Just a fun question (+:

Juno is approaching Earth for a gravity assist on her way to Jupiter. Her approach will bring her, at the nearest point, a mere 559KM above Earth's surface.

ISS orbits just a little lower down, an average of 415KM above Earth. Tiangong-1 is still lower down, an average of 357KM above Earth.

All three craft have nearly comparable velocity around 7KM/s (I may be wrong on this one!), although Juno's will increase a fair bit doing the fly-by (Why do we call it fly-by? She isn't even in air!).

Between Earth, ISS, and Tiangong, which will be the first habitat to get closest to Juno during the fly-by?

  • $\begingroup$ In response to "Why do we call it fly-by? She isn't even in air!"... Fly can mean "go or move quickly". $\endgroup$ – called2voyage Oct 8 '13 at 20:06
  • $\begingroup$ @called2voyage: No sense of humour q+: $\endgroup$ – Everyone Oct 9 '13 at 9:25
  • $\begingroup$ Sometimes humor doesn't transfer over the internet well. I'll take the blame for reading it the wrong way. $\endgroup$ – called2voyage Oct 9 '13 at 12:40

Looking at STK and the public elements for each object. Unfortunately I can't do a conjunction report, as I can't seem to get JUNO into STK unfortunately... But here's a few photos:

Juno Flyby:

enter image description here

ISS/Tiangong at the time of closest approach:

enter image description here

Given this, hands down the answer is Tiangong. I don't have an exact distance for you, but it will be within 4 track minutes of being in the same area as Juno, and they actually fly along a similar trajectory for most of the closest approach period. I'm guessing they will pass within about 1000 km of each other, maybe closer, whereas the ISS won't pass within 5000 km, or so I would expect.

However, the Earth will no doubt beat both of them, being only 500 km or so away from the surface of the Earth. Still, Tiangong will fly surprisingly close.

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