If a science project requires observations with both Chandra, sponsored by the U.S. National Aeronautics and Space Administration, and the XMM-Newton Observatory, then a single proposal may be submitted to request time on both observatories to the XMM-Newton Announcement of Opportunity, so that it is unnecessary to submit proposals to two separate reviews.
By agreement with the Chandra Project, the XMM-Newton Project may award up to 400 ks of Chandra observing time. Similarly, the Chandra Project may award up to 400 ks 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 in justifying both the scientific and technical reasons for requesting observing time on both missions. It is not essential that the project require simultaneous XMM-Newton and Chandra observations. No Targets of Opportunity, either pre-planned or unanticipated, will be considered for this cooperative programme. For this solicitation, no Chandra time will be allocated without the need for XMM-Newton time on the same target to complete the proposed investigation.
Establishing technical feasibility is the responsibility of the PI, who should review the XMM-Newton and Chandra documentation (http://cxc.harvard.edu/proposer/ POG) or consult with the Chandra Guest Observer Facility (http://cxc.harvard.edu /helpdesk). 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. Simultaneous longe duration observations with XMM-Newton may violate restrictions at some Chandra satellite pitch angles, which can be evaluated using Chandra PRoVis http://cxc.harvard.edu/cgi-bin/provis/provis_load.cgi. Any observation(s) deemed to be not performable as indicated above would cause revocation of observations on both facilities.
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 Chandra instrument modes and scheduling constraints.