Improve the radio link as a complete system

S5Lab’s mission timeline records a June 2018 change from 1,200 to 9,600 baud after improvements to the Rome ground station. That is an eightfold increase in the stated symbol rate. The ground work is part of the explanation: changing a spacecraft setting only helps when the receiving system can use the resulting signal.

Baud counts symbols per second, while bits per second counts information bits. Their relationship depends on modulation and coding. Useful image delivery also depends on headers, repeated data, reception quality and time in view. The source’s radio milestone should therefore not be turned into an unconditional promise of eight times as many usable images.

Use an invented link with 8,000 transmitted bits per second, of which 75 percent are useful payload. Its useful rate is 6,000 bits per second. A 120,000-bit payload then requires 20 seconds of useful transfer at that effective rate. These numbers are original teaching values, not a reconstruction of 1KUNS-PF’s modulation or protocol.

Now imagine a faster setting offers twice the transmitted rate, but losses reduce the useful fraction to 30 percent. Its 16,000 times 0.30 equals 4,800 useful bits per second, below the original 6,000. A higher setting alone is not the right optimization target. Compare correct, useful data delivered per available interval.

Compare useful throughput

To compare two configurations, record the receiver settings, spacecraft version, pass geometry and chosen outcome. Otherwise a strong overhead pass with the old setting and a weak low-elevation pass with the new setting could make the configuration change appear worse or better for an unrelated reason.

A fictional evaluation might compare repeated passes with similar elevation ranges, then report useful bytes, failed integrity checks and missing packets. That does not remove every environmental difference, but it makes the comparison more informative. Radio rate, successful reception and a reconstructed image are connected stages with separate measurements.