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Absolute Photometric Calibration of the Infrared Camera (IRC) aboard AKARI
The absolute photometric calibration of imaging observations with theInfrared Camera (IRC) aboard the AKARI satellite was performed bymonitoring the same stars regularly and by observing aset of standardstars. By our monitoring observations, we confirmed that all channels ofthe IRC were stable to within 4% and that their sensitivities wereconstant until the liquid helium was exhausted. Using the data of theserepeated observations, we evaluated the intrinsic errors as afunction ofthe brightnesses of objects and found that the errors increase rapidlytoward fainter objects. We also checked the consistency between shortand long exposure times, and confirmed that the data sampling had beenexecuted as designed. Finally, by comparing the estimated in-band fluxdensities and the observed data values of standard stars, we obtainedconversion factors to the absolute flux densities of all theband/exposure configurations. Their absolute uncertainties are estimatedto be less than 6%.
| Near-Infrared and Mid-Infrared Spectroscopy with the Infrared Camera (IRC) for AKARI
The Infrared Camera (IRC) is one of the two instruments on board theAKARI satellite. In addition to deep imaging from 1.8 to 26.5 ×
| Absolute Calibration of the Infrared Array Camera on the Spitzer Space Telescope
The Infrared Array Camera (IRAC) on the Spitzer Space Telescope isabsolutely calibrated by comparing photometry of a set of A stars nearthe north ecliptic pole to predictions based on ground-basedobservations and a stellar atmosphere model. The brightness of pointsources is calibrated to an accuracy of 3%, relative to models forA-star stellar atmospheres, for observations performed and analyzed inthe same manner as for the calibration stars. This includes correctionsfor the location of the star in the array and the location of thecentroid within the peak pixel. Long-term stability of the IRACphotometry was measured by monitoring the brightness of A dwarfs and Kgiants (near the north ecliptic pole) observed several times per month;the photometry is stable to 1.5% (rms) over a year.Intermediate-timescale stability of the IRAC photometry was measured bymonitoring at least one secondary calibrator (near the ecliptic plane)every 12 hr while IRAC was in nominal operations; the intermediate-termphotometry is stable, with a 1% dispersion (rms). One of the secondarycalibrators was found to have significantly time-variable (5%)mid-infrared emission, with a period (7.4 days) matching the opticallight curve; it is possibly a Cepheid variable.
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