Harvey Tananbaum and Belinda Wilkes welcomed the committee on behalf of the CXC.
Roger Brissenden presented the "CXC Manager's Status Report" in which the current status of the CXC and the observatory were summarized. Roger reported that the FY07 cuts to the CXC budget were absorbed without major impact, partly by shifting some expenditures into FY08. However, he predicted that further budget cuts could not be suffered without a real impact on CXC resources or staffing. The CUC continues to appreciate the professionalism with which the CXC has dealt with the budget situation and, in particular, the manner in which they have aggressively protected GO funds. It was also reported that NASA-HQ has directed MSFC to formulate an operating plan through to 2014 as well as an additional year of post-operations for data analysis. The CUC welcomes this news.
In terms of CXC facilitates and operation, it was reported that the equipment for the backup OCC has been purchased and received, and is currently being installed at the Cambridge Discovery Park site. The spacecraft and ground operations continue to proceed extremely smoothly. No spacecraft anomalies were reported during this period (April 2007 to September 2007) and observers continue to receive their data approximately one day after it is taken. The CUC is grateful for CXC's continued efforts to ensure smooth operations and rapid data distribution.
Harvey Tananbaum summarized the use of Director's Discretionary Time (DDT) during the period from Apr-07 to Sep-07. In particular, Harvey discussed the allocation of 1Ms of DDT to the Chandra Deep Field South (CDFS), increasing the total exposure on this field to 2Ms. The CUC continues to support the Director's approach to DDT. On behalf of the community, the CUC also appreciates being consulted during the time that the CFDS DDT program was being considered.
Harvey Tananbaum discussed proposed modifications to the LP and VLP programs. These modifications were prompted by the decision not to proceed with the Extremely Large Project program (ELP; see April 2007 CUC report). The motivation for these changes is to make very ambitious programs (requiring 3Ms of Chandra time) feasible should the scientific return be justified. The current policy is that, from a total pool of 6Ms, at least 3Ms be assigned to LPs and at most 3Ms be assigned to VLPs. The CUC was asked to comment on two possible modifications to this policy:
a) Create a single pool of time (6Ms) in which LP and VLPs would openly compete.
b) Within a 6Ms pool, allocate at least 2Ms to LP, and at least 2Ms to VLP. The remaining 2Ms can be openly competed by either LPs or VLPs.
The Director also requested feedback from the CUC concerning proprietary data rights for LPs and VLPs. At the current time, LPs carry the normal 1 year proprietary data rights whereas VLPs do not carry proprietary data rights.
See RECOMMENDATIONS for the committee's response to these requests.
Belinda Wilkes presented a summary of the Cycle-9 peer review. As summarized in the last CUC meeting, a total of 661 proposals were received resulting in an overall over-subscription by time of 5.5. There were two changes to the peer review process as compared with previous cycles. Firstly, observing constraints were now sub-divided into three categories (easy, average and hard). It was found that the "easy constraint" time was oversubscribed by a large factor (11) whereas the "average constraint" time was oversubscribed by only 1.4. During the review, the CXC made the decision to combine the easy and average time in order to smooth out this discrepancy. The CUC agrees with this decision. Secondly, a new web-based system for dealing with conflicts of interest was implemented and worked very well. The CUC continues to be extremely happy with the professionalism with which CXC runs the peer review.
In response to the recommendations of the previous CUC meeting, Belinda reported on a PI survey aimed at assessing the impact of the archival and theory program. At the time of the CUC meeting, the deadline for responding to the survey had recently elapsed and so the results of the survey had yet to be processed. The CUC thanks the Director's Office for responding to our recommendation and looks forward to seeing the results of this survey.
Paul Plucinsky described the current status of the ACIS. No instrument anomalies were reported during the Apr-07 to Sep-07 period. During this period, thermal constraints led to the turning off of "optional" CCDs in only three observations - in all cases, only one optional CCD was turned off.
Thermal constraints continue to be the most challenging issue facing the ACIS team. In particular, heating of the focal plane by tail-Sun irradiation is becoming a significant issue. It was reported that the ACIS team is continuing to explore possible procedures to mitigate this heating, including turning off the ACIS DH heater. Tests of this procedure were planned for October, including the use of one segment of the DDT CDFS observation to check the effect of turning off the ACIS-DH heater on the final astrometry of the data. The CUC was encouraged by the CXC's initial assessment of the degree to which mission planning constraints may be relaxed if this heater turn-off procedure is validated.
Larry David presented an update on calibration. Larry reported that time-dependent HRC-I gain tables have now been released, as have revisions to the LETG effective area near the O-K edge. It was also announced that the verified Linux version of SAOsac had been delivered to SDS and is in the process of being packaged into a user-downloadable version. A release date for this software appears not to have been established. The CUC was also updated on the current status of the ACIS filter contamination. The optical depth of the contaminant continues to grow, but the rate of increase has definitely decreased compared with early times. The CUC continues to appreciate the excellent work of the calibration group.
Jonathan McDowell discussed activities within the Science Data Systems (SDS) group. Beta releases of CIAO-4.0 are proceeding as planned, with a full release planned for Dec-15 2007. The second beta release was the first deployment of Python within CIAO - some bugs have been discovered (concerning conflicts with pre-existing versions of python that happen to be present on a given system), but the deployment generally went well. Jonathan also announced plans to drop support for CIAO under RedHat-8. Finally, Jonathan presented science updates for the catalogue effort. The CUC continues to appreciate the excellent work of SDS.
Jonathan posed two questions to the CUC. Firstly, he asked for suggestions on output products that would be most valuable for grating analysis. Secondly, he asked for CUC recommendations for future CIAO developments. The CUC will consider these questions (in consultation with members of the wider community) and report them in the next CUC report.
Ian Evans presented an update of efforts related to Chandra Source Catalogue. It was reported that the schedule has slipped by approximately 2 months since the last CUC meeting 5 months ago. In response to questioning from the committee, it was explained that this delay was incurred at the beginning of the period (i.e., was due to "start-up" problems) and that work had been proceeding at the expected rate since that time. The revised date for the first data release is June-2008, with a full catalogue release in October-2008. Ian explained that the processing of large volumes of data had uncovered subtle issues in some central CIAO tools such as discontinuities in distributions of source extent as measured by wavdetect. Discoveries from catalogue related issues are being fed back to SDS for examination.
The CUC continues to believe strongly in the scientific importance of the Chandra Source Catalogue and is very pleased to see real progress towards the construction of this catalogue.
Finally, Sabina Bucher presented the prospects and technical issues involved in achieving a 15 year mission for Chandra. It was shown that there are no known issues related to spacecraft health which should be problematic for a 15 year mission. Sabina presented detailed orbit modeling, showing that the orbit will elongate. The elongation of the orbit will have several effects on mission planning. The more rapid passage through the radiation zones could, by itself, produce a gain of up to 7 hours of science time per orbit. However, the lower perigee dramatically increases tidal torques on the spacecraft and momentum off-loading issues can be expected to dominate mission planning. Sabina also discussed the on-going strategy to relax the constraints on the allowable temperature for the EPHIN. Detailed modeling was presented, showing how this strategy will improve pitch angle constraints from the current time through to beyond the 15 year mark.
This presentation underscored the complex set of constraints that the mission planning team must manage in order to make the observatory function smoothly. The CUC would like to thank the mission planning team for this excellent and crucial work.
The CUC continues to be extremely satisfied with the quality and professionalism of support that the CXC brings to the spacecraft operations, data systems, and the user community. The CUC is also extremely pleased by the responsiveness of the CXC to previous CUC recommendations and requests.
On the basis of the presentations and subsequent committee discussion, we have a number of specific comments, suggestions and recommendations for the CXC.
LARGE AND VERY LARGE PROJECTS : The CUC is mindful of the need to allow for ambitious projects that may produce very high-impact results while not adversely affecting the community's ability to perform the more modest (but still significant) investigations that are often proposed as LPs. The CUC supports the care exercised by the Director in considering modifications to the LP and VLP programs.
RECOMMENDATIONS : The CUC recommends that the 3Ms "barrier" between the LP and VLP programs be removed. In other words, the LP and VLP proposals should be allowed to openly compete for a 6Ms pool of observing time, with the peer review deciding upon the division of time between the two categories depending upon the scientific value of the proposals. We believe that this will promote (or at least make possible) ambitious projects requiring ~3Ms of observing time while, at the same time, ensuring that only the most worthy of such projects with extremely high scientific return are selected.
At the present time, we do not recommend changing the policy regarding proprietary time for LPs and VLPs, i.e., we recommend that data from LPs be awarded to the PIs with the usual standard 12 month proprietary time (unless the PI voluntarily waives these data rights) but that data from VLPs be awarded with no proprietary time. We do, however, recommend that CXC continues to review this policy over the coming cycles with an eye to a possible policy change in the future.
SPECTROSCOPIC OBSERVATIONS : A portion of the user community continues to feel that the high-resolution spectroscopic capabilities of Chandra are under-utilized, and that the basis for this under-utilization is a perceived difficulty in winning a spectroscopic proposal (which usually requires significant observing times). The CUC notes that the percentage of successful grating proposals is similar to that of non-grating proposals, which does not support the hypothesis that grating proposals are more difficult to win than non-grating proposals with the exception of Cycle 9 when HETG success rate decreased substantially. However, we caution that the community is extremely sensitive and responsive to both real and perceived trends and/or biases in the review processes, and so many potential grating proposals may not even be submitted as a result.
At a previous CUC meeting, we recommended that the awareness of the community to the promise of high-resolution X-ray spectroscopy be increased via a scientific workshop. The CUC congratulates the CXC and the Scientific Organizing Committee on running a successful workshop in July 2007 on X-ray Grating Spectroscopy. This meeting was a valuable forum in which to present the most exciting results that have been obtained from X-ray grating spectroscopy, as well as discuss future potential. Unsurprisingly, however, the conference attracted scientists who were already well-acquainted with high-resolution X-ray spectroscopy. We encourage the CXC to continue to explore ways of increasing the awareness and use of grating spectroscopy, most especially to the parts of the community that have not traditionally been engaged in this field. This could involve more outreach at more general-interest conferences, improved documentation for existing software, or other methods.
CHANDRA SOURCE CATALOGUE : The CUC continues to believe in the high scientific value of the Chandra Source Catalogue, and commends the CXC on making progress on the construction of this catalogue.
RECOMMENDATIONS : The CUC reiterates its previous recommendation that, barring unexpected mission-critical occurrences, the CXC/SDS/DS should commit to remaining on the current schedule. We also recommend that the catalogue requirements and specifications document as well as science study reports be made publicly available as soon as possible and linked to the CXC website.
The CUC recommends that the CXC explore including research based primarily on the source catalogue within the purview of the Archival Program. As there may be significant interest in the broader multiwavelength community to use the new catalogue as part of a larger study, the question of how closely related such a proposal must be to Chandra should be explicitly considered by the CXC.
CONSTRAINTS AND MISSION PLANNING : The CUC continues to be extremely satisfied with the highly professional and competent manner in which the mission planning team manages a complex set of constraints. The CUC supports the steps taken by the CXC to sub-classify "constrained observations" into easy, average and difficult constraints. We also agree with the decision made during the peer review process to combine the easy and average constrained time in order to achieve balance between these two categories.
RECOMMENDATION : The CUC requests an update at a future meeting on the practical implementation of the sub-classified constrained observations, and whether the sub-classification of constrained observations aided the mission planning team in a meaningful manner.
CIAO : The CUC continues to be extremely satisfied with the highly professional and competent work of SDS and DS. We are, however, concerned that a large fraction of the user community may feel unable to use the advanced functionality of the new CIAO, Sherpa and CHIPS.
RECOMMENDATION : The CUC recommends that the CXC make steps to educate the wider user community on the advanced functionality of CIAO and related packages. We suggest that this be achieved via CIAO workshops at relevant large meetings (such as the AAS meetings), as well as web-based "advanced science threads" that walk the user through how to script and then execute a particular data analysis task.
In addition, the long-term prospects for supporting both Python and S-lang in CIAO seem poor and potentially wasteful to both the CXC and users as eventually one of the two will dominate most uses. We recommend that the CXC consider a mechanism by which, on the timescale of a couple of years, a decision can be made to support just one of these languagues.
CHANDRA FELLOWS PROGRAM : The CUC is extremely pleased by the success of the Chandra Fellowship Program, with 104 applicants last year for 5 positions. Chandra Fellowships continue to be one of the top Fellowship programs in the field.
RECOMMENDATION : The Chandra Fellows' Symposium is a valuable resource to the community. The CUC recommends that talks at the Symposium should be recorded and archived. In addition, the CXC may wish to consider live-streaming of the symposium. These steps would allow the wider community to benefit from these high-quality presentations.