ARGOS (ARTIC R2) Satellite Communication Guide
PaulZC 
ARGOS Message Formats
The table below summarizes the properties of each ARGOS message format as supported by the ARTIC R2:
| Message Format | Mode | Data Rate (bits/sec) # | Min Length (bits) * | Max Length (bits) * | Notes |
|---|---|---|---|---|---|
| A2 | ARGOS-2 | 400 | 52 | 276 | |
| A3 | ARGOS-3 | 400 | 52 | 276 | |
| ZE | ARGOS-3 | 400 | 28 | 28 | |
| A3 HD | ARGOS-3 | 4800 | 60 | 4636 | HD = High Data rate |
| A4 HD | ARGOS-4 | 4800 | 992 | 4960 | HD = High Data rate |
| A4 MD | ARGOS-4 | 1200 | 480 | 960 | MD = Medium Data rate |
| A4 VLD | ARGOS-4 | 200 | 28 | 84 | VLD = Very Low Data rate |
# The data bit rate quoted in the table is the bit rate before convolutional encoding (where used)
* The message lengths quoted in the table include the 28-bit Platform ID but exclude the message length identifier or any required tail bits. The ARTIC R2 always calculates and transmits the FEC for A3 HD and the FCS for A4 HD/MD. The quoted maximum message lengths exclude the FEC/FCS.
The ARGOS-4 VLD mode is exciting since the uplink can use much lower transmit power (100mW or even less) compared to the other modes. The message are short, including only the 28-bit Platform ID, or the Platform ID plus 56 bits of user data. However, 56-bits is enough to encode GNSS position (latitude and longitude) to 4 decimal places and accurate to ±5.55m at the equator.
ARGOS-3 ZE and ARGOS-4 VLD (Short) messages contain only the 28-bit Platform ID. ARGOS is still able to calculate the position of the transmitter using Doppler location.
If you want to dig further into the message formats and encoding schemes, they are defined in the CNES Physical Layer Requirements:
| Message Format | CNES Physical Layer Requirements |
|---|---|
| A2 | AS3-SP-516-2098-CNES |
| A3 + ZE | AS3-SP-516-274-CNES |
| A3 HD | AS3-SP-516-273-CNES |
| A4 HD/MD | A4-SS-TER-SP-0078-CNES |
| A4 VLD | A4-SS-TER-SP-0079-CNES |