As it was mentioned at various times, the amount of data one would ideally like the GAIA satellite to transmit to the ground is far larger than the available telemetry rate. Any observing proposal must therefore provide an estimate of the necessary effort in terms of telemetry rate which is implied by the suggested observations. Generally speaking, we would like to observe galaxies in all sky areas that trigger the detection and from a suitable surrounding area, and to send the corresponding data to the ground. Galaxy Data Transmission. The solid squares indicate the sky areas where an excess surface brightness has been detected, while the dashed line delimits the sky area from which galaxy data are trasmitted to the ground.
Right arrows indicate the satellite scan direction.
The GAIA Astro Airy Disk is also shown to illustrate the high resolution achievable in galaxy observations. The outlined observation strategy appears to satisfactorily cover the galaxy regions whose surface brightness is just below the detection limit, thus allowing to study the galaxy morphology in greater detail. In the following, however, in order to estimate the telemetry rate required for galaxy observations, a few simplifying assumptions will be made. The overall sky area within a radius for all galaxies brighter than could then be used as a rough estimate of the overall sky area from which data should be transmitted to the ground in order to observe all galaxies down to this magnitude. Fraction of sky within a radius for all galaxies brighter than for some values of and .