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Chandra Users' Committee Meeting (10-11 October 2012)

Report issued on 30 Oct 2012

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Lee Armus (by phone)
Franz Bauer
Tiziana DiMatteo
Jimmy Irwin
Tim Kallman
Carol Lonsdale
Hironori Matsumoto
Jon Miller (Chair; jonmm@umich.edu)
Rachel Osten
Pedro Rodriguez (ESA)
Wilt Sanders
Allyn Tennant
John Tomsick

Chandra User's Committee Meeting Report - October 10/11/2012

The Chandra User's Committee met on October 10 and 11, 2012, and heard reports on all aspects of the mission. The observatory is the flagship mission of high energy astrophysics, and will be for the foreseeable future. It continues to function exceedingly well. Community interest in the mission remains very high, based on publications and proposal statistics. The report below briefly details some specifics and makes a few suggestions.

Summary of the Presentations and Interactions

The CUC congratulates the observatory on an excellent performance in the 2012 NASA Senior Review. The review recognized that Chandra is a flagship mission that serves a critical role in the astronomy and astrophysics community. With the encouragement and endorsement of the CUC, the observatory requested an augmentation to its nominal allocation to boost funding available through the Guest Observer program, and this augmentation was awarded in part. This will help users take advantage of the "extra" observing time afforded by a favorable evolution of the spacecraft orbit.

Spacecraft Health

The observatory is in excellent shape. There is no hardware issue that should prevent a 25 or 30 year mission. In particular, the CUC is impressed by the way that the observatory proactively anticipates possible hardware issues that could affect mission performance, and develops solutions before the problems arise.

A very small issue is that a calibration source is fading, which would negatively affect the instrument calibrations at low energy. However, the observatory outlined alternative means of calibration at low energy that will easily solve this small problem.

Recommendation: The CUC recommends continued tracking of the ACIS contaminant, and we would like annual updates on this issue.

Proposal Reviews and Coming Cycles

Interest in Chandra remains very strong, with a high over-subscription factor: 5.2 overall, and even higher for large and visionary programs. The theory and archive programs, previously flagged by the CUC as important and worth retaining, also remain vibrant, with over-subscriptions of 5.8 and 4.2, respectively. The observatory once again has "extra" time to award in Cycle 15 owing to evolution of the orbit, and plans to continue the "X-ray Visionary Programs" category that allow for proposals that require millions of seconds of observing time.


  1. The CUC endorses the principle of a new XVP round in Cycle 15, and urges that the mission be particularly careful to balance the "Large Program" category - which remains the most highly over-subscribed - with the XVP category. Most of the XVPs awarded previously were in the 1-3 Msec regime, and none in the 5-6 Msec regime. In particular, the peer review should be able to borrow time from the XVP category if particular Large Programs are deemed to be of superior quality and higher importance.
  2. If the observatory plans to continue the XVP program in future cycles when the orbit provides less observing time, the CUC would like a report in October 2013 on how the XVP program will then be implemented, minimum and maximum observing times, and its ongoing scientific role.
  3. Proposal PIs and Co-Is who have more than one affiliation should list their primary institution on their proposal(s). PIs/Co-Is whose primary institution is non-U.S. should not be eligible for NASA funding. U.S. Co-Is eligible for funding would not be affected by this policy.

Joint Observing Programs

The CUC heard reports and had a productive discussion about future joint observing programs. In particular, the CUC noted the importance of joint programs with NRAO, and that interest in Chandra + JVLA programs is especially high. The ALMA observatory is different from other NRAO facilities in that it is international and still in an early phase.


  1. The CUC sees strong potential for unique science gains if a joint Chandra + ALMA program can be developed, and we encourage both Chandra and NRAO to quickly work toward this goal. The CUC is willing to help develop science use cases in order to help frame the discussion on this matter.
  2. The CUC also encourages Chandra to pursue joint observing programs with NuSTAR and Astro-H, in future observing cycles, when those missions begin GO phases.

Tracking Publications and Impact

The observatory is doing an excellent job of tracking the manner in which its observations are utilized and published. Based on CUC feedback, attempts are also being made to track the manner in which theory and archive proposals are used.

Recommendation: The CUC sees these efforts as important and urges their continuation. We would like to encourage automation and expansion of these efforts by better explaining to users the metadata required to do proper tracking, by developing online tools that users can access to assist with tracking, the inclusion of a readme file in data downloads, and the inclusion of dataset IDs in observing proposals and budget forms. We feel that automation and online tools are important so that these efforts can continue efficiently.

The Chandra Source Catalog

The CUC heard a talk on the Chandra Source Catalog and its utilization. The CUC sees this as an important tool that will have a broad impact. Indeed, only lower limits to that impact can be estimated.


  1. Some time has passed since the release of the first catalog. The CUC would like to see the release of the second catalog before our next meeting in October 2013.
  2. The CUC recommends the development of "threads" that walk through different use cases and outputs of the catalog tool. It is possible that this is another area where videos may help users.


The CUC heard a detailed talk concerning the current status of CIAO, its utilization, and plans for the future. As with the spacecraft itself, the observatory continues to be proactive where software is concerned, and responsive to the needs of its user community. The CUC is particularly impressed and excited by the development of new mid-level scripts that partially automate some analysis tasks, without sacrificing the detailed control that is possible with lower level tools. Prominent among these is "merge_obs", which should be an especially powerful tool that will be utilized widely.

The CUC noted that there is some uncertainty about future CIAO workshops. The initiative to put CIAO lessons in video (currently on YouTube) seems particularly profitable, and the CUC looks forward to seeing more of these videos. The videos have the potential to increase the penetration of Chandra and X-ray astronomy into other areas of astronomy, and countries where Chandra is not widely used. Last, the CUC wonders if "webinars" may be able to replace CIAO workshops. The CUC would like to hear a presentation on metrics and evaluations of penetration into the wider astronomical community in the October 2013 meeting.

Einstein Fellowship Program

The CUC heard an update on the Einstein Fellowship program. Interest in this fellowship remains extremely high, with 18-20 applicants for every fellowship position. Oversight and guidance of this program appears to be excellent. New software has been tested that should better facilitate the proposal review process, as well as tracking of fellows as their careers progress. The CUC is grateful that its recommendations were followed regarding limitations on how many fellows an institution may host, and we request the opportunity to comment on any proposed changes in the future.


The calibration of the instruments aboard Chandra is already very good, and here again the observatory is doing an excellent job of tracking and characterizing small changes in instrument performance.

Recommendation: Calibration updates presented to the CUC appeared to be placing renewed emphasis on the HRC-I and HRC-S cameras. The vast majority of observations are made with Chandra using the ACIS-S and ACIS-I cameras, however, and indeed an high fraction of the observations made with HRC-I and HRC-S are calibration observations. The CUC recommends that calibration efforts reflect the relative use of the instruments.

Upcoming Federal Budgets

Mandatory spending cuts that may trigger on January 1, 2013, will have a dramatic impact on discretionary spending. It is possible that this will result in a change in Chandra funding.

Recommendation: If these cuts are triggered and NASA specifies a cut for Chandra, the CUC strongly desires the chance to make comments and advise the observatory.

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