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2. Changes Since AO-7

This page summarizes the main changes to the Suzaku Technical Description since the last AO and re-emphasizes several important issues to consider for the preparation of proposals. Please note that this should not prevent the user to carefully read the new version of the Technical Description.


  1. The total time nominally available for observations to the community is again 11902ks in AO-8 (11902ks in AO-4 to AO-7, 12038ks in AO-3, 11722ks in AO-2). 2Ms will be used for continuing Key projects, accepted in or before AO-7; any remaing time will be added to the Joint Japan-US time. 5451ks are assigned to Japanese observations, this includes 909ks for proposals submitted to ESA as joint Japan-ESA observations, and 3963ks go to US observations. The remaining 488ks are foreseen for joint Japan-US investigations.

  2. Every possible measure to enable normal observations through the end of the AO-8 period (2014 March 31) will be taken, but still the operation of a subset of the instruments might have to be stopped if the power shortage becomes serious enough. Further degradation of the power supply may even lead to premature termination of AO-8. A simple extrapolation of the power history implies that a partial shutdown of the scientific instruments should be considered around early 2014. However, this estimate depends on the radiation environment on orbit, such as the activity level of the Sun.

  3. Given this, all new Cycle 8 proposals should stand on their own merits, in the sense of not requiring future (Cycle 9) Suzaku observations.

  4. Previously, targets with Sun angles in the range 65 to 110 degrees were accessible for Suzaku observations. Considering the power situation, the Sun angle range will be restricted to 70-110 degrees for AO-8 observations.

  5. It is conceivable that the amount of time available for target-of-opportunity and time critical observations will have to be reduced.

  6. The Key Project proposal category was introduced in AO-4 for comprehensive observing programs sampling a number of objects of a particular class or surveying a large region of the sky, in order to take maximal advantage of the unique attributes of Suzaku to address important astrophysical problems. While no new Key Project proposals will be solicited in AO-8 given the power supply degradation, the project team decided to concentrate on completing Key Projects that have been accepted in previous cycles.


  1. The category of ``Long Program'' for proposals with a total exposure time $>$300ks, available in (only) the US from AO-3 to AO-6 has not been offered since AO-7 anymore.

  2. As before all projects with total exposure times equal to or more than 300ks are open to the public immediately.

  3. Regular US proposals may request no more than 1Ms of observing time for practical reason (ISAS/JAXA proposals may not exceed total exposure times of 400ks). Note that for TOO proposals this 1Ms limit applies to the actually requested observing time. It is therefore possible to request 400ks per target for up to 2 triggers among 5 potential targets, for example.

  4. Since AO-5, individual raster scan observations have to have the same minimum exposure time of 10ks per pointing as other observations.

  5. XIS1 suffered a micro-meteorite hit in December 2009. Following diagnostic measurements showed that the scientific impact is minimal. See section 7.3.6 for more information about previous micrometeorite hits and their effects.

  6. The use of the HXD nominal aim point is discouraged. To this end the HXD team will no longer provide response matrices for simulation for observations at the HXD nominal aim point. The XIS team will no longer support observations at the HXD nominal aim point that use the P-sum mode, the Window option or the Burst option.

  7. Two Suzaku memos provide information about the jitter of the pointing direction that can affect observations since the end of 2009
    ( and
    Note that the first one describes an effect - the observed light curves being modulated due to telescope vignetting - that is mitigated by not using the HXD aim point.

  8. Proposals using the P-sum/Timing mode of the XIS are encouraged. There is no longer a limit on the amount of P-sum/Timing mode observations that can be accepted. Proposers should be aware of the properties of the P-sum/Timing mode. Photon pile-up scarcely occurs in this mode, and a time resolution as fast as 7.8ms can be achieved, but only a 1-dimensional image can be obtained. Note that the P-sum/Timing mode can be adopted only for the XIS3, and neither the Spaced-row Charge Injection nor a CTI correction can be applied. The energy resolution is therefore significantly worse than in the normal imaging mode. The calibration accuracy is not as good as that for the normal imaging mode, either.

  9. XIS recipes for P-sum data reduction and pile-up detection have been released which are useful for planning observations requiring high time resolution and pile-up mitigation. Please see

  10. For feasibility studies of HXD data analyses proposers should simulate observations with the responses and background files provided for the XIS aim point, then analyze them by varying the background by typically $\pm3$% for the PIN and $\pm1.5$% for the GSO. This procedure mimics the level of systematic uncertainties in the current HXD background models (see sections 5.5.2 and 8.5). The background files were generated based on the Lockman hole observation performed on 2009-06-12. The PIN threshold of Epoch 9 has been applied. Channels below 15keV should be ignored due to uncertainties in the response and background. As long as this is done, simulations based on these files are suitable for simulating AO-8 observations.

  11. Note that the Suzaku project has an agreement with the Fermi project as well as with the Chandra project to make a modest amount of Suzaku time available for allocation through their proposal review processes for investigations that take advantage of joint observations. See Chandra and Fermi calls for proposals for further details.

  12. Real-time TOO proposals (outside the AO process, through for gamma-ray bursts can be submitted by all investigators, including those who are not part of the Suzaku science working group.

next up previous contents
Next: 3. Mission Description Up: Suzaku Technical Description Previous: 1. Introduction   Contents
Michael Arida 2012-10-19