ISO is making new and unexpected discoveries and, in many cases, ISO itself is the only facility for many years capable of follow-on investigations of these discoveries. Additionally, compelling new observations may become apparent between the time of the Call deadline and the end of ISO's in-orbit life. Thus, a small pool of ``discretionary time'' is being kept available, outside the normal ``Call-Proposal-Review'' cycle. It is emphasised that this time is only for observations that could not have been foreseen at the time of proposal submission. An average of 30 minutes of discretionary time observations per day is foreseen.
To use this discretionary time, a request must be made to the scientific head of the Observatory, the Project Scientist. Whenever possible, the Chairman of the Observing Time Allocation Committee will be consulted by the Project Scientist before any additional observations are authorised. The Project Scientist will report to the next meeting of OTAC on all discretionary time observations.
The procedure for requesting Discretionary Time may be found on the World Wide Web; the URL is
http://www.iso.vilspa.esa.es/discrete/disc_time.html