If a science project requires observations with both NuSTAR and XMM-Newton, then a proposal may be submitted to request time on both observatories.
By agreement with the NuSTAR Project, the XMM-Newton Project may award up to 1.5 Ms of NuSTAR observing time. Similarly, the NuSTAR Project may award up to 1.5 Ms of XMM-Newton time. The time will be awarded only for highly ranked proposals that require use of both observatories and shall not apply to usage of archival data. The only criterion above and beyond the usual review criteria is that both sets of data are required to meet the primary science goals. Proposers should take special care to justify both the scientific and technical reasons for requesting observing time on both missions. It is not essential that the requested NuSTAR and XMM-Newton observations be simultaneous, however clear discussion of the required level of coordination is essential for evaluating feasibility. No NuSTAR time will be allocated without the need for XMM-Newton time on the same target to be obtained within this AO cycle.
Establishing technical feasibility is the responsibility of the PI, who should review the XMM-Newton Calls for Proposals and the NuSTAR web-page. For efficiency reasons NuSTAR observations should not be shorter than 20 ks. For each target the total requested XMM-Newton observing time should be comparable (within approximately a factor two of) to the total requested NuSTAR observing time. Observations of high count rate targets with NuSTAR (50 cps/NuSTAR module) require special planning and increased downlink capacity. Such observations should be carefully justified, and should not be feasible with other less-sensitive hard X-ray observatories. High count rate (50 cps/module) observations of duration 30 ksec are difficult and can be accepted only if well-motivated. High count rate observations longer than 75 ksec cannot be accepted.
No observations with a reaction time of less than 2 working days from an unknown triggering date will be considered for this cooperative programme. It is the responsibility of the PI to inform both observatories immediately if the trigger criterion is fulfilled. For proposals that are approved, both projects will perform detailed feasibility checks. Both projects reserve the right to reject any approved observation that is in conflict with safety or mission assurance priorities or schedule constraints, or is otherwise deemed to be non-feasible.
Apart from the above, both missions' general policies and procedures currently in force for the final selection of the proposals, the allocation of observing time, the execution of the observations and the data rights remain unchanged.
Scientists can apply for the joint programme in the ``Observation Form'' of the XMM-Newton RPS. For each observation the PI has to specify the required observing time for both observatories. The ``Comment'' field should be used to briefly describe the NuSTAR instrument modes and scheduling constraints.