Short answers, pulled from the story.
The Soviet Union launched Sputnik 1 on the 4th of October 1957. This small metal sphere sent back radio signals that scientists used to study the ionosphere and marked the first occurrence of satellite remote sensing in human history.
NASA launched TIROS-1 on the 1st of April 1960. This spacecraft sent back the first television footage of weather patterns taken from space showing clouds and cloud systems moving across the globe.
Satellites such as ERS-1, ERS-2, and Envisat operated at altitudes of about 800 kilometers above the atmosphere. The Proba-1 and SMOS spacecraft observed Earth from an altitude of roughly 700 kilometers while DubaiSat-1 and DubaiSat-2 also placed themselves in Low Earth orbits.
A geostationary orbit sits much higher at approximately 36,000 kilometers where the orbital period equals 24 hours. It allows a satellite to hover over a constant spot since three such satellites spaced 120 degrees apart can cover the whole Earth.
The 2002 oil spill off the northwest coast of Spain was watched carefully by European ENVISAT. This spacecraft flew an instrument called ASAR which could see changes in the sea surface despite not being a dedicated weather satellite.