GLAST LAT ProjectMarch 24, F Tracker Peer Review, WBS GLAST Large Area Telescope: Tracker Subsystem WBS F: On-Orbit Calibration and Test Bill Atwood Santa Cruz Institute for Particle Physics University of California at Santa Cruz Gamma-ray Large Area Space Telescope

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

GLAST LAT ProjectMarch 24, F Tracker Peer Review, WBS 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

GLAST LAT ProjectMarch 24, F Tracker Peer Review, WBS 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.

GLAST LAT ProjectMarch 24, F Tracker Peer Review, WBS 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.

GLAST LAT ProjectMarch 24, F Tracker Peer Review, WBS 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.

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

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

GLAST LAT ProjectMarch 24, F Tracker Peer Review, WBS 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)

GLAST LAT ProjectMarch 24, F Tracker Peer Review, WBS 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.