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Suzaku Guest Observer Facility

Call for Suzaku Proposals


September, 2007

Institute of Space and Astronautical Science / Japan Aerospace Exploration Agency
Kazuhisa Mitsuda, Tadayuki Takahashi, and Hideyo Kunieda

Suzaku Announcement of Opportunity (AO-3)

1. Overview

The Japanese-US X-ray Astronomy satellite Suzaku was launched by ISAS/JAXA on 2005 July 10, and has since successfully carried out astronomical observations using the 4 X-ray CCD cameras (XISs) and Hard X-ray Detector (HXD), although one CCD camera (XIS) is no longer operational. After the initial operation for instrument calibration and performance verification, which confirm the wide-bandpass, high-sensitivity, moderate spectral resolution capabilities of Suzaku, we entered the international AO phase of the mission in 2006 April, performing observations based on proposals received from the astronomical community world-wide.We plan to start AO-3 observations in 2008 April, and hereby invite submission of observing proposals as follows.

This version is applicable to scientists based in the US.
Scientists in ESA member countries should consult the version at ESA, while scientists in all other countries, including Japan, should consult the version at ISAS/JAXA.

2. The Suzaku Observatory

The Suzaku satellite carries four X-Ray Telescopes (XRTs) that focus X-rays up to 12 keV with a high efficiency, each with an XIS unit at its focus. The XIS has a high sensitivity particularly for extended sources, as well as good spectral resolution, for soft X-rays below 0.8 keV, a capability that is superior to those of Chandra and XMM-Newton. At the same time, the HXD, though non-imaging, has unprecedented sensitivity in the wide energy range up to several hundred keV. The wide bandpass coverage with the XIS and the HXD is an important characteristic of the Suzaku mission, so we invite observing proposals that make strong use of their sensitivities. The details of the instruments (Technical Description document), and a list of targets that have been observed or will be observed within the SWG (see below) time and AO-1 & AO-2 can be found at the Suzaku GOF home page as well as at the ISAS/JAXA Suzaku home page.

We plan to update the Technical Description document, as well as planning tools, with latest information in October. Existing versions should suffice for early planning of proposals, except that proposers should now assume the use of 3 XIS units, not 4.

3. Mission Phases and Time Allocation

The Suzaku mission has been developed as a Japanese-US collaboration, and the Science Working Group (SWG) that consists of researchers involved in the development and operation oversees the project overall. After the end of the SWG phase of the mission (through 2006 March), normal observations during AO-1 and AO-2 are entirely through an open proposal process. Similarly, observing time during international AO-3 (1 year period starting 2008 April) is open. This, however, excludes the following categories.

  1. Observatory Time (3%) for satellite maintenance and related purposes
  2. Calibration time (5%) for routine calibration of instruments
  3. Director's Discretionary Time (4%) for gamma-ray bursts or any genuinely unpredictable events, and other important observations granted at the discretion of the mission director.
The remaining 88% of total time is available to proposers. This will be divided into (1) 50% for Japanese observations; (2) 37.5% for US observations; and (3) 12.5% for joint Japanese-US observations. The joint time will be used if proposals were received for the same target both in Japan and in the US, and if both PIs accept such merging (the proposal form will have a check box for the PI to indicate yes or no). This allocation is based on an ISAS-NASA agreement. Additionally, within the "Japanese" allocation, 8% of the total observing time is reserved for proposals submitted to ESA as joint Japan-ESA observations, thus the purely Japanese time is 42%. The total time available to US researchers is 4514 ks, plus 1505 ks of joint time, assuming 38 ks of good time per day and 360 days of operation per year. Proposals from non-US, non-ESA countries will be accepted within the Japanese time up to the ESA portion.

4. Observing Constraints

Over 700 objects will have been observed with Suzaku by the end of the AO-2 period. A full listing can be found on the web. Observations of accepted priority A and B targets are guaranteed, while those of priority C targets and Targets of Opportunity (TOOs) are not (see below for definitions of target priorities). Proposals for targets already observed are allowed, but must include a justification for an additional observation, such as a much longer exposure, different pointing within an extended object, or different observing window of a variable object. Proposers with accepted C or TOO targets must re-propose if they wish to ensure that their observations are carried out (these targets are in principle open to competition). It must be noted that if the C target is observed in AO-2 with more than 70% of the accepted time, normally it will not be observed in AO-3. If the C target observation is not completed (<70%) in AO-2, it will be ignored, and new observations will be performed in AO-3 according to the new proposal, unless it is by the same team as in AO-2.

The length of the observation should be justified based on the specific scientific objectives, preferably using simulations. However, we set the minimum observing time at 10 ksec, considering the efficiency of satellite operation. Longer observations will naturally require stronger scientific justifications. Ordinary proposals can request less than 300 ksec.

In AO-3, we introduce a new category of Long program (L), for projects requiring between 300 ksec and 1 Msec, to encourage long exposure of single objects, mapping of of diffuse objects and other large programs to maximize the scientific return from Suzaku. The data from long program observations will be open to public immediately. In the review process, long program proposals are treated slightly differently, including a longer page limit for the scientific justification.

It is possible to specify the time of observations (time critical, or TC, observations) to observe specific phases or for simultaneous observations. Monitoring observations (repeated observations with a specified interval) or roll-angle constrained observations are also considered time critical, and must be so flagged on the proposal form. Those interested in submitting TC or TOO proposals in the Long Program proposal should contact Suzaku Manager e-mail beforehand to ensure its feasibility.

Target of opportunity (TOO) proposals are allowed for short-lived events on known objects whose timing is uncertain. The name and coordinates of the object(s) as well as the triggering conditions must be specified. We also require a derivation of the estimated probability during AO-3 of such an event, as well as its duration. Generic TOOs without a specific target (such as "a nearby supernova") will not be accepted. In the same spirit, the number of targets in TOO proposals should not exceed 5.

Gamma-ray bursts or any genuinely unpredictable events may be observed outside the proposal process, as part of the 4% Director's Time. Data from such observations will not have a proprietary period. To request such unproposed TOO observations, please e-mail:
Suzaku Manager e-mail

5. Review Process and schedule

Researchers based in the US and affiliated with a US institution should submit their proposals to NASA. The deadline is 2007 November 30 at 4:30 pm EST for proposals submitted to NASA. After the US national review, a Japan-US merging committee will be convened in February, and the final observing program will be published soon thereafter.

Accepted targets will be classified into four categories. L targets and priority A targets will be preferentially observed during the AO-3 period (2008 Apr to 2009 Mar). Priority B targets will be scheduled in this period as much as possible, but may be carried over to the next cycle. Priority C targets will be used as fillers when there are gaps in the schedule. For the total available time T, we currently plan to accept 0.6T, 0.3T, and 0.5T as L+As, Bs, and Cs (for a total oversubscription by 40%). If the utilized amounts of observatory, calibration, and director's times add up to less than 12%, then the remainder will be used to observe additional C targets.

TOOs and time critical observations will be accepted only as priority A targets.

6. Data rights

Observers will have exclusive rights to the data for a 1 year period after receipt of processed data. This, however, does not apply to L targets, the data for which will be released immediately as mentioned above. Similary, there will not be a proprietary period for real time TOO observations and Gamma-ray burst data. We will deem an observation complete if 90% (for L and A targets) or 70% (for B targets) of the accepted time is obtained.


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This file was last modified on Wednesday, 25-Jan-2017 10:47:39 EST

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