Deviations from Observing Schedule

A deviation from the schedule and its execution as described in the previous section becomes necessary if:

• the spacecraft shows anomalies,
• the safety of any of the instrument is endangered
• there is an unforeseen astronomical event, such as a nova or supernova in an area of the sky which is accessible from ISO at the time this event occurs; this is called a Target of Opportunity - ToO.

In either case the schedule will be halted or abandoned and commanding will be switched to `manual' mode. In the case of a Target of Opportunity (see Section 12.4) an appropriate pre-defined command sequences will be submitted for uplink by the SOC staff. A revised observing schedule, which takes into account the appearance of a ToO, may then be generated. This requires a lead time of at least three revolutions.