The paper International Space Station Medical Operations mentions

Private medical conferences (PMCs) are conducted regularly and upon crew request with the ISS crew via private audio and video communication links from the biomedical MPSR (multipurpose support room) at MCC Houston.

What specific changes to the audio communications loop setup are done to "privatize" the loop?

(Info about the video link would be OK but I'm primarily interested in the Space-to-ground audio loops).

Do the configuration changes take place solely in the Mission Control Center, or are changes to the onboard voice loop configuration required?

Inspired by this question Can an astronaut have a private communication during a spacewalk? to ask something I've been meaning to ask for a while.

An acceptable answer would describe the nominal, non-privatized audio loop configuration inclusive of the astronaut at ISS and the person they are communicating with at MCC, and then describe the specific changes that are made to privatize it.

  • $\begingroup$ Just a guess, but since video is included I'm guessing it's done with the Space Station Computer laptops via the internet data link and secured with one of the many standard internet security measures that one could take with those. Not sure if the SSC application list is public or not. $\endgroup$
    – Erin Anne
    Jun 11, 2020 at 21:29
  • 1
    $\begingroup$ Maybe, but they were privatizing the loops for Shuttle back in the 80s before the internet was really a thing. $\endgroup$ Jun 11, 2020 at 21:36
  • $\begingroup$ Fair. Based on your other answers you definitely know more about COMSEC than I do. :) $\endgroup$
    – Erin Anne
    Jun 11, 2020 at 21:40
  • $\begingroup$ I only know that it happens, nothing about how. $\endgroup$ Jun 11, 2020 at 21:45

1 Answer 1


From conversations I have personally had with people who work in the Medical and Psychological divisions at the Johnson Space Center, the use of the term privatization is less about securing the connection, as making sure that nobody can physically eavesdrop on the conversations. The astronaut on the space station goes to a module where they are alone, so that they can avoid being overheard by their colleagues, and the audio is routed to bypass the CAPCOM in Houston and directly connect to a doctor in a private room.

Additionally, the ISS does have an internet connection that is routed through the TDRS satellites, so they would be able to use standard internet connections to encrypt any communication. As a matter of fact, they have an IP phone that links down to be from Houston, allowing them to call any phone on earth, including calling 911 (the emergency number in the United States) by mistake.

My apologies for not being able to provide sources, as this is mostly based off of conversations I have personally had with NASA Employees.

  • $\begingroup$ I don't know the specifics, but I know that the entirety of Houston mission control is networked. (Every mission control station can be accessed remotely from a laptop, in case of an emergency, or to bring in experts not currently in Houston), so I suspect that re-routing to a different room would be similar to how one re-routes a conservation on a IP phone network: A few button presses on a computer $\endgroup$ Jul 17, 2020 at 20:44
  • $\begingroup$ A simple diagram would be: ISS->TDRS->White Sands Ground Station->CAPCOM->Mission Controllers->Public Broadcast. When switching to private communication, it would be ISS->TDRS->White Sands Ground Station->Doctors laptop Like I said, I do not know more specifics, but the last things that I can say is that I know is that they software is custom-in house, the computers run Windows 10, and one of the backup locations is a Hotel in Round Rock Texas. $\endgroup$ Jul 17, 2020 at 20:52
  • $\begingroup$ I worked (part of the time) in Mission Control for about 20 years, so I'm good with the big picture. I just never understood how this privitization stuff worked. $\endgroup$ Jul 17, 2020 at 20:59
  • $\begingroup$ Sorry that I cannot give you the technical answer then, this I have not had a chance to talk to people about that stuff in the way I was able to talk to some flight surgeons about the biological/psychological side. $\endgroup$ Jul 17, 2020 at 21:28

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