HESSI Imager and RAS Recovery Plan Review Brian R. Dennis, GSFC with input from Zehnder, Thomsen, Henneck, & Fivian at PSI and Hurford, Clark, Amato, Schmahl, Orwig, & Uribe at GSFC Wednesday, May 17, 2000

Brian R. Dennis 5/17/2000 Recovery Plan Review HESSI Imager Grids –Initial Alignment at Goddard (not repeated after vibration overtest) Grid characterization measurements – optical, X-ray, and mechanical Shims under grid mounts to align fields of view to telescope axis –Alignment in Switzerland after vibration overtest Grids 2 & 3 fine aligned using adjustable mounts on front tray only Grid 5 mounting screws loosened & grid realigned on both trays Grid-6 aluminum block mounts remade and installed with new screws All mounting screws retightened to 4 Nm torque CMM measurements of grids & trays at ETH in Zurich Alignment of trays on telescope tube using TMS & CMM at PSI

Brian R. Dennis 5/17/2000 Recovery Plan Review HESSI Imager Telescope –Tests at PSI after vibration overtest Visual inspection yielded no evidence of damage other than surface scratches Ultrasonic inspection of impact points and undisturbed material for comparison –no conclusive results Static pull test at 300 N (corresponding to 20 G) - no remaining deformation Mounted on 6 struts to a new ring to be retained for direct mounting to spacecraft support ring. Struts –Tests at PSI after vibration overtest Pull test at 5000 N showed identical behavior in all struts tested One new FM strut and cone used to replace broken strut Five surviving struts and cones individually inspected and refitted

Brian R. Dennis 5/17/2000 Recovery Plan Review HESSI Imager –Grids and Telescope Confirmation of Alignment after vibration overtest –TMS measurements of grids 1 – 8 and both trays at PSI –Gridlet test for grids 1 – 6 at PSI –Direct optical confirmation for grids (not repeated after vibration overtest) –Tilt test for grids 1 – 6 at PSI –Regular TMS measurements from now to launch Imaging Simulation Test (to be repeated at SSL)

Brian R. Dennis 5/17/2000 Recovery Plan Review HESSI Imaging Solar Aspect System (SAS) - Functional SAS CCDs and electronics (after vibration overtest) –Removed from tray at PSI and visually inspected –Thermal cycled, 3 cycles from -20 to +50  C –Full functional at extremes showed no problems SAS solar exposures at PSI with 3 CCD’s (to be repeated on ~5/16/2000) –<0.5 arcsecond (1  ) spatial resolution verified Functional electrical tests on spacecraft at SSL (to be repeated) –Baseline read-out speed = 128 Hz –Dark level negligible (<1 ch – 0.5 mV) –Not affected by any noise source on spacecraft SAS generated ACS signal for S/C (redundancy for FSS) tested at PSI (not retested after vibration overtest) SAS Alignment Optical axis measurements of SAS lenses at Fisba (Switzerland) to 2 – 3  m (not repeated after vibration overtest) CMM measurements of SAS CCD pixels and lens fiducials at ETH in Zurich (repeated after vibration overtest)

Brian R. Dennis 5/17/2000 Recovery Plan Review HESSI Imaging Roll Angle System (RAS) CCD RAS provided by PSI Functional test at PSI after vibration overtest - no anomalies Optical inspection of pin puller after vibration overtest - no problem Thermal cycled electronics after vibration overtest –-25  C to +50  C, 3 cycles –no anomalies during functionals at extreme temperatures –noise anomalies seen at SSL not repeated at PSI Exposed to stars at the Jungfraujoch in Switzerland (planned for June 2000) –Limiting sensitivity determined with m~3 stars –Confirm focus and PSF of 0.52 pixels (1 sigma) with m~0 stars –Confirm achievement of required 1 arcminute roll angle accuracy –Test response to simulated Earthshine –Test the transmission of selected matrix in time and space around star signal Functional electrical tests on spacecraft at SSL (to be repeated) –Functional electrical tests with lasers for star simulation & photodiodes for Earth albedo simulation –Confirm RMS = 0.3mV (0.7 ch.) – baseline m2 star gives 12 chs.

Brian R. Dennis 5/17/2000 Recovery Plan Review HESSI Imaging Roll Angle System (RAS) CCD RAS Alignment Measurements (to be repeated) –Optical axis determined at PSI relative to tooling balls Stable to <1 arcminute through vibration –Portable CMM alignment measurements of CCD RAS on spacecraft at SSL –Optical alignment measurement of RAS on spacecraft at SSL (proposed) Redundant PMT RAS provided by SSL –Optical alignment measurement on spacecraft at SSL (to be repeated) Using pulsed laser diode at two positions in front of RAS Diode moved perpendicular to direction to RAS RAS output plotted vs. diode position to determine position for peak response

Brian R. Dennis 5/17/2000 Recovery Plan Review HESSI Imaging Environmental Tests Performed and Planned –Before JPL vibration overtest Vibration and thermal cycling of all grids and mounts at GSFC Telescope vibration and thermal cycling at Contraves in Switzerland CCD RAS vibration at PSI and thermal cycling at PSI and SSL PMT RAS tests at SSL –After vibration overtest Soaking of QM telescope tube in vacuum for 1 month to test for dimensional changes – results expected ~5/18/2000 Thermal cycling of SAS electronics at PSI Thermal cycling of RAS at PSI Plans for checking imaging capability after environmental tests TMS measurements of grids 1 – 8 and grid trays SAS functional electrical tests with photodiode simulators RAS functional electrical tests with lasers for star simulation and photodiodes for Earth albedo simulation CCD RAS portable CMM alignment measurement

Brian R. Dennis 5/17/2000 Recovery Plan Review Grid Twist Status

Brian R. Dennis 5/17/2000 Recovery Plan Review Gridlet Test Setup

Brian R. Dennis 5/17/2000 Recovery Plan Review GRIDLET-2 TEST (Gridlet test repeated at PSI in May 2000) Objective is to verify relative twist of the front and rear grids. Any subsequent changes in twist can be monitored by the TMS. Method: –Cd 109 source is located behind a ‘gridlet’ located in front of imager –Two side-by-side detectors measure X-ray transmission through subcollimator. –Motion of the source perpendicular to slits modulates the observed count rates. –Grid twist is indicated by difference in modulation phase as seen by twin detectors. –Modulation is due to 2 nd harmonic response of front grid. Results are completely independent of GSFC grid characterization data. Modulation phase is independent of any test setup misalignments. Test-setup misalignments affect only the amplitude of the modulation, not the phase.

Brian R. Dennis 5/17/2000 Recovery Plan Review GRIDLET-2 TEST SAMPLE RESULT

Brian R. Dennis 5/17/2000 Recovery Plan Review GRIDLET-2 TEST RESULTS

Brian R. Dennis 5/17/2000 Recovery Plan Review GRIDLET-2 TEST RESULTS

Brian R. Dennis 5/17/2000 Recovery Plan Review GRID TILT TEST (Repeated at PSI in May 2000) –Objective is to measure the angle between the direction of maximum grid throughput and the imager axis. –Tilt test results verify: Correct calculation and installation of shims; Flatness of trays; Absence of tilt due to grid-frame distortion. –Test setup is same as for gridlet test, except: Gridlet tray is removed. Source displacement steps are ~cm, instead of ~microns Slit over detector to limit range of angles –Correct tilt is confirmed if maximum count rate is achieved when source is positioned on subcollimator axis.

Brian R. Dennis 5/17/2000 Recovery Plan Review Tilt Test Sample Results

Brian R. Dennis 5/17/2000 Recovery Plan Review RESULTS OF MAY 2000 TILT TESTS AT PSI

Brian R. Dennis 5/17/2000 Recovery Plan Review HESSI Imaging Simulation Test (to be repeated at Berkeley after the vibration overtest)

Brian R. Dennis 5/17/2000 Recovery Plan Review Imaging Simulation Test Results Single gaussian source, 2 arcseconds wide, 10,000 photons/s/collimator for 4 s Test ImageOutput Image