GLAST LAT ProjectDec 17, 2003 Page 1 GPR Design & Requirements Grid Perimeter Ring (GPR) Design –Ring is comprised of four lengths of Aluminum bolted together Cross Section of each length is 4” x 6” 90º Corner Joints are bolted using four ½” Dia 180 KSI Bolts Each Corner Joint Bolt is preloaded to ½ of bolt capability Each corner includes two capped Taper Pins & marking to ensure consistent assembly-disassembly-reassembly Outer dimensions of GPR “square” are 95.5” x 86” –Clearances for hand work about Grid / LAT exterior perimeter: »TBD” on Radiator sides »TBD” on Non-Radiator sides Meets EWR Factor of Safety Requirement of 5+ x against Ultimate Material Strength for 1g Operations –Factor of Safety reduces to TBD with consideration of SLAC Seismic Requirement –Assumes fairly tight tolerance for interface between LAT Grid and Grid to GPR Brackets

GLAST LAT ProjectDec 17, 2003 Page 2 GPR Design & Requirements, Cont. GPR to LAT-Grid Interface –Tight tolerance at Radiator corner Mount Bracket (RMB) clevice This reduces shock load in earthquake and ensures load sharing between all four RMBs and GPR to RMB system Plan is to attach Grid to GPR Brackets to GPR, use LAT Lift Fixture to lower GPR Brackets into RMB interface and match locate final clevice hole through GPR to Grid bracket RMB to Grid is the weakest link in the GPR to LAT chain of interfaces) (Design Integration to confirm with values ? TBR) LAT Grid is much stiffer than GPR-Bracket system –1 st harmonic of GPR is ~ 2 Hz; Well below earthquake excitation frequency –LAT Grid and GPR-Bracket system must share load in earthquake »RMBs must have Design Factor of Safety of > 1.4 against yield for earthquake due to personnel working under load

GLAST LAT ProjectDec 17, 2003 Page 3 GPR Design & Requirements, Cont. Design Integration has requested a stiffer GPR –Need more explanation of need and rationale, but easiest ways to obtain stiffness are: Make GPR of Stainless Steel –GPR should not be magnetically permiable –1 st Harmonic with CRES GPR is TBD Increase “height” of beam for each desired LAT rotation orientation (i.e., this means the entire cross-section due to LAT assembly orientations) –Can dramatically increase stiffness this way –Conflicts with Optical Survey Lines of Sight Requirements

GLAST LAT ProjectDec 17, 2003 Page 4 GPR Design & Requirements, Cont. Optical Survey Issues –Top of TKR must be within a zone that is 0.2 mm [ 0.008” ] wide about its perimeter (This needs confirmation, so TBC for now) To make measurements consistent with NIST protocol, the measurement system shall have a resolution that is ten times the item being measured; In this case, a resolution of 0.02 mm [ ” ] Laser Tracker Measurement System, typically used at SLAC and proposed for use with the LAT has a resolution of 100 microns [ ” ], or roughly 0.004” –A resolution that is about half of what we’re trying to measure –Further measurement accuracy complications exist due to 1g effects to LAT-Grid system as it is built up –Not consistent with NIST protocol »What will be done with measurement data? Go-No-Go Feeler Gauge can be used to make clearance measurement –What to do if Go-No-Go Gauge doesn’t fit ?