20200924 Mirror Temp Statistics Action Item for Trent

[trentjbrendel]

• Andrew has asked me to compute statistics on the mirror cell (and some) temperatures

• John Hill sent an email on June 6th, 2020 that details the thermistors on the mirror cell, etc.

• See this thread: THREAD

• [ ] Look up thermal telemetry data from Monday, Sep. 21 data collection events

• [ ] Compute something like a Chi-squared statistical model to analyze correlation of data

• [ ] Explore possible electrical correlation of all thermistors and AD950's (mirror cell + air and steel comparisons)

Also... Look into LBC image issues and FPIA

• [ ] Yang will send issue number for us to look into

[trentjbrendel]

Heejoo, Here's a brief description of LBT temperatures in Telemetry. You say "compensation of OPD fluctuations" - I hope you mean seasonal fluctuations and not local microthermal turbulence, as these measurements are all very slow compared to turbulence. Ciao, John

Here's a quick summary of the temperature measurements on the LBT that are reported in Telemetry. See link to DMS.

Primary Mirror Thermocouples

There are many (~50) thermoouples in and around each of the primary mirrors. These are engineered to be precise relative temperature measurements, but are sometimes displayed as absolute temperature measurements by summing them with one of the thermistors in the next paragraph. The relative temperature is accurate to 0.05 degC. The absolute temperature is accurate to 0.5 degC. There's a drawing in VCAN that shows the exact location of these thermocouples. Beware of individual noisy channels. Typical channel names are "faceplate->mtcf01".

system = pmc stream = thermal

Primary Mirror Thermistors

Each primary mirror has 8 thermistors that are used for things that need an absolute temperature scale. Names are like "thermistor->mtm1" and the descriptions tell you something about the location. Telemetry includes average glass temperatures and average air temperatures on each side derived from these sensors.

system = pmc stream = thermal

Telescope Structure and Air

There are a few dozen AD590 temperature sensors mounted around the telescope structure. Mostly they come in pairs where one measures steel and the other measures adjacent air. The names are boring like "channel 201", but the description in telemetry is mostly useful like "middle C ring steel".

system = ecs telemetry stream = thermal_computer

Weather

LBT weather sensors are mounted on towers on the roof.

system = env telemetry stream = lbt_weather

Other

Other systems measure temperatures in various places, but they aren't at all useful for TMS purposes.