Test flight claims against telemetry

A 2023 CPUT thesis studied ZACube-2 telemetry primarily from January 2019 through July 2020. Its radio analysis found that ground-station signal-strength readings were relative to the receiver’s digital full scale. Comparing them directly with absolute received-power values created an apparent large offset. A number on a graph is not automatically in the same units or on the same reference as the requirement beside it.

Calibration applies known inputs and records how the instrument reports them. Suppose an invented receiver displays −45 relative units for a known input of −100 dBm. That one test establishes one correspondence; it does not prove that subtracting 55 will be correct at every level, frequency or gain setting. Test multiple known inputs across the required operating range before claiming a universal conversion or a link margin.

The study also discusses sparse spacecraft sampling during short receiving passes and higher-rate ground records. To compare records, their clocks, time bases and sampling intervals must be understood. Interpolation can estimate a value between measurements for a calculation or a display. It cannot turn an unobserved moment into a newly acquired measurement.

For an invented nine-minute interval, measurements at minutes zero, three, six and nine provide four samples. A brief disturbance at minute two could occur between them. A smooth line through the four points does not prove the system was stable throughout. To test a short-lived event, use measurements with suitable timing and resolution, or state that the available record cannot settle the question.

A line between samples is an estimate

The thesis’s operating review is evidence about particular data and conditions. It does not establish flawless behavior at every unmeasured instant or for the remainder of the spacecraft’s life. Missing telemetry should trigger investigation of the recording chain, ground reception and spacecraft state; it should not automatically be labeled a space-weather failure. A plausible cause needs evidence that distinguishes it from alternatives.

The CEOS mission catalogue now lists ZACube-2 as complete, with an end-of-life date of 24 April 2024. That catalogue status is separate from the thesis’s earlier measurement interval, and an end-of-life field should not be silently rewritten as a precisely observed reentry event. Future programs can use the design and operating lessons while maintaining their own acceptance tests. Flight heritage provides evidence to examine, not a guarantee transferred to every successor.