There are many methods that could be used to perform a time series analysis.  It would be best to go to the literature to see which methods have performed well in the past.  If you are comparing imagery from different times, the data should be normalized.  You could calibrate the data to reflectance using either ENVI's Landsat calibration tool to get at-sensor reflectance, or calibrate to radiance and then perform an atmospheric correction using something like FLAASH, Empirical Line calibration, Dark Subtraction or some sort of method to account for atmospheric conditions.

Hello everyone I'm using time series data from Meris Terrestial Chlorophyl Index (MTCI) and i have 2 questions to ask: 1)First of all is there any way to get something like a summary MTCI profile for all the days that you have available data in order to evaluate changes in MTCI during this period, or you have to study each profile, for each day individualy, in ENVI? 2) is there any way in ENVI to fill gaps with missing information in order to remove to remove the 'no data' areas? Thank you for your time Stathis

Hello everyone I'm using time series data from Meris Terrestial Chlorophyl Index (MTCI) and i have 2 questions to ask: 1)First of all is there any way to get something like a summary MTCI profile for all the days that you have available data in order to evaluate changes in MTCI during this period, or you have to study each profile, for each day individualy, in ENVI? 2) is there any way in ENVI to fill gaps with missing information in order to remove to remove the 'no data' areas? Thank you for your time Stathis

As for my first question i meant all days and all pixells Stathis