The planning and scheduling of XMM-Newton observations is a work-intensive and complex process. The goal of this process is to maximize simultaneously the scientific return and the observation efficiency.
The planning and scheduling has to take into account the visibility of
the targets, scientific constraints, times with expected high
radiation background, handover between ground-stations and
feasibility of slews.
Observations with XMM-Newton must comply with a number of celestial
constraints, such as
solar,
Earth limb,
Moon
or Jupiter avoidance angles.
Examples of additional scientific constraints are
specific spacecraft position angles, ``Fixed-Time'' observations, ``Triggered Observations'',
or requests for simultaneous observations.
Depending on the solar activity, a part of the science window at the
start and at the end of an XMM-Newton orbit can be affected by a high
radiation background, which forbids opening of the filters of the
EPIC camera.
During the handovers between the different ground-stations
used in each XMM-Newton revolution, observations can be continued but
commanding is not possible and slewing has some restrictions.
Even if a target is well visible according to the visibility
constraints, it may not be reachable from the perigee
position at
the start of a revolution, because the slew would violate
some of the constraints mentioned above.
Other targets may not be scheduled because the slew back to
the perigee position is forbidden.
Whenever possible, the priority of an observation as allocated
by the OTAC is considered for the mission planning and scheduling.
However, for operational reasons, no guarantees can be given that
any particular observation will, in fact, be executed, regardless
of its grade.
The SOC prepares the final detailed timeline about 3-4 weeks
in advance.
Given the various constraints, listed above,
the mission planning and scheduling team can not avoid that
some observations are split in multiple parts.
Additionally, the actual performance of the instruments and the
corresponding observing modes are taken into account,
i.e. requested observing modes may be replaced by a
similar but better one based on the performance reports from the
instrument teams.
The PIs are automatically informed via e-mail when their
observation is scheduled.
It is the responsibility of the PI to check carefully
the scheduling details within three days and report about any observation
which is not in agreement with the enhancement or the rules and
procedures in force.
After three working days, the SOC assumes that the PI
agrees with the implementation of the observation.
It is the PI's responsibility to communicate the SOC any
change of her/his e-mail address, by e-mail to xmmpi@sciops.esa.int
with the proposal number in the subject line.