Read telemetry as evidence with context

Telemetry — open definition is information transmitted from a spacecraft about its measurements and state. A display might show voltage, temperature, equipment modes or recorded events. Before interpreting a value, ask when it was measured, when it reached Earth, which units it uses and whether it is current or replayed from storage.

A delayed packet can be perfectly valid evidence of an earlier state while being a poor description of the present one. Similarly, a flat line can represent a stable quantity, a frozen sensor or repeated old data. A graph’s appearance alone does not distinguish those explanations.

Consider a fictional thermal trend of 18, 19, 20 and 21 degrees in equal time intervals after a heater turns on. A rise may be expected in that mode. The same rise with the heater supposedly off could deserve a different investigation. Alarm thresholds help draw attention, but interpretation still requires knowledge of the operating state.

Independent measurements can narrow the possibilities. If one sensor jumps while nearby sensors and power draw stay steady, investigate the sensor or data path as well as the physical system. If several related quantities change together, a shared physical explanation becomes more plausible. Neither pattern proves a cause by itself.

Put the reading on the right timeline

A good report distinguishes “the reported voltage fell” from “the battery failed.” The first states the observation. The second is a causal diagnosis that may require additional evidence. ESA’s telemetry-analysis tools support comparisons of measurements, event records and command history because those relationships help investigators test explanations.

For a classroom exercise, a display at 12:00 shows a packet measured at 11:52. The reading is eight minutes old before considering any later processing delay. State that age explicitly. Treating the receipt time as the measurement time could put an event in the wrong place in the spacecraft’s history.