temperature and pressure monitoring

Temperature monitoring

The temperature of the whole instrument is monitored continuously during the observations and displayed in the status server. Up to six temperature sensors are installed within the instrument, two within the Cassegrain unit (one in the calibration box and one in the polarimeter, with an accuracy of about 0.1deg), and four within the spectrograph inner enclosure (one at the bottom of the transfer collimator, one at the top of the transfer collimator, one on the spectrograph camera and a last one close to the ccd dewar, the three first being accurate at a level of about 0.01deg and the last one at a level of about 0.2deg).

The observer can also visualise this information on a specific window (see example on the left) indicating the temperature from each sensor (first four lines for the spectrograph sensors and last two lines for the Cassegrain unit sensors) as well as the average value and the rms deviation over the last 50 measurements (all information being updated every second whenever the window is active).

With this, the observer can follow in particular temperature drifts within the spectrograph, evaluate the consequences on the spectrograph stability and work out the impact on the data being collected (see thermal response and spectral stability of ESPaDOnS).

Pressure and hygrometry monitoring

The relative atmospheric pressure and hygrometric level within the inner spectrograph enclosure are also monitored during the observations, and displayed in the status server and in the sensors window (see above image, line 6 and 5). In particular, the pressure (measured at an accuracy of about 0.01mbar) is the second most important factor on the spectrograph stability and can thus be used in conjunction with the temperature to evaluate the impact on the data being collected.

© Jean-François Donati, last update May 18 2004