TABLE 3
Relevant Iris Telemetry Fields for Computing PN Range
| Field Name | Size | Description |
|---|---|---|
| PN Epoch Count | 4 bytes | Index of PN epoch; increments each time PN chip 0 is received; count begins when the PN ranging correlators are locked; resets to 0 when lock is lost; rolls over to 0 after 65,535 |
| PN Chip Index (q) | 4 bytes | PN component sequence delays; can be used to calculate index of current PN chip (0 to 1,009,469) using the Chinese remainder theorem; valid when PN ranging correlators are locked |
| PN Chip Accumulator (PCA) | 8 bytes | PN symbol clock phase accumulator from the STL; accumulation begins when the PN ranging correlators are locked; determines a floating-point estimate of the fractional chip phase using  |
| ETT Epoch | 4 bytes | PN epoch count to which the current value of the ETT register belongs |
| ETT | 4 bytes | 32-bit ETT; bit 31 corresponds to the bit encoded in PN chip 0 of the epoch reported in the ETT epoch register |