Chandra Users Committee June 25-26, 2002

Members Attending: M. Arnaud, J.P. Henry, J.P. Hughes, W. Latter, J. Krolik, J. Mohr (by telecon), and F. Paerels
Others: A. Tennant, H. Tananbaum, B. Wilkes

Manager's Report (Roger Brissenden):

Roger reported that the S/C is performing superbly and operations are routine. His reports on status, operations, expendables usage, observing efficiency, observations, data systems, data delivery, and grant awards are all appreciated by the committee. Roger reported that SAO and NASA have begun negotiations on the 5 year extension to the CXC contract. It was decided that any action by the CUC on this issue would be premature at this time.

Director's Report (Harvey Tananbaum):

Harvey reported on the use of the Director's Discretionary Time from February through June 2002. About 585 ks of cycle 3 DDT have been used already, making it unlikely that a significant chunk of time will be available for a single large observation as happened in the past two cycles (RXJ1856.5-3754 in cycle 2 and the CDSF in cycle 1). It was noted that over the three month period from 3 March to 3 June there were 8 load interrupt ToOs of which 4 were DDTs while the remainder were ToOs awarded by the peer review. Nominally the peer review gives out 9 ToOs, HST one, and the Director two.

Summary of issues from Chandra AO-4 proposal submission and peer review (Fred Seward):

This round Fred avoided using reviewers from previous cycles. The Large Projects in AO4 received 23% of the total available time which is similar to the fraction awarded in previous cycles (AO2: 25%, AO3: 20%). Seventy percent of the GTO proposals submitted after the deadline in reaction to a conflict with a GO target were successful. Fred noted that he has not been able to figure out a way to disguise the GTO proposals from the panels.

TOO and time-constrained proposals turned out to be a problem, because not all such proposals were properly indicated by the proposer. Fred presented a few examples and suggested that the CXC staff put some effort into a technical review of proposals beforehand. Theory and archive proposals are not currently constrained by a "budget" as observing proposals are constrained by the available time for the entire cycle. Fred notes that ultimately it may be necessary to go to a dollar budget for theory and archive proposals, but it's not necessary yet.

Plans for AO5 (Belinda Wilkes):

Regarding the Chandra/XMM deadline collision for next year, Belinda reported that the two observatories have worked out a schedule that has the Chandra deadline on 15 March and the XMM deadline in late April. This seems to be the best that can be done for now. The XMM AO3 cycle will be for 1.25 yr, leading ultimately to a 3-6 month spread in schedules between the Chandra and XMM review cycles.

Belinda reported on two new joint time programs for AO5: with NRAO (details to be worked) and RXTE (500 ks). Both of these will be one-way like the NOAO joint time agreement. The CXC will investigate a joint time program with SIRTF during their second review cycle. Other changes for AO5 include requiring proposers to list previous Chandra awards as well as relevant publications in the submitted forms.

For the Chandra AO5 review, the CXC will send out paper copies of proposals as well as CD-ROMs.

Belinda explained the reasons behind the lack of advertising for the Chandra theory program which premiered during the last cycle. She indicated that the CXC will investigate wider distribution for any future new initiatives.

The question of allowing for multi-year proposals was raised for consideration by the CUC. Harvey briefed the committee on his view of the "GTO beyond prime phase" issue in preparation for Paul Hertz's call after lunch. He mentioned that the AXAF Level 1 Policy Document (recently found by M. Weisskopf, signed by Alan Bunner) stated that IPIs would be awarded GTO time in the amount of 15% of the observing time for the duration of the mission. More on this topic below

ACIS Modeling and Analysis (Dan Schwartz):

Dan described the research of a group of CXC scientists working under his supervision to address two important issues related to the performance of ACIS: the decrease in low energy quantum efficiency (LEQE) and CTI correction of the FI chips.

Dan presented an excellent summary of what is known about the change in LEQE, which appears to be a result of the build-up of an unknown contaminant on the ACIS filters and/or CCDs. As of the time of the meeting the chemical composition was not well-determined. There is evidence for a strong C absorption edge and the O edge is directly detected. N and F are also likely to be present. The LEQE appears to be decreasing at a rate of 10% per year at E=0.67 keV and the degradation appeared to commence within 2-3 months of on-orbit insertion. Dan outlined plans for further analysis, modeling, and the need for additional calibration observations.

The other portion of Dan's presentation covered work on implementing a CTI correction for FI chips. They are using an algorithm recommended by the PSU/MIT IPI team. As of the time of the meeting a new version of acis_process_events had been verified and shown to produce an improvement in both the width of spectral features and their amplitude (gain). Dan then went on to describe a new and improved method for generating RMFs for ACIS. They have developed a technique (based on a clever idea by Alexey Vikhlinin) that significantly reduces the labor (i.e., Dick Edgar's) required to produce RMFs.

Calibration (Larry David):

Larry gave the Chandra calibration status report covering new and improved calibration products (ACIS, HRC, LETG, and HETG), caveats associated with these, uncertainties and issues remaining, the AO4 calibration plan (totaling 911 ks of observing time), and Chandra/XMM-Newton cross calibration issues. Larry announced that the CXC was holding a Chandra Calibration Workshop in the fall, which would be open to the entire scientific community, and encouraged CUC members to attend.

GTO time beyond prime phase (Paul Hertz, by telecon):

Paul reported that NASA headquarters is transitioning to the extended phase mission for Chandra and is planning all activities, such as the budgets for GOs and public outreach. They wish to establish an appropriate policy for GTO during this phase. He claimed that the various documents related to this are ambiguous at best. The issue is not one of money, but rather the best way of allocating Chandra observing time. He notes that generally NASA policy is evolving toward less GTO time for new missions. Headquarters would like our input, including points they should consider, and they plan to make a decision by the end of the calendar year.

[CXC Note: Since the meeting NASA HQ announced an official extension of the GTO time at 15% for the full, extended mission]

SDS: CIAO 3 Plans and Status (Aneta Siemiginowska):

Aneta talked about the Slang scripting language in CIAO as well as plans for CIAO 3. She noted that CIAO has a lot of capabilities, which are not fully used by the users and that users have problems, but are unable to identify directly the reason. CIAO 3, the so-called Infrastructure Release, will help to solve these problems.

SDS: Analysis Using CTI-corrected Products (Antonella Fruscione):

Antonella reported on the official Chandra software for CTI correcting ACIS-I data. The plan is to release all new ACIS-I FEFs for CTI-corrected data and software in the fall 2002. The software update will likely be a patch to CIAO2.2.2.

SDS: CIAO Documentation Plans (Doug Burke):

Doug talked mainly about providing users with analysis threads. There are now almost 100 threads accessible from the Chandra web site. Keep up the good work.

SDS: Web_SAOSAC (Margarita Karovska):

Margarita presented information about ChaRT - Chandra Ray Tracer - which is a Web interface to SAOsac.

SDS: ATOMDB (Randall Smith):

Randall described the ATOMDB which is an atomic database that includes the Astrophysical Plasma Emission database (APED) and Astrophysical Plasma Emission Code (APEC).

E&PO (Kathy Lestition):

Kathy reviewed the scope of the CXC Education and Public Outreach effort from Jan to June 2002. Chandra is getting good coverage in the national press. NASA headquarters wants to have more Chandra Space Science Updates (SSUs) and the E&PO group is hiring additional staff to support this, including a dedicated scientist, animator, image processor, and graphic illustrator.

Before adjourning, Harvey Tananbaum raised the following issue that he wanted the CUC to consider.

Harvey noted that deep surveys were a unique science for Chandra. Considerable resources have been devoted to this already: 2 million seconds of time in the Chandra deep field north and 1 million seconds of time in the Chandra deep field south. However he expressed concerns that future increases in time on these fields might be difficult to obtain through the standard pool of time. He therefore suggested that a new category of proposals, presumably for very large allocations of time, be initiated for deep surveys. A group of people who do this type of science would be assembled and tasked to decide upon an optimal observing strategy and to put forth the best proposal argument. A separate panel of non-deep-survey scientists would then review this.