Telemetry, from the Greek tele (far) and metron (measure), is the collection of data using automated sensors that transmit their results to a central monitoring point. A telemetric sensor may be stationary (e.g., fixed on the sea floor) or aboard a mobile platform (e.g., airplane, spacecraft, missile, submarine). The quantities sensed are usually simple variables that can be reported at regular intervals, such as temperature, pressure, humidity, altitude, fuel level, battery voltage, salinity, vibrational intensity, alarm status, or the like. Complex, high-speed signals such as video are usually not termed telemetry, even when they are collected remotely by unattended devices.
The raw output of a remote sensor is often an analog signal, that is, a voltage or current that varies smoothly with time. Before transmission, such a signal is usually converted to digital form by the process of analog-to-digital conversion or sampling. In sampling, an analog signal is examined at evenly-spaced moments and a binary number assigned to its magnitude; the larger the sensor output, the larger the binary number. The raw bitstream produced by sampling is organized by the telemetry device into standard-length frames containing added information specifying data type, time of acquisition, and so forth. If the transmission channel is noisy, the signal may also be subjected to error-correction coding to allow recovery of data from errors. The signal may also, in some military applications, be encrypted before transmission. The final telemetry signal is sent from the data-collection point using radio, sonar, coaxial cable, or some other medium to a receiving station, where it is recorded and monitored by computers or human operators.
Telemetry is employed for many purposes throughout the commercial, scientific, and military sectors. For example, controllers of missiles, torpedoes, spacecraft, or remotely piloted aircraft such as the Predator require access to numerical information of many sorts in order to monitor and adjust the performance of these complex machines. Telemetric data may also be used for surveillance purposes, as when deep-sea acoustic sensors are used to track submarine movements, and is essential to the control of spacecraft, whether crewed or robotic.
█ FURTHER READING:
Wilson, Elizabeth. Introduction to AMMOS Telemetry Processing. Jet Propulsion Laboratory, NASA. October 18, 2001. <http://tel.jpl.nasa.gov/~betsy/mm/intro.htm> (Nov. 14, 2002).
Codes and Ciphers
"Telemetry." Encyclopedia of Espionage, Intelligence, and Security. . Encyclopedia.com. (March 20, 2018). http://www.encyclopedia.com/politics/encyclopedias-almanacs-transcripts-and-maps/telemetry
"Telemetry." Encyclopedia of Espionage, Intelligence, and Security. . Retrieved March 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/politics/encyclopedias-almanacs-transcripts-and-maps/telemetry
Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).
Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.
Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:
Modern Language Association
The Chicago Manual of Style
American Psychological Association
- Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
- In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.