There are three principle goals with decreasing priority:
- Provide seasonal-long light curves of all targets in the long-duration northern PLATO field. Determine the eclipsing binaries in the field and extract a variability flag for all accessible stars on the basis of the long-term brightness rms. Aim for n ≈ 100 visits per star in one observing season with a time resolution of (at best) one day. It will enable the determination of precise photometric periods, in particular stellar rotation periods, and the expected degree of spot activity from time changes in the light curves.
- Determine the target contamination down to 2.5′′ for every PLATO pixel on the sky (its pixel size is 15′′). Aim for a magnitude difference of 5 mag in V, i.e. list contaminating targets down to V≈18mag;
- Optional, if a two-filter operation is decided: provide 1% – 5% Johnson V and I brightness and V-I colors for all stars in the PLATO FOV. Calibrate a zero point with respect to GAIA photometry. From this, determine T eff .
- Cross correlate targets with the 2MASS JH magnitudes if available and construct J vs. V plots (or J vs. “C”-filter band) and, optional, V-I vs. J-H diagrams. According to, e.g., Bilir et al. (2006a, AN 327, 72; 2006b, AN 327, 693; 2008, MNRAS 384, 1178) it shall allow a statistical separation of dwarfs from giants and a crude separation of early-type from late-type stars.