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How long would it take for a 12U cubesat on a circular polar orbit with altitude 600 km to fall down to 500 km?

Please, add references/calculations to your answer.

mpv
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Tarlan Mammadzada
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  • I don't consider any thrusters. The question is, how long would it be on orbit? – Tarlan Mammadzada Feb 25 '18 at 10:05
  • The question is, how long would a 12U cubesat remain on this orbit. I don't carry about maneuvers now – Tarlan Mammadzada Feb 25 '18 at 10:12
  • @uhoh It is initially on a sun-synchronous orbit... – Tarlan Mammadzada Feb 25 '18 at 10:16
  • Firstly, how did you assume thousands of years? Secondly, how did you get 574 km? Could you please specify this in answer form? – Tarlan Mammadzada Feb 25 '18 at 10:20
  • I read it. It doesn't specify, that these orbits are the only possible.. "As an example, for a = 7200 km (the spacecraft about 800 km over the Earth surface) one gets with this formula a Sun-synchronous inclination of 98.696°." – Tarlan Mammadzada Feb 25 '18 at 10:25
  • Ah OK, if it is only sun-synchronous for uninterrupted solar power, but not for repeat ground track for Earth's surface, you are right. It's still true that you will need precise orbital insertion for your cubesat, and that it will become non-synchronous much much sooner than it would reenter the atmosphere. OK I will clean up my comments in a few minutes. – uhoh Feb 25 '18 at 10:40
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    @uhoh - A sun-synchronous orbit does not require an integral number of orbits per day. – David Hammen Feb 25 '18 at 10:46
  • @DavidHammen ya I've figured that out and said as much already. For some reason I keep linking sun-synchronous to repeat ground track as well. When I first learned about sun-synchronous, the raison d'etre explained to me was spy satellites and repeatable Sun angle for similar shadows between separate images, and I haven't been able to shake that off yet. – uhoh Feb 25 '18 at 10:56
  • @DavidHammen Guys, my question still remains unanswered – Tarlan Mammadzada Feb 25 '18 at 10:59
  • Related: https://space.stackexchange.com/questions/13851/how-long-can-a-leo-satellite-maintain-its-orbit-if-it-loses-all-power/13852 – David Hammen Feb 25 '18 at 11:43
  • The atmospheric drag model in the website linked in this answer and its accompanying documentation suggest up to hundreds of years for a quiet Sun and 12U + 20kg, depending on the spacecraft's orientation. A real answer would require information about the shape - will there be external panels as well as a prediction of space weather for decades into the future – uhoh Feb 25 '18 at 11:51
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    @tarlan - it is not generally considered appropriate to try to remind people the question is unanswered after only a couple of hours. If there is no activity for a few days or a week it would probably be okay. – Rory Alsop Feb 25 '18 at 14:43
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    @tarlan I don't consider it appropriate at all. No one is required to answer your question. Make it an interesting and well-written question, that helps getting answers. –  Feb 25 '18 at 15:22

1 Answers1

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There is no one answer to this question. How long a 12u cubesat will remain in orbit depends on a number of factors, including solar activity, orientation, and mass. Atmospheric density at 600 km varies by well over an order of magnitude over the course of the eleven year solar cycle. Flying with the long axis of the satellite along or across track changes drag by 50%. Since drag acceleration is inversely proportional to mass, a very light 12u cubesat will suffer greater drag acceleration than will a very heavy one.

That said, a 600 to 700 km orbit is on the cusp of violating the 25 year lifespan used by NASA and ESA. If your 12u cubesat flies such that the small face faces the wind and the cubesat mass is over 17 kg, the odds are quite high the spacecraft will remain on orbit for over 25 years.

David Hammen
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