Scope and Restrictions of Open Time

ISO is operated in a pre-planned manner without any significant routine real-time interaction. Observers are not expected to be present for the conduct of their observations. Thus, all observations have to be specified in full detail by the proposers by the end of the Phase 2 data entry process. For a variety of reasons including efficiency and sky coverage constraints, observing time is distributed on a ``per observation'' basis. However, it is emphasised that --for operational reasons-- no guarantees are given that any particular observation will, in fact, be executed, regardless of its grade.

Open time proposers may apply to use any of the spacecraft and instrument modes described in the five Observer's Manuals. A summary of the available instrument observing modes (listed as Astronomical Observation Templates, AOTs) is given in Appendix D of the ISO Observers Manual. Specific points to note are:

• Polarisation observations (see also section 4.3.3 re release status) with ISOCAM and ISOPHOT are implemented in operations by a different route than that for the standard ``AOT-based'' observing modes; from the point of view of proposers, there is no difference in the procedure to enter polarisation proposals until after the end of the Phase 1 review by OTAC. A co-investigator from the SOC will be added -if not already present- to all proposals including polarisation observations, because the different route (see section 7) needs expert assistance within the SOC.
• The Parallel modes of ISOCAM and LWS and the Serendipity mode of ISOPHOT are not available to proposers. The data from these modes need to be taken and reduced in a systematic and complete manner. This will be done by the respective instrument consortia and the SOC, with the data being published after the mission. Some preliminary serendipity mode data may be published during the mission; in this case, applications will be considered for discretionary time to follow-up these results.

Observations in the Guaranteed Time programme (priorities 1, 2 and 3) and in successful Open Time proposals from the pre-launch Call (all of priorities 1 and 2 and some special cases from priority 3) are reserved. Proposers for the Supplemental Call not allowed to duplicate any of these. Checks for duplications will be made during the processing of proposals. See section 4.3.2 for further discussion of duplication issues.