Instrument Overview Larry Springer HMI Program Manager larry.springer@lmco.com 650-354-5793

HMI Heritage HMI evolved from the MDI instrument on SOHO SOHO was Launched in 1995 MDI is still providing excellent data after taking 75 million images The HMI Mechanism designs are based on those used on MDI, TRACE, and other programs (C,D,F) The HMI detectors are similar to the 4k x 2k CCDs developed by e2v and used on a previous program (D) The HMI camera electronics is based on the camera electronics developed by RAL for a previous program (F) The HMI structure is an evolution of the structure developed for a previous program (D) The HMI electronics design is an evolution of the electronics designs used on MDI, TRACE, other programs (C,D) The HMI Software is built on the software developed for previous programs (A,C,D,F)

HMI Instrument Components The HMI Flight Instrument consists of the following components The HMI Optics Package The HMI Electronics Box The HMI Intra Instrument Harness The HMI Software

HMI Optics Package Subsystems The HMI Optics Package Includes the following subsystems: Optics Filters Mechanisms CCD Cameras Mechanical Structure Thermal control Image Stabilization Split between Optics Package and Electronics Box

HMI Optics Package

HMI Electronics Box HMI Electronics Box Mounted inside the SDO Spacecraft Contains: Power Converters Control Computer CCD Camera Interface and Data Compressor Mechanism Controllers ISS Electronics Housekeeping The Oven Controller and Limb Sensor Preamp are in the OP

HMI Reliability HMI has the following features to enhance system reliability Redundant Power Converters Redundant Computer and Bridge Board Cross strapping between Camera interface boards and Compressor boards allows one compressor to handle the full HMI data stream Redundant mechanisms for wavelength tuning and polarization selector. Multiple mechanism controllers boards designed with failure isolated in combination with redundant mechanisms controlled by different boards eliminate potential single point failures Redundant Limb Tracker sensors Redundant Filter Oven Thermal Control The Reliability presentation will provide more detail

HMI Peer Reviews leading to PDR September 17, 2003 Mechanisms Optics Package Structure October 8, 2003 Electronics Flight Software October 15, 2003 Optics Package Thermal October 22, 2003 Optics Filters October 29, 2003 Telescope Focal Plane Assembly Reviews had LMSAL experts in each discipline as Peers The SDO Project participated via Telecon connection Review Minutes and Action Items are maintained on the HMI website Action Items tracked to closure by HMI systems engineer Action Items reviewed periodically at the HMI Team Meeting

HMI Summary Schedule

HMI Risk Management Plan The HMI Risk Management Plan (2H00075) was provided to the SDO Project on 1 July 2003 as part of the HMI Concept Study Report It was written to be compatible with the then current SDO Risk Management Plan An updated SDO Risk Management Plan - (464-PLAN-003) was received on 3 October 2003 The HMI Risk Management Plan will be updated to make it compatible with the revised SDO Risk Management Plan after Comments on the original plan are received.

HMI Risk Assessment The large format high speed CCD Camera systems are a technical and schedule risk Assessment: Moderate reducing to low after delivery of Evaluation CCDs Mitigation: Excellent vendors started early in program to provide evaluation devices and developmental camera between the PDR and CDR. Precision Michelson Interferometers key to science observation Assessment: Low, MDI shows that it can be done Mitigation: Excellent vendor (MDI & GONG experience) selected with early evaluation of the polarizing beam splitter (the heart of the Michelson) to reduce risk Precision control of filter oven key to science observation Assessment: Low, MDI shows it can be done Mitigation: Early development of a brassboard oven & controller to demonstrate performance. Redundant oven controller to improve reliability Hollow Core Motors and Shutters require 80 Million operation lifetime Assessment: Low, Not a large step beyond reliability demonstrated on MDI Mitigation: Life test to 160 Million operations with several samples, and redundant critical mechanisms