Chandra X-Ray Observatory

CXC Response to CUC Recommendations following 2013 October CUC Meeting

Responses are presented in-line below. In some cases where the CUC Report presented comments rather than recommendations, for compactness we do not reproduce those comments.

> Observatory health and performance:
> The CUC received thorough reports from Roger Brissenden and Sabina
> Hurley concerning the overall health of the observatory.
> The most important finding is that the spacecraft and instruments are
> still in excellent shape, with no issues that will impact the
> completion of a 20 year mission, nor even a longer mission.
> The CUC notes that the mission is proactive in anticipating events and
> trends that could potentially impact the operation of the spacecraft
> and operations, and developing workarounds and mitigations in advance
> of any difficulties. A particularly good example is the move from the
> degraded EPHIN radiation monitor, to monitoring with the HRC and ACIS
> instruments themselves.
> Another good example is switching from the aging A-side Momentum
> Unloading Propulsion System (MUPS) to the B-side MUPS, and exploring
> ways of combining A and B MUPS thrusters. The CUC notes that 6 of 8
> thrusters currently work well; while only 3 are strictly required for
> normal science operations, loss of additional thrusters may reduce
> observing efficiency and would increase risk if certain other failures
> were to occur.
> Recommendation: Flight operations and mission planning and scheduling
> is clearly quite complex, especially with regard to the interplay
> between instrument/spacecraft heating and observatory pitch angle, and
> the manner in which observations are conducted now can impact the
> longevity and efficiency of the mission.  Efforts have already been
> made to exploit efficiencies in the staffing (e.g. cross-training
> different tasks). But it is also clear that any further reduction in
> staffing levels will have a negative impact on the mission now, and
> going forward. NASA and Chandra should continue to recognize the
> importance and value of maintaining staffing levels in flight
> operations, and in mission planning and scheduling.
> The CUC requests continued updates in future meetings, from these
> segments of the mission. 

The Chandra Director's Office (CDO) appreciates this evaluation, and
the support of the CUC in our efforts to continue optimizing science
return from the mission, even as the spacecraft ages.

> Education and Public Outreach
> The CUC was updated on the status of E/PO by Roger Brissenden. The
> situation is clearly a complex one, with unclear direction provided in
> proposed presidential budgets and continuing resolutions. The E/PO
> team has continued to deliver in a difficult situation.
> Recommendation: The CUC strongly endorses all efforts made by Chandra
> to connect with the public and to communicate the science done by the
> mission. The Great Observatories are flagships for science in the US,
> and they have a special obligation and ability to communicate the
> unique science that they achieve. We are particularly impressed by the
> way in which Chanda shares science with the public through the web and
> social media, and hope to see these efforts continue.
> The CUC encourages any and all efforts made by the Chandra E/PO team
> to partner with other NASA missions in articulating the importance of
> their efforts to NASA and other organizations. 

The CDO and E/PO groups appreciate this feedback. 
We are continuing our efforts, jointly with other institutions, to
articulate the importance of NASA mission-based outreach in fully
engaging the public.  We will present an update on E/PO activities in
this direction at the next CUC meeting, or before if requested. 

> Proposal Cycles: Update and Plans for Joint Programs
> The CUC heard from Belinda Wilkes an update on the Cycle 15 peer
> review and future plans. The CUC notes that the oversubscription
> remains very high (5.3), that 636 total proposals were submitted, and
> that approximately 20 Ms of observing time was allocated. The
> oversubscription clearly signals that the scientific relevance and
> centrality of the mission continue at a high level.
> Recommendation: The mission should continue to pursue existing and new
> joint programs in order to maximize its scientific reach.
> The CUC reiterates its support for the theory and archive proposal
> categories. These should be retained even in the event of future
> mission funding reductions.
> Supporting the community to analyze Chandra data is the primary way
> that forefront science is achieved. The CUC would like to discuss any
> future budgetary reductions in an effort to ensure a balanced approach
> that does the utmost to preserve general observer funding.
> The CUC endorses the plan to create one final XVP category in Cycle 16
> by allocating 2 Ms from Cycle 17. This will take advantage of the
> evolving orbital parameters that will provide a small amount of
> additional observing time in the next two cycles.
> With some very large XVPs approved, and with continued high
> oversubscription in the LP category, we urge that panelists and
> pundits evaluating XVPs explicitly compare them against the most
> highly-ranked but unapproved LPs, with the chance of approving a few
> such LPs instead of lower-ranking XVPs. XVP programs should not
> allocate time from the LP category. 

The CDO has initiated a new Joint program with NuSTAR for Cycle 16,
and will be negotiating an expansion of the joint NRAO program for
Cycle 17.  We will keep the CUC in the loop as that effort progresses.

The CDO also recognizes the importance of theory and archive
as well as general GO program support, and appreciates the support of
the CUC as we work to ensure their continued strength.

Cycle 16 has included the 2-cycle XVP allotment, and the CDO
appreciates CUC's endorsement of the plan. CDO will provide updates at
the next meeting of proposer's response to the revised XVP program,
and plans for the future.  While discussion and comparison of
border-line LPs vs borderline XVPs has generally been part of the BPP
final deliberations, following the CUC recommendation the BPP will be
explicitly requested to make this comparison in Cycle 16.

> Publication tracking
> Sherry Winkelman presented new efforts to track data use, grant
> awards, and publications. This effort was undertaken partly based on
> prior advice from the CUC, and we are grateful for this quick and
> effective response. It is early, but there are already indications
> that these efforts are yielding an improved view of how Chandra data
> are used. We look forward to a report in 2014. 

ArcOps is expanding its ability to track publications from all types
of Chandra programs, which has already proven fruitful for ensuring
completeness and consistency of the publication database. ArcOps is
also developing tools that will make it easier for proposers and others to
find and/or update Chandra-related publications, and match them with
PIs, proposals and grants.  For Cycle 17, we expect a new thread to
facilitate proposers providing further relevant bibcodes to ArcOps
that may have been undiscovered to date.

> Chandra Source Catalog
> The CUC was provided with an update on the Chandra Source Catalog by
> Ian Evans. We wish to thank the team for their efforts, especially
> given the difficulty of the tasks.
> Prior releases of the source catalog are clearly of high value and
> help astronomers who work in other wavelengths to make use of Chandra
> data. The catalog efforts are an important means of expanding the
> reach of the mission, and have had positive ancillary impacts
> including the development of valuable new software tools in the CIAO
> suite. The addition of command-line access to the Chandra Source
> Catalog should allow a larger fraction of the user community to gain
> rapid and efficient access to many useful catalog products.
> Release 2.0 of the catalog is behind schedule, and will likely be
> completed over the next 12-24 months. The delays are the result of the
> specific demands of making robust detections of fainter sources, the
> complications of stacking fields, and other functions. Reductions in
> staffing have contributed to these delays.
> Recommendation: The CUC endorses the efforts being undertaken to
> complete Release 2.0. The mission has clearly been responsive to the
> CUC in making improvements over prior releases. The mission continues
> to prioritize the GO program and the CIAO suite over the source
> catalog, in the face of staffing reductions. We support this
> prioritization but we urge the completion and release of the catalog,
> and recommend a hard look at essential catalog aspects versus ideal
> catalog aspects. We also urge the consideration of staged releases,
> where certain parts of the sky (those that overlap with large survey
> efforts in other wavelengths, for instance) might be released ahead of
> others. Finally, the CUC was told that there are computing
> limitations, and we urge that the observatory explore this, as
> improved capacity must be available with only modest costs.

The Chandra Source Catalog team appreciates the CUC's support for the
effort to complete release 2 of the CSC.  The team is committed to
making the release available as soon as possible, while prioritizing
essential support for the operating Chandra mission.  Since the CUC
meeting, we have made considerable progress in resolving some of the
outstanding source detection issues.  We will continue to review the
catalog plans to ensure that unnecessary aspects do not delay the
schedule further.  Our primary goal is to ensure that the user finds
release 2 of the CSC to be as trustworthy as release 1, with
comparable completeness and false source rates for comparable S/N
source detections.  As noted during the presentation, a tabular
release of a highly limited subset of catalog source properties
derived from the source detection phase is feasible prior to the final
catalog release, and we will investigate whether this can be done in a
staged manner.  We are exploring improving computational capacity to
speed catalog processing, and have recently received a loaner machine
to better evaluate possible performance improvements and associated

> Calibration
> Larry David presented the committee with a summary of ongoing and new
> calibration efforts. The calibration team was very responsive to prior
> recommendations, for which the CUC is grateful. The dedication of the
> calibration team is one of the reasons why Chandra is a remarkable
> mission.
> Particularly impressive efforts were undertaken to understand the
> nature of the PSF anomaly. Its nature remains uncertain, but it does
> not likely derive from simple mirror misalignment. The most important
> outcome of these investigations is that the anomaly is small, well
> characterized, and likely represents as little as 1% (or less) of the
> flux in the PSF core.
> Recommendation: Chandra will continue to be an important spectroscopic
> mission over the next 10 years. Even after Astro-H launches, Chandra
> will offer the best spectral resolution below 4 keV. We strongly
> endorse the efforts of the calibration team to improve the
> characterization of various HETG modes and observations. An improved
> characterization of the zeroth order image and spectrum, in all
> aspects, will have broad positive impacts.
> We request an update on cross-calibration efforts with other missions,
> in addition to updates to internal calibration efforts, at the next
> CUC meeting. 

The calibration team will continue to evaluate the HETG calibration
status in all operating modes.  A memo describing the analysis of
CC-mode data, in both faint and graded mode, will be posted in early
2014. As noted at the CUC meeting, there appears to be a 5% offset
between fluxes derived from zeroth and first orders in HETG
spectra. Only data sets with marginal pile-up in the zeroth order can
be used to investigate this effect. We are in the process of analyzing
a few more candidate data sets to determine if there is any energy
dependence to the off-set.  Once this study is complete, the
calibration team will release an update to the HETG zeroth order

The calibration team will present an update at the next CUC meeting
on the cross-calibration status of Chandra with other X-ray missions.

> The CIAO Software Suite
> Jonathan McDowell presented updates and improvements to the CIAO
> suite.
> As before, the CUC is impressed by CIAO and ongoing efforts. The team
> continues to add helpful new tools, and to simplify the execution of
> important existing tools.
> The development of the "srcflx" script is particularly important in
> that it will help astronomers with no prior X-ray experience to get
> model-independent flux estimates from sources in Chandra mission. This
> tool will improve the reach of the mission.
> The HELPDESK is particularly efficient at resolving problems.
> We look forward to the upcoming release of CIAO 4.6.
> Recommendation: The CIAO teams continues to deliver an excellent
> software suite in an efficient manner, and to make sensible and useful
> improvements. Please keep it up.
> Especially in an era of reduced staffing, it is clear that the
> HELPDESK staff cannot be expected to provide advice and assistance
> that is not directly related to Chandra data and software tools, and
> the team should allocate its time accordingly.

The CIAO Team thanks the CUC for its kind words about the scripts and
the helpdesk.  We agree with and will take into account its advice
about balancing the scope of support with available resources.

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