XMM-Newton is operated in a pre-planned manner, i.e. observers are not present at the SOC during the execution of their observations. Thus, all observations must be specified in full detail in advance by the proposers.
Proposers for ``Open Time'' are not allowed to duplicate any of the planned observations and should carefully justify duplications with performed observations (see section 5.9.1 for the exact definition and further discussion of duplication issues). Proposers for ``Open Time'' observations should avoid the violation of data rights of planned or performed observations (see section 5.9.2 for the exact definition and further discussion of this issue). Checks for duplications and violation of data rights will be performed by the SOC during the processing of the proposals prior to the Scientific Review.