Data Acquisition, Telemetry, and Communications
Domain focus
This domain covers how sensor signals become time-stamped, transmitted records: sampling, logging, telemetry, power, and data-path reliability.
Core rules
- Sampling and averaging are separate: a 1 Hz sample can be averaged to a 6-minute observation; record the averaging method.
- Use UTC timestamps and document the interval; local time and daylight saving cause avoidable errors.
- Telemetry options include GOES satellite Data Collection Platforms, cellular, Iridium, spread-spectrum radio, microwave, and fiber. Each has latency, bandwidth, and outage characteristics.
- One-way links (GOES) cannot request retransmission; two-way links can. Design buffering and backfill so outages do not become permanent gaps.
- Power budgets: solar panels, batteries, and charge controllers must support worst-case cloud and heat conditions; low voltage is a common root cause of garbled data.
- NTRIP is used for streaming GNSS corrections; it is not a general PORTS telemetry protocol.
Worked example
A station transmits 6-minute water level via GOES every hour. A storm knocks out cellular backup, but GOES continues. The logger must retain data and retransmit missed records when the link returns; otherwise the archive has a gap even though the sensor worked. The fix is buffer-and-backfill logic, not a new sensor.
Traps
Confusing sample rate with transmit rate; using local time; assuming satellite and cellular have the same latency; failing to monitor battery voltage; treating telemetry loss as sensor failure.