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What is the distinction (if any) between spacecraft data and spacecraft telemetry? Do these terms tend to represent different kinds of information?

While each case is different, in what ways do they tend to impact spacecraft resources (e.g. memory, power, bandwidth, weight) differently?

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    $\begingroup$ This is far too broad. Every spacecraft have different navigational telemetry, implementation, specification, ... Please tie it down to a single space craft model. $\endgroup$ – Antzi Jan 26 '17 at 5:09
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    $\begingroup$ I believe this should be reopened and answered in the most broad definition: What IS telemetry (dictionary definition), plus some basic examples - an example minimal case (Sputnik's beep-beep-beep), vs most obscure parameters from advanced probes. $\endgroup$ – SF. Jan 26 '17 at 9:40
  • $\begingroup$ Does video count as telemetry or not? I hope this is re-opened so we can find out - enquiring minds want to know! $\endgroup$ – uhoh Jan 26 '17 at 11:32
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    $\begingroup$ As it stands the question is far too broad. If you narrowed down the question to be about a definition of the term "telemetry" (so only the first part of the question "What is telemetry") and what it encompasses, then it might be answerable. $\endgroup$ – Polygnome Jan 26 '17 at 23:11
  • $\begingroup$ The first part of the question "What is the disctinction..." is a sensible question with a clear answer, as provided by Hobbes, the second part "...in what ways do they tend to impact resources" is the open ended bit. $\endgroup$ – Puffin Jan 28 '17 at 12:48
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Telemetry is a subset of data.

  • Telemetry: data related to the status of the spacecraft itself. Fuel level, temperature, engine speed, position information etc. This data is needed for the operation of the satellite.
  • In addition to telemetry, the spacecraft's payload generates data. This is data that is useful for people other than the operator of the spacecraft.
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I agree with Hobbes about TM being a subset of data, but from my experience I would define it differently:

  • Spacecraft data: just all data that is inside the spacecraft at some time, no matter whether it is stored, transmitted or a transitional state information.

  • Telemetry: data that is transmitted on a monitoring & control link in the "monitoring" direction. That could be from spacecraft to the ground operator or from a device inside the spacecraft to a central data processing unit inside the spacecraft.

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    $\begingroup$ This is just an opinion, albeit a perfectly reasonable one. An answer here should really be objective and supported by calculation or references. So in this case, for instance, a reference to a technical dictionary or information from NASA or elsewhere would be appropriate. $\endgroup$ – Steve Linton Apr 17 '18 at 14:33
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To answer one aspect of one the several questions, the telemetry data rate deemed necessary to establish and maintain spacecraft health drives the emergency data communication link. This is usually on low-gain antennas that require little to no pointing of the antennas, in case the spacecraft goes into a safe mode where the primary objective is to get the solar panels pointed at or close to the Sun.

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  • $\begingroup$ I'd add that the antenna type used for the telemetry depends on the type of mission. In my experience, a GEO bird usually has the telemetry sent out of a medium gain antenna, with the omnidirectional being the backup antenna (usually two hemispherical antennas actually). $\endgroup$ – ChrisR Apr 18 '18 at 4:15
  • $\begingroup$ So it sounds like the link needs to be designed to support the omni, being the lowest gain antenna that would be used for emergency communications. $\endgroup$ – Mark Adler Apr 18 '18 at 16:01

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