AKARI, the first Japanese satellite dedicated to infrared astronomy, was launched on 2006 February 21, and started observations in May of the same year. AKARI has a 68.5 cm cooled telescope, together with two focal-plane instruments, which survey the sky in six wavelength bands from mid–to far-infrared. The instruments also have a capability for imaging and spectroscopy in the wavelength range 2-180$\mu$m in the pointed observation mode, occasionally inserted into a continuous survey operation. The in-orbit cryogen lifetime is expected to be one and a half years. The All-Sky Survey will cover more than 90% of the whole sky with a higher spatial resolution and a wider wavelength coverage than that of the previous IRAS all-sky survey. Point-source catalogues of the All-Sky Survey will be released to the astronomical community. Pointed observations will be used for deep surveys of selected sky areas and systematic observations of important astronomical targets. These will become an additional future heritage of this mission.

The Far-Infrared Surveyor (FIS) is one of two focal plane instruments on the AKARI satellite. FIS has four photometric bands at 65, 90, 140, and 160 µm, and uses two kinds of array detectors. The FIS arrays and optics are designed to sweep the sky with high spatial resolution and redundancy. The actual scan width is more than eight arcmin, and the pixel pitch is matches the diffraction limit of the telescope. Derived point spread functions (PSFs) from observations of asteroids are similar to the optical model. Significant excesses, however, are clearly seen around tails of the PSFs, whose contributions are about 30% of the total power. All FIS functions are operating well in orbit, and its performance meets the laboratory characterizations, except for the two longer wavelength bands, which are not performing as well as characterized. Furthermore, the FIS has a spectroscopic capability using a Fourier transform spectrometer (FTS). Because the FTS takes advantage of the optics and detectors of the photometer, it can simultaneously make a spectral map. This paper summarizes the in-flight technical and operational performance of the FIS.

Context. The edge-on starburst galaxy M 82 exhibits complicated distributions of gaseous materials in its halo, which include ionized superwinds driven by nuclear starbursts, neutral materials entrained by the superwinds, and large-scale neutral streamers probably caused by a past tidal interaction with M 81. Aims. We investigate detailed distributions of dust grains and polycyclic aromatic hydrocarbons (PAHs) around M 82 to understand their interplay with the gaseous components. Methods. We performed mid-(MIR) and far-infrared (FIR) observations of M 82 with the infrared camera (IRC) and far-infrared surveyor (FIS) onboard AKARI. Results. We obtained new MIR and FIR images of M 82, which reveal both faint extended emission in the halo and very bright emission in the center with signal dynamic ranges as broad as five orders of magnitude for the MIR and three for FIR, respectively. We detected MIR and FIR emission in the regions far away from the disk of the galaxy, reflecting the dust and PAHs in the halo of M 82. Conclusions. We find that the dust and PAHs are contained in both ionized and neutral gas components, implying that they have been expelled into the halo of M 82 by both starbursts and galaxy interaction. In particular, we obtain a tight correlation between the PAH and Hα emission, which provides evidence that the PAHs are well mixed in the ionized superwind gas and flowing out from the disk.