r00t.cz

Big thanks goes to Paul from UHF-SATCOM for providing me recordings of this signal.

Signal spectrum and modulation

Modes seen so far:

• Failsafe: PM carrier with BPSK 80Bd sideband at 25000Hz
• Normal basic telemetry: BPSK 60000Bd

Coding and framing

Normal downlink uses CCSDS 1/6 Turbo coded frames with frame length of 8920 bits while failsafe uses 1/2 Turbo code with 3712 bit frames.
AOS frame protocol is used with spacecraft id 0xA8. So far only virtual channel 0 was in use.

Filler packets to APID 2047 contain following nice message from the team:

Note that this isn't first time I have found such message. SMAP satellite had similar message from JPL, see bottom of the S-band sats page for details.

CCSDS packets have 6 bytes of secondary header containing time stamp.

APIDs

Active APIDs seen so far:

006 007 008 009
0F7 0FD 0FE 0FF
104 105
202

APID 0x006,0x007,0x008

Not much data, but contains following ASCII text strings:
seqctr seqeng sfp_15001 cmd upl

APID 0x009

This is most active APID, probably containing all the basic telemetry. There is rather long header of about 60 bytes followed by list of tag+value pairs. A lot of double precision floating point data, as well as 32bit ints and other data types. Looks a lot like a serialized data from data object.

APID 0x0F7

Data looks like download of stored recording of same data as used by APID 0x009. Data are fragmented to multiple packets and header does have fragment offset and other flags required for reassembly.

APID 0x0FD

Same fragmented data download protocol as above, but different type of data this time, looks like short status report of various subsystems with these ASCII names (maybe this is booster stage):
cbm crcmgr dwn fbm fbmavs fbmpwr fbmsaf rm scfg smm upl

APID 0x0FE

Again same fragmented download protocol, with different data and more subsystem names (maybe this is the Perseverance):
acs btp cmd csm edlcam eha fbm fbmpwr fvs helo l_mcam mca mot moxi pammgr pixl pwr pyro r_mcam reumgr rimfax scam sdst seqctr seqeng smm srlc sspa thrust twta uhft upl vcemgr

APID 0x0FF

Another fragmented download protocol, with just short data and a few ASCII strings:
cmd seqeng

APID 0x104

Also uses fragmented data protocol. Very short data with ASCII:
fbm therma

APID 0x105

Again uses fragmented data protocol. Very short data with ASCII:
fbmavs seqctr sfp_00002 smc_00003

APID 0x202

Fragmented data protocol with binary only data.

Analysis of data and used protocol continues...