Elon Musk's recent tweet shows a video clip of a modest-sized dish on fairly fast-slewing mount located:

At SpaceX Boca Chica launch site in Texas

In the question Why is the reflector on this millimeter-wave antenna spinning? I show another dish antenna used for tracking spacecraft (one image (GIF) shown below) and the rotating secondary is used to sense the direction of motion of the target so that as it moves away from the dishes direction, it can detect the direction and slew back again to continue to track the object.

Almost for sure that's the reason for the four parabolic dishes merged into one in the standard "Romashka"("Chamomile") telemetry station... installed at all tracking stations and ships. shown in @A.Rumlin answer to the question Where is the “antenna farm” from which this Soyuz launch photo was taken?.

Even some DSN antennas have experimented with electronically rotating offsets.

But this dish does not appear to have any method to sense the offset direction in order to track. Instead, at the focus there looks like only enough room for one feed horn. How does it track?

SpaceX Boca Chica launch site SpaceX Boca Chica launch site SpaceX Boca Chica launch site

enter image description here Source

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above: from Why have four parabolas on a ground-side array instead of just a single large one

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above: cropped from here


1 Answer 1


It looks like there might be instrumentation at the center of the dish:

enter image description here

If that’s the case, there might be multiple receivers there to provide directional feedback. There’s s description of that (with much older tech) in the AN/FPS-16.

  • $\begingroup$ Extremely cool link btw! $\endgroup$
    – uhoh
    Dec 25, 2018 at 3:29
  • $\begingroup$ Do you really think this is a two-mirror system? I think the receiver is up at the focus, and so I don't understand how receivers behind the dish would work. That's why I included images of the primary focus from three different angles. I don't see anything large enough to be a reasonable secondary mirror up there. Still, the stuff in the center of the mirror does suggest something is going on there. $\endgroup$
    – uhoh
    Dec 25, 2018 at 3:30
  • $\begingroup$ This one certainly could have two mirrors. I wonder if it is a companion (there are two pads shown) or if this is an upgrade from the tweeted video? youtu.be/WbWgoV2gxRY $\endgroup$
    – uhoh
    Apr 27, 2019 at 8:10
  • $\begingroup$ by knowing the spin position at the time of the strongest and weakest peaks, it is possible to determine the direction to move. $\endgroup$
    – user20636
    Apr 28, 2019 at 8:43

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