Mid‐Infrared All‐Sky Survey with the Infrared Camera (IRC) on Board the ASTRO‐F Satellite

An all-sky survey in two mid-infrared bands which cover wavelengths of 5-12um and 12-26μm with a spatial resolution of ~9" is planned to be performed with the Infrared Camera (IRC) on board the ASTRO-F infrared astronomical satellite. The expected detection limits for point sources are few tens mJy. The all-sky survey will provide the data with sensitivities more than one order of magnitude deeper and with spatial resolutions an order of magnitude higher than the Infrared Astronomical Satellite (IRAS) survey. The IRC is optimally designed for deep imaging in pointing observations. It employs 256x256 Si:As IBC infrared focal plane arrays (FPA) for the two mid-infrared channels. In order to make observations with the IRC during the survey mode of the ASTRO-F, a new operation method for the arrays has been developed - the scan mode operation. In the scan mode, only 256 pixels in a single row aligned in the cross-scan direction on the array are used as the scan detector and sampled every 44ms. Special cares have been made to stabilize the temperature of the array in the scan mode, which enables to achieve a low readout noise compatible with the imaging mode (~30 e-). The flux calibration method in the scan mode observation is also investigated. The performance of scan mode observations has been examined in computer simulations as well as in laboratory simulations by using the flight model camera and moving artificial point sources. In this paper we present the scan mode operation method of the array, the results of laboratory performance tests, the results of the computer simulation, and the expected performance of the IRC all-sky survey observations.