1. GLAST LAT ProjectMarch 24, 2003 7F Tracker Peer Review, WBS 4.1.4 1 GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 7F: On-Orbit Calibration and Test Bill Atwood Santa Cruz Institute for Particle Physics University of California at Santa Cruz atwood@scipp.ucsc.edu Gamma-ray Large Area Space Telescope

2. GLAST LAT ProjectMarch 24, 2003 7F Tracker Peer Review, WBS 4.1.4 2 Relevant Documents Applicable LAT documents to this review: –LAT-TD-00249 - Tracker Front-end Readout ASIC Wafer Test Procedure –LAT-TD-00248 - Tracker Readout Controller ASIC Wafer Test Procedure –LAT-TD-00249 - Tracker Multi-Chip Module Test Plan These Plans are in a formative state – This report is meant to convey our present thinking only.

3. GLAST LAT ProjectMarch 24, 2003 7F Tracker Peer Review, WBS 4.1.4 3 Logic Functionality GLAST Tracker Front End ASICs are a specialized, programmable “computer.” Two ASICs GTFE (analog and digital sections) GTRC (digital section only) Functional Testing Developed as part of parts testing during construction Load & Read-Back Control Registers & DAC Settings (TEM GTRC GTFE) - Trigger Masks - Data Masks - Threshold DAC’s & Charge Calibration DAC’s

4. GLAST LAT ProjectMarch 24, 2003 7F Tracker Peer Review, WBS 4.1.4 4 Analog Testing Calibration Run - Setting the Charge Injection Masks - Setting the Charge Injection DACs - Cycling through Threshold DAC settings - Record the number of hits from each channel - Compare with results obtained prior to launch Example from First Tests of Flight GTFE Flight Chips For On Board Testing – a linear fit to the transistion Region would be made and the results sent to the ground.

5. GLAST LAT ProjectMarch 24, 2003 7F Tracker Peer Review, WBS 4.1.4 5 Analog Testing Noise Occupancy Check - Fire random trigger - Accumulate counts per channel distribution - Check for (new) noisy channels Example from Mini-MCM Testing Lines are the average channel noise For each of the 6 chips (one SSD Ladder’s worth) Shows threshold setting corresponding to ¼ MIP.

6. GLAST LAT ProjectMarch 24, 2003 7F Tracker Peer Review, WBS 4.1.4 6 Online Monitoring Output from Tracker is minimal: 1) Address of an SSD channel indicating the presence of the passage of a charged particle through the active area associated with it (i.e. a “hit”) 2) The address of each X & Y plane of silicon strip detectors with the collective OR of all the strips in that plane set - used for triggering 3) Time-over-threshold (TOT) for the entire layer – for the OR’d signal. This time is correlated with the amplitude of the largest single SSD single in that layer.

7. GLAST LAT ProjectMarch 24, 2003 7F Tracker Peer Review, WBS 4.1.4 7 Online Monitoring Hit Strip Distributions - 884736 channels - 2 bytes/channel ( 2 MB storage) - Expect: ~ 200 counts/channel/orbit (3900 counts/ch/day) Layered OR Distributions - 1152 Layered OR’s (all GFRC working) – 4 bytes/channel (4.5 KB storage) Tower Trigger Distributions - 16 Towers – which initiated the trigger TOT Distributions - 1152 channels – keep mean and RMS for each ( 9 KB storage).

8. GLAST LAT ProjectMarch 24, 2003 7F Tracker Peer Review, WBS 4.1.4 8 Online Monitoring House Keeping Items (Periodically read, monitored & downlinked) - Temperatures (18 Thermistors per Tower) - Voltages (SSD Bias, various Analog & Digital supply voltages)

9. GLAST LAT ProjectMarch 24, 2003 7F Tracker Peer Review, WBS 4.1.4 9 Alignment High energy cosmic rays (mostly protons at several GeV) produce straight trajectories in GLAST Boot-Strap proceedure - Fit 3D straight lines to Tracker Hits - Off-sets in Fit Residuals tray-to-tray alignment off-sets - Linear Dep. Of Fit Residuals tray-to-tray rotations Align Trays within Towers Align Towers-to-towers Procedure being developed in conjunction with I & T ( H. Tajima et al)

10. GLAST LAT ProjectMarch 24, 2003 7F Tracker Peer Review, WBS 4.1.4 10 Turn-on and First Triggers - Perform Logic Check-out and Test - Perform Analog Check-out - Enable 3-In-A-Row trigger - Accumulate cosmics into online monitoring histograms - Check rates - Select MIP subset to downlink (for alignment checks) - Enable Gamma Triggering & Filtering - Initial Operation may toggle between “gamma” data and “straight-through” cosmic ray data. - Helpful to have capability of several downlinks/day during this phase.