1. LAT Test Results GLAST Large Area Telescope LAT Pre-Shipment Review
Gamma-ray Large Area Space Telescope
GLAST Large Area Telescope
LAT Pre-Shipment Review
LAT Test Results
J. Eric Grove
NRL
Stanford Linear Accelerator Center
LAT Test Results

2. Purpose / Contents Demonstrate LAT functionality
Verify performance requirements
Note: majority of sell-off done during/after environmental test
Monitor LAT performance via CPT and calibrations throughout Commissioning and Environmental test
CPT
Detector subsystems
Copper paths, interfaces
Calibrations
LAT Test Results

3. Data products, analysis, and reports
“Online” analysis – Mobile Computing Rack
Data converted from CCSDS to LSF to LDF
Same data format used in LATTE era (i.e. prior to FSW)
Analysis scripts and reports from LATTE
“Offline” analysis – SLAC computer farm
Two reports produced for all runs, corresponding to data products
Digi report (basic detector quantities)
Trigger info: Total rate; Rates of trigger types; Arrival times
ACD: Occupancy; Threshold info; Hit map
CAL: Occupancy
TKR: Number of strips and layers hit; Time over threshold
Reconstruction report (derived quantities)
Number of tracks
Reconstructed energies, directions, positions
TKR-CAL alignment, track extrapolation to ACD
Full GLAST community has access and tools for offline products
LAT Test Results

4. Test matrix
LAT Test Results

5. Script/Test Status Liens against LAT CPT Detector CPTs
Data collected and analyzed; trending is in process
No known script issues in CAL, TKR CPTs
ACD CPT
AcdTciRegRange (front end gain and linearity test) shows systematically lower gain (~5-10% lower) than GSFC test. Likely cause: change in ACD timing config.
Full AcdVetoCal (30 min runtime) is in use; should abbreviate it.
LAT-22x (Science Ops Demo)
Needs to exercise onboard event filter
Needs additional analysis steps (data and trigger aliveness). Coding is in process.
LAT-23x (GRB Handling)
Test is being coded
LAT-14x (SIIS test)
SIIS brought up and checked out. Test case is being coded
LAT Test Results

6. Test status Data integrity issues
Dropped word on 256-byte boundary within packet
Rare loss of data word, likely caused by dropped read from the SDI board in the VSC.
Fixed? To be verified…
Firmware upgrade and change in a configuration parameter in the SBC made on Mon 24 Apr.
Dropped word at end of packet
Last word is dropped when length of packet is some particular modulo value. Affects many LPA, LCI runs.
Cause is VHDL bug in EBM output chip.
Workaround in FSW B0-6-8: add one cell of padding if packet has this particular length
Need B0-6-8 installed and operating on LAT before final CPTs
Compression error in LCI
Occasional error in generation of compression key
Rare but repeatable (e.g. affects 1 of 64 configs within a single CAL script)
Still under investigation
LAT Test Results

7. T&DF performance T&DF functionality
Trigger system demonstration in CPT
Trigger primitive aliveness
Scheduler, Engine, and Messaging functionality
Trigger and veto efficiency
Collected with LATTE, analysis on-going
Collected with FSW, analysis on-going
Detector subsystems timed-in (calibration)
TREQ aligned
ACD veto and TKR time-aligned with CAL-LO
TACK delay optimized
ACD and CAL MIP peaks maximized
TKR hit occupancy maximized
LAT Test Results

8. Trigger summary
LAT Test Results

9. ACD performance Subsystem performance
Minimum-ionizing particle (MIP) peaks
Veto rates
Veto thresholds
Electronics
Pedestal centroids and widths
Width is measure of noise
Gain
Calibration quantities
MIP peaks
MIP spectra (PHA)
LAT Test Results

10. ACD trending Pedestal trend Centroid and width difference Two epochs
Apr 06 CPT
GSFC preship
Typical Veto threshold ~ 100 bins
Pedestal changes are small
Veto occupancy
Aliveness test for all Veto signals
“GEM Veto List”
Muons during LAT CPT show all channels are alive
LAT Test Results

11. CAL performance Subsystem performance Gain (“MeV/bin”) Linearity
Electronic performance
Pedestal centroids and widths
Width is measure of noise
Gains
Front-end linearity
Threshold DAC gains
Calibration quantities
Gain
Hit occupancy
LAT Test Results

12. CAL trending Time evolution of pedestal width Front-end linearity
Typical FWHM ~ 4 bins (HEX8)
Plot shows stability of 32 channels
Front-end linearity
Typical avg non-linearity ~ 0.2%
Stable to ~0.02% or better
LAT Test Results

13. TKR performance Subsystem performance Dead strip list Noisy strip list
Electronics
Noise occupancy
Calibration quantities
TOT gain
Hit occupancy
LAT Test Results

14. TKR trending Disconnected channel trend
Increase in disconnects < 1.5% since delivery of TKR towers.
LAT Test Results

15. Calibration Calibration
Datasets collected with cosmic muons and test charge injection
Both under LATTE and FSW
Collections with FSW are on-going
Test cases LAT-07x, LAT-70x, and LAT-71x
No known problems with scripts
Analysis
Combination of online (near real time) and offline processing
Online processing of FSW data is complete
Offline processing in progress
Output is set of calibration constants for each detector subsystem
Trending system for constants is under development
Constants need review by subsystems
LAT Test Results

16. Sample events Gamma ray converting in TKR
Cosmic muon traversing multiple towers
LAT Test Results

17. Summary LAT assembled and operating under FSW LAT CPT in place
Except: GRB Handling
Liens: Minor mods to speed acquisition or add analyses
Calibrations
Data collected with LATTE are analyzed and in use
Data collected with FSW are under analysis
Calibration constants maintained in SAS/ISOC database
Performance trending
Trending processes exist, and subsystems are involved
Large data volume to consume
Status
Detectors are operating daily with flight settings
Test results with FSW show (approximately) same instrument that we assembled and tested with LATTE
Leave SLAC with a baseline reference for entry into environmental test program
LAT Test Results