A Generalized Approach to the Calibration of Cassini CIRS Observations of the Saturnian System
Abstract
The Composite Infrared Spectrometer (CIRS) on Cassini has been measuring thermal radiation of the Saturnian system over the past four years. The ability to successfully exploit the data is highly dependent on the quality of the calibration, which should effectively take account of sampling errors, phase errors and thermal uncertainty.
We mine the database to collect data that match the instrument states and build reference averaged interferograms that will be used for calibration. The large number of measurements available allows the state distributions of the reference dataset to be well fitted with the input data through principal component analysis. To ensure the quality of the data produced, we have developed algorithms that detect and attempt to correct sampling and phase errors by analyzing the imaginary part of the data at all stages. A final check is performed by comparing the data to synthetic spectra. This study led us to refine our knowledge of the instrument, to establish the different origins of the noise in the resulting spectra and thus improve the quality of the calibrated data in terms of random noise, systematic error and wavelength calibration accuracy. Such improvements will be illustrated by comparing our previous localized approach to this new approach using observations of Titan. Our improvements have important benefits to the scientific results, including improved detectability of trace compounds and improved measurement accuracy for atmospheric composition and temperature.- Publication:
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AAS/Division for Planetary Sciences Meeting Abstracts #41
- Pub Date:
- September 2009
- Bibcode:
- 2009DPS....41.3601G