Density and metallicity gradients in the galactic halo

An extension of the observations of stars in the galactic halo beyond the observing limits of ground based telescopes is recommended for the following investigations: the determination of chemical gradients, i.e., changes of stellar metal abundances in the galactic halo as functions of the distance from the galactic plane or the galactic center. The solution of these problems involves observations in: (1) RGU three color photometry of faint halo stars down to corresponding UBV magnitudes M_V approximately 24 and M_U approximately 26; (2) multicolor (N or = 4) photometry of star fields down to a correspondance magnitude M_V approximately 25, observed in a photometric system being designed for three dimensional classification of stars of spectral types later than about K5; and (3) spectral scans of selected faint halo stars used for optimum design and calibration of the RGU and multicolor systems.