The general policy of the XMM-Newton Observatory is to avoid repeating the same observation, i.e. to avoid duplications.
In general, a duplication is determined by consideration
of the target coordinates and of the main observing parameters
(especially the instrument(s) and the observing modes).
A proposed observation duplicates another one if the expected science
data are essentially the same or of lower quality (e.g. lower
exposure time). It is, for
example, allowed to observe the same target with the same
instrument configuration several times for variability studies.
On the other hand, observations of hard X-ray sources with EPIC using different
filters only (which mainly affects the soft energy
response) may be classified as a duplication.
The responsibility for defining and resolving cases of
duplication rests with the OTAC in consultation with the
Project Scientist as needed.
Within a single observing cycle, duplications are forbidden.
The OTAC can allow duplications between a proposed observation
and an observation of a previous cycle.
These should be restricted to proposals which provide
convincing evidence that additional data are of
scientific relevance and that the scientific case
cannot be fulfilled with the existing data.
All observations which are not considered as being successfully
observed, as well as the calibration observations already
foreseen at the time of the announcement are made public
for each Announcement of Opportunity.
Proposals in response to this call are
not permitted to duplicate these observations.
Proposers are requested to check for duplications of their
preferred targets against already performed or planned
observations, using the XMM-Newton Observation Lokator tool.
This tool includes all types of XMM-Newton observations
like guaranteed, open, TOO and routine calibration.