In the absence of any communication satellite in 1958, back in Mercury times, how did the tracking centers, which were spread world across, communicated with each other, passed on their data to the next tracking station, and thus kept a track of the spacecraft?
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NASA report SP-6, chapter 2 describes the tracking network in detail. It provides this overview schematic explaining how the various stations communicated with each other:
(source: NASA SP-6, chapter 2, figure 2-8)
Communications were via the following channels:
- Radio
- Submarine cable
- Land line
The submarine lines and land lines were direct-line links, used exclusively by NASA. It was a mix of leased existing lines and newly installed lines.
The NASA report "Historics of the Space Tracking And Data Acquisition Network (STADAN), the Manned Space Flight Network (MSFN), and the NASA Communications Network (NASCOM)", available here as PDF download (100MB), provides a ton of background information.
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2$\begingroup$ For the submarine lines, did NASA lease some capacity or some of the physical wires within a larger submarine cable, or were dedicated NASA cables laid across the bottom of the ocean for this application? $\endgroup$– uhohCommented Oct 15, 2021 at 11:46
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1$\begingroup$ @uhoh I believe the answer is in this massive report, but so far I have only found this remark on p100: "Requirements like this forced network designers to lease or install many alternate, redundant communication links.", implying that there was a mix of leased existing lines and newly laid lines. Will search more when I have the time. $\endgroup$– LudoCommented Oct 15, 2021 at 15:40
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$\begingroup$ This covers a good portion of the globe, but there's a lot of longitude between London and Perth - was there a gap in communication when Mercury was on that side of the world? Or was the orbit high enough that it could bridge that gap without losing connection? $\endgroup$ Commented Oct 15, 2021 at 17:59
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$\begingroup$ @DarrelHoffman In the same chapter 2 of report SP-6 you can find a table of the tracking stations (the open circles). Between Londen and Perth there's CYI (Gran Canary Island), KNO (Kano, Nigeria), ZZB (Zanzibar, off the coast of Tanzania) and IOS (Indian Ocean Ship). $\endgroup$– LudoCommented Oct 16, 2021 at 7:43
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$\begingroup$ Ah, okay, so map not-to-scale I guess. Now I'm curious about that Indian Ocean Ship - being mobile there's a wide area where it could've been stationed, or it could possibly even move to track with Mercury? (Obviously it couldn't be fast enough to keep up with an orbiting vessel, but it could possibly extend the range a bit by following in the same direction?) $\endgroup$ Commented Oct 18, 2021 at 13:52