Transition Times

Transition Times are applied to Sensor Modes, and represent time gaps that must be respected between mode activations.

Check Slew: for agile sensors and for sensors capable of right / left slewing (e.g. Cosmo Skymed) it checks that the transition times are compatible with a slew operation and with the maximum slew rate allowed for the satellite, according to the satellite's attitude object.

If the satellite is Agile (see Satellite properties) mode activations require satellite slewing from one mode to another. The slewing requires a time lag which is dependent on the slew angle and the maximum slew rate. The lower priority swath (or the later swath in case of equal priorities) will be clipped to ensure that the maximum slew rate is respected.
If the satellites performs left / right slewing (e.g. Cosmo Skymed) the slewing time lag will be calculated for the angle distance between left and right slewing. Note that for this feature to work you need to link Left and Right modes with the same non-empty Grouping tag.

The Entry Transition Time represents a time gap before Sensor Mode switch ON.

The Exit Transition Time is the time gap after Sensor Mode Switch OFF.

The Max Gap is a maximum margin or freewheel allowed between consecutive data takes of the same instrument mode before applying transition times. The rationale is that if the instrument is not operating for a brief period of time it will still remain switched on, sparing mode transitions.

The Grouping is a text string that identifies a transition times group within the same satellite. Sensors of the same group will apply transition time constraints in a combined way

If two swaths of the same sensor are too close together, breaching transition times, one swath will be trimmed following a priority criteria. In the case of same priorities then the earlier swath will be scheduled, and the later trimmed.

E.g. when planning MODE1 and MODE2 in sequence the minimum time gap equals MODE1.Exit + MODE2.Entry.

No Constraints

Transition Times ON

Entry = 15 sec, Exit = 15 sec

REMARK: Transition Times are better managed with a Transition Times matrix because transitions are often dependent of the mode source and mode destination (see e.g. agile satellites). The transition matrix allows to define minimum transition times to be respected between acquisitions of different sensors within the same satellite. The acquisitions will be shortened as needed to comply with the transition time.

The matrix can be edited by right click menu in the satellite scenario, or in the satellite's constraint properties pane. The user may save and load the matrix to and from Excel or CSV file.