**GLAST USERS COMMITTEE MEETING (GUC)**

August 9-10, 2004

Goddard Space Flight Center, Bldg 16W, Room N76

**Present:**

*Committee members:*

Josh Grindlay (Chair), Dave Bertsch, Roger Brissenden, Jim Buckley, Wim
Hermsen, Jim Ling, Alan Marscher, Reshmi Mukherjee, Rene Ong, Rita
Sambruna, Greg Stacy, Marc Strickman, Ann Wehrle

*Ex Officio Committee members:*

David Band, Don Kniffen, Chip Meegan, Peter Michelson, Jay Norris (by
telephone), Steve Ritz

*GSSC staff and colleagues:*

Jim Chiang, Robin Corbet, Masa Hirayama, James Peachey, Julie McEnery,
Tom Stephens, Dave Thompson, Kathy Turner

Note: presentations posted on website marked as "posted talk"

**August 9, 2004**

**Introduction:**

Josh opened the meeting and thanked all for attending. Introductions
were made.

Minutes (terse) will be kept by David Band, and reviewed/edited by Josh
Grindlay

Action items will be assigned.

No GUC Charter exists yet since Don Kniffen was waiting for Josh to take
over as chair

**Mission update:**

**Don (NASA HQ Report)**---Dan Blackburn is the new Program Executive (a
role once called Program Manager); GLAST is his only responsibility.
Given the recent NASA reorganization, little progress has been made in
filling positions, e.g., Paul Hertz\'s (Paul was moved to a position in
the 'front office,' which subsequently went away!).

GLAST's budget and schedule are being watched carefully. But external
factors may have a big effect. For example, STIS on HST just died, which
may increase the pressure for HST servicing. The expense for the
servicing mission is not budgeted, and will probably have to come out of
other space science missions. Other space science missions are
off-limits, which may put additional budget pressure on GLAST.

GSFC did not compensate GLAST sufficiently in \'04 and \'05 for the
effects of full cost accounting.

**Kathy Turner (DOE Report)**, posted talk---DOE is happy with GLAST,
but is concerned about budget and schedule. DOE participation in GLAST
has 2 parts: construction (\$42M) and operations, which includes I&T.
The operations budget from DOE is \~\$7M/yr; the operations budget is
fairly flexible. The total US construction budget is \$138M until I&T,
most of which is already spent. In the operations phase NASA's spending
will be \~\$7M for the GI program.

**Steve Ritz (Mission Report)**, posted talk---The relationship between
the Science Working Group (SWG) and the GUC was discussed. As for other
missions, the SWG may be phased out at launch, with some of its members
merged into GUC.

NASA's confirmation review of GLAST was in December, which allows the
mission to go forward. NASA is committed to a launch on 2/28/07. The
confirmation review was before NASA's new vision was announced, and
GLAST has been untouched by the vision thus far.

Data Challenge 1 (DC1) was a success. Steve emphasized that DC1 was
'messy,' as was planned! Roger Brissenden suggested the DCs should
eventually include the HEASARC server in the system. He also asked about
the relation of the DCs to formal software testing and whether there are
official software releases. Answer: the software must have specified
capabilities by the DCs, and the DCs show that the analysis system has
the desired capabilities.

Ann Wehrle asked whether DCs are linked to software Pipeline releases.
For example, will DC3 be Pipeline release 0.8?

DC2, currently planned for July, 2005, will be more realistic background
simulation and also include source variability.

Discussion followed about how the GUC should play a role in evaluating
future DC2 and DC3.

Recent and upcoming reviews:

-   May---S/C CDR

-   June---GBM CDR

-   August---Ground System Design Review

-   September---Mission CDR

**Peter Michelson (LAT Report)**, posted talk---The schedule is
challenging, but it is more important to get it right. The first TKR
tower will be done in September, and the first CAL module soon
afterwards. The pre-ship review is12/1/05, allowing 4 weeks of float.

-   Subsystem status:

TKR: The SSDs are completed (with a very low reject fraction), the
ladders are half done, but less than 1% of the trays are completed.

-   CAL: Doing well, but capacitors needed to be replaced, resulting in
    a hit to the schedule.

```{=html}
<!-- -->
```
-   GRID: Machined.

-   DAQ: A test bed has been created.

```{=html}
<!-- -->
```
-   ISOC: Rob Cameron will be manager. A working group chaired by Seth
    Digel and Isabelle Grenier will design the Level 3 products (e.g.,
    catalogs). The LAT will monitor sources and post their fluxes for
    duration of the mission. The list for sources that will be monitored
    will start at \~10-20, but will grow.

**Chip Meegan (GBM Report)**, posted talk---GBM has a 60 day float. RFAs
issued at reviews have added unanticipated expenses.

The final (of 4) CDRs was successfully passed in June. Detector
development has been delayed by procurement problems and funding
difficulties at MPE.

A silicon pad behind the NaI window will hurt the low energy
performance; this was a result of miscommunication between people in
different countries. The GBM will not meet the 5 keV sensitivity goal,
and will have 25% transmission at 10 keV. Thus the GBM will miss the
Level 3 requirement specifying the effective area at 14 keV (although
the 14 keV effective area is projected to be 75cm^2^ instead of
\~100cm^2^ ). Since these are flight detectors, there is no remedy. This
assessment of the decrease in capabilities is based on calculations, not
hardware tests. First tests of GBM LE performance are expected in
September.

Use of the GBM as an all-sky monitor is not funded. Developing this
capability could be done as a GI project. It would be good to have this
capability at launch, but this would require starting the GI funding
before launch.

**Jim Ling (GBM as sky monitor)**---The GBM's sensitivity will be \~3X
below that of BATSE at energies above 25 keV, and thus the GBM will do
less at high energy. But at low energy (10-25 keV) the GBM was projected
to do better, though this must now also be questioned in view of the
reduced GBM sensitivity below \~15 keV. The MSFC and JPL groups both
have software from BATSE that might carry over to the GBM. The JPL group
modeled the background, while the MSFC group's approach was more
empirical and faster.

Mark Strickman pointed out the backround for the GBM, as a (primarily)
zenith pointed instrument, will be different from BATSE.

The use of the GBM for source monitoring will not change the data sent
down. This monitoring will provide context for LAT observation, and will
probably not trigger LAT observations. It probably will be useful only
for relatively bright galactic sources (e.g., X-ray novae) but not be
useful for AGN. The MSFC group (i.e., the GBM instrument team and
colleagues in Huntsville) probably can be ready earlier with less
effort.

Josh suggested that the GBM team provide 1) an updated (for likely GBM
sensitivity at low energy) estimate of the GBM vs. BATSE sensitivity for
source monitoring and 2) a rough estimate of cost to implement
BATSE-based software to enable source monitoring.

**GSSC Report:**

**Jay Norris (Status)**, posted talk---There were many questions about
the management and responsibility for developing the Standard Analysis
Environment (SAE):

Jim Ling asked how data analysis software is shared between the GSSC and
SLAC?

Roger Brissenden asked who has final control over S/W development and
specifications?

Jay responded that frequent meetings ensure coordination. There is a 7
member GSSC-LAT working group to coordinate issues. Seth Digel is the
manager of SAE development. Jay will provide a chart to make the
boundaries clearer.

**David Band (User Support)**, posted talk---Various suggestions from
the Committee were made in the course of the talk:

-   The Committee members strongly advocated including many examples and
    analysis 'recipes' in the software documentation.

```{=html}
<!-- -->
```
-   When the GSSC sends a TOO order to the MOC, it should also send out
    e-mail to interested scientists in addition to posting information
    about the TOO on its website. An RPS form similar to that used by
    RXTE should be used to enter TOO\'s.

```{=html}
<!-- -->
```
-   Joint GLAST-other mission proposals should be considered.

```{=html}
<!-- -->
```
-   The Committee recommended there should be a Science Policy document
    beyond the PDMP.

**Data Policy:**

**Steve Ritz, posted talk**---Steve proposed a *revised data policy for
the first year*: The GIs in Cycle 1 will not have access to LAT photon
data; this will reduce the LAT team's work while it calibrates the
instrument. In return, the LAT team will release more processed data
such as information about transients (when, where, how bright) and
lightcurves in different energy bands for \~20 sources that the LAT team
will monitor. Peter Michelson will propose precisely which data will be
released. The monitoring of bright and interesting sources by the LAT
team could continue in Phase 2.

The GUC will be involved in choosing the list of sources that will be
monitored. Consequently multiwavelength correlations might be the main
Cycle 1 project.

GIs would be selected in Cycle 1 to work on these \~20 sources being
monitored. Data (processed) on these sources are released to full
community.

To prepare the user community to analyze data during Cycle 2, the GSSC
will provide simulated data to play with the SAE during Cycle 1. In
addition, transients need to be defined. There was general GUC approval
of Steve\'s Year 1 policy.

Users should not be required to agree to an Honor Statement, but a
statement on the GSSC website would state that users should respect the
accepted proposals. Some questioned whether the abstracts of accepted
proposals should be posted, thereby letting successful GIs get 'scooped;
however, posting these abstracts is probably a legal requirement.

Regarding the size of funding grants, NASA HQ advocates a minimum of
\$50K and prefers at least \$75K.

Steve advocated a GLAST Fellows program with 3 Fellows chosen every year
for 3 years of funding. GUC members pointed out that universities do NOT
waive the overhead on Fellows program grants.

The GUC was supportive of a GLAST Fellows program even if it meant fewer
funds available for GI investigations.

**Data Analysis Software:**

**David Band (Overview)**, posted talk.

**Jim Chiang (Likelihood)**, posted talk---The major issue is the
running time for analyses with many photons. Whereas EGRET used binned
likelihood, LAT will use unbinned likelihood. Will likelihood be useful
mostly for short observations? Analyses may require two steps: other
tools will find sources, and likelihood will refine the positions and
fit spectra. Prototype system has been developed: \~2000 events in 30º
FoV takes \~1min on a PC to process.

**David Band (GRBs)**, posted talk---Likelihood code (based on LAT)
could be used for GRBs with small numbers of photons. GRB detection
software NOT being provided to user community; rather, will rely on GBM
or LAT trigger.

**Masa Hirayama (Pulsars)**, posted talk---The tools being developed do
not (yet) allow for incorporating binary pulsar ephemeris information.
Jim Buckley pointed out that observing modes (e.g., scanning vs.
pointing) might be tailored to optimize window functions and deal with
sidebands.

**James Peachey (SAE Implementation)**, posted talk---Roger Brissenden
asked about SAE requirements. Answer: they are posted.

Jim Ling asked about the GUC beta testing the SAE, and James suggested
that this could occur after DC2. Jim Ling asked about the tools'
configuration management. James answered that this depended on the stage
of software development.

Marc Strickman asked whether cygwin was required to run the FTOOLS on
Windows. James answered that the old tools that include Fortran require
cygwin. The new HEADas will have native Windows support. In many cases
the GLAST tools might become the Windows version for a given capability.

Steve Ritz asked when tools can be reviewedby the GUC. Starting with the
next meeting, one analysis thread will be demonstrated at each GUC
meeting.

**Observing Plans:**

*Pointing vs. Survey Mode time allocation:*

First, currently no Project Scientist discretionary time is set aside.
Presumably such time would be used for pointed observations. Second,
Steve Ritz is concerned that a minority of GIs requesting pointed
observations may hurt the science of a silent majority of investigators
who want survey mode, but don't propose survey mode observations because
it is the default. Setting a maximum fraction of pointed observations
may therefore be wise. Steve proposed that in Phase 2 (the GI cycles
after Cycle 1) 80% of the observing time be dedicated to survey mode and
GI-proposed pointed observations, and 20% to Project Scientist
discretionary time and instrument calibrations. The Project Scientist
discretionary time might be spent adding to a GI's pointed observation.
LAT calibrations may not require many special observing modes; for
example, alignments can rely on survey mode observations. Special modes
might reject fewer cosmic rays onboard. Therefore, only \~5% calibration
time may be needed.

Rene Ong pointed out that Project Scientist discretionary time provides
flexibility to respond to scientific and mission needs, and Roger
Brissenden said that Chandra's discretionary time is 5%. Don Kniffen
stated that the Project Scientist will have guidance as to the use of
discretionary time. Peter Michelson suggested that discretionary time
would be useful for testing new observing modes. Josh Grindlay
summarized the consensus that \~10% discretionary time is a good idea,
and that TOOs not proposed by GIs should come out of this allotment.

The pressing issue is the breakdown of the 80%. Roger Brissenden pointed
out that the cost for one mode vs. another needs to be considered, and
that this cost includes the effort for scheduling observations. Steve
Ritz said that we need *figures-of-merit* to help decide between
observing modes, and to decide whether to perform a TOO. For example, a
multiwavelength campaign may be messed up by a TOO. We need a mechanism
indicating that the default survey mode should be maintained because of
a multiwavelength campaign or the window function for a temporal study.
A figure-of-merit that would allow weighting by effective area and
angular resolution per unit solid angle should be derived.

Josh Grindlay asked whether a deep survey would be useful. Rita Sambruna
stated that we need a study to show the relative merits of different
observing modes.

It was noted that no current pointing scheduling software (e.g., Tako,
developed for Astro-E and planned to be used for Swift) deals with the
very large FoV issues that GLAST presents.

Finally, Jim Buckley asked whether CAL-only events or ACD-observation
modes would be useful. Steve Ritz stated they would not, and were not
planned.

**Committee Discussion At End of 8/9/04**

Josh---Issues that could become Action Items:

-   Merits of survey vs. pointing mode, using which figures-of-merit?

-   Project Scientist discretionary time and its uses: tentative
    decision that 10% is appropriate

-   Advance GI funding (e.g., for a GBM monitoring program)? Decision
    not to pursue as an action item

-   Definition of data products released in first year

-   How SAE is integrated, LAT-GSSC interface, pipeline vs. SAE

-   GUC Charter

-   Next meeting in 1/2 year? If less frequently, telecons?

-   Joint SWG-GUC meeting?

-   Include GUC in DC2? Might intimidate.

-   SAE walk-throughs, beta testing

-   Remove honor statement.

-   GUC report to HQ, letter to Don?

-   Merge the SWG into the GUC after launch? However, the SWG members
    might dominate the GUC, as happened with CGRO.

-   Size of the GI program awards. \$6-8M/yr is currently planned.
    *Steve needs support in writing a justification.*

-   Get size of CGRO GI program from Chris Shrader.

-   Get comments to David Band and Steve Ritz on PDMP by Sept. 10.

**August 11, 2004**

**PDMP:**

**David Band**, posted overview talk---The GUC decided that the science
policy statements (data access, transients, frequency of TOOs and
autonomous repoints) should be pulled out of the PDMP and kept in a
separate document, if consistent with NASA policy. The website and NRAs
can then refer to the policy document.

The GUC felt that the PDMP includes insufficient information about
instrument calibration, even if the data products are archived
internally by the instrument teams. Although data archiving is
described, it is not emphasized sufficiently. The contents of the burst
alert telemetry should be included as a table in §5. The section (§6)
summarizing the responsibilities of each ground element repeats much of
the content in earlier sections, and should be eliminated (after
ensuring that no content is lost).

The GUC decided that there should not be a Timeline Committee that would
have meet once a year after the peer review panels had provisionally
selected GI observations, but that instead an operations working group
with expertise from the instrument teams should work on technical issues
such as technical implementation (but not policy).

It was agreed the PDMP should include a mission description. There was
considerable discussion about the PDMP vs. a Data Policy or Science
Policy document. Roger Brissenden noted that for AXAF the PDMP was
indeed a plan (1 year before launch) but that data policy has evolved
with the mission . The PDMP is more of a \"data-centric\" plan to ensure
the Project has well defined data flow and dissemination plans.

It was agreed that the PDMP should be revised, although major changes
can be incorporated later if needed. In contrast, a Science Policy
document should be more evolutionary.

**Multiwavelength Observations:**

**Steve Ritz (Multiwavelength)**---The mission and the LAT team have
separate multiwavelength plans. Dave Thompson has set up a mission
website supporting multiwavelength efforts. Steve asked if the GUC
supported setting up a Mission Multiwavelength Working Group? Although
there are Interdisciplinary Scientists to support multiwavelength
programs, there is no formal WG.

**Dave Thompson (Multiwavelength)**, posted talk---A LAT WG (Roger
Blandford and Dave Thompson, co-chairs; Seth Digel, Greg Madejski, Roger
Romani and Steve Thorsett) has considered the tasks needed to support
multiwavelength observations before and during the mission. Before the
mission we need new blazar catalogs and a prioritized list of pulsars to
be monitored. During the mission the identification of new gamma-ray
sources should start from the X-ray. Major problems are that by GLAST's
launch the Spitzer's cryogen will be consumed, creating an FIR gap in
the multiwavelength coverage, and insufficient X-ray monitoring
capability will exist during the GLAST mission since the RXTE/ASM will
likely no longer be operational and future ASMs are not certain (e.g.,
the status/schedule of MAXI on the ISS?).

Issues to be considered are: maintaining the LAT's multiwavelength
efforts into Phase 2; balancing multiwavelength discovery (identifying
gamma-ray sources) vs. exploration (studying identified sources);
balancing GI and LAT team interests; and incorporating observers
involved in multiwavelength into the LAT team. The discovery vs.
exploration issue is significant: the effort taken for identification
and followup of individual blazars discovered with EGRET (e.g.,
J2006-2321) cannot be done realistically for the projected 3000 that
might be discovered with GLAST.

Discussion focused on using the first year GI program to support
projects crucial to the success of the mission, especially
multiwavelength and source monitoring research. Rita Sambruna noted that
key questions should be science driven. This will be called the 'legacy'
program. While the community will propose the projects, we want to make
sure all necessary programs are done, and therefore may need to recruit
if necessary. These would be multiyear (3 year?) grants. It was
suggested that pre-launch funding might be possible using the
contingency budget, although it seems doubtful this would be allowed (to
use contingency). Should there be key projects in addition to the legacy
projects?

The GUC agreed that a significant component of any legacy program should
be multiwavelength monitoring campaigns and the long term preparations
needed to carry them out. Consequently, the \~20 monitored LAT sources
should be announced in advance. A remaining question is whether the
supported OIR observations should be proprietary to the observers.

**Miscellaneous Issues:**

Greg Stacy asked whether solar flares can trigger autonomous repoints.
Steve Ritz sees no reason why not. Note that the sun will be observed in
survey mode and there is no instrumental or spacecraft restriction
against pointed observations. The GBM flight software will distinguish
between transients likely to be bursts and those likely to be solar
flares, and therefore autonomous repoints for solar flares will have to
be enabled. Intense solar flares can flood the ACD and saturate the LAT.
Turning off the ACD veto and using the inner 4 towers during solar
flares has been thought about but not implemented.

Greg Stacy also asked about the role of the GSSC 'ambassadors' to
instrument teams in supporting GIs. This has not been worked out, and
needs to be discussed with Jay Norris. Clearly they will be conduits of
information about the instruments back to the GSSC.

The LAT team is planning to provide space for GIs to visit the ISOC. The
GSSC is not planning to provide facilities for GIs to receive onsite
assistance in analyzing their data, although scientists will not be
barred from visiting.

The GSSC plans to run workshops on analyzing the GLAST data (e.g.,
similar to the Chandra CIAO workshops, which have been very successful)
and to provide assistance electronically, e.g., through a help desk.
Roger Brissenden stated that although Chandra planned a small amount of
space for visitors there was little or no demand since users\' needs
were met through the web and other user support interfaces provided by
the CXC.

**Suggestions for Roles for the GUC**

The Committee then discussed various roles for the GUC which may be
incorporated into the Charter. Roles for the GUC, and those suggesting
them, were:

-   Advisory committee on GSSC\'s functioning---Josh Grindlay

-   Review NRA---Peter Michelson

-   Relationship to other missions---Steve Ritz

-   Sponsor GLAST symposia---Steve Ritz

-   Review SAE---Peter Michelson

-   Advocate continuing support---Dave Bertsch

-   Chair should attend SWG---Steve Ritz

-   Involvement in SWG-LAT symposia---Steve Ritz

-   Balance of resources between GI and GSSC---Roger Brissenden

-   Outreach---Josh Grindlay

-   Membership: NASA terms are usually 3 years, but because the terms
    should be staggered, the terms for some of the initial set of
    members may be more than 3 years.

**Next Meeting**

The next GUC meeting will be at Stanford, tentatively on March 3-4,
2005. Seth Digel will be asked to make a presentation on the diffuse
gamma-ray background.

**Formal Action Items:**

The GUC concluded the meeting by reviewing and assigning Action Items
and due dates, which allow for incorporation of these into the next
meeting of GUC in March, 2005.

1.  Determine the relative merits of pointed vs. survey mode. This will
    require developing different figures of merit and performing trade
    studies. Assigned to David Band, Jim Buckley, Julie McEnery, Peter
    Michelson, and Reshmi Mukherjee, with Julie coordinating the effort.
    Due date: Feb. 15

2.  Define the policy for Project Scientist Discretionary Time. Assigned
    to Steve Ritz and Rene Ong. Due date: Feb. 15

3.  Determine the GBM's sensitivity as a sky monitor and the effort
    necessary to apply BATSE software to the GBM. Assigned to Chip
    Meegan and Jim Ling. Due date: Feb. 15

4.  Summarize a) the division of responsibility between the GSSC and the
    LAT team for the SAE, b) the development plan, and c) the software
    updating plan. Assigned to Peter Michelson and Jay Norris. Due date:
    March 3

5.  Develop the GUC Charter. Assigned to Josh Grindlay and Don Kniffen.
    Due date: Sept. 11.

6.  Develop the plans for the Cycle 1 GI program, particularly the LAT
    data release in the first year. Assigned to Peter Michelson. Due
    date: Feb. 15

7.  Develop the Science Policy document. Assigned to Roger Brissenden
    and Steve Ritz. Due date: Feb. 15

8.  Organize a demonstration of an analysis thread using the SAE.
    Assigned to Jay Norris. Due date: March 3

9.  Determine the size of the GI programs and DOE\'s support plans.
    Assigned to Josh Grindlay, Steve Ritz, and Peter Michelson. Due
    date: Feb. 15

10. Send comments on the PDMP to David Band and Steve Ritz. Assigned to
    GUC. Also, determine NASA HQ's PDMP policies. Assigned to Don
    Kniffen. Due date: Sept. 11.

11. Develop the policy for legacy proposals. Assigned to Josh Grindlay
    and Rita Sambruna. Due date: Feb. 15

**Recommendations:**

1.  There should be 2 GUC meetings per year

2.  The data access policy should not include an honor statement that
    investigators should respect the accepted GI proposals.

3.  The GUC supports having a GLAST Fellows program.