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Lee Armus
Franz Bauer
Tiziana DiMatteo
Erica Ellingson
Jimmy Irwin
Tim Kallman
Hironori Matsumoto
Jon Miller (Chair; jonmm@umich.edu)
Pedro Rodriguez (ESA)
Massimo Stiavelli
John Tomsick
Joan Wrobel (by phone)
The committee is extremely impressed by the science returns of the observatory, and the dedication of the observatory staff at all levels to supporting the community of users. Both in an absolute sense and in a science per dollar sense, Chandra is achieving remarkable and valuable results that make contact with numerous missions and all available wavelengths. The returns of the mission appear to be undiminished since its start. The spacecraft itself is in excellent shape; aging in the detectors is extremely slow and well characterized. The calibration of the mission, its software suite for science analysis, the data archive, helpdesk, and user funding are all exemplary. The CUC sees Chandra as a flagship mission at the forefront of US astrophysics efforts.
Chandra Status: Ed Mattison summarized the current status of the mission, with emphasis on the health of the spacecraft. In particular, Chandra experienced a rare safe mode incident in July 2011; this resulted from an on-board calculation of momentum change that exceeded allowable limits. The team ascertained that the calculation was erroneous (due to a subtle combination of a large, gravity-gradient induced torque, the scheduling of a grating move, and flight-software timing) and that there were no hardware issues or failures on-board Chandra. Procedural changes have been implemented that will prevent a re-occurrence of an event like this one.
An unanticipated benefit of the safe mode episode is that some hot pixels in the guide star camera annealed; there are fewer hot pixels now. Separately, the HRC anti-coincidence screen is now able to do the job of EPHIN, which has previously served to impose some pointing constraints. At least 18 years of fuel remains in the main tank, and there is a backup tank as well; there is a ready supply of consumables and they are used sparingly. In short, the spacecraft is in excellent health, and poised to complete a 20-year mission.
It was also noted that Chandra, like other missions, received a mid-stream budget cut, independent of the recommendations of the prior Senior Review. Chandra has worked hard to absorb these cuts by realizing efficiencies and by making cuts in staffing, rather than cuts to e.g. guest observer grants. (A recommendation on guest observer grants follows below.) For instance, 30 positions will be cut between FY2011 and FY2016. The cuts are being made in a manner that will have the smallest possible impact on the mission, but some impact will be felt by users.
The overall observing efficiency of the mission is extremely high, now reaching 75-80%. Evolution of the orbit has benefitted the mission in that there is now more observing time in each cycle than was anticipated at the start of the mission. The X-ray Visionary Projects proposal category makes use of the additional time that has become available, thus affecting the normal proposal categories minimally.
Calibration updates are continuing at a good clip, with seven in the last year. Grant awards go out very promptly, usually within 2-3 weeks. And public outreach continues to be a noteworthy Chandra effort. Chandra has a particularly good presence on Facebook and communicates through Twitter as well.
Directors Discretionary Time: Director Harvey Tananbaum reviewed the DDT program. A number of short, high-impact observations were made, as per usual, with a particular emphasis on events that might be due to the tidal disruption of stars by massive black holes. The DDT program has remained fixed at 700 ksec per year, despite the increase in observing time in recent cycles due to orbital evolution. There is no desire for additional DDT allocation from the Director's office. The CUC asked how the publication rate or impact of DDT observations compares to standard proposals; these metrics are not currently tracked by the mission. (A recommendation about tracking follows below.)
Cycle 13 Summary: Belinda Wilkes summarized the proposal review and selected program for Cycle 13. Overall, the observing time over-subscription of the mission remains extremely high, at 5.4. The CUC noted that this is impressive for at least two reasons: (1) the over-subscription has not dropped though considerably more observing time has been available in recent cycles, (2) the complement of instruments has not been updated regularly like HST. This signals that Chandra fills a critical and enduring role in observational astrophysics. The mission has worked particularly hard to shield guest observer funding from cuts. The total GO funding available has been flat at 10.5 million USD in real dollars. The median award has gone down because the available observing time has gone up. (A recommendation about guest observer funding in the face of additional observing time follows below).
Cycle 14 Planning: Belinda Wilkes also summarized planning for the coming observing cycle. In particular, over the next 3 cycles (14-16) Chandras evolving orbit results in 13%, 10%, and 6% additional observing time. This makes it possible to offer a second call for X-ray Visionary Projects in Cycle 14 those projects that require several Msec of observing time to complete. The mission will solicit letters of intent from the community. The CUC voiced its enthusiasm for the XVP program and noted the success of the previous call for such proposals.
The Cycle 14 GO budget is slated to decrease by 600,000 USD and the mission solicited feedback from the CUC on how this might best be realized. Following a productive discussion, the consensus view of the CUC is that the funding cuts should be realized uniformly across all of the proposal funding categories (guest observer, archival, theory) rather than by eliminating e.g. theory outright, as they are all important to the success of the mission. (A recommendation on proposal funding follows below.)
The CUC also asked about plans for Chandra to have joint programs with new and upcoming observatories, especially ALMA. (A recommendation on joint observing programs follows below.)
Aimpoint/Alignment Shift: Scott Wolk reviewed evidence of a small shift in the relative alignment of the aspect camera with respect to the optical axis of the X-ray telescope. This is a minor issue with little or no impact to observers, and the CUC was impressed by the numerous cross-checks in place that catch small changes of this sort. There is already a plan to implement small changes into the database of calibration files (aka CALDB) to reflect the new relative alignment.
The Einstein Fellowship Program: Andrea Prestwich reviewed the Einstein Fellowship Program. Interest in the program is extremely high and growing, with an enormous oversubscription factor (174 proposals for just 10 slots in the prior round). Eleven fellowships can be awarded in the coming cycle, and 12 can be awarded in the cycle after that. Twelve is expected to be the steady state thereafter. The CUC voiced strong approval for excellent management of this program, its considerable success, and the expertise and visibility that the fellows bring to the field.
Feedback was solicited from the CUC regarding the possibility of changing the rules to allow institutions to host more than one fellow per year. The CUC noted several things that argue for retaining the current rules: (1) The Einstein Fellowship program has functioned extremely well under the current rules, with as few as two of 30 fellows less than completely satisfied with their host institution Š essentially a 93% success rate. (2) Even under the current rules, the data presented actually suggest a mild degree of pile-up at three institutions. (3) The Hubble Fellowship enforces similar restrictions on host institutions and is also highly successful. (4) Feedback from the Chandra UserÕs community is strongly in favor of the current fellowship rules. (5) The CUC chair contacted the Fermi UserÕs Group chair, Alan Marscher, who also voiced support for the current Einstein Fellowship rules. (6) The sentiments of the Chandra community, the CUC, and the FUG chair reflect the need to think broadly and about the long term: the health of high energy astrophysics and the Physics of the Cosmos program depends on many institutions being invested in these research areas. (A recommendation regarding the Einstein Fellowship follows below.)
Chandra Workshops: Paul Green gave a brief summary of the Chandra summer workshops. These focused meetings have proved to be very effective, usually with over 100 scientists in attendance. The abstracts are put on to the ADS to increase visibility and to generate a record. Those abstracts include links back to the workshop websites. The CUC felt that the coming workshop, celebrating 50 years since the discovery of Sco X-1, will be a timely and interesting meeting.
Chandra Calibration: Larry David gave an extensive review of the Chandra calibration efforts. It should be noted that the overall calibration of Chandra is excellent in all aspects, but the teams continue to push on calibration to ensure the best possible science return of the mission. Specific updates have included the release of new ACIS products for TE and Graded modes, new models for the contaminant that slowly changes the low-energy performance of ACIS (these are updated yearly, in fact), and new HRC-S quantum efficiency maps and responses. New products and calibrations for ACIS continuous clocking mode data taken in combination with the HETGS are nearly ready for release; this will be of benefit to observers of bright Galactic sources.
A relatively new effort is to examine the spatial distribution of the contaminant, which appears not to be axisymmetric. The CUC felt that this was an important effort and should continue, as it may be of particular importance to galaxy clusters, both for their own purposes and for cosmological constraints. A second new effort is to better characterize the response curve in the Si K region in HETG spectra of bright sources, as small, unexplained residuals persist in that region.
The CUC asked a number of questions about how the detectors are aging. The performance of the detectors remains excellent, with no evidence of substantial changes (e.g. bright pixels and bad columns are not appearing in ACIS).
The CUC also asked about the status of cross-calibration with XMM-Newton and Suzaku. Larry David reported that essentially nothing has changed within the past year. Chandra does participate in the IACHEC meetings, and the CUC supports this.
The Chandra Source Catalog: Ian Evans gave a summary of the Chandra Source Catalog. The CUC is particularly impressed by these efforts. In particular, the functionality of the catalog and its implementation into viewing packages such as DS9 is extremely useful to the entire astrophysical community. The CUC also strongly encourages continued work on Release 2, with a target release date in late 2013 or before.
CIAO Update: Jonathan McDowell gave a summary of the CIAO reduction and analysis suite. So far, there have been almost 1500 downloads of CIAO 4.3, which serves to indicate that the base of active Chandra users doing hands-on analysis is remarkably large. The CIAO helpdesk is a particularly valuable resource, with a median time of just 1.7 hours to make a first response to a user. Overall, the CUC is again extremely impressed by the CIAO suite and the support offered to users.
CUC feedback was requested on a desire to stop supporting Solaris. This is one way of realizing an efficiency, but moreover very few users work on Solaris in 2011. (A recommendation on Solaris support follows below.)
The CUC agrees with the CXC that it is time to phase-out support of Solaris platforms, as they are a very small fraction of the total CIAO downloads. Users will still be able to build CIAO from source distributions for Solaris platforms.
The CUC congratulates Chandra on the implementation of the XVP program previously, and we note the high over-subscription. The CUC endorses the initiative to have a second round of XVP to be implemented in Cycle 14.
The CUC encourages Chandra to investigate joint observing programs with new and upcoming observatories and missions, including ALMA, NuSTAR, and Astro-H. In particular, ALMA is now making observations and a joint program would be timely.
The CUC strongly supports the continuation of the theory proposal funding program. In the last cycle, this program was over-subscribed by a factor of six, which is comparable with observing program categories. The 2010 Decadal Survey has recommended expansion of theory funding. NASA is proposing to increase its funding of theory; however, until NASA opens a clear venue for funding of single- year, focused, mission-based proposals, it is highly uncertain that there will be support for the type of investigations covered by the Chandra theory program. The science return of the mission partially depends on the ability of theorists to conduct focused studies to address Chandra observations.
The CUC recommends that the theory program should be preserved, and that cuts by NASA beyond the recommendations of the 2010 Senior Review should be absorbed uniformly through the various funding programs.
The CUC feels that a high level of GO funding must be retained, in order to ensure the science return of the mission. We encourage that GO funding should be insulated - to the greatest extent possible - from additional cuts to the observatory budget. The CUC notes that augmentation of the GO funding program is needed to compensate for the additional observing time available in Cycles 14-16 (due to orbital evolution) while the GO funding level has remained flat in real dollars. Funding for archival research is also important, as it is an entry point for observers who typically work in other wavelengths.
The CUC encourages Chandra to make GO funding the highest-priority augmentation to the in-guide funding level from the 2012 Senior Review.
The Einstein Fellowship program is highly competitive (174 applications for 10 places last year), and the data presented by the CXC strongly indicates that the current rules work extremely well. The CUC notes that the Hubble Fellowship program is also highly successful and has always adhered to a one fellow per institution rule; Hubble has a longer track record and offers a larger number of fellowships.
The Physics of the Cosmos program is an important NASA endeavor that enables breakthrough research at a large number of institutions around the country. The Einstein Fellowship is an essential means of maintaining and broadening the research base of the Physics of the Cosmos program and its missions. Relaxation of the current hosting rules would result in greater concentration of fellowships at fewer institutions, which would not serve the scientific or programmatic goals of the Einstein Fellowship.
The CUC strongly recommends the continuation of the Einstein Fellowship program according to the current rules, including a limit of one fellow per institution per year.
The CUC recommends that Chandra adopt a means of tracking the outcome of theory proposals, DDT proposals, and archive proposals, in addition to the tracking that is performed for regular observing proposals.
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