Time will be allocated within the standard observing schedule for targets which cannot be pre-scheduled due to their intrinsically variable nature. These are targets such as AGN in outbursts which are to be monitored (utilizing a single telescope in the B2 mode of operation), gamma-ray bursts, and discretionary targets such as flaring Galactic black hole candidates or transient X-ray binary targets. Of course, as with all observatories, a certain amount of engineering time will be required. Experience has shown that a 10% allotment is usually sufficient once stable operation has been achieved.