Harvey Tanabaum opened the meeting and welcomed the committee on behalf of the CXC. Members of the CUC then introduced themselves.
Roger Brissenden gave the "CXC Manager's Status Report". The current budget is on track with the FY09 Operating Plan. FY 10-13 budget guidelines have been released by NASA HQ, and are currently being assessed. The proposal is under development reponding to the RfP for the CXC contract extension for a further 9 years.
The testing of the OCC backup computer system has been completed, and the system has been shown to be capable of supporting mission operations. A new flight software manager has been appointed, who is performing well.
The spacecraft continues to operate well. A transition to normal sun mode occurred on 10/21/08, with the loss of one orbit (168 ks) of data. The possibility of rare Interface Unit resets caused by SEUs was known prior to launch and accepted and designed for in the safing system.
There have been three such events in recent months, during a time of deep solar minimum. The CUC are confident that the situation is being monitored with "due diligence".
The science instruments continue to operate extremely well. ACIS flight software v.44 is performing nominally.
Mission metrics are good and do not pose limitations to the lifetime of the mission. The observing efficiency remains constant at around 68%.
Thermal constraints (from EPHIN) once again are impacting viewing efficiency, as seen for example in the observing statistics for February 2009. As a result, the EPHIN temperature limit has been increased and the observing efficiency has returned to its expected level. The continued warming of EPHIN leads to degradation in its preformance, so the HRC anti-coincidence has been inserted as a second monitor for radiation events which are used to protect ACIS.
Guest observers continue to receive their data within approximately 36 hours. Grant issuance is typically carried out within 3 weeks of data delivery. In all aspects, the CUC remains very impressed with the degree of professionalism in the operation and management of the Chandra program.
Harvey Tananbaum described the use of Director's Discretionary time. Within Cycle 9, a further 50 ks have been awarded to be added to 233 ks previously allocated, leaving a significant portion of the 700 ks available unused. Pitch angle constraints due to the warming of the EPHIN are starting to restrict the use of DDT. The CUC continues to support the director in his use of DDT, and in particular the conservative approach to relaxing the thermal constraints.
Andrea Prestwich summarized the Cycle 11 peer review so far. A total of 668 GO proposals, requesting a total of 92623 ks, were received, representing a 5.6 oversubscription in time. These include 50 LPs and 9 VLPs. Compared with Cycle 10, 9% more time was requested in total, but the LP and VLP request is down by 6%, possibly reflecting the preoccupation of many members of the community with the decadal survey. In other categories, there were 65 archive proposals (oversubscription of 4.4) and 40 theory (oversubscription of 5.3), both similar to cycle 10. The peer review is scheduled for 23-26 June, with no big changes from last years' procedures anticipated. The CUC is gratified that demand for Chandra in the X-ray astronomy community remains high 10 years into the mission, even as newer missions such as Swift and Suzaku become available.
Larry David reviewed the status of the Chandra calibration. There have been three CALDB releases (4.1.0, 4.1.1, & 4.1.2) since the last meeting, as the calibration of the HRMA is improved. In analyses of cluster temperatures, using CALDB 4.1.1 instead of 3.2.1, agreement with XMM MOS is improved in the 2.0 - 7.0 keV band, and also, but to a lesser degree, in the 0.5 - 7.0 keV band. However the flux in low temperature clusters seems now to have a 9% difference as measured by Chandra with respect to not just XMM, but all other recent X-ray missions as well (ROSAT, ASCA, and Suzaku; see e.g. Snowden, S.L., 2002, http://xxx.lanl.gov/abs/astro-ph/0203311 Published in ESTEC Symposium 'New Visions of the X-ray Universe in the XMM-Newton and Chandra Era';Table 1, especially column 3).
The understanding of the ACIS filter contamination has progressed. A more complete calibration spectrum from the 55Fe electron capture source has been compiled. The contamination appears to be more subtle than previously thought, having a spatial dependence on the filter as well as the temporal variation. A new contamination model is scheduled for release in June.
Further work has revised the HETG efficiencies, checked the HRC-I/ACIS cross calibration with the new HRMA effective areas, and refined the HRC-S quantum efficiency.
Jonathan McDowell summarized progress within the Science Data Systems (SDS) group. CIAO 4.1 was released in December, with a 4.1.2 patch due in April, containing more catalog tools. Also included are grating threads for Sherpa, as the CUC recommended in the previous report. CIAO 4.2 is scheduled for release late in 2009, and planning for new science tools is underway. One issue to be faced is whether to continue supporting both S-lang and Python as scripting languages. Previous CUC recommendations have been to phase out S-lang and the move over to Python. We return to this (and other issues) in our recommendations below.
The CIAO helpdesk has received 90 new tickets, of which 11 are still open as of the time of the meeting. The initial response times and the median time taken to resolve a ticket (measured in hours to days) remain completely satisfactory.
Ian Evans reported on the Chandra catalog release on 3/4/09. The catalog includes 94676 unique Chandra sources among 135914 individual source locations. Papers detailing the catalog and the statistical characterization are in preparation. The current release includes point and compact sources up to 30 arc seconds angular size, and a statistical characterization of the derived source properties.
The CUC was also fascinated by the demonstration of the catalog with the interface to ds9, and the plans for a Google Sky interface. We return to this in our recommendations section.
Dave Huenemoerder described the grating catalog released on March 25th 2009 (no longer a beta release). The catalog processed 863 observations of 290 distinct sources. The CUC were very impressed by many features of this work; the thumbnail spectra available as one browses, and possibility to download a reduced spectrum together with the script that produced it to give the user a starting point for their own scripting.
Mike Nowak outlined the development of threads to assist in analysis of grating data. The "grating spectroscopy" threads have been moved to a more prominent position among the science threads, and a grating analysis thread guide has been included to indicate a minimal "bare bones" path through the threads. Different detector/grating combinations are treated separately, threads to perform simple analysis tasks have been provided, following CUC recommendations in the previous report. All in all the CUC believe these last two presentations (Huenemoerder & Nowak) represent important progress in making grating data analysis accessible to a wider community of users.
Nancy Evans reported on the first Einstein Fellows competition. The committee met in January to review 156 applications. Only 12 offers needed to be made to achieve 10 acceptances. The CUC are satisfied with the outcome of the reorganization of the fellowship program, and compliment Nancy Evans once again on its success.
Ken Ebisawa gave a presentation concerning a graphical browsing tool for the Chandra archives. He demonstrated tools developed for Suzaku and JAXA/ISAS; the JUDO (JAXA Universe Data Oriented) tool that displays Suzaku, ASCA, ROSAT, and IRAS images with a mouse interface, and UDON (Universe via DARTS ON-line) that can display Suzaku pseudo-color images and extract light curves and spectra, and discussed the possibility of producing a new Chandra tool to navigate the Chandra database using a graphical "sky" interface.
DISCUSSIONS AND RECOMMENDATIONS
Calibration. As mentioned above, while the agreement in cluster temperatures between Chandra, and XMM and Suzaku appears to have improved with the latest updates, the 0.5 - 2 keV Chandra flux now appears to be in disagreement not just with XMM and Suzaku, but many other x-ray astronomy missions as well. While the CUC do not consider that agreement with other missions should be the ultimate goal of calibration, and endorse the approach of the Chandra calibration team of trying to understand the instrumentation in as much detail as possible, we remain concerned at the continuing problems surrounding the Chandra HRMA calibration. We cannot really find fault with the technical approach, but wonder if better communication with the user community could be facilitated.
RECOMMENDATIONS1.1 Giving the changes in fit parameters for e.g. cluster source and AGN with power laws (extreme thermal and nonthermal sources) for each change in the CALDB. This would allow users a clearer idea of by how much their fit parameters could be in error due to the calibration uncertainties.
1.2 A significant update to the instruments and calibration section on the Chandra website is needed. The initial table describing all calibration topics and their current status is useful, but there is no way for a user to know which topics are under active investigation; some bolding or use of color would help. At the next level down, however, we note that old archived powerpoint presentations are not adequate. We suggest written memos, possibly short, that describe the issues being worked by the calibration team. These can be then categorized as "Open Issues", "Best Working Guess" and "Obsolete Items" (or similar). Short reports on the HRMA A_eff (re)calibration and ACIS contamination represent especially important and timely items to include in the revamped Cal section of the (newly reworked) CXC website.
1.3 Working with the CIAO team to annotate the CIAO analysis threads with warnings regarding the calibration at the appropriate places. Many users may just skim the real documentation (we know they should read it properly, but this is human nature!) and warnings in the threads would force them to take notice.
1.4 The HRMA discrepancies were found and certainly addressed as an on-going effort of the IACHEC group that looks into the cross-calibration of several X-ray missions. We strongly recommend that CXC continues its involvement in this consortium.
Software. As with the calibration, we have no real complaints about the technical quality of the work of this group, but similarly do have some concerns about their relationship to the user community. We now have two versions of CIAO, 3.4 and 4.1 that are currently widely used, and suspect that despite the 731 downloads of CIAO 4.1, the vast majority of users are still working with CIAO 3.4, largely due to the overheads associated with learning the new interface. We make the following recommendations:
RECOMMENDATIONS2.1 Survey current CIAO users to determine which version they are using and why, along with what they would like to see included in the next versions. A selected sample of recent authors of Chandra data based papers would work, or some other criteria to avoid self selection bias -- follow up may be needed to get a complete, or near-complete survey. As one example, the CUC believes that the software industry is going to go with Python and recommend that the Chandra software do the same, but this would be a good question for the survey.
2.2 Make more example files available for the new interface. The service available to translate users' scripts is valuable, but the Chandra SDS group should understand that many people will be nervous about revealing their programming techniques (or lack thereof) to software professionals. [Some authors of this report would certainly be in this category!] In addition, even if the translation were perfect, the user would still have to explain the purpose of the code to the team, then test the results, and finally understand how it works -- a significant effort, even if less than rewriting it themselves. Making (many!) more example scripts available would allow users to make their own substitutions or translations as needed.
2.3 The SDS need to market their software more effectively to the Chandra community. Something like an EPO effort (although of course this is not really public outreach, but outreach to professional astronomers) to motivate users to upgrade to CIAO 4.1 and Sherpa seems to be required. We are really suggesting that more effort be put into making better use of the existing functionality of the software, rather than developing more.
2.4 It would also be good to hear (for example at the next CUC meeting) about CXC medium and long term plans for CIAO: which platforms will be maintained for how long, what is the planning for the time after the operational phase (i.e. post-existence-of-CXC, will the number of builds have to be decreased, are there any plans to go for virtual machines, grid solutions, etc)?
2.5 Put mean/median helpdesk response times on the Chandra website so that people know they are fast.
Catalogs: As mentioned before, the presentation of graphical interfaces for accessing source catalogs generated much interest and discussion among the CUC. So far, these interfaces all seem to be isolated efforts (the Chandra Source Catalog, TGCat, the JUDO and UDON interfaces developed for Suzaku) so:
RECOMMENDATIONS3.1 At a minimum we recommend that the various catalogs and interfaces have links to each other. In particular a link to SIMBAD would be desirable. Since most astronomers use this to search for sources, it would be a shame if Chandra sources did not show up in a SIMBAD search. It is also particularly important for a user to be informed that just because a position returns no 'hits' in the (evolving) Chandra source catalog does NOT mean that that position has not yet been observed by Chandra. In the longer term the CUC would be very excited to see a uniform graphical interface that allows access to all of the data of interest of a particular source from the various missions.
3.2 The user interface to the catalog should be reconsidered, perhaps with advice from the ds9 developers -- who themselves have a goal of immediately-usable software. The current interface, tool tips and help, and error messages need quite a bit of attention in the very near term. Most of the CUC members who have tried the interface have found things confusing or gotten unexpected results. It is important to address the new-user experience now, since the first impression may drive away many potential users. The HEASARC Browse interface will provide a base level that most users are familiar with, so the goal for the CSC should be that an astronomer be able to immediately use the Chandra catalog (without reading any documentation) to get more useful information than will ever be available in Browse.
Website. Finally, we just add a 'kudos' on the new website design. We encourage the CXC to go public with the new design ASAP, and to view its release as an opportunity to make major facelifts to individual team pages (the Calibration portion being a problem area, as noted above).