Dvorak Aug 15 '16 at 22:21
  • @JanDvorak: Yeah, I made a comment stating I'm interested in cases purposed for science or simply beeing required for stability or that alike. but that comment got lost. So yeah except those. – Zaibis Aug 15 '16 at 22:25

1 Answers1

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Yes, there have been changes of > 40 km, as shown in this graph. The X axis scale is not showing, but it is from Nov 1998 to July 2008.

enter image description here

Reference

Edit: I checked to make sure the graph is not just a theoretical math problem. It's not, the same graph appears here.

Organic Marble
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  • It would be good if you could add the reason for these variations. – called2voyage Aug 15 '16 at 18:42
  • I thought about it, but that isn't in the question. The 2nd link explains them, though. – Organic Marble Aug 15 '16 at 18:47
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    Fair enough, that would probably make a good follow up question. – called2voyage Aug 15 '16 at 18:48
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    The period covered by the graph doesn't show the largest change, when the orbit was raised from ~ 350 km to ~ 420 km after the retirement of the space shuttle. – pericynthion Aug 15 '16 at 20:11
  • That's a 70 km change, which is approximately the same as the largest change shown in the above graph (400 to 330). – Organic Marble Aug 15 '16 at 20:14
  • Out of curiosity, do you know what is emant by 90 day margin? I could assume 1 or 2 meanings but am not sure. – Zaibis Aug 15 '16 at 20:38
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    My guess is that it's the altitude the station was supposed to stay above, to be safe in case no visiting vehicles could come and reboost for 90 days. But that doesn't explain why it fell below that... – Organic Marble Aug 15 '16 at 20:39
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    @OrganicMarble: Those are the exact same 2 questions I made up my self when seeing it. Would this be a reasonable followup question? – Zaibis Aug 15 '16 at 22:27
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    The 90 day minimum is based on high solar activity. Solar activity peaked in 2001, but the very long and very deep solar min from mid 2007 to early 2010 meant that that 90 day margin no longer applied during that period. The reason solar activity is important is that high solar activity makes the upper atmosphere swell, which in turn increases drag on the ISS. The atmosphere contracts with low solar activity, decreasing drag on the ISS. – David Hammen Aug 15 '16 at 23:03
  • If this data is from TOPO, it's from the mission controller responsible for altitude. In other words, the horse's mouth. – Ike Stoddard Aug 15 '16 at 22:45
  • "If there haven't been, then why not?" There is no mission reason not to be at the altitude that resupply can reach comfortably. Shuttle Orbiter first before August 2011, then Russian Progress/Soyuz.

    You also asked: "Would the ISS technically be able to change its altitude and be able to surive at other altitudes?" Yes, but not far, and we don't want to.

     – Ike Stoddard Aug 15 '16 at 22:49
  • @IkeStoddard we have a question about that:http://space.stackexchange.com/questions/10494/what-is-the-iss-maximum-altitude – Antzi Aug 16 '16 at 05:31