2013 September 3 Vesion 1
2013 October 28 Version 2

Announcement of Opportunity (AO-9) of Suzaku

Kazuhisa Mitsuda (Project manager, ISAS/JAXA)
Tadayuki Takahashi (Project sub-manager, ISAS/JAXA)
Hideyo Kunieda (Project scientist, Nagoya University)

1. Overview

The X-ray Astronomy satellite Suzaku was developed under collaboration of Japan and the United States, and was launched by ISAS/JAXA on 2005 July 10. Suzaku has successfully carried out observations of celestial objects 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. In the meanwhile, however, the amount of electric power supply from the Solar Array Paddle (SAP) has reduced.

This figure shows yearly profile of the amount of electric power supply with the origin of the ordinate being set at the launch date of Suzaku, 2005 July 10. The numbers at the right end of the panel, arranged vertically, are the numbers of years since the launch. The power amount started to decrease immediately after the beginning of the 7th year (yellow dots), and eventually cannot supply enough power to retain full functionality of the spacecraft on 2012 January 24, at which date Suzaku entered into the automatic power reduction mode (so called "Under Voltage Control" mode). After this, for half a year, the power amount reduction seemed to continue, and the project team suspected, at around the end of the 7th year, that even the fulfillment of the AO-7 observations might be impossible. In the early 8th year (orange dots), however, the power reduction seemed to stop. Accordingly, the project team decided to issue AO-8 on 2012 October 1.

As the data of the 8th year being accumulated, it is found that the reduction of the SAP electric power supply stopped at around the 140th day in the 7th year. After that the power reduction from the 7th to 8th year is around 50W. The minimal electric power necessary for Suzaku to retain current performance is 800W, which was indicated by the horizontal dashed line around the bottom of the figure. On the other hand, simple extrapolation of the electric power supply history suggests that the minimal electric power during the AO-9 period is probably in the range 850W-900W, and thus it seems, at this moment, possible for Suzaku to survive until the end of the AO-9 period. Accordingly, the Suzaku project team hereby solicits submission of observation proposals for AO-9 starting in 2014 April. But the team would like proposers to note the following points.

  • Although the project team will take their best effort to continue Suzaku normal observation, part of the observation instruments can be shut down before the end of AO-9 (2015 March 31). Further crisis of the electric power supply may lead to termination of AO-9 in mid-course.
  • Accordingly, the project team solicits proposals whose scientific objectives can be achived within this AO (AO-10 may not be released). The team also welcomes resubmission of past successful proposals under certain conditions. Please refer to section 4-(1) for further details.
  • As in AO-8, the project team limits the observable sky area in the range 70-110 degrees from the sun. This may lead to reduction of the number of ToO and Time-critical proposals to be accepted (see below for more detail).
  • We resume solicitation of the Key Project proposal submission, which was suspended in AO-8. Note, however, that a proposal continuing beyond a single AO period that had been accepted until AO-7 is prohibited in AO-9; the Key Project proposals solicited this time should achieve their scientific purpose within the AO-9 period.

    The Key Project program was initiated in AO-4, in order to fully utilize unique capabilities of Suzaku. The Suzaku project team expects to carry out observations that challenge important astrophysical issues and will be utilized for a long time after the observations as legacy of Suzaku.

During the AO-9 period, observations on the basis of Suzaku-Fermi joint program initiated in AO-6, and those of Joint Chandra/Suzaku proposals initiated in AO-4 will be carried out. We refer those who are interested in these programs to the home pages of Chandra and Fermi, respectively.

US based scientists should consult the parallel announcement at while scientists in ESA member countries should consult the version at Present version is applicable to scientists based in all other countries.

2. Suzaku Observatory

The Suzaku observatory carries four modules of the X-Ray Telescope (XRT) that focus X-rays up to ~10 keV with high efficiency. In the focal plane of each XRT is mounted an X-ray CCD camera (XIS) module. The XIS has high sensitivity and moderate spatial resolution, which is especially advantageous in scrutinizing extended sources, as well as good spectral resolution for the soft X-ray below 0.8 keV, which is superior to that of Chandra and XMM-Newton. Moreover, we have applied so-called Spaced-row Charge Injection technique for the XIS since AO-2 to suppress 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. The technical description of the Suzaku instruments, the list of the targets that were observed or accepted can be found from the following Suzaku homepage.

3. Mission phases and time allocation

The Suzaku mission has been developed and maintained under collaboration of Japan and US, and the Science Working Group (SWG) that consist of researchers involved in the development and the operation oversees the project overall. Since the end of the SWG phase of the mission (2006 March), all observation time except
(a) Observatory Time (3%): for satellite maintenance and related purposes,
(b) Calibration time (5%): for calibration of the instruments,
(c) 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 dedicated for AO observations. The AO-9 program (1 year period starting on 2014 April) will be run under the same policy. ToO observations based on proposals from the MAXI team have been carried out within (c) DDT since AO-5.

The remaining 87% of the total time, which amounts to 360d x 38 ksec/d x 0.87 = 11902 ksec per year, is open to the AO-9 observation program, and is distributed among Japan, US, ESA and other countries as follows:

(1) Japan time: 5451 ksec (ESA 909 ksec, Japan and others 4542 ksec)
(2) US time: 3963 ksec
(3) Joint Japan-US time: 488 ksec
(4) Key project time: 2000 ksec
Here the Japan time includes joint Japan-ESA time, which amounts to 909 ksec. Accordingly, the remaining 4542 ksec is the time for Japanese scientists in AO-9. All proposals out of Japan, US and ESA member states 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 should not 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 PIs to indicate whether they accept the merging). Observation time from Suzaku-Fermi joint program and Joint Chandra/Suzaku proposals are included in either one category of (1)-(3), depending upon the PIs' affiliation. The time (4) is dedicated for the Key Project observations, the allocated time to which is the same as in AO-7.

4. Proposal Policies

(1) The complete list of the targets accepted until AO-8 can be found at the following URL. Observations of the priority A and B targets are guaranteed. New proposals for these targets are difficult to be approved unless there is a strong 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. As mentioned at the top of this document, it is possible that this AO-9 becomes the final one of the Suzaku mission. Accordingly, proposals which are similar to those submitted and accepted in the past AOs are welcome if the observations are expected to strengthen or finally establish excellent results from the past AOs. They include, for example, enhancement of statistics of a certain object by simply adding exposure time, completing a mapping observation to entirely cover a diffuse object, increasing the number of samples from a certain source category, and so on. In addition, the next generation X-ray observatory ASTRO-H will be launched in the Japanese fiscal year 2015. Proposals whose scientific purpose can be extended with ASTRO-H are also welcome.

On the other hand, some of the priority C targets and ToO targets are not observed in AO-8. This can be checked at the following URL.

Anyone can submit proposals for the C or ToO targets that are unobserved. It must be noted, however, that they are possible to be observed by the end of AO-8 period (March 2014). In this case, the observations of the C targets are regarded as being completed if the exposure time exceeds 70% of the proposed time, and no further observation will be carried out in AO-9. If the exposure time is less than 70 %, on the other hand, a complementary observation will be carried out to fill the requested time, if a proposal for the same target from the same PI is accepted at a higher priority (A or B) in AO-9. Otherwise the observation carried out in AO-8 (less than 70% filled) is ignored, and the target is open for competition in AO-9.

(2) The exposure time of the observation should be justified based on scientific objectives, preferably using simulations. The project team sets the minimum exposure time of a single pointing observation at 10 ksec, considering the observation efficiency. On the other hand, the upper limit of the total exposure time per proposal should be 400ksec in AO-9. The proposals whose total exposure time exceeds 400ksec should be submitted to the Key Project program which is solicited separately. In addition, note that observations based on a proposal whose total exposure time is equal to or longer than 300ksec will be opened to public immediately after the initial processing of the data is done. No proprietary period is awarded to the PI.

(3) An uninterrupted continuous observation is guaranteed for up to 100ksec. This limitation originates from moon light constraint to the star trackers' field of view, conflict with other time critical observations (see item (5) below), and other operational/planning difficulty. The operation team accepts a request of an uninterrupted observation longer than the 100ksec, but conducts it on the best-effort basis.

(4) Target of opportunity (ToO) proposals are allowed for short-lived events on known objects whose timing is uncertain. This category is referred to as ''Reserved ToO observation''. In this case, condition to trigger the observation, estimated probability of the event to take place during the AO-9 period, and the expected duration of the event should be specified in the proposal as well as other information required for the ordinary observation proposals (see section 5-(2) of "Call for Proposals of the Suzaku AO-9 period" below). Any proposal without specifying a target name, such as ''Observation of a forthcoming nearby supernova'', or ''Next nova explosion in M31'', is not to be accepted. The number of targets that is allowed to be written in the target list is limited at most 5 per proposal. It is requested to specify in the scientific justification how many targets should be observed to fulfill the scientific goal of the proposal. Note that the maximum total exposure time per proposal is limited up to 400 ksec (see (2) above). If, for example, five targets with 100 ksec exposure for each are proposed, the trigger number is limited up to four (= 400 ksec exposure = the exposure limit). In addition, note that, if the trigger number is 1 or 2, the PI will be awarded the proprietary period of 1 year, whereas if it is 3 or 4, the data will be immediately opened to public (total exposure time is equal to or more than 300ksec).

(5) It is possible to submit proposals specifying the time of observations as TC (Time Critical) observations. These include all the observations that require, of the operation team, consideration of operational/planning constraints other than the solar angle limitation. They include, for example, a roll-angle-constraint observation, multi-pointing observations of a variable target (even with a lax constraint of once per half a year, for example), a background observation planned closely in time with the main target observation, an observation of a certain binary phase, coordinated observations with other wavebands, and so on. The Suzaku operation team will do their best to perform the observations as requested. In all these cases, the PI has to raise the TC flag in the application form. Even if the coordination with other instruments is not planned in detail at the time of the proposal submission, the PIs are requested to check the TC box if they would like to do so after the approval of the proposal. The Suzaku longterm/shortterm schedules are possible to be revised even just before the observation starts, due to interruption by a ToO observation. The operation team cannot guarantee the coordination if the TC flag is off, even in the case that the other instruments follow the Suzaku schedule.

(6) Any genuinely unpredictable events such as, gamma-ray bursts and supernovae and so on, can be observed as part of the DDT. This category is referred to as a ''Realtime ToO observation''. The observation proposals of this category are received at any time and are refereed out of the ordinary proposal selection process. Any proposer who would like to propose a Realtime ToO observation is requested to fill the form and send it to the Suzaku manager via e-mail
suzaku_managers 'at' astro.isas.jaxa.jp
The proposer has no proprietary on the Realtime ToO observation data. Note that Realtime ToO observations on gamma-ray bursts will be accepted from any investigators worldwide in AO-9, which had been planned by the Suzaku Science Working Group by AO-6.

(7) The Suzaku project team will accept proposals using P-sum/timing mode for the XIS, as well as the normal imaging mode. In the P-sum/timing mode, photon pile-up scarcely occurs, and a time resolution as fast as 7.8 msec can be achieved, although only 1-dimensional image can be obtained. Note, however, that the P-sum/timing mode can be adopted only in the XIS3. Neither Spaced-row Charge Injection nor CTI correction can be applied, and hence the energy resolution is significantly worse than in the normal imaging mode. Calibration accuracy of the energy response is not as good as that in the normal imaging mode, either. Refer to the technical description document for the P-sum/timing mode in detail.

(8) The project team had supported the two default pointing positions since AO-1--- the XIS nominal and HXD nominal positions. Of them, the team ceased to support the HXD nominal position from AO-7. As a result, the standard HXD response matrices will not be supplied, and XIS observations with non-standard readout clock (P-sum/timing mode and window/burst options) have not been available since AO-7. Note, however, that the operation team does not prohibit the proposers to carry out their observations at the HXD nominal position. In this case, they should make the response matrices by themselves by utilizing the response builders of the XIS and the HXD.

(9) We resume solicitation of Key Project proposal submission in this AO-9, which will be refereed separately from the ordinary proposals. The announcement of opportunity of the Key project will be issued separately. There is no observing time limitation in the Key project. This will provide with a unique opportunity to carry out various projects, such as an extremely long observation of a single object, mapping observation of a certain area of the sky, a long term monitoring observation of an object, and so on, by fully utilizing unique capabilities of Suzaku. Note, however, that due to the SAP power supply concern, the observation plan that extends over the AO-9 period is prohibited. The dead line of the Key project proposals are the same as that of the ordinary proposals (solicited by this announcement), 2013 Nov. 13. They are sent to the initial refereeing process in Japan and US separately. The PIs of the proposals survived the initial refereeing process are requested to make a presentation in a workshop, which is open to all investigators. Immediately after this workshop, Japan-US merging committee finally selects the Key Project proposals in AO-9. The data taken in the Key Project program are opened to public immediately after the data are ready for analysis.

(10) If a proposal to this ordinary program and another proposal to the Key Project program contain the same investigator(s), and part of the targets overlaps between the two proposals, they are referred to as ``duplicated proposals". A duplicated proposal to the ordinary program is allowed only if its targets comprise of a subset of those in the conterpart Key Project proposal. The duplicated proposals to the ordinary and to the Key Project programs are both rejected if the proposal to the ordinary program contains any target that is not included in the counterpart Key Project proposal, or if the exposure times of some targets that are included in the ordinary program proposal exceed those of the same targets in the conterpart Key Project proposal. Only one duplicated proposal to this ordinary program can be submitted from a parent Key Project proposal.
Except for the case described here, proposing the same targets to both this ordinary program and to the Key Project program is strictly prohibited, even if the scientific purpose or observation methodology are different between the two. Any investigator that plans to submit a duplicated proposal to this ordinary program should declare so in the counterpart Key project proposal. It is not necessary, in the duplicated proposal to this ordinary program, to mention that there is the parent Key Project proposal.

(11) There is a problem in an equipment of the ground tracking station (Uchinoura Space Center), and the accuracy of time assignment to X-ray events is somewhat degraded. In case absolute time accuracy better than about 1 msec and/or clock stability better than 1.7x10-7 is necessary to achieve the main purpose of the proposal, the requirements should be written in the proposal (for detail see section 5-(2)(e)).

5. Schedule of the reviewing process

(1) Researchers who affiliate with Japanese institutions or who belong to institutions out of US nor ESA member states should submit their proposals to ISAS/JAXA according to this AO document. The deadline of proposal submission is at noon of 2013 November 13 (JST). All proposals submitted to ISAS/JAXA are to be reviewed in the same process in Japan. Selection of proposal will be made in early February 2014 in Japan side. The ESA-selected proposals are merged at this stage. The Japan-US merging committee will be convened in mid February 2014. The final observing program of AO-9 will be released soon thereafter.

(2) Accepted proposal are classified into three categories according to their priorities (A, B, and C) which are assigned on the basis of their mark given by the referees. The priority A targets will be preferentially observed during the AO-9 period (2014 Apr to 2015 Mar), and the observation is regarded as completed if the exposure time is more than 90% of the requested time. The priority B targets are tried to be observed during the AO-9 period. This is on the best-effort basis, and hence, they may be carried over to the following AOs. Observations of the priority B targets are regarded as completed if the observation covers more than 70% of the requested time. The priority C targets will be used as fillers if there remains a room in the time line after scheduling the priority A and B targets. Of the total available time T (=11902 ksec = 360 d x 38 ksec/d x 0.87), we will accept 0.6T (= 7141 ksec) for Key+A (Key project time is at most 2000 ksec), 0.3T (= 3571 ksec) for B, and 0.5T (= 5951 ksec) for 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.

(3) Reserved ToOs and TC observations pose constraint on scheduling observations. Hence total fraction of them is limited to some 15% of the total available time. Note, however, that this number may be reduced in the discussion of the Japan-US merging committee meeting (mid February 2014), based on the prospect of the SAP power supply degradation.

6. Data right

The data taken in the ordinary observation program are immediately delivered to the PI. The PI has proprietary to the data for 1 year after the data are ready for scientific analysis. This does not apply to the data based on realtime ToO proposals, and the proposals whose total exposure time is equal to or more than 300ksec, which are immediately opened to public after the initial data processing is completed.

Call for Proposals of the Suzaku AO-9 period

1. Observations solicited in AO-9

We call for X-ray observations with the Suzaku observatory from April 2014 through March 2015.

2. Applicant eligibility for submitting proposals to the Japan time

Principal investigators (PIs) who plan to submit their proposals to ISAS/JAXA have to affiliate with institutions or universities located in Japan. Graduate students can apply the AO as a PI, but they must include at least one of their supervisors as a Co-I. PIs belonging to US institutions or to ESA member states institutions should submit to NASA and ESA, respectively. Japanese investigators who stay out of Japan in the AO-9 period but are supported by any Japanese fund (such as JSPS fellow) can submit their proposal to ISAS/JAXA. NASA and ESA researchers who spend most of their time during AO-9 period in Japan can submit their proposals to ISAS/JAXA. PIs in the other countries should submit their proposals to ISAS/JAXA. The proposals submitted to ISAS/JAXA can include US/ESA researchers as Co-Is. It is not allowed to submit identical proposals to both ISAS/JAXA and NASA. They will be ignored on both sides.

3. Due date of proposals

The observation proposals should be submitted by 12:00 JST (03:00 UT) on November 13, 2013. Only electronic submission through the Remote Proposal-submission System (RPS) is allowed (see below for detail).

4. Proposal submission

The forms summarized in the next section should be submitted electronically with the Remote Proposal-submission System (RPS).

5. Proposal form

The proposal form consists of the following items.

(1) Cover Page: general information including investigators' name, title and abstract of the proposal.

(2) Target Form: information on the proposed targets including target name, its celestial coordinates, expected counting rate, and preferred observation mode. The target information in this form is automatically registered in the observation database and utilized in making the long-term observation time line of AO-9. The proposers are therefore strongly required to provide accurate information. All information that is indispensable for operation planning should be provided in the electronic form. The PIs are advised to utilize the ``Remarks" area if they have detailed requests which cannot be expressed with the check boxes/pull-down menus. Special care should be paid in the following points;

(a) From AO-6, the XIS3 can be used in the P-sum/timing mode (the other two modules XIS0 and XIS1 can be operated only in the normal imaging mode). In using the P-sum/timing mode for the XIS3, the PI is required to select ''PSUM'' in the XIS mode pull-down menu, and describe the mode setting of the other XIS modules, such as window or burst options in the ``Remarks" area.

(b) Be sure to mark the TC check box if the proposed observation is time critical (see section 4-(5) of "Announcement of Opportunity (AO-9) of Suzaku" above). Provide all information necessary to plan/conduct the observation in the ``Remarks" area.

(c) Provide in the ``Remarks" area the conditions to initiate the ToO observation, and probability of those conditions being met within the period of AO-9. If there is no description on the trigger probability, the project team cannot help assuming the probability of 100%, and accordingly, accumulating the exposure time as written in the proposal. This will hamper acceptance of other ToO proposals with lower mark which would have been accepted if there were description on the trigger probability. In order to utilize valuable Suzaku time among the community, the project strongly ask proposers of ToO observations to specify the trigger probability.

(d) It will take ~3 days to start a reserved ToO observation in the P-sum/timing mode since the trigger from the PI, during which the operation team prepares the mode setting commands.

(e) In case absolute time accuracy better than about 1 msec and/or clock stability better than 1.7x10-7 is necessary to achieve the main purpose of the proposal, the requirements should be written in the scientific justification, and in the ``Remarks" area as well.

(3) Scientific Justification: Background of the proposal, scientific issues to be resolved, and technical feasibility of the proposed observation should be summarized within 4 pages including text, figures, charts, tables, and references.

Of them, the forms (1) and (2) should be created electronically by logging in

The form (3) can be made off-line. The PIs can use any editors/word processors they like. It should be, however, either in pdf or ps formats at the time of submission. The allowed language for (3) is either Japanese or English. The PI should submit the forms (1) and (2) through the RPS first, and after confirming the acceptance of them (the proposal ID number is provided), the form (3) is allowed to be uploaded. If the proposer would like to revise (3) after submission, it is possible to re-submit it by adding a revision index (a, b, or c) following the proposal ID number. Note that the revision is allowed up to three times. For example, if the ID number is 110, the revised file of (3) should be tagged as 110a, 110b, 110c.

6. Supplement Information

Detailed information on the Suzaku instrumentation, such as capabilities of scientific instruments, is summarized in the Technical Description (TD) document, which can be found at We plan to update the TD document, as well as the proposal planning tools, in the middle of October, 2012. Until then, the proposers are advised to use existing versions of them. For those who are not familiar with Suzaku data, we summarize how to “walk through Suzaku analysis” and a few set of test data (of Crab and other typical X-ray objects) at

7. Contact point

Feel free to contact

suzaku_ao9 'at' astro.isas.jaxa.jp
if you have any question on AO-9.