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@Ludo's answer to If I wanted to reconstruct an entire Apollo mission's crewed spacecraft trajectories, what are the key sources of historical data I'd look for? links to Apollo Mission 11, Trajectory Reconstruction and Postflight Analysis Volume 1 (PDF) which contains terms like

  1. RTCC SS1 and SS2
  2. MSFN free flight trajectory
  3. Langley model
  4. NAT trajectory
  5. VHF ranging

For the last one (VHF ranging) I would guess that this is a range-rate measurement using VHF frequencies, possibly using some coherent "bent pipe" transponder on one module receiving and rebroadcasting signals from one thing to another. But is this only between the command and lunar modules, or does this also include range-rate measurements from Earth?

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    $\begingroup$ For ranging see my question. But VHF is the range 30 to 300 MHz, S-band is 2 to 4 GHz. Were two different ranging systems used? $\endgroup$ – Uwe Dec 1 '19 at 11:08
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    $\begingroup$ The S-band ranging was used from ground to the LM on the Moon. But the VHF ranging was an addition for LM to CSM distance measurement using the voice chanel. Thus a lightweight system was possible besides the radar. See this page. $\endgroup$ – Uwe Dec 1 '19 at 11:22
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    $\begingroup$ NAT trajectory is redundant as it means "NASA Apollo Trajectory" (see page 3 of the document). $\endgroup$ – Polygnome Dec 1 '19 at 13:17
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    $\begingroup$ MSFN = manned space flight network, the network of ground tracking stations. $\endgroup$ – Russell Borogove Dec 1 '19 at 17:49
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    $\begingroup$ Langley would be en.m.wikipedia.org/wiki/Langley_Research_Center ; “Langley model” might be context-dependent. $\endgroup$ – Russell Borogove Dec 1 '19 at 17:51
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Community Wiki answer: I've incorporated "translations" from existing comments on the question; feel free to edit/improve:


1. RTCC SS1 and SS2

RTCC = real time computer complex; the Mission Control computer system

2. MSFN free flight trajectory

MSFN = Manned Space Flight Network, the network of ground tracking stations.

3. Langley model

Langley would be https://en.wikipedia.org/wiki/Langley_Research_Center ; “Langley model” might be context-dependent.

4. NAT trajectory

NAT trajectory is redundant as it means "NASA Apollo Trajectory" (see page 3 of the document).

5. VHF ranging

For ranging see How to get an initial setting of the range gate for a Lunar Laser Ranging using a new Retro Reflector for the first time?. But VHF is the range 30 to 300 MHz, S-band is 2 to 4 GHz. Were two different ranging systems used?

The S-band ranging was used from ground to the LM on the Moon. But the VHF ranging was an addition for LM to CSM distance measurement using the voice channel. Thus a lightweight system was possible besides the radar. See this paper.

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    $\begingroup$ From context in the document, the SS1 and SS2 refer to different algorithms, but I have no details. $\endgroup$ – Organic Marble Dec 2 '19 at 1:16

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