SUGGESTIONS ON PROPOSING FOR VSOP AO4 OBSERVATIONS

ARCHIVAL VSOP OBSERVATIONS: Many sources have already been observed with HALCA (or are scheduled for the near future). Please look at the archival list of observations before submitting a proposal. If a source has already been observed, then strong justification for additional time should be included in the proposal. Results from previous HALCA observations will be important in the justification of additional epochs.

MULTI-EPOCH OBSERVATIONS: Periodic HALCA observations have severe constraints. Except for sources near the poles, a source can be observed just two times a year, separated about six months. Each window is open for only about three weeks, and the u-v coverage for the two observing windows are generally very different. Observations of Intra-Day Variable sources, over a period of a few weeks, can be done very well even with the present HALCA constaints of difficult maneuvering between sources.

COORDINATED HALCA and GROUND OBSERVATIONS: Your proposal may be associated with concurrent ground VLBI proposals. For example, you may be proposing for ground VLBI observations at 15 GHz to complement VSOP observations at 5 GHz. Please indicate such connections clearly in your proposal since refereeing of these ground and HALCA proposals should be made in a coordinated way. All such complementary ground-only observations must be proposed independently to the appropriate ground array, even if it is intimately related to a HALCA proposal. As an example, if you propose for a source at 5 GHz using HALCA, but also wish to observe at 15 GHz with a ground array (even during the HALCA observation period), a separate proposal must be submitted to that ground array.

`NON-STANDARD' OBSERVATIONS: Although we anticipate that most proposals will be for continuum observations of active galaxies, proposals for the OH line (all four lines), pulsars and the brighter radio stellar objects are invited. Recent test phase-referencing observations, where the calibrator is within the HALCA beam (10' at 4.9 GHz; 30' at 1.6 GHz), have been relatively successful and such proposals will be entertained. Please send questions to pge@vsop.isas.ac.jp and to efomalon@nrao.edu about this technique.

GROUND RESOURCES: The specification of the ground resources for your experiment is not necessary, but can be included especially for non-standard experiments. It is important to specify the need for big ground telescopes if the correlated flux density with the HALCA observations is expected to be less than (or measured in previous experiments) about 0.1 Jy, or if the science goals of the observation require the additional sensitivity. The available time on these large telescopes is limited and must be used judiciously.

LINEAR-POLARIZATION EXPERIMENTS: Linearly Polarized images have been made with HALCA data and such proposals can be submitted. However, the tape consumption is twice that of normal HALCA experiments, so that the observing time for polarization experiments are limited. Since the VLBA, VLA, ATNF and Effelsberg are generally allocated for these experiments, they must have high priority for scheduling. Reduced bandwidth for strong sources would aid in their scheduling, although most polarization experiments are signal to noise limited.

U-V PLOTS AND WHEN TO OBSERVE: Inclusion of (u-v) coverage plots are not needed for your VSOP proposal. The observations will be scheduled with the best (u-v) (generally highest resolution with reasonable two-dimensional coverage), consistent with the scientific rating and the allotment of resources. However, recommendations of specific observing times, (u-v) coverages, and ground resources will be used if possible. The proposer should give some consideration of the changing (u-v) coverage and source observation availability when asking for source monitoring observations, and coordinating with other ground observations or with x-ray observations. Please use the u-v tables and explanations given elsewhere.

WHEN TO SUBMIT A PROPOSAL: Although the intention is to call for VSOP proposals every four months, in concert with many ground telescopes, the possible loss of observing time in the future may preclude a call for proposals on Feburary 1, 2001 or June 1, 2001. For that reason we suggest that you submit a proposal for sources even though they may not be observable with good u-v coverage until late 2001. It is possible that the constraints associated with the viewing area of sky or the slewing between sources may change; in which case the mission can be scheduled much more efficiently if the proposal queue is full.