When placing ground stations for a deep space communications network, there is a well-established benefit to spreading out the stations by longitude. In particular, having at least three stations separated by 120° longitude ensures that a spacecraft is in the line-of-sight of at least one station at all times. This is the case for NASA's DSN (Canberra, Australia; Madrid, Spain; and Goldstone, California) as well as ESA's ESTRACK (New Norcia, Australia; Ceberos, Spain; and Malargüe, Argentina).

Is there also an advantage to having stations at different latitudes? For example, both the NASA and ESA networks have stations in both the northern and southern hemispheres.


For a minority of missions, yes. Most deep space missions stay in/near the plane of the ecliptic so they're visible from a large range of latitudes.

But the Voyagers are at significant angles to the ecliptic, which reduces the amount of time they're visible from wrong-hemisphere DSN stations (or blocks some stations completely, depending on the exact geometry).

Ulysses had an even bigger angle to the ecliptic (inclination 80º).

  • $\begingroup$ There are some relevant Voyager numbers here, but Ulysses is a whole 'nother ball of wax! $\endgroup$
    – uhoh
    May 17 '19 at 23:24
  • $\begingroup$ The extreme latitude stations are good for talking/tracking polar orbiting spacecraft. $\endgroup$ Jun 3 '19 at 22:00
  • $\begingroup$ Yes, but spacecraft in a polar Earth orbit don't need the DSN and its gigantic deep-space antennas. $\endgroup$
    – Hobbes
    Jun 4 '19 at 7:22

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