2009 August 28
Announcement of Opportunity (AO-5) of Suzaku
Kazuhisa Mitsuda (Project manager, ISAS/JAXA)
Tadayuki Takahashi (Project sub-manager, ISAS/JAXA)
Hideyo Kunieda (Project scientist, Nagoya University)
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 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-5 observations in 2010 April, and hereby solicit submission of observing proposals.
In AO-5, we will accept observations using P-sum/timing mode for the XIS up to 5% of the total ordinary observation time.
We will continue to solicit the Key Project proposals, which was initiated in AO-4, in order to fully utilize unique capabilities of Suzaku, and allocate 2000 ksec for them. In the Key Project program, 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. The data taken in the Key Project program and those of ordinary proposals with an exposure time equal to or greater than 300 ksec are to be opened immediately after the initial data processing is completed and no proprietary is rewarded to the proposer.
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 satellite carries four modules of the X-Ray Telescope (XRT) that focuses X-rays up to ~10 keV with a high efficiency. In the focal plane of each XRT is mounted an X-ray CCD camera (XIS) module. The XIS has a 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
(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 dedicated for AO observations. The AO-5 program (1 year period starting on 2010 April) will be run under the same policy. The remaining 87% of the total time, which amounts to 360d x 38 ksec/d x 0.87 = 11902 ksec, is open to the AO-5 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 4541 ksec is the time for Japanese scientists in AO-5. All proposals out of 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 decided 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. Proposal Policies
(1) The complete list of the targets accepted by AO-4 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 except for 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. On the other hand, some of the priority C targets and ToO targets are not observed. 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 these unobserved C targets or ToO targets are possible to be observed by the end of AO-4 period (March 2010). 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 from the same PI is accepted at a higher priority (A or B) in AO-5. Otherwise the observation carried out in AO-4 is ignored, and the target is open for competition in AO-5.
(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 is, however, required stronger scientific justification. Note also that any observations based on a proposal whose approved total observation time is equal to or greater than 300 ksec are to be opened to public as soon as the data are ready to analyze (No proprietary is rewarded to the proposer).
(3) As in AO-4, we solicit Key Project proposals in AO-5, 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 on the Key project. This will provide 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 over several years, and so on, by fully utilizing unique capabilities of Suzaku. The dead line of the Key project proposals are the same as that of the ordinary proposals (solicited by this announcement), 2009 Nov. 20. They are sent to the initial refereeing process in Japan and US separately. The principal investigators 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-5. The data taken in the Key Project program are opened to public immediately after the data are ready for analysis.
(4) Submission of the same proposals both to the Key Project and the ordinary observation is strictly prohibited. If the same researchers are found in the Co-I lists of both proposals, they are rejected without being sent to the refereeing process.
(5) 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-5 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. 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. If the total exposure time to complete the requested number of targets is equal to or greater than 300 ksec, the data will be opened to 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 certain 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 has to activate 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 PI is requested 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 should be carried out in the style that the other instruments follow the Suzaku schedule.
(7) 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 by e-mail
The proposer has no proprietary on the realtime ToO observation data. Realtime ToO observations on gamma-ray bursts will be planned by the Suzaku Science Working Group, referring to information from various other observation networks.
(8) In AO-5, 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-dimentional image can be obtained. Note, however, that the P-sum/timing mode can be used only for XIS0 and XIS3, and 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 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. Swiching the XIS to the P-sum/timing mode poses relatively high load to the operation team. Hence, total time of the P-sum timing mode observations will be limited up to 5% of the ordinary observation time (11902 ksec, see section 3).
5. Schedule of the reviewing process
(1) Researchers who affiliate with Japanese institutions or who do not belong to US nor ESA institutions should submit their proposals to ISAS/JAXA according to this AO document. The deadline of proposal submission is at noon of 2009 November 20 (JST). All proposals submitted to ISAS/JAXA are to be reviewed in the same process in Japan. Selection of proposal will be made in February 2010 in Japan side. The ESA-selected proposals are merged at this stage. The Japan-US merging committee will be convened in labe February - early March 2010. The final observing program of AO-5 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. Priority A targets will be preferentially observed during the AO-5 period (2010 Apr to 2011 Mar), and the observation is regarded as completed if the exposure time is more than 90% of the requested time. Priority B targets are tried to be observed during AO-5 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. Priority C targets will be scheduled 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.
6. Data right
The data taken in the ordinary observation program are immediately delivered to the proposer. The proposer 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 the ordinary observation proposals whose total exposure time is equal to or more than 300 ksec, those based on Key project proposals and realtime ToO proposals.