GLAST Science Support CenterFebruary 14, 2003 HUG Meeting The GLAST Data David Band (GLAST SSCGSFC/UMBC) GLAST Science Support Center February 14, 2003 HUG Meeting2 Outline Description of the GLAST Mission Novel Aspects of GLAST Data Analysis The Ground System The SSC Community Access to the Data Analysis Software Databases Programmatics Summary GLAST Science Support Center February 14, 2003 HUG Meeting3 What Is GLAST? Gamma-ray Large Area Space Telescope (GLAST) successor to CGRO Large Area Telescope (LAT)GLASTs main instrument, a follow-on to CGROs EGRET. The LAT is a NASA-DOE collaboration with foreign contributions. PI: Peter Michelson (Stanford & SLAC) GLAST Burst Monitor (GBM)a smaller version of CGROs BATSE. The GBM is a MSFC-German collaboration. PI: Chip Meegan (NSSTC) Scheduled launch is September, 2006, into low earth orbit The minimum mission is 5 years, with a goal of 10+ years! Additional details in the extra slides at the end. GLAST Science Support Center February 14, 2003 HUG Meeting4 The LATCharacteristics The LAT will be a pair conversion telescope. E= 300 GeV, E/E 8000 cm 2. FOV>2 sr, with A eff ~1/2 of normal at 55 1 angular resolution MeV, GeV Only a few Hz out of the 30 Hz events telemetered to Earth will be photons. The basic data are event lists. In normal operation GLAST will survey the sky, thus most sources will be observed at a variety of angles to the LAT. The LAT will be >30 more sensitive than EGRET! The EGRET 3rd Catalog had 271 sources, LAT catalog should have >9000. Localizations will allow observations. GLAST Science Support Center February 14, 2003 HUG Meeting5 The GBM 12 NaI(Tl) detectors (5 diameter)25 MeV The combination of the GBM and LAT will provide spectral coverage from ~10 keV to ~300 GeV--7.5 decades! Bursts will be localized both onboard and on the ground. GCN should receive the first notification in ~7s. The GBM will provide: binned background data; and binned and event data after a trigger. GLAST Science Support Center February 14, 2003 HUG Meeting6 The Science of GLAST Blazars & AGNrelativistic jets, transients Gamma-ray burstsrelativistic outflows, efficient emission of gamma rays, new emission component? Pulsarsdistinguish between outer gap and polar cap models, young sources Unidentified sourcesfaint blazars? New Galactic population? Diffuse Galactic emissioncosmic rays interacting with Galactic gas. Both an annoying background and an intrinsically interesting phenomenon Extragalactic IRattenuates extragalactic gamma rays Solar flaresparticle acceleration Exotic particlesdecay or annihilation GLAST Science Support Center February 14, 2003 HUG Meeting7 Data Analysis Issues The PSF is large at low energy, small at high energy. With the LATs large effective area, many sources will be detected; their PSFs will merge at low energy. Analysis is inherently 3D2 spatial and 1 spectral (& users are interested in temporal!) Complicated, multi-parameter source models will include: All sources within a few times the PSF of the region of interest Diffuse sources (e.g., supernova remnants) Diffuse Galactic and extragalactic emission (modeled) The LAT will usually survey the sky. Therefore a source will be observed at different instrument orientations. The instrument response function will be a function of many quantities. GLAST Science Support Center February 14, 2003 HUG Meeting8 Planned Basic Analysis Strategy We plan to detect sources, determine source intensities, fit spectral parameters, set upper limits, etc., using the likelihood of the observed counts given a source model. Calculating the will be difficult because many counts will sparsely populate an enormous data space (both the observed counts and the absence of counts must be considered). The will be calculated many times. Therefore we want to isolate the factors that are not model-dependent, and calculate them once for a given analysis. Many of these quantities will have units of exposure (area time). GLAST Science Support Center February 14, 2003 HUG Meeting9 Special Cases Bursts are (relatively) short, and the pointing will not change significantly during the burst Within the bursts PSF no non-burst photons are expected during the burst. Thus bursts can be analyzed as an isolated source: Many burst photonsbin in time and energy, fit spectra (e.g., with XSPEC) Few burst photonsfit spectra using likelihoods; energy is the only observable The detection of pulsars will rely on their periodicity. Because of the low count rate, long time ranges will be searched, requiring both P and P-dot. Analysis of pulsar spectrum and intensity will require standard point source analysis. GLAST Science Support Center February 14, 2003 HUG Meeting10 The Ground System GLAST Science Support Center February 14, 2003 HUG Meeting11 The Role of the SSC The SSC is the interface between GLAST and the general scientific community. It is responsible for: Providing data and analysis tools to the scientific community Running the guest investigator program Supporting mission operations, primarily through maintaining the mission timeline Archiving the mission data, eventually in the HEASARC Supporting the dissemination of results through the SSC website, running conferences and contributing to public education The SSC consists of scientists, scientific programmers and support staff housed within LHEA at GSFC. The SSC is NOT responsible for the basic data processing, and will not support a guest observer facility. GLAST Science Support Center February 14, 2003 HUG Meeting12 Community Access to the Data During the first year GLAST will survey the sky. The LAT team will verify their data and produce a point source catalog from the survey. A limited number of GIs will access the data through the instrument teams. In subsequent years all the data are public immediately. At all times data from transients are public immediately. GLAST will have a large, well-funded GI program. GIs may request pointed observations. The SSC will post results on its website (e.g., exposure maps). The PDMP has been drafted but not baselined. The PDMP will have the official statements of the data and transients policies. GLAST Science Support Center February 14, 2003 HUG Meeting13 The Standard Analysis Environment Standard analysis environment (SAE): tools and databases needed for routine analysis of GLAST data by both the instrument teams and the scientific community. SAE defined jointly by the LAT team and the SSC, and will be developed under the LAT teams management with SSC participation. Mock data challenges in late 04 and late 05. The tools will support: Likelihood analysis for source detection and spectral analysis Gamma-ray burst spectral and temporal analysis Pulsar periodicity analysis Simulations Catalog comparisons GLAST Science Support Center February 14, 2003 HUG Meeting14 Software Paradigm Our tools will be FTOOLs and use the HEADAS libraries: Data I/O through FITS files, using existing types where possible The PIL interface will extended to support GUIs The LATs software development environment will be used: CVS for storing the software CMT for configuration and build management DOXYGEN for documenting the code C++ for most new code Support for Windows and Linux platforms Scripting language: Python (probably) Graphics (& GUI): Root (or plplot, with DS9) Existing tools will be used where possible (e.g., XSPEC for analysis of burst spectra). The systematic definition and design of the tools has begun. See the tables at the end. GLAST Science Support Center February 14, 2003 HUG Meeting15 Databases The SSC will maintain all its databases in a form compatible with HEASARC norms. The SSCs databases will be owned jointly by the SSC and the HEASARC, and will remain as the mission archive after the SSC is disbanded. The list of photons must be searchable rapidly, and will probably be installed on a Beowulf system. The CPUs of the SSCs computer system will be provided by the HEASARC while the data disks will be purchased by the SSC. The SSCs computers will be part of the HEASARCs system, and will participate in the HEASARCs computer security plan. Data ingest from the other ground system components will be tested in Ground Readiness Tests (11/04, 9/05). Ground system end-to-end tests are planned. Ingest into the databases will also be tested in the analysis system mock data challenges. GLAST Science Support Center February 14, 2003 HUG Meeting16 Programmatics Mike Corcoran is the SSCs contact at the HEASARC and the GLAST archive scientist. The HEASARC-SSC MOU is nearly complete; an ICD is planned. An ad hoc Data Products Working Group developed descriptions of the data products (down to FITS headers and table columns) that will be passed between ground system components. ICDs with the ground system components will be drafted by 11/03 and finished by 6/04. The SSC Functional Requirements Document has been baselined. GLAST Science Support Center February 14, 2003 HUG Meeting17 Summary GLASTs primary instrument, the LAT, will be a large leap in capability and complexity relative to EGRET. The GBM is a smaller version of BATSE. The standard analysis of LAT data will be complex because: narrow PSF at high energy, broad at low energy; a region must be modeled to study a source; and GLAST will usually scan the sky. Most analysis will use the likelihood of the observed counts given a source model. Analysis of gamma-ray bursts and periodicity studies of pulsars will use the sources temporal properties. After the first year data will be public immediately. Transients are public even during the first year. There will be a large GI program. The instrument teams will process the telemetry into photon lists. GLAST Science Support Center February 14, 2003 HUG Meeting18 Summary, Cont. The SSC at GSFC will provide the scientific community with data and analysis tools through its website. The tools will be FTOOLs, extended to provide a GUI interface. Where possible we will use existing tools. New tools will be written in C++, and supported for Windows and Linux. The databases will be in a HEASARC-standard format. The photon list will be loaded onto a Beowulf cluster. After the mission the databases will remain at the HEASARC as the archives. Mike Corcoran is HEASARCs liason with SSC. PDMP drafted, SSC-FRD baselined, HEASARC-SSC MOU drafted, data products defined. GLAST Science Support Center February 14, 2003 HUG Meeting19 Additional Slides GLAST Science Support Center February 14, 2003 HUG Meeting20 GLAST Science Support Center February 14, 2003 HUG Meeting21 The LATStructure The LATs Tracker subsystem will consist of 16 tungsten planes (for pair production) and 18 silicon strips planes (to track the pairs). Below these W-Si planes are 8 planes of CsI logs to measure energies. Surrounding the LAT are plastic anti-coincidence scintillator tiles. Photons that pair- produce in the trackers front or back may be analyzed separately. Anticoincidence Detector Tracker Calorimeter GLAST Science Support Center February 14, 2003 HUG Meeting22 LAT Science Performance Summary 5 arcmin