I asked Perplexity,
CPM stands for Counts Per Minute, which is a measure of the number of radiation detection events registered by a Geiger counter or similar radiation measuring instrument in one minute15. ACPM likely stands for Adjusted Counts Per Minute, though this is not explicitly stated in the search results. CPM is a raw measurement of radiation events detected by the instrument, but it does not directly indicate the strength or type of radiation5. The CPM value depends on factors such as: The type and sensitivity of the detector used6 The type of radiation being measured (alpha, beta, or gamma)1 The distance between the detector and the radiation source3 ACPM is probably an adjusted value that takes into account some of these factors to provide a more standardized or comparable measurement across different instruments or situations. However, without more context about the specific chart or instrument you're referring to, it's difficult to say exactly what adjustments are being made to calculate ACPM. It's important to note that CPM alone is not a reliable indicator of radiation dose or health risk. For that, measurements in units like microsieverts per hour (μSv/h) or millirems per hour (mR/h) are more appropriate
Disclaimer - I am not a plane expert, just posting observations I notice since opening the app every day for 4 years.
Monkey Werx is probably the guy you want to listen to. I get info from him, but I cant watch entire videos, he skips around too much for me, but does have good info.
Oops... here is the Venus plane
https://globe.adsbexchange.com/?icao=adfeb9&lat=38.375&lon=-12.730&zoom=2.8&showTrace=2024-12-16
holy shit! please warn us to turn down volume when starting the video! lol