Suzaku Announcement of Opportunity (AO-7)
Tadayuki Takahashi (Project sub-manager, ISAS/JAXA)
Hideyo Kunieda (Project scientist, Nagoya University)
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-7 observations in 2012 April, and hereby solicit submission of observing proposals.
We have made the following changes since the last AO.
We continue to solicit Key Project proposals, for which 2,000 ksec per year of observing time has been reserved. The Key Project program was initiated in AO-4, in order to fully utilize unique capabilities of Suzaku. Suzaku project team expects to carry out observations that tackle important astrophysical issues and will be utilized for a long time after the observations as a legacy of Suzaku. The data taken in the Key Project program and those of other proposals with an exposure times >300 ksec will be placed in the public archive immediately after the initial data processing is completed, and no proprietary period is awarded to the proposers.
During the AO-7 period, observations can also be accepted through the Suzaku-Fermi joint program (initiated in AO-6) and the Suzaku-Chandra program (initiated in AO-4). We refer the interested parties to the Fermi and Chandra home pages, respectively.
This call for proposals 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 modules of the X-Ray Telescope (XRT) 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 moderate spatial resolution, and is particularly suitable for the studies of extended sources. The XIS also has a good spectral resolution for the soft X-ray below 0.8 keV, which is superior to those 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 and the list of targets that have been observed or accepted can be found from the Suzaku Guest Observer Facility homepage.
3. Mission Phases and Time Allocation
The Suzaku mission has been developed and maintained under a 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:
- Observatory Time (3%) for satellite maintenance and related purposes
- Calibration time (5%) for ongoing calibration of the instruments; and
- Director's Discretionary Time (DDT; 5%) for observations of gamma-ray bursts or any genuinely unpredictable events, and other important observations granted at the discretion of the mission director.
The AO-7 program (1 year period starting in 2012 April) will be run under the same policy. TOO observations based on proposals from the MAXI team have been carried out within the 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-7 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-6. 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 principal investigators (PIs) are not Japanese nor from ESA member states is 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).
Observation time from Suzaku-Fermi and Chandra-Suzaku joint programs are included in one of the above nationality-based categories, depending on the PI's affiliation. The Key Project proposal submission is solicited separately.
4. Proposal Policies
(1) Only researchers based in the US and affiliated with a US institution are eligible to submit their proposals to NASA as the PI. In rare cases, a single PI may be considered eligible to submit Suzaku proposals through multiple agencies. Such a PI must, however, choose a single agency for all his/her AO-7 proposals; it is forbidden for a single PI to submit proposals to multiple agencies during a single cycle, even if they are for independent projects. On the other hand, there can be co-Investigators from any countries in proposals submitted to NASA.
(2) The complete list of targets accepted through AO-6 can be found in the Timeline & Mission Information section of the Suzaku GOF site. The observations of 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.
Any PI can submit proposals for the C or TOO targets that are unobserved. It must be noted, however, that unobserved AO-6 C or TOO targets may be observed by the end of AO-6 period (March 2012). 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-7. Otherwise, the observation carried out in AO-6 is ignored, and the target is open for competition in AO-7.
(3) 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 ready for analysis (no proprietary is awarded to the proposer).
(4) An uninterrupted continuous observation is guaranteed for up to 100 ksec. This limitation originates from moon light constraint to the star trackers' field of view, conflict with other time critical observations, and other operational/planning difficulty. The operation team accepts requests for uninterrupted observations longer than 100 ksec, but these will be carried out on a best-effort basis.
(5) We also solicit Key Project proposals in AO-7, with a separate announcement. There is no upper limit for observing time of a Key Project. This will provide a unique opportunity to carry out various projects, such as an extremely long observation of a single object, mapping observations of a certain area of the sky, a long term monitoring observation of an object over several years, that fully utilize the unique capabilities of Suzaku. The deadline for Key Project proposals are also 2011 Nov 10. PIs whose Key Project proposals are highly ranked are requested to make a presentation at a workshop in Japan, which is open to all investigators. Immediately following this workshop, Japan-US merging committee will make the final selection of the Key Project proposals in AO-7.
(6) It is prohibited for a single team to propose an observation that is part of a Key Project proposal also in a regular proposal. Similarly, it is prohibited for a single team to propose the same observation to multiple agencies. If the same researchers are found in the Co-I lists of both proposals, such proposals are subject to automatic rejection.
(7) 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, the estimated probability of the event to take place during the AO-7 period, and the expected duration of the event should be specified in the proposal, as well as other information required for 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. The scientific justification of TOO proposals must specify how many targets should be observed (the number of "triggers") to fulfill the scientific goals 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 public as soon as the first observation is finished. See (3) above.
(8) 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-constrained observation of diffuse sources, and so on. Multi-pointing observations of a variable target (even with no other constraints, such as "3 separate observations any time during the AO-7 period") are also considered TC. So is a background observation to be carried out close to the time of the main target observation. 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 coordinated observation can only be carried out in the other telescopes follow the Suzaku schedule.
(9) Any genuinely unpredictable events, such as gamma-ray bursts and supernovae, can be observed as part of the DDT ("realtime TOO observation"). Proposals for realtime TOO observations are accepted at any time outside the selection process of ordinary proposals. See this ISAS page for further details. There are no proprietary data rights for realtime TOO observations. Note that real-time TOO proposals for gamma-ray bursts will be accepted from any investigators in AO-7..
(10) The Suzaku project 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 is unimportant, 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 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. In addition, calibration accuracy is not as good as that in the normal imaging mode. Refer to the technical description document for the details of the P-sum/timing mode.
(11) The project team has supported two default aim points since AO-1: the XIS nominal and the HXD nominal positions. The support for the HXD nominal poisition will be dropped in AO-7. As a result, the standard response matrices will not be provided for the HXD nominal pointing. No observations with non-standard readout clocks (P-sum/timing mode and window/burst options) will be carried out at the HXD nominal position. Note, however, that the operation team does not prohibit observations at the HXD nominal point with a standard XIS mode, at the proposers' own risk.
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 2011 November 10 at 4:30 pm EST for proposals submitted to NASA. After the US national review, a Japan-US merging committee will be convened in late February or early March, 2012, 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-7 period (2012 Apr to 2013 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 (=7141 ksec), 0.3T (=3571 ksec) and 0.5T (=5951 ksec) 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.
Reserved 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.
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