Chandra Users Committee Meeting (19-20 Sept. 2007)

SUMMARY Report received 27 November 2007


Mark Dickinson
Vicki Kalogera
Maria Santos
Nobuyuki Kawai
Chris Mauche
Chris Reynolds (chair)
Randall Smith
Leisa Townsley
Harry Ferguson (phone)
Smita Mathur (phone)


Jon Miller
Lisa Storrie-Lombardi



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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.