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ASCA Guest Observer Facility

The AO1 and AO2 Program and Status

--R. Petre, GSFC

AO2 Scheduling Overview

The ASCA AO2 observing program officially began on May 15, 1994, with the implementation of a new six-month timeline. This timeline included newly-selected AO2 targets as well as held-over AO1 targets. Most of the scheduled AO1 targets were US or US/Japan priority C targets, whose priority had been raised to B to ensure that they would be scheduled. A few Japan/US and Japan targets also had their priority raised. As a consequence of the heavy time subscription from new targets and the need to schedule additional carry-over observations of underexposed AO1 targets, it was not possible to schedule any category C targets in AO2. While the AO2 observing period formally ends on November 14, 1994, we expect that the delayed deadline for AO3 proposals will result in an unofficial two-week extension of the AO2 period (with provision for AO3 time critical targets which must be observed in that interval).

New Target Category

A new aspect of the AO2 program is the inclusion of a new target category. Under an independent agreement between ISAS and ESA, scientists in ESA member states have been invited to participate in the ASCA program. Approximately 10 percent of the ASCA observing time is awarded to ESA proposals. These observations are formally executed as ESA/Japan collaborations, as the observing time originates in the 60 percent Japan-only share (and thus does not affect the fractional time awarded to US or US/Japan proposals). In the event of an overlap between an ESA/Japan target and a US or US/Japan target during the merging process, the ESA/Japan target is dropped. This procedure is unlike a US-Japan overlap, where the default is to merge the two observations.

US and US/Japan C targets

Virtually all of the priority C US and US/Japan targets were recommended by the U.S. proposal evaluation panel as priority B. A gross oversubscription of the entire program forced the Japan/US merging committee to drop virtually all targets recommended by the US review as C priority, and downgrade many of the priority B targets. Since the tight ASCA schedule precludes the possibility of many or any of the category C targets being observed, it is our plan to continue the policy implemented for AO1 of raising the priority of these targets back to B for AO3. For AO3, we plan to reduce the number of accepted targets so that further extension of this policy is unnecessary. Ultimately, we would like the US and Japanese programs to follow the same guidelines, whereby unobserved priority C targets are dropped, and must be reproposed in a subsequent AO.

Observation Completion

The policy for deciding whether an observation has been completed is normally based on the amount of good observing time obtained using the GIS instruments. For priority A observations, this is 95 percent of the requested time; for priority B and C observations it is 70 percent. There are circumstances when this criterion is not appropriate. For instance, a number of observations in April of this year were complete using the GIS good time, but had virtually no good SIS data because of telemetry saturation from scattered solar X-rays. For those observations, and for any observation for which the PI believes the good time does not meet the completion criteria, we will consider a follow-on observation. This is not automatic. While the ASCA mission operations team makes a sincere effort to keep track of which observations are successful, it carries out no comprehensive check. Also, a decision regarding rescheduling is sometime subjective and based on a judgement of whether the data accumulated allows the observer to perform the proposed investigation. If you have an observation that you consider incomplete, please contact Rob Petre at

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