A method of weather observations by a constellation comprises at least a first cluster of three micro-satellites each orbiting around earth, and each micro-satellites comprises a spectrometer. Orbiting the three micro-satellites of the first duster around the earth in three separate orbits offset with respect to one another. Staggering the three micro-satellites with respect to one another as they orbit. Selecting the offset and the staggering, of each of the three micro-satellites with respect to one another, so that each one of the three micro-satellites have a substantially identical viewing area as each one of the three micro-satellites orbits around the earth. Sequentially collecting observations, from each of the three micro-satellites, as the micro-satellites orbit around the earth and observe substantially identical viewing areas, to separately gather atmospheric measurements and provide critical data for weather forecasting by infrared temperature and humidity soundings and motion vector winds of the earth.