Chandra X-Ray Observatory

CXC Response to CUC Recommendations following 2012 October CUC Meeting

> 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.

The CAL group is pleased to continue annual updates, which have
been delivered by Larry David.  Greater detail is available for future
meetings if the CUC so desires, from analyses by Larry David, Herman
Marshall, Paul Plucinsky and/or Alexey Vikhlinin. 

> 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.
> Recommendations:
> (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.

Upon review of the available observing time for next cycle, we
estimate the following allocations: 11 Ms for GO programs, 4 Ms
for LPs and 5 Ms for XVPs. This latter allows proposals for up to 5 Ms
to be submitted as XVPs in Cycle 15.

With the CUC's support, we will continue our practice of the past 
2 years of asking the peer review to separately assess the LPs and XVPs,
and then allowing some motion of allocatable time between categories
as the final lists are discussed and compared.

We note that the available observing time will again be reviewed in
the month before the peer review, i.e. including the performance and
events of the first few months of Cycle 14, and the final allocations
decided at that time. We do not anticipate major changes from the
numbers listed above at that time.

> (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.

We will seek CUC input on the future of XVPs (beyond Cycle 15), or
a smaller equivalent, as the Chandra orbit evolves and the available
observing time decreases back to its more typical state.

> 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 update.  

Following the recommendations of the CUC, we have included in the
Cycle 15 CfP the requirement that a PI or co-I list their primary
institution on their science proposals, and that a PI or co-I whose
primary institution is non-US will not be eligible for NASA funding.

> 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.
> Recommendations:
> (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.

Both the CXC and NRAO are enthusiastic about a potential 
Chandra/ALMA joint program.  Our initial exchanges with the new NRAO
Director revealed strong interest from both observatories. 
We appreciate CUC contributions towards science use cases, and
we will solicit such input from users as well from a review of the
literature.  We will continue discussions with NRAO and report on
progress October 2013.   
> (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.
We have been in contact with NuSTAR, who are enthusiastic about a
joint program.  Programmatically, the appropriate time to start joint
observations would have to be later than about September 2014,
after the baseline mission, since they are not yet in a GO phase,
so we will initiate further discussions well before the Chandra
Cycle 16 CfP.

Astro-H has not yet launched, but their GO phase is scheduled
to begin about the same time. We will be in contact with Astro-H
representatives in mid-2013.

For the just-released Cycle 15 CfP, the CXC has revived the Spitzer
joint program, and initiated a new one with Swift.

> 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, by including 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. 

For Cycle 15, we have considerably expanded the information available
to users at including two new
sections entitled Linking Data and Publications, and Chandra-Related
PhD Theses.  These give detailed motivations and instructions for
including the necessary metadata, and for making sure that existing
Chandra-related publications have been appropriately tracked.  A link
to this information was included for the first time in the Cycle 15
CfP, will be highlighted in an upcoming Announcement, and in README
files provided as part of user data distributions.  We are scoping the
possibility of online tools for linking all PIs to their
Chandra-related publications.

We will include information on how to facilitate tracking along with
data downloads in a revised README file. We are evaluating several
options for online tools to assist with tracking, and will implement
at least one in the coming year.  The best solution may not be a
stand-alone service provided by CXC, particularly in the case of
searches by PI name.   

> 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.
> Recommendations:
> (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.

The CSC team greatly appreciates the CUC's input regarding the
catalog.  We are committed to making release 2 of the CSC available as
soon as practicable, and (as mentioned during the catalog presentation
to the CUC) are currently targeting late 2013 for release 2.

However, almost all CSC team members have primary duties that support
the operational Chandra mission and guest observers, and which
therefore typically have higher priority than catalog work.  These
mission-related tasks may result in some delays to the current catalog
release 2 schedule.  We highlight this fact because the operational
Chandra data system will be migrating from 32-bit Solaris to 64-bit
Linux in 2013, and many of the CSC team members will be heavily
involved in this extensive and complex process.

> (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 YouTube videos may help users.

There are currently a half-dozen threads that describe simple usage of
the CSCview catalog tool accessible from the "CSCview Help" page
linked off the main catalog website.  We intend to develop additional
threads that demonstrate common catalog queries and usage of CSCview,
CSC Sky, and the command line interface as resources permit.  More
sophisticated usage that involves interactions between CSCview and
other applications such as ds9 and topcat are best demonstrated using
video threads, and we have shown some prototypes of these at previous
CUC meetings.  We will consider updating these videos and making them
available via YouTube.

Because of the enormous range of possible scenarios using the catalog,
we are happy to hear from any members of the CUC that have particular
suggestions for threads that may be of broad interest.  All
suggestions will be prioritized for thread development, and may also
have the side benefit of developing enhancement requests for the
catalog tools for CSC release 2.

> Software
> 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 onto 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.

We are of course gratified that the CUC shares our view that the
scripts work is useful. On reaching the community, we will investigate
webinars and other approaches as the CUC suggests. As far as measuring
reach to the wider astronomical community, we feel that is challenging
to do well.  We will certainly track metrics on the use of on-line
materials, analyze helpdesk tickets, and gather anecdotal information to
gauge the level of penetration into the community. However, we caution
that quantitatively evaluating reach into the wider community is very
hard to do with any degree of completeness.  We will make our
best effort to brief the CUC on this issue, commensurate with the
resources available.

> Calibration
> 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.
> Recommendations: 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 made with Chandra use the ACIS-S and
> ACIS-I cameras, however, and a significant number 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.

During the past year, the calibration team did spend more time
than usual calibrating the HRC-S.  This was mainly due to the
declining gain and QE of the HRC-S, which necessitated an increase
in its operating voltage.  In his CAL presentation to the CUC, 
Larry David therefore spent more time than usual discussing HRC-S
issues due to this effort.  While there are a large number of
HRC calibration observations in the Chandra archive, most of these
observations are very short.  For example, we perform yearly 21 point
raster scans of AR Lac on the HRC-I and HRC-S, but these are each
only 1 ksec observations.  We also observe Vega on all five HRC
filters every four months to monitor the health of the UV/ION shield,
since the HRC is placed in the focal plane during passages through the
radiation belts. All of the Vega observations have exposure times of 
1 to 2 ksec. 

Over the past 4 years (cycles AO-10 through AO-13) the average
yearly calibration time has been 620 ksec, which is 2.7% of the
total Chandra observing time.  The average yearly calibration
time for HRC imaging observations has been 107 ksec, which is 0.5%
of the Chandra observing time.  Thus, the calibration team
only spends an average of 50 ksec per year per detector to monitor the
gain and QE of the HRC-I and HRC-S.  It would be very difficult to
reduce the observing time further and still obtain the necessary
statistics to accurately calibrate the HRC detectors.

> 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.

We thank the CUC for their concern and engagement on the topic of the
NASA budget and will schedule a CUC telcon to discuss our 
response/decisions should any major cuts to CXC funding be announced.  

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