SECCI/COR2 Status Report SECCHI CONSORTIUM MEETING D. Socker, S. Plunkett, A. Vourlidas

Science Objectives 3D structure of CMEs. CME evolution (speed, mass, etc). Structure of outer corona (streamers, plumes).

Performance Specifications Field of View2-15 R  (nominal) Pixel resolution14"/pixel Exposure Time4 seconds, (3 exposures /19 sec) Image Cadence30 minutes (synoptic) 22 seconds (max for pB) Passband~ nm

Observing Modes pB sequence –Three (0, 120, 240 deg) polarizer position image set. –Three images transmitted to the ground. Total B sequence –Two (0, 90 deg) polarizer position image set. –On-board processing of images. –Single processed image transmitted. ROI (Region Of Interest) –Selected sub-fields processed and transmitted.

Observing Modes Sum/Difference –On board comparison of two (or more) images. – Sum or difference transmitted. Calibration –Lamp and dark images for CCD calibration. –Images in several (~18) redundant polarizer positions from 0º-360º. Pixel binning –In SEB (digital) or (analog) CCD.

COR2 Layout

Design Status Significant changes from proposal level concept –Vignetting in 12R-15R region eliminated. –Singlet objective replaced with doublet (“air” spaced). –Halfwave retarder plate replaced by polarizer (Polarcor or polaroid,TBD)

Design Status Mechanical –Layout level complete –Design level in progress Optical –Still using proposal singlet design as placeholder. –Intermediate level design initiated.

Design Status Thermal –Critical locations (A0, occulter, heat rejection mirror) being modeled. –Thermal bending < 5”. Contamination control –Layout (for SCIP box case) completed. Radiation damage issues –Using same optical materials as LASCO C2. –Looking at some optical materials testing (glass, cements, AR coatings).

Instrumental Backgrounds Studies A0 –Modeling serrated and circular edge generated backgrounds. A0-A1 tube section baffles –Modeling baffles to minimize machining cost without degrading optical performance. Heat rejection mirror –Modeling to determine optical surface requirements.

Instrumental Backgrounds Studies A1/heat rejection mirror interface –Model details of design to avoid interface becoming a significant background. Shutter leakage model. O1, O2 aberration modeling –Detailed ray trace studies to optimize rejection at internal occulter and Lyot stop.

Instrumental Backgrounds Studies External occulter model and test –Straight edge (model & test) Point source, multiple wavelengths. Edge bevel effects. Polarization effects. –Single circular disk (model & test) Point and extended sources, multiple distances. Fresnel model matches test results. –Multiple (2/3) disks (model & test in LASCO/C3 EM). –Serrated disk (model & test in LASCO/C3 EM). –Smooth cone and tear-drop shapes (test in LASCO/C3 EM).

Instrumental Backgrounds Studies O1 Coating and Polish Scatter Tests –Flat glass samples Conventionally polished (fussed silica tested, BK7 future). Ion milled polish (fussed silica tested, BK7 future). AR & non AR coated (hard coating). –Results to date AR coating has negligible effect on scattering. Scattering from samples with conventional and ion-milled surface polish is similar. Near-specular angles dominated by point-like defects.

Instrumental Backgrounds Studies Future flats tests –Flat samples of radiation resistant BK7 will be delivered to NRL by end of July. Future singlet & doublet objective tests. –Aberration optimized O1 lenses will be mounted in C3 EM and stray light measured in vacuum.

Calibration Based on LASCO experience –LASCO in-flight calibrations verified the ground calibrations to within <10-30% overall. Ground-based calibrations –Measure expected flight performance and will provide a baseline for comparison with in-flight calibrations. In-flight calibrations –Measure actual performance and monitor instrument stability.

Ground Calibrations Ground-based calibrations will take place at NRL Solar Instrument Test facility (Building A13). Calibration products include: –Radiometric calibration. –Stray light background. –Vignetting and distortion function. –Filter and CCD QE and spectral response. –Polarization calibration (polarization analyzer and instrumental polarization).

In-flight Calibrations (Door Closed) Diffusing window in door for photometric calibrations, measurement of instrument polarization and stability checks. Three LED calibration lamps at TBD locations for CCD calibrations. Dark images for CCD calibrations and stability checks.

In-flight Calibrations (Door Open) Background stars. –Pointing, plate scale, time corrections, vignetting, distortion, photometry. Spacecraft rolls. –Polarization and stray light. Time series of coronal images. –F-corona, stray light. Cross-calibration with COR1/HI, COR2 A/B, LASCO, and ground-based observations.