ECR Title: ECR: Add In-Air DC PD for red transmission	DCC No: E1300404-v1
Date: 5/8/2013
Requester: Daniel Sigg	Impacted Subsystem(s): ISC
Description of Proposed Change(s): Proposed changes: Add a DC photodetector (PDA100A) to measure the in-air transmitted beam in EX and EY.
Reason for Change(s): This will allow for additional diagnostics in the EtherCAT system. It will be useful to determine if the red and green resonance coincide. It can be used to measure the relative stability of the red locking point (off resonance DC measurement) with minimum alignment coupling. It will support the search opto-mechanical instabilities. It will allow the identification of parametric oscillations (using high BW readout).
Estimated Cost: Electronics hardware: none; use extra PD freed by E1200938. Optical components: none; use spares.
Schedule Impact Estimate: None.
Nature of Change (check all that apply): Safety Correct Hardware Correct Documentation	Improve Hardware Improve/clarify Documentation Change Interface Change Requirement
Importance: Desirable for ease of use, maintenance, safety Desirable for improved performance, reliability Essential for performance, reliability Essential for function Essential for safety	Urgency: no urgency desirable by date/event: __June 2013__ Essential by date/event: __HIFO_Y___ Immediately (ASAP)
Impacted Hardware (select all that apply): Repair/modify. List part & SNs: ______________________ Scrap & Replace. List part & SNs:_____________________ Installed units? List IFO, part & SNs: _________________ Future units to be built	Impacted Documentation (list all dwgs, design reports, test reports, specifications, etc.): D1100670, E1300151, D1002803, T1100472, D1100607, D1201448, D1100683, E1300109
Disposition (to be completed by Systems Engineering): TRB CCB Approved Additional information required. Define: [Requester re-submits with new information with the same DCC E-number for the ECR but the next version number.] Concurrence by Project Management: (Acknowledged Electronically in DCC) Project Systems Engineer: Dennis Coyne Project Systems Scientist: Peter Fritschel