The electron temperature T e as the often most essential parameter forapplications of low pressures plasma has been derived from comparative in situmeasurements with a single and a double electrostatic probe, and with optical emissionspectroscopy OES and energy dispersive mass spectrometry EDMS as remote techniques.Electrodeless rf discharges maintained by electron cyclotron wave resonance ECWR in pure Arand N2 in the pressure regime from 10−2 to 1 Pa have been used as sample plasmas.The evaluation of the OES- and EDMS-signals is described in detail. The pressure dependenceof the T e-results derived therefrom is found to compare well with the data from theprobe measurements, and with calculations from a charge carrier balance equation. Bymatching the OES data to the absolute T e-values from the probe measurements, numerical expressions have been obtained by which T e can be quantitativelycalculated from the intensity ratios between selected emission lines from the Ar- and theN2-plasma. Furthermore, the EDMS-results are also shown to deliver quantitativeinformation about T e.