Belinda Wilkes welcomed the committee on behalf of the CXC. New members of the committee were introduced.
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 current year budget is unchanged from the POP07, although the out-years have seen budget reductions. Staffing levels remain at FY06 levels; the only major staffing change is the Flight Operations Manager with Sabina Bucher replacing Dan Stropshire.
In terms of CXC facilitates and operation, it was reported that backup OCC equipment has now been installed and is expected to be operational in Summer 2008. The OCC itself passed an extensive security audit and was given formal Authority to Operate in September 2007. A major upgrade of the storage cluster was also undertaken.
The spacecraft and ground operations continue to proceed extremely smoothly. All mission metrics are good and do not pose limits to mission lifetime. No spacecraft anomalies were reported during this period (September 2007 to April 2008) and observers continue to receive their data approximately one day after it is taken. During this period, tests were performed to gauge the impact of turning off the ACIS detector housing heater to alleviate some aspects of the thermal constraints. These tests were successful and the heater was turned off permanently in April 2008.
In all respects, the CUC continues to be impressed by the professionalism and competence with which the CXC and the observatory are managed.
Harvey Tananbaum summarized the use of Director's Discretionary Time (DDT) during the period from Sept-07 to Apr-08. The largest allocation of DDT during this period was the completion of the Chandra Deep Field South (CDFS), bringing this field to a total of 2Ms. This establishes CDFS as a prime very deep field for multiwaveband follow-up. Harvey reported that a total of 10 proposals were received as part of the special call for proposals to support work on the CDFS data. Four proposals were accepted (PIs : Brandt, Ptak, Cardamone, Hickox), supporting a range of complementary investigations. A number of smaller DDTs were also described. The CUC continues to support the Director in his use of DDT time, and feel that he strikes the correct balance in his operation of this program.
Belinda Wilkes presented a summary of the community's response to the Cycle-10 Call for Proposals. A total of 639 proposals were received, representing a 5.6 oversubscription of observing time. While the total number of proposals is less than previous cycles, the oversubscription in time is flat compared with previous cycles demonstrating the expected move to fewer, longer proposals. Thus it is very clear that the demand for Chandra remains extremely high, even going into Cycle-10. In response to the CUC recommendations from the Sept-2007 meeting, the policy concerning time allocated to the LP/VLP proposals have been amended so that both of these programs can openly compete for the full available 6Ms (rather than previous asymmetric rule that limited the VLP program to no more than 3Ms and the LP program to no less than 3Ms). We thank the Director's Office for being responsive to our recommendation.
Paul Green summarized results obtained from a "Gratings survey" which asked for suggestions to enhance the high-resolution spectroscopy aspect of the Chandra mission. The survey generated 34 responses out of 170 requests. Generally, the community appeared content with grating-related aspects of the mission, although some responses stressed concern about the apparent difficulty of winning grating proposals (which typically require significantly longer exposures than imaging projects). Some survey responses advocated a separate spectroscopy panel at the proposal review. Other responses stressed the need to inform the wider astrophysical community about the power of Chandra grating spectroscopy.
The CUC thanks the CXC for being proactive in the initiation of this survey. See RECOMMENDATIONS for the committee's response to the survey's findings and the various community suggestions.
Pat Slane explained in some detail the classification of observatory constraints, and settings in which even formally unconstrained observations can be challenging to accommodate. During this discussion, it was reported that the project has halted the relaxation of the EPHIN thermal constraints (discussed in the Sept-2007 meeting) due to the onset of anomalous behaviour. The CUC continues to support the cautious manner in which CXC are investigating and dealing with the thermal constraints.
Larry David presented an update of calibration related issues and progress. Most of the calibration releases during this period have been at the level of general maintanence. Significant progress has been made in the calibration of continuous-clocking (CC) mode data using 3-column charge trailing corrections to the event grades. The CUC is pleased to see significant progress with CC-mode data given its importance to grating observations of the brightest targets.
The most significant calibration issue discussed relates to the effective area of the High Resolution Mirror Assembly (HRMA) and was uncovered via a comparison of galaxy cluster temperatures as measured by the XMM/EPIC detectors and Chandra/ACIS. Larry David reported that the correction for the HRMA "overlayer" (i.e., the layer of hydrocarbon that appears to contaminate the surface of the HRMA) seems to have been implemented twice, once via an empirical (pre-flight) correction and once as a physical contamination model. The result is a ~3% energy-dependent error in the HRMA effective area above 2keV. At the time of the presentation, investigations into this issue were on-going with some degree of urgency, and the calibration team was planning to issue a calibration update asap. The CUC was a little surprised to see a signficant calibration issue come to light this far into the mission operation, but is satisfied by the urgency and high degree of competence with which the issue has been investigated and essentially solved. This issue does, however, highlight the crucial importance of on-going cross-observatory cross-calibration programs. The CUC applauds the CXC for their leadership in these cross-calibration programs, and strongly encourages a continuation of these efforts.
Jonathan McDowell discussed activities within the Science Data Systems (SDS) group. The full release of CIAO4.0 is now complete (with a patch for the Leopard operating system iminent), and an upgrade (CIAO4.1) is baselined for the end of the year. Outreach efforts aimed at publicizing the capabilities of CIAO4 are continuing, with successful events at the HEAD meeting. As part of this, a CIAO workshop is planned for the end of the year. The CUC congratulates SDS on the successful launch of CIAO4, and strongly endorses plans to re-start the CIAO workshops.
Jonathan also updated the CUC on Repro-3, updates to acis_process_events, issues associated with ACIS afterglow detection, the beta release of the DM ascii tool and improved tools for grating analysis.
Ian Evans summarized progress on the Chandra Source Catalog. Important progress has been made during the period since the last CUC meeting, although there has been an approximately 3 month slip since September 2007. Internal software releases required for the catalogue have now been made, and a test has been conducted in which 550 ObsIDs have been run through the pipeline producing a catalogue of approximately 25000 sources. Currently, the first release of the catalogue is scheduled for September 2008, with the formal release to the public scheduled January 2009. Following the recomendations from previous CUC meetings, catalogue science is now explicitly included within the CfP under the archive proposal category.
The CUC continues to believe that the Chandra Source Catalogue will be an extremely important part of Chandra's legacy; the committee was disappointed to hear that, yet again, the schedule has slipped significantly (3 month slip in a 7 month period). We renew our recommendation that the Catalogue be given the highest possible priority subject, of course, to critical mission operations. See the committee's RECOMMENDATIONS on the beta-release of the catalogue.
Partly in response to previous CUC concerns about under use of Chandra's high-resolution X-ray spectroscopic capabilities, there were three presentations focusing on grating related issues.
Norbert Schulz updated the CUC on the special session on high-resolution X-ray spectroscopy at the Los Angeles HEAD meeting. The session was constructed to focus on physical processes, with a talk by Tim Kallman on photoionized plasmas and by Marc Gagne on shocked plasmas. The session was well attended. The CUC commends the CXC for the organization of this session.
Joy Nichols presented a new gratings catalog, TGCat; the goal is to have a web-based interface to the catalogue, allowing the user to access calibrated spectra and visualization products. The alpha release is already complete, with a beta release due this summer. The CUC were very impressed by this project and feel that it could be a powerful tool. See RECOMMENDATIONS.
The final gratings presentation was by John Houck who discussed updated gratings threads aimed at aiding proposal planning as well as analysis. Feedback was requested from the CUC on the most important areas for development of gratings threads. See RECOMMENDATIONS for the committee's response.
Finally, Nancy Evans discussed a proposal to require all host institutes to assign mentors to Chandra Fellows. In addition, Nancy summarized discussions within NASA on combining the various Fellowship programs. See RECOMMENDATIONS for the CUC's response to these issues.
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.
RECOMMENDATIONS : We renew our recommendation that the Catalogue be given the highest possible priority subject, of course, to critical mission operations. We also recommend that the beta-version of the catalogue be released to a limited set of interested parties in order to work out any initial bugs. The set of investigators who *proposed* for (rather than won) Cycle-10 catalogue-related archive proposals would be one such subset.
RECOMMENDATIONS : Although it was suggested by several members of the community via their responses to the gratings survey, the CUC does NOT support a special gratings/spectroscopy panel at the proposal review. We felt that such a panel might lack the topical/contextual expertise to properly assess the scientific merits of a given proposal.
The CUC also recommends that the CXC underwrites the support of TGCat to ensure that this effort continues.
In terms of the gratings-related threads, the CUC feels that both proposal-planning and analysis threads are important, but that the proposal-planning threads should probably be given priority at this stage. The CUC also notes the importance of making these threads XSPEC friendly... at the very least, they should be constructed so that there is a clearly identified break-point where the user can break with the thread (which will probably head down a Sherpa/CHIPs path) and use XSPEC to fit the spectra.
CIAO : The CUC is pleased by the successful launch of CIAO4.0, and the continuing efforts to educate the community about its capabilities. The CUC strongly encourages the CXC to proceed with the CIAO workshop later this year. Following on from the request by SDS to the CUC last Fall, we have solicited suggestions from colleagues for future CIAO improvements/capabilities. We are currently compiling the responses into a coherent form and will send it to the CXC as a separate amendment to this report.
SCHEDULING : The CUC applauds the sterling efforts of the mission planning team to managed the increasingly restrictive thermal constraints. At this stage, we simply ask that we are kept informed about further developments in the thermal constraints.
RECOMMENDATION : The CUC recommends that the Chandra Fellow's office include clear statements about the importance of mentorship in the letter that is sent to the host institutes of successful candidates. However, we recommend against a policy of requiring mandated mentors.
FUTURE OF THE CHANDRA FELLOWSHIP PROGRAM : The CUC has always, and continues to, support the Chandra Fellows Program in the strongest possible terms. It is without doubt considered one of the world's most prestigious postdoctoral fellowships in astrophysics, and supports (or has supported) many of the most successful young high-energy astrophysicists in the country. In addition to simple name recognition, the importance of "community ownership" (in this case, the high-energy astrophysics community) cannot be underestimated...the Chandra Fellowship program is widely acknowledged as the premier high-energy astrophysics fellowship program, and the existence of this program is a crucial back-stop in creating an optimistic environment for young high-energy astrophysicists. For these reasons, we feel that subsuming this program into a more general NASA fellowship program would be damaging to the sociology of the field and, ultimately, the scientific base of the country.
RECOMMENDATION : The CUC supports the ongoing efforts to solve the HRMA effective area issue with high priority. We also recommend that steps are made to inform the community about this issue (including a discussion of the kinds of scientific investigations that could be affected by the calibration problem), possibly via the newsletter or an email bulletin.
JOINT SUZAKU/CHANDRA OBSERVING TIME : The CUC recommends that the CXC explore the possibility of a joint-time agreement with the Suzaku program (such as currently exist with HST, XMM, Spitzer, RXTE, NOAO and NRAO). If such an agreement is possible, we suggest that it be included in the CfP for Cycle-11.
CXC WEBSITE : The CUC feels that the CXC website (http://cxc.harvard.edu) requires some general updating and tidying. The site seems to have evolved into four rather long and unstructured lists of links. We also suggest replacing the current search engine with a modern commercial engine such as Google.