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ASCA Guest Observer Facility


Mission Phases

Since the conclusion of the initial "Performance Verification" (PV) phase in October, 1993, for which the data belong to the ASCA mission team, observing time on ASCA has been open to competitive proposals. The observing time is apportioned as follows:

  • 60 per cent for Japanese investigations
  • 15 per cent for U.S. investigations.
  • 25 per cent for U.S./Japan collaborative investigations.

The current AO (A03) and subsequent AOs cover 1 year of ASCA observations. Observations selected in this round commence on November 15, 1994. U.S. observers can propose either for U.S.-only time or for the U.S./Japan time. U.S. investigators bidding specifically for U.S./Japan time must arrange for a Japanese collaborator. If the U.S. investigator expresses no preference, a Japanese collaborator may be assigned.

Proposal Preparation and Submission

General Observing Parameters

The guest observer phase of the ASCA mission began on 1993, October 15. Observational data are subject to proprietary data rights for 1 year after the data have been made available to the Principal Investigator (PI) in a form suitable for scientific analysis.

ASCA typically performs two pointings per day. This limitation is driven by the long (1- to 2-hour) settling time required by the attitude-control system after a maneuver to a new pointing position. Given a satellite observing efficiency of 50 percent, this means that the minimum allowable observing time on a particular target is 20,000 seconds. Proposals must take this into account and justify the need for an exposure of this (or longer) duration. In some well-justified circumstances, shorter observations (10,000 seconds) might be considered. Also, for targets having limited spatial extent (lt; 1 degree), it will be possible to specify a "raster" observation: multiple brief pointings at slightly offset locations. The total time on a specific region of sky still must exceed the minimum.

There are no restrictions regarding the amount of observing time or the number of targets requested in guest observer proposals. Proposals may be submitted for single targets with a relatively short observation time, or for larger programs involving multiple targets or greater amounts of observing time. All proposals will be reviewed together in the same peer review, and we expect some mix of large, medium, and small programs. For this third observing period, data rights for about 150 new observations will be awarded to U.S. PI's as either U.S.-only or collaborative targets.

Time-critical observations, i.e., observations with scheduling constraints, impose a particular burden on ASCA mission planning. In particular, for "short-lived" phenomena, i.e., phenomena where timing within a spacecraft orbit matters, the observability of an event may only be assessed a few weeks prior to scheduling. Too large a percentage of such time-critical observations would compromise the ability of the mission planning and operations team to effect properly the full set of requested observations. Because all time-critical observations drive the scheduling process and, therefore, must receive highest scheduling and scientific priority, their total share must be kept relatively small. For ASCA, about five percent of the time will be made available for truly time-critical observations (observations requiring a specific day, such as coordinated observations). An additional five per cent will be made available for less constrained time-critical observations, such as regular visits to a source or observations that require a specific orbital phase.

The first 7 months of the mission were used for calibration and performance verification; the following 12 months for observations proposed in AO1 and AO2. During this time, stars, binaries, supernova remnants, galaxies, clusters of galaxies, active galactic nuclei, and the x-ray background will be observed. Guest investigators should check whether their targets of interest already have been observed; if this is the case, investigators are asked to justify the need for additional observations.

Who May Propose

Every ASCA proposal must identify a Principal Investigator (PI), who assumes full responsibility for the budget and the scientific study. The intent of this program is to enhance U.S.-Japanese scientific cooperation, in keeping with the bilateral agreement between the U.S. and Japan. Thus, only individuals affiliated with U.S. institutions and located in the U.S. are eligible to propose for ASCA guest investigations through NASA. The requirement of affiliation with a U.S. institution does not extend to co-Investigators.

Proposers have three choices. They may specify (on the general form) whether the observing time is to be taken from the 15 percent assigned specifically to the U.S. or whether collaborative time is requested. If collaborative time is requested, both the U.S. and Japanese investigators must be identified. Proposers may also specify "no preference" between U.S. time and U.S./Japan time, in which case a Japanese co-investigator may be assigned. If a proposal for the U.S./Japan block of time is accepted, the observation's time is taken from that block.

The purpose of the block of observing time assigned to U.S.-Japan scientific collaboration is to maximize the scientific return for the ASCA mission and to create an opportunity for cooperative research between U.S. and Japanese scientists. A proposal should be submitted only to the ASCA program of the country of the PI. Specifically, collaborative proposals should be submitted to either the U.S. or Japan, but not to both.

As stated in the agreement, NASA and ISAS will each bear the cost of discharging their respective responsibilities, which depend on the nature and extent of the proposed cooperation. As usual, U.S. proposals that include non-U.S. participation are made on a "no exchange of funds" basis.

U.S. proposers who propose as co-investigators on collaborative proposals submitted to Japan may submit a proposal to NASA for funding only. This should be specified on the general form, and the number of targets requested on the cover sheet should be entered as "0." Funding in such cases is contingent on acceptance of the corresponding proposal that has been submitted to the Japanese.

A bilateral agreement also exists between Japan and ESA, through which 10 percent of the total observing time is allocated from the Japanese 60 percent time share for collaborative Japan-ESA proposals. U. S. scientists who propose as co-investigators on collaborative proposals submitted through ESA also may submit a proposal to NASA for funding only, following the guidelines listed above.

Similar proposals with similar source lists involving essentially the same consortium of investigators should not be submitted to different national programs even if the formal PI's are explicitly different. A consortium of investigators from the U.S. and Japan may choose to split a large observing program and submit to different agencies, but in doing so they should also, in the spirit of these rules, split their source lists; each individual proposal submitted to each agency must be capable of being evaluated on its own merit.

Following selection, the mission timeline team will deal only with the person identified as Principal Investigator or lead Co-Investigator. It will be the Principal Investigator's duty to respond to any questions about detector usage or observational modes.

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This file was last modified on Monday, 25-Jun-2001 11:49:14 EDT
Curator: Michael Arida (SP Sys);
HEASARC Guest Observer Facility

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This file was last modified on Monday, 25-Jun-2001 11:49:14 EDT

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