PLATO has a flexible observing approach. Two observing strategies are reflected in the science requirements, long-duration observation of the same field versus shorter coverage of shorter different fields, or step-and-stare. These strategies complement each other and allow for a wide range of different science cases to be addressed. Long-duration pointings would be devoted to surveys for small planets out to the Habitable Zone of solar-like stars. Short pointings would be devoted to shorter-period planet detections and will address a number of different science cases such as galactic exploration.
In its nominal science operations, PLATO’s current baseline observation scenario assumes a Long-duration Observation Phase (LOP) consisting of continuous observations of two sky fields, lasting 2 years each. An alternative scenario would consist of a LOP of three years and a step-and-stare phase (SOP) of one year. The current mission design constraints impose the centre of the LOP fields to be at least above 63 degrees or below -63 degrees in ecliptic latitude. The LOP fields preliminary selected are shown as blue areas in the drawings.
Schematic comparison of observing approaches. Red area: the Kepler target field. Large areas: size of the PLATO field. A combination of short (orange) and long (blue) duration pointings is able to cover a very large part of the sky. Note that the final locations of long duration and step-and-stare fields will be defined two years before launch and are drawn here for illustration only
Although the nominal science operation duration is four years, the satellite will be built and verified for an in-orbit lifetime of 6.5 years, accommodating consumables for 8 years. Consequently, four years of mission operation extensions are possible conditional upon approval by the SPC, in which LOP sky fields may be re-observed or new LOP sky fields may be added. In addition, step-and-stare pointings may be carried out, lasting 2-5 months each.
In view of the exceptionally fast development of exoplanet science, this reference scenario will be investigated throughout the mission development and adapted to the needs of the community about two years before launch.
References
PLATO – Revealing habitable worlds around solar-like stars
Definition Study Report, ESA-SCI(2017)1, April 2017
platomission.com 
