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Suzaku Guest Observer Facility

Call for Suzaku Proposals


September, 2008

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

Suzaku Announcement of Opportunity (AO-4)

1. Overview

The X-ray Astronomy satellite Suzaku was developed under the collaboration of Japan and the United States, and was launched by ISAS/JAXA on 2005 July 10. Suzaku has successfully carried out astronomical observations using the X-ray Imaging Spectrometer (XIS) and the Hard X-ray Detector (HXD). 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-4 observations in 2009 April, and hereby solicit submission of observing proposals.

Changes made since the last AO can be summarized as follows:

(1) In addition to the "Long Program," which was introduced in AO-3, there is now a "Key Project" category, for which we reserve 2,000 ksec in total. The announcement for Key Project is being issued separately.
(2) In Japan, "Long Program" will cease to be a separate category for the purposes of proposal submission and review, although proposals requesting more than 300 ksec are still welcome. In the US, "Long Program" category will be maintained since the the peer review system typically favors shorter proposals in the absence of a reserved category.

Note that Key Program data and observations obtained for proposals with exposure time >300 ksec (whether the proposal is labeled "Long Program" or not) will be opened to the public immediately after the initial data processing is completed, and no proprietary period is awarded to the proposer.

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 ~10 keV with a high efficiency. An X-ray CCD camera (XIS) module is mounted in the focal plane of each XRT. The XIS has a high sensitivity and a moderate spatial resolution, and is particularly suitable for the studies of extended sources. The XIS also has a good spectral resolution for soft X-rays below 0.8 keV, which is superior to those of Chandra and XMM-Newton. Moreover, we have applied the so-called Spaced-row Charge Injection technique for the XIS since AO-2 to suppress the degradation of energy resolution. The HXD has unprecedented sensitivity in the wide energy range up to 600 keV, although it has no imaging capability. The wide bandpass coverage of 0.2 keV through 600 keV with the XIS and the HXD is an important characteristic of the Suzaku mission.

3. Mission Phases and Time Allocation

The Suzaku mission has been developed and maintained under a collaboration of Japan and the US, and the Science Working Group (SWG) that consists of researchers involved in the development and operation oversees the project overall. Since the end of the SWG phase of the mission (2006 March), all observation time except:

  1. Observatory Time (3%) for satellite maintenance and related purposes
  2. Calibration time (5%) for calibration of the instruments
  3. Director's Discretionary Time (DDT; 5%) for gamma-ray bursts or any genuinely unpredictable events, and other important observations granted at the discretion of the mission director.
has exclusively been allocated through an open AO process. The AO-4 program (1 year period starting on 2009 April) will be run under the same policy. The remaining 87% of the total time, which amounts to 360 d x 38 ksec/d x 0.87 = 11902 ksec, is open to the AO-4 program, and is distributed among Japan, US, ESA and other countries as follows.

(1)Japan time5451 ksec (ESA 909 ksec, Japan and others 4542 ksec)
(2)US time3963 ksec
(3)Joint Japan-US time488 ksec
(4)Key project time2000 ksec

Here the Japan time includes joint Japan-ESA time, which amounts to 909 ksec. Accordingly, the remaining 4541 ksec is the time for Japanese scientists in AO-4. All proposals from outside Japan, US and ESA should be submitted to the Japan time. Note, however, that the total approved exposure time of proposals whose PIs are not Japanese nor researchers from ESA member states is restricted not to exceed the joint Japan-ESA time. The joint Japan-US time will be used if proposals for the same targets are accepted both in Japan and US, and if both PIs accept such merging (the proposal form has a check box for the PI to indicate whether he/she accepts the merging).

4. Observing Constraints

(1) The complete list of the targets accepted through AO-3 can be found in the Timeline & Mission Information section of the Suzaku GOF site. Observations of the priority A and B targets are guaranteed. New proposals for these targets will not be approved without an explicit justification for an additional observation, such as much longer exposure, different pointing position on the same extended object, or a different phase of a variable object. On the other hand, some of the priority C targets and TOO targets are not observed. This can be checked at this page at ISAS.

Anyone can submit proposals for the C or TOO targets that are unobserved. It must be noted, however, that unobserved AO-3 C or TOO targets may be observed before the end of March 2009. In this case, the observations of the C targets are regarded as being completed if the exposure time exceeds 70% of the proposed time. If the exposure time is less than 70 %, on the other hand, an additional observation will be carried out to fill the remaining time only if a proposal for the same target by the same PI is accepted at a higher priority (A or B) in AO-4. Otherwise the observation carried out in AO-3 is ignored, and the target is open for competition in AO-4.

(2) The exposure time of the observation should be justified based on the specific scientific objectives, preferably using simulations. However, we set the minimum exposure time of a single pointing observation at 10 ksec, considering the efficiency of satellite operation. On the other hand, we set no upper limit on the exposure time for a long observation. A longer observation, however, requires a stronger scientific justification. Note also that any observations based on a proposal whose approved total observation time exceeds 300 ksec are open to the public as soon as the data are available for analysis (no proprietary is awarded to the proposer).

(3) In AO-4, we introduce a new category of "Key Project," There is no observing time limits on Key Project proposals. See the separate announcement for details.

In the US, the category of "Long Program" will be retained for proposals requiring between 300 ksec and 1 Ms of observing time. In Japan, there will not be a separate "Long Program" category, although such proposals are allowed within the regular proposal category. However, see (2) above for proprietary rights.

(4) It is prohibited for a single team to propose an observation that is part of a Key Project proposal also in a regular proposal.

(5) Target of opportunity (TOO) proposals are allowed for short-lived events on known objects whose timing is uncertain. In this case, condition to trigger the TOO observation, estimated probability of the event to take place during the AO-4 period, and the expected duration of the event should be specified in the proposal as well as other information required for the non-TOO observation proposals. Any proposal that does not name a specific target, such as "Observation of a forthcoming nearby supernova," or "next nova explosion in M31," will not be accepted. The number of potential targets for a TOO proposal is limited to at most 5 per proposal. It is requested to specify in the scientific justification how many targets should be observed (the number of "triggers") to fulfill the scientific goal of the proposal. If the total exposure time to complete the requested number of targets is equal to or larger than 300 ksec, the data will be open to the public as soon as the first observation is finished. See (2) above.

(6) It is possible to submit proposals specifying the time of observations as TC (Time Critical) Observations. These include observations of a specific binary phase, coordinated observations with other wavebands, monitoring a target several times with certain time intervals, roll-angle-constraint observation of diffuse sources, and so on. The Suzaku operation team will do their best to perform the observations as requested. In all these cases, the PI must check the TC flag in the target form. Even if the coordination with other instruments is not planned in detail at the time of the proposal submission, the PI is required to check the TC box if he/she would like to do so after the approval of the proposal. The observation without a TC flag is treated as non-TC observation, and the coordinate observation can only be carried out if the other telescopes follow the Suzaku schedule.

(7) Any genuinely unpredictable events such as, gamma-ray bursts and supernovae, can be observed as part of the DDT. Proposals for such observations are accepted at any time, outside the selection process of regular proposals. See this ISAS page for further details.

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 2008 December 5 at 4:30 pm EST for proposals submitted to NASA. After the US national review, a Japan-US merging committee will be convened in March, 2009 and the final observing program will be published soon thereafter.

Accepted targets will be classified into three categories (A, B, and C) based on proposal ranking. Priority A targets will be preferentially observed during the AO-4 period (2009 Apr to 2010 Mar), and the observation are regarded as completed if the exposure time is more than 90% of the requested time. Priority B targets will be scheduled in this period as much as possible, but may be carried over to the next cycle. Observations of the priority B targets are regarded as completed if the observation covers more than 70% of the requested time. Priority C targets will be used as fillers when there are gaps in the schedule. Of the total available time T (=11902 ksec = 360 d x 38 ksec/d x 0.87), we will accept 0.6T, 0.3T, and 0.5T for Key+A, B, and C proposals. This implies the oversubscription fraction of 40%. The oversubscribed targets will be scheduled if observing time remains after the observatory time, the calibration time, and DDT are assigned.

TOOs and time critical observations pose constraint on Suzaku operation. Hence total fraction of them is limited to be some 15% of the total available time.

6. Data Rights

Normally, proposers of regular proposals have proprietary rights to the data for 1 year after the receipt of processed data. This does not apply to the data based on the proposals whose total exposure time is equal to or more than 300 ksec ("Long Program" proposals in the US) and those based on Key Project proposals. The realtime TOO data utilizing DDT is also open immediately in principle, although this can be postponed for a short period at the discretion of the Suzaku managers.

We will deem an observation complete if 90% (Key Projects 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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