What is CRC and why is it used in telemetry?

• A. Cyclic Redundancy Check; it detects accidental changes to raw data in transmission.
• B. Critical Redundancy Code; it doubles the data for reliability.
• C. Constant Redundancy Check; it ensures constant bitrate.
• D. Cybersecurity Response Code; it encrypts data.

Answer: (A)

CRC is a Cyclic Redundancy Check, a type of checksum used to detect errors in data as it moves through a communication channel. In telemetry, sensor data travels over links that can pick up noise and interference, causing accidental changes to the raw data. The sender computes a CRC value from the data and sends it along with the message. The receiver re-computes the CRC from what was received and compares it to the transmitted value. If they match, the data is likely intact; if they don’t, the data has been corrupted and can be rejected or retried. This works well because polynomial-based CRCs can catch many common error patterns, including bursts of errors, with relatively little extra data and minimal processing. It’s not about doubling data, keeping a constant bitrate, or encrypting information—it's about reliably detecting accidental changes to ensure telemetry integrity.