XMM RPS Users' Manual

   
Filling in time constraints

For each ``Fixed'' (i.e., fixed-time) observation, a special details form must be filled in. A screen shot of this page is displayed in Fig. 11.

  

Figure 11: Screen shot of the ``Time Constraints'' page in which entries for time-constrained observations must be made.

Inputs can be made either in the ``Earliest Start Time'' and ``Latest Start Time'' input field (where absolute times are required) or in the ``Start at orbit'' and following fields (where a start orbit number and relative timing information is required). Entry of a set of numbers on this page will, after successful committal of the information to memory, lead to an update of the upper part of the main frame, in which the newly specified time details will be listed. For repetitions, there will be one line per requested observation. Either absolute or relative values can be enterted. For absolute entries, values from 2000.021.00.00.00 to 2019.359.23.59.59 are allowed. Either absolute or relative time constraints can be defined for an observation; combinations of both are not permitted. Accordingly, the form sheet returned to the user after the first entry will contain only the input fields for the appropriate type of constraint. For relative entries the allowed range of start orbits for AO-1 is 4-432.

Example: To ask for repeated observations, spaced at certain time intervals, but at no particular time, enter an earliest start time of 2000.021.00.00.00, a latest start time of 2010.001.00.00.00 and specify at which intervals (orbits or hours) and how often the observation should be repeated. Note that if intervals are chosen in units of hours, all repetitions must be within one (48-hour) orbit. If more are needed, a second set of entries must be made.

The XMM SOC will handle absolute and relative time entries into XRPS in the following way:

Observations which MUST be conducted at a fixed time

For observations which MUST be conducted at a fixed time, like e.g. an occultation experiment, absolute time entries must be entered into the proposal database via the ``Time Constraints'' page. The required format, as displayed on the formsheet, is YYYY.DDD.HH24.MI.SS (i.e., four digits for the year, three digits for the day of the observations [the number of the day in that year] and hours, minutes and seconds in the 24 hours format. The separator is a dot, not a colon. The absolute entry can be used by the SOC to check whether the target will be visible. If so, the observations, if accepted by the OTAC, will be scheduled at precisely the requested date and time. A visibility check should also already be performed by the proposer, using the XMM Target Visibility Tool, and mentioned in the proposal text.

Time-constrained observations that are not fixed to a particular date/time

For proposals to observe a source, for example, repetitively, but not necessarily at always exactly the same time interval (which might not be schedulable!), a conversion of the start orbit and related entries into absolute times constitutes an unnecessary restriction. Therefore, relative time entries are not translated by XRPS into absolute times instantaneously, but at a later stage (in the process of proposal optimisation for execution), when the exact orbital parameters are known.

Note: In the case of repeated observations, the science duration specified on the observation page applies to each observation. It is not the sum over all repeated observations (because each is, as the name suggests, handled as an individual observation).