GLAST LAT Project LAT System Engineering 1 GLAST Large Area Telescope: LAT System Engineering Pat Hascall SLAC System Engineering Manager Gamma-ray Large Area Space Telescope

GLAST LAT Project LAT System Engineering 2 Topics Meeting goals –Lay out plan for completing the I&T requirements Mechanical Integration Details Electrical Integration Details Functional and Performance Tests (CPT, LPT, Aliveness, other) –Test development strategy Develop tests that take advantage of Subsystem Tests/Scripts at LAT I&T Focus is on integration testing, will phase in development of tests to be performed later Establish FSW functionality requirements –limit to functionality required for in orbit ops, but may include special test only version

GLAST LAT Project LAT System Engineering 3 Assumptions/Initial Conditions The following set of initial conditions is my understanding of the current approach - feedback? Subsystems will have a thorough interface verification at the subsystem level –Electrical interface waveforms tested and margin demonstrated –No I&T electrical characterization is required TEM and TEM/PS are delivered with no additional tests required Calorimeter, Tracker and ACD have been tested with flight design TEM equivalents, so no pin-out verification is necessary cables will be pinout verified If this is true, other than the use of connector savers as defined in the assembly plan, integration begins with plugging in subsystems and running test scripts

GLAST LAT Project LAT System Engineering 4 I&T Requirements Strategy Overview Baseline tests will include –Functions tested at Subsystems level –Functions tested by Flight software tests –Flight software in-orbit special processing (e.g. calibration mode) –Timing in Tracker layers, Tracker to Cal, between Towers and between ACD and Towers –Data collection required by SVAC –LAT to spacecraft interface verification tests –Any other source of test requirements (besides JJ) ? Will begin by defining earliest required tests first (based on updated subsystem test plans) I will be asking for help to get clear definitions for each of the tests

GLAST LAT Project LAT System Engineering 5 LAT Performance & Operations Test Plan Contents Will focus on electrical tests –Mechanical operations defined elsewhere Assembly Sequence Environmental Test Sequence Dynamics Test Plan Alignment Plan Thermal Test Plan Will contain a list of tests, with a test ID, test title, test description and where possible relationship to subsystem test Will contain a matrix to define which test is run in which test phase (test instance)

GLAST LAT Project LAT System Engineering 6 Test Definition Sample Tracker GTRC configuration register and readback –The GTRC chips are sequentially addressed and their configuration registers loaded with a bit pattern. Each time the register is read back and checked for errors. The test is repeated with the complement of the bit pattern. The test then is repeated with a broadcast address for writing the register, followed by sequential readback. (Based on Tracker Test TE201) FSW Tracker Configuration Test –This test shall verify the ability of the SIU to configure the TKR subsystem as desired and read back the necessary configuration information to completely determine the TKR subsystem configuration (Based on FSW test nnn)

GLAST LAT Project LAT System Engineering 7 Test Instance Format Sample

GLAST LAT Project LAT System Engineering 8 S/C Interface Verification DC Power –Measure total power consumption in all operational modes (including calibration mode) and in survival mode 1553 interface –Verify signal voltages and waveforms are compliant to beginning of life values based on the 1553 standard (may be done at DAQ/SIU subsystem level) –Verify ability to receive commands from the spacecraft (SIIS) and return telemetry to the SIIS Verify that all commands can be sent (not necessarily send all commands) verify that all telemetry is sent to the SIIS Science Data Stream –Verify signal voltages and waveforms are compliant to beginning of life values based on the LVDS standard (may be done at DAQ/EPU subsystem level) –Verify that the transport of the information is working correctly by successful ingest of the science data Analog telemetry, Control and monitor discretes –TBD

GLAST LAT Project LAT System Engineering 9 Integration Test Configurations

GLAST LAT Project LAT System Engineering 10 Test Stand Capabilities Test stand functionality –1 - Supports testing of a tracker, calorimeter, or integrated single tower –2 - Supports testing of multiple towers without SIU using the “backdoor” –3 - Uses SIIS through SIU to perform testing, use of “backdoor” access is possible Must use “backdoor” for early integration testing, since SIU and flight software will not be available

GLAST LAT Project LAT System Engineering 11 Test Implementation Strategy Overview Use subsystem level test scripts during integration –Scripts should run in a multi tower environment –I&T will have to merge some subsytem scripts for tests that must run in parallel For some cases, change over to tests run through flight software –Matches the way we fly it –Means that some algorithms imbedded in scripts will be ported to flight software Need systematic approach to defining and documenting those requirements, baseline is only the functionality needed for in-orbit operations –One issue is comparison of results between subsystem baselines, initial I&T testing, and final testing using FSW –Likely need to capture some data for off line processing to confirm flight software processing –Will need toolbox of offline processing, but not part of formal acceptance testing For some cases use the “backdoor” access –May be faster or may provide a more direct measurement of the parameter

GLAST LAT Project LAT System Engineering 12 Implementation Plan Hold meetings (what else?) Goals of meetings will be to –Define the requirements Test definitions for the required tests Gather a complete list of formal tests –Work the implementation issues Define subsystems tests/scripts to be used during integration testing Define which subsystem scripts are to be combined to perform integrated tests Define what functionality from the subsystems and I&T LATTE scripts is required for on-orbit operations and ensure that that functionality is in the FSW requirements Define which additional tests are needed for science verification and calibration (SVAC plan) Define which additional tests are needed to support interface or other requirements that can only be observed at LAT level (e.g. power consumption during calibration mode)

GLAST LAT Project LAT System Engineering 13 Redundancy Verification The tests shall use redundancy combinations that verify all cross strapping During TV testing, the time on redundant units shall be spread approximately evenly trending requirements