# Why does the ISS HDEV camera switch from rear view to front view just before rear view is aiming towards Antarctica?

I've obviously not seen every orbit but every one I have seen switches from rear view to front view just before it would have been aiming towards Antarctica. I ask this as I am interested to see what is happening in and above Earth's atmosphere in this region.

• The noctllucents are back! There's a satellite for that, but it would be nice to see them from the ISS. However, based on it's current orbit, I don't think the ISS can see the atmosphere farther south than about 72 degrees South latitude. A few of them might be visible though. nasa.gov/feature/goddard/2016/… – uhoh Dec 4 '16 at 2:06
• I'm watching just now. The ISS is now over the South Atlantic, briefly after the southernmost part of its orbit, and HDEV is showing a rear view. – oefe Dec 4 '16 at 10:34
• HDEV Final Report: eol.jsc.nasa.gov/ESRS/HDEV/files/HDEV-Final-Report_20200715.pdf – Jim Grisham Feb 18 at 14:43

Because of the path of the orbit of the ISS, you can never see Antarctica from the space station, even in the most ideal circumstances.

This Aerospace Corporation map shows the potential re-entry paths of Russia's doomed Progress 59 spacecraft, with re-entry plots for Friday, May 8 at 1:40 a.m. ET (0540 GMT), plus or minus 5 hours. Credit: The Aerospace Corporation. Source Accessed: space.com

Note that the path of the space station (Yellow+Blue lines) passes a few hundred miles north of the northern most point in Antarctica. You might be able to just barely see the tip of the Antarctic Peninsula, but certainly no more than that.

• Nnice image - can you add a link showing where it comes from? It's always good to cite the source of information - and with images, the location where it came from or the program you used to generate is always good to include. Maybe other readers in the future would like to generate similar images. – uhoh Dec 6 '16 at 9:24
• Sorry about that. I was answering pretty quickly and just grabbed it from google. Source is space.com – Brian C Dec 6 '16 at 9:33
• Great! Can you add that to your answer when you get a chance to edit it? It's best to put that with the image, not in a comment. – uhoh Dec 6 '16 at 9:52
• @uhoh Google fu and found the space.com source. It's in the edit now... please update further if the original Aerospace Corporation source is located. – Sarah Bailey Dec 6 '16 at 14:57
• The picture is a bit confusing because it contains information about Progress 59, which is irrelevant to the question. The only better one I could find was unattributed and happened to be used here earlier: space.stackexchange.com/questions/18553/… – user10509 Dec 9 '16 at 8:55

What you're describing is pure coincidence. The HDEV cameras don't know where the ISS is over the earth.

http://nasa.gov/mission_pages/station/research/experiments/917.html states that normal operation is to automatically cycle through the cameras at regular intervals (which can be adjusted by ground command). The cycle rate is discussed in this answer: https://space.stackexchange.com/a/9571/512

I used a current TLE for the ISS and Skyfield to make an approximate ground-track plot on top of a Blue Marble Next Generation w/ Topography and Bathymetry image from NASA. Surface locations potentially visible from the ISS are those within the cartesian distance $$r$$ calculated from the simplest distance to horizon formula:

$$r = \sqrt{(R_{earth} + altitude)^2 - R_{earth}^2}$$

Of course if you are looking at thinks above the surface then this is an underestimate, it also potentially underestimates by not accounting for atmospheric refraction. But it's good enough to get a rough idea.

I've plotted dots at 1 minute intervals for 12 hours as an example. In the first image I've reset the value of all pixels that are never within view of the ISS to black. If I ran for longer, it would just be a band around the Earth extending to about +/- 72 degrees latitude. The second image is without masking, to roughky show how much of Antarctica is not visible. Again, this applies to the surface and not high in the atmosphere or in space above antarctica.

• I've used a script similar to the one in this question but since I'm waiting for an answer to do it more nicely, I won't past the script here yet. – uhoh Dec 9 '16 at 4:30
• Nice work, but worth mentioning that practically speaking, if the angle between the ground and the ISS is very shallow ( <10 degrees), it would be very difficult to make out any discernible detail on the surface. – Brian C Dec 9 '16 at 18:39
• @BrianC while that may be true the question is not related to discerning anything on the surface at all. It states "I ask this as I am interested to see what is happening in and above Earth's atmosphere in this region." an actual precise calculation would be altitude dependent and include refraction. As stated this is just a supplement to BrianC's answer which contains statements about how far south could be seen without any support at all, so I have said "*This is a little math just to add" (to the seat-of-the-pants estimate there.) – uhoh Dec 10 '16 at 2:48