# Presentation: 841392

## Large Area Telescope(LAT) Overview

**Peter F. Michelson **
**Instrument Principal Investigator**
**Stanford University**
**peterm@leland.stanford.edu**
**William E. Althouse**
**LAT Project Manager**
**Stanford Linear Accelerator Center**
**wea@slac.stanford.edu**

## GLAST Large Area Telescope: Overview

**LAT: wide field-of-view high-energy gamma-ray telescope**
**Design optimized for Key Science Objectives**
- Particle acceleration in Pulsars, SNRs, AGN, & galaxies
- High-energy behavior of GRBs & Transients
- Probe dark matter and the Early Universe
**More than 7 years of design, development & demonstration efforts**
- 1993-95:  First GLAST mission studies as New Mission Concept in Astrophysics
- 1997-2000:  LAT Technology Development and Demonstration  Program
**LAT design based on proven technologies**
- Precision Si-strip Tracker
- Hodoscopic CsI Calorimeter
- Segmented Anticoincidence Detector
- Advantages of modular design

- 9/27-28/2000

## GLAST Large Area Telescope:  Overview

**GLAST LAT flight instrument and science investigation proposal submitted in response to NASA AO 99-OSS-03 – November 1999**
- Baseline instrument configuration defined
- Instrument team defined:  US led (supported by DOE & NASA), with international partners
- Draft international agreements with all foreign partners
**Flight Proposal selected – February 28, 2000**
**  **

**Organizations with LAT Hardware Involvement**
**Stanford University:  SLAC & HEPL**
**NASA Goddard Space Flight Center**
**US Naval Research Laboratory**
**University of California at Santa Cruz:  SCIPP**
**Hiroshima University, University of Tokyo, ISAS & ICRR, Japan**
**INFN, Italy**
**Laboratorie du Commissariat a l’Energie Atomique & IN2P3, France**
**Royal Institute of Technology, Sweden**

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## Experimental Technique

-    Instrument must measure the _direction_, _energy_, and _arrival_ _time_ of high
-     energy photons (from approximately 20 MeV to greater than 300 GeV):
-       - photon interactions with matter in GLAST
-         energy range dominated by pair conversion:
-  	determine photon direction
- 	clear signature for background rejection

-       **- **limitations on angular resolution (PSF)
**            ****low  E: multiple scattering => many thin layers**
**            ****high E: hit precision & lever arm**

- •  must detect -rays with high efficiency
-    and reject the much higher flux (x~104)
-    of background cosmic-rays, etc.;
- •  energy resolution requires calorimeter
-    of sufficient depth to measure buildup
-    of the EM shower. Segmentation useful
-    for resolution and background rejection.

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## LAT Instrument

**LAT Instrument**

- TKR+CAL:
-      prototypes + 1 engineering model
-      16 flight  +1(qualspare)  +1(spare)
- ACD:
-      1(qual)  +1 flight

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## Pair-Conversion Tracker Design Considerations

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##     LAT Instrument Performance

- More than 40 times the sensitivity of EGRET
- Large Effective Area (20 MeV –  > 300 GeV)
- Optimized Point Spread Function
- (0.35o @ 1 GeV)
- Wide Field of View
- (2.4 sr)
- Good Energy Resolution
- (***E/E* < 10%,
-            E >100 MeV)

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## GLAST LAT Organization

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## Institutions & Responsibilities

| Institution(s) | Areas of Responsibility |
| --- | --- |
| SU-SLAC | Management of GLAST LAT project Instrument systems engineering, electrical 
   systems engineering
Tracker subsystem mechanical design, construction, testing, integration
Software management, Grid development, Instrument integration and test
Level-1 data processing, Performance and Safety Assurance
DAQ engineering support |
| SU-HEPL | DAQ Subsystem development; Inst. Ops. Ctr. |
| SSU | Education and Public Outreach Program |
| GSFC | ACD Subsystem; thermal blanket/ micrometeorite shield;
Instrument Scientist |
| NRL | DAQ/CPU, DAQ/DSF, S/C Interface Unit; calorimeter digital electronics; calorimeter integration and test |
| FRANCE -     CEA/DAPNIA
 IN2P3/France | Calorimeter analog front-end photo-diodes and electronics readout; management 
   of French effort
Calorimeter module mechanical design and assembly; calorimeter & inst. 
   simulation |
| KTH, Stockholm
   University | Calorimeter CsI crystals |
| UCSC | Tracker Subsystem: electronics, mechanical design, assembly, testing |
| JGC, Japan | Tracker: Silicon-strip detectors |
| INFN, Italy | Tracker: Silicon-strip ladders and tracker tray assembly |

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## GLAST LAT Schedule

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