Re:Voyager 1 stops communicating with Earth
by Someone on Friday December 15, 2023 @03:57AM
(#38652344)
The Voyager had an experimental reed-Solomon encoder. Encoding ‘just’ is a lookup table from a n-bit value to a m-bit one with m > n. Such a table takes 2^n × m bits.
Decoding also can be table-driven, but then takes 2^m × n bits, and that’s larger.
For example, encoding each byte in 16 bits (picking an example that leads to simple math), the encoding table would be 256 × 16 bits = 512 bytes and the decoding one 65,536 × 8 bits = 64kB.
Problem for Voyager was that 2^n × m already was large for the time.
Decoding also can be table-driven, but then takes 2^m × n bits, and that’s larger.
For example, encoding each byte in 16 bits (picking an example that leads to simple math), the encoding table would be 256 × 16 bits = 512 bytes and the decoding one 65,536 × 8 bits = 64kB.
Problem for Voyager was that 2^n × m already was large for the time.