``Open Time'' proposals can be submitted as ``Guest Observer'', ``Large Programs'', ``Triggered Observations'', joint ``XMM-Newton/Chandra'' or joint ``XMM-Newton/ VLT(I)'' proposal.
The large majority of proposals will fall under the type ``Guest Observer''.
For observations where the schedule time can not be planned in advance,
the proposal type ``Triggered Observations'' has to be selected.
Proposers, who want to apply for time of the joint XMM-Newton/Chandra
or joint XMM-Newton/VLT(I) program have to choose the corresponding
type, either ``XMM-Newton/Chandra'' or``XMM-Newton/VLT(I)''.
All types of proposals are explained in detail below.