The format of the Astro-D attitude file (AF) will be designed in 1992 by ISAS and NEC (Nippon Electric Co.). The AF will contain, in a time series of 130-byte records: the attitude of the satellite (expressed as a four-vector comprising the RA and dec of two principal axes of the satellite, one being the telescope pointing direction), the estimated error of the attitude solution, and a parameter to show what information was used to calculate the attitude (star-tracker or gyro, for example).