Calibration of the AKARI Far-Infrared Imaging Fourier Transform Spectrometer

摘要

The Far-Infrared Surveyor (FIS) onboard the AKARI satellite has aspectroscopic capability provided by a Fourier transform spectrometer(FIS-FTS). FIS-FTS is the first space-borne imaging FTS dedicated tofar-infrared astronomical observations. We describe the calibration process ofthe FIS-FTS and discuss its accuracy and reliability. The calibration is basedon the observational data of bright astronomical sources as well as twoinstrumental sources. We have compared the FIS-FTS spectra with the spectraobtained from the Long Wavelength Spectrometer (LWS) of the Infrared SpaceObservatory (ISO) having a similar spectral coverage. The present calibrationmethod accurately reproduces the spectra of several solar system objects havinga reliable spectral model. Under this condition the relative uncertainty of thecalibration of the continuum is estimated to be $\pm$ 15% for SW, $\pm$ 10% for70-85 cm^(-1) of LW, and $\pm$ 20% for 60-70 cm^(-1) of LW; and the absoluteuncertainty is estimated to be +35/-55% for SW, +35/-55% for 70-85 cm^(-1) ofLW, and +40/-60% for 60-70 cm^(-1) of LW. These values are confirmed bycomparison with theoretical models and previous observations by the ISO/LWS.