Movements down to the next lower level are always easy, because special function keys (buttons) are offered at the bottom of the higher-level page (web interface).
A PI can choose one of the proposal drafts from the list previously left in memory by clicking on the proposal title. At the next level, two buttons are offered, named ''Add Co-I'' and ''Add Observation''. The ''Add Co-I'' button is used to modify Co-I details e.g. in case of changes in their contact details. The ''Add Observation'' key leads the user to the level where information about the target of a proposed observation is entered.
One level lower, function keys are offered again to ''Add EPIC MOS'', ''Add EPIC pn'', ''Add RGS'' and ''Add OM''. These four allow the user to enter exposures for the different types of XMM-Newton science instruments. Note that there are two EPIC MOS cameras and also two RGS detectors, for each of which exposures must be defined. Below this first line, we find, ''Add Standard Exposures'' and ''Adjust Exposure Time''. The first is used to add standard exposures for all X-ray instrumnets. The later is used to adjust the exposure time of the X-ray instruments automatically based on the Total Observation Duration introduced. This is the level of input at which the schematic with the pre-planned sequence of exposures within an observation (§ 3.1) comes in handy.
In addition to the above function keys, three more are available at this level, namely ''Copy Observation'', ''Add Time Details'' and ''Delete Observation''. The names of the first and last are self-explanatory. The second, is used to enter time constraints, if any, and will only show up if the ''Observation Type'' is declared as ''Fixed''.
At the end of each exposure page one also finds the functional buttons to add exposures or to copy/delete the current one. These operations do not lead to a lower level, but create or remove entries at the same (i.e., the exposure) level.