Dragon and ISS Space-to-Ground

RadioDitch

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Has anyone yet been able to definitively confirm what digital protocol is being used by SpaceX for space-to-ground voice comms in S-band?

Also, and I apologize if this particular query is redundant, but does anyone have the frequencies and digital protocol that is being used for Space-Ground 1 and Space-Ground 2 between MCC Houston and the ISS? Still VHF or is it all S-Band via the TDRSS now?
 

RichardKramer

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Has anyone yet been able to definitively confirm what digital protocol is being used by SpaceX for space-to-ground voice comms in S-band?

Also, and I apologize if this particular query is redundant, but does anyone have the frequencies and digital protocol that is being used for Space-Ground 1 and Space-Ground 2 between MCC Houston and the ISS? Still VHF or is it all S-Band via the TDRSS now?
I searched the 108 - 118 MHz, 137 - 138 MHz, 225 - 406 MHz, 240 - 270 MHz ranges during the mission and heard nothing in those freq ranges in relation to the Dragon X mission.
Listening to Nasa's live u-stream after the Dragon X docking, Nasa ground said they were disconnecting the S-band link from the Dragon to the ISS; and putting them on the ISS "big loop". From Larry Van Horn's Communications Satellite book I found the following S-band freqs in use during the Shuttle period. The book is a 1985 edition.
Shuttle:
2250.0 FM downlink 10F9
2205.0 FM downlink DFI
2287.5 PM downlink 3/5/6F9
2217.5 PM downlink 2F9
2106.4 PM uplink 6F9
2041.9 PM uplink 3.6F9
Other TDRSS freqs:
2035.96 A
2211.0 downlink
2232.5 A downlink
2215.0 TV downlink
15000.85 Ku band
DOD uplink:
1831.8 Primary
1775.7 Secondary
UHF AM comms:
259.7 - 279.0 - 296.8

Rich - N3VMY - KAG0096
 

RadioDitch

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Listening to Nasa's live u-stream after the Dragon X docking, Nasa ground said they were disconnecting the S-band link from the Dragon to the ISS; and putting them on the ISS "big loop".
The "Big Loop" refers to the TRDSS, referring to the system encompassing the circumference of the earth. That much I know. And what they were disconnecting was the terrestrial link that allows MCC Houston to access SpaceX's communications system through a fiber-optic connection. Basically a really expensive talkgroup patch.

I'll definitely take note of the frequencies you listed. I am still curious about what digital protocol they're using. It almost sounds like DMR in audio quality, but, that's obviously an evidenceless assumption.

A good place to ask about Dragon comms would be the hearsat IRC channel (on freenode these days)
I'll definitely hop on there! Thanks!
 

danesgs

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Too bad we don't have the digital gear to decode voice comms that high and in the clear (some of us do) I know. Would love to hear the unencrypted comms of what goes on up there.
 

RadioDitch

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Too bad we don't have the digital gear to decode voice comms that high and in the clear (some of us do) I know. Would love to hear the unencrypted comms of what goes on up there.
Assuming it is encrypted. There's a reason to believe SpaceX is not, and to my knowledge, nobody has unilaterally confirmed the ISS Space-Ground frequencies are either. The Shuttle S-band allocations definitely were encrypted though.
 
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