Starting with AO3, VSOP Announcements of Opportunity will occur three times per year, coordinated with the calls for proposals by the ground VLBI networks. HALCA's orbital elements precess with periods of the order of a year, so AO3 proposals are particularly encouraged for sources in those regions of sky allowing good (u,v) coverage during the first half of 2000. All-sky (u,v) coverages are available from the the VSOP World Wide Web site as images and as a text version; as a result proposers no longer have the option of including one page of (u,v) coverages per source in addition to the scientific and technical justification with their proposals (see section 4.3 of the AO). HALCA will experience a series of long eclipses during apogee passes between 13 April and 7 May 2000 and little, if any, observing will be possible during this time. Proposals will be scheduled for up to a year after they are accepted. If an observation is not scheduled within this time a new proposal will need to be submitted in response to a later Announcement of Opportunity.
From AO3, proposers will be expected to take responsibility for preparing the schedule files for the ground radio telescopes assigned by the VSOP Science Operations Group for their observation. Proposers with little experience in preparing these schedule files may request assistance or consultation from the VSOP Science Operations Group on the proposal cover sheets. Finally, starting with AO3, the scientific justification may be submitted either by e-mail in postscript form or by surface mail (see section 4.3.2 of the AO).