Sun Test Overview: Interdependencies and Criteria

1. Sun Test Overview

2. Sun Test Overview – Interdependencies • At least three tests are prerequisites for other tests • Focus • Can use either Sun or lamp • Needed to reduce length of other tests • Not needed for many tests due to bad seeing or spatial averaging • Wavelength dependence • Either Sun or laser can be used • Needed to set tuning positions • Not needed for lamp or polarization tests • Polarization calibration • Lamp or Sun can be used • Needed to make observing sequences. Especially LOS. • Note that none of these are dependent on each other • Others are needed before analysis can be completed

3. Sun Test Overview – Other prerequisites • There are a number of other tests we need to perform before starting • Determine exposure times • Lamp • Sun • Laser • Test various targets • Determine spatial power and quality of each • Alignments • Stim tel • Laser • Heliostat • Existing focus test procedure may be used for these

4. Sun Test – Go/no go criteria • Several types of criteria • Prerequisites done – See separate charts • Equipment available and properly configured • Laser and wavemeter working • PCU properly configured • Targets available/installed • Sunlight • Some require long stretches of clear skies • Others can use shorter stretches and/or light clouds • STOLs working • Procedural issues resolved • See overview chart and individual tests for details

5. Sun Test – Pass/fail criteria • This is not an acceptance test! • However, we are looking for gross errors • Note that in many cases all we need is characterization NOT pass/fail • Two levels • Do we have the required data? • If no pass/fail then we only need to know when we have data of sufficient quality • Have we analyzed the data? • If pass/fail needed or if test is prerequisite for other tests we need short turn around • Analysis software for prerequisites is ready • Preliminary results and decisions will be part of calibration meetings • In case of gross errors high level decisions needed • Abort Sun test and fix problem • Continue with other parts of test

6. Sun Test – Priorities • Several competing criteria for priority • Make good use of sunlight • May not get that many days • Do prerequisites first • Equipment constraints • Don’t want to fire up laser too often • Don’t want to change PCU configuration too often • Allow efficient development and testing of STOL procedures • Easy ones first • Test various types • Maximize time to develop and run analysis procedures • Data of marginal quality (eg. clouds) may still allow for some testing • May need data from other instruments • MDI under our control, but keyhole • May like to have data from ground based. GONG, SOLIS, ASP,… • Near real time flexibility will be required to be efficient! • With this in mind…

7. Sun Test – Attack plan • Get STOLs for prerequisites ready before test starts • Focus done. Wavelength dependence and PCU both well defined • Run all relevant STOLs we have as soon as we can • Can check for proper functioning – may do abbreviated versions to save time • Gives sample data for analysis code development • POR – Don’t do extensive real time debugging • Run STOLs even if ideal source not available • With luck we can have prerequisites done on day one! • Does depend on PCU operational • Does depend on Sun shining or laser working • Don’t use laser on day one • Probably takes too long to get set up • Can use other sources for initial tests • But do get it to work soon, especially if forecast calls for solid overcast • Plan further tests depending on weather, people and equipment availability • Try to get prerequisites done as soon as possible • Do weekly and daily planning

8. Data Processing • Will use MDI data system (DSDS) for storing data • Should easily be able to handle data volume • Will use HMI data system (DRMS) for metadata • Still in beta test, but alternatives exist • A few basic utilities will be available • Data query, selection and export • Image reconstruction (remove cross) • Etc. • Analysis will be done with ad-hoc code • Mostly IDL • Observables code may have to be optimized to reduce computing time • Codes for prerequisites exist

9. Image Quality: Focus • Purpose • Determine the nominal focus position • Requirements • Need to take images for other tests near optimal focus. Also needed to set secondary shim. • Description • Determine spatial power as a function of focus setting. Fit model to determine ideal focus. • Test configuration • Stimulus telescope with lamp and desired target(s) (dots). Sun may also be used to illuminate target. • Also do with direct sunlight from heliostat. • Test plan • Take images at all 16 focus positions. • Data analysis • For each focus position determine the amount of spatial power. Fit parabola to three highest points to determine best focus. • For the Sun it may be possible to use the sharpness of the limb. • Codes are ready. • Procedure • STOL status: Exists. • Shop order status: Does not exist • The test timeline: 16 images of 10s or 3 minutes. Little setup required. • No particular personnel required.

10. Image Quality: Distortion • Purpose • Determine the amount of optical distortion. • Requirements • 0.001% (0.02 pixels) based on Korzennik et al. (204) 0.01pixels desirable. • Description • Determine parameters in distortion model by offpointing instrument using alignment legs. • Test configuration • Stimulus telescope with lamp and desired target(s) (dots). Sun may also be used to illuminate target. • Test plan • At each of 5x5 leg offsets, take images at a few positions around the nominal focus. • Data analysis • For each focus position determine the offsets between each pair of images for a grid of points in the images. • Fit distortion model to the measured offsets. • Codes are ready. • Procedure • STOL status: Does not exist • Shop order status: Does not exist • The test timeline: Each series is 25 offsets times 5 focus positions for a total of 125 images. At 10s per images this will take 20 minutes. Needs to be run for a few targets plus setup so a few hours. • No particular personnel required.

11. Mechanism induced images motions and distortions • Purpose • Determine the image motions and distortions introduced by rotating the optics in the hollow core motors. • Requirements • CPS gives 0.1” (0.2 pixels). IPD 4.3 gives a goal of 0.1 pixels. • Description • Determine offsets by taking images of fixed target at various HCM rotation angles. • Test configuration • Stimulus telescope with lamp and desired target(s) (dots). Sun may also be used to illuminate target. • Test plan • For each of 7 HCMs and each of 10 or so angles, take images at a few positions around the nominal focus. • Data analysis • At each focus position determine the offsets between each pair of images for a grid of points in the images.. • Code is ready. • Procedure • STOL status: Does not exist • Shop order status: Does not exist • The test timeline: About 100 images. At 10s per images this will take 20 minutes. Needs to be run for a few targets plus setup so a few hours. • No particular personnel required.

12. Image Quality: Field curvature • Purpose • Determine the amount of field curvature. • Requirements • The change of focus as a function of image position should be a fraction of a focus step. • Description • Determine spatial power as a function of focus setting, leg offset and image position. Fit model. • Test configuration • Stimulus telescope with lamp and desired target(s) (dots). Sun may also be used to illuminate target. • Also do with sunlight. • Test plan • Same as for distortion. Also use sun focus series. • Data analysis • At each leg position and image position fit mode power as a function of focus position to determine best focus. • For Sun test no additional analysis required. • For lamp test analyze focus as a function of offset and position to separate stim tel and HMI curvature. • Codes are mostly ready. • Procedure • STOL status: Exists for Sun test. Does not exist for lamp test. • Shop order status: Does not exist • The test timeline: Same data as other tests, so no additional time required. • No particular personnel required.

13. Image Quality: MTF • Purpose • Determine the MTF variation as a function of image position. • Requirements • Astigmatism should be a fraction of a focus step. The MTF at any k should not be degraded by more than that corresponding to a(?) focus step. 10% or better knowledge is desirable. • Description • Determine spatial power as a function of k and image position at best focus. • Test configuration • Stimulus telescope with lamp and desired target(s) (dots). Sun may also be used to illuminate target. • Also do with sunlight. • Test plan • Same as for distortion. Also use sun focus series. • Data analysis • At each leg position and image position fit mode power as a function of k at best focus. • For Sun test no additional analysis required. • For lamp test analyze power as a function of offset and position to separate stim tel and HMI MTF. • Codes are mostly ready. • Procedure • STOL status: Exists. • Shop order status: Does not exist • The test timeline: Sama data as for other tests so no additional time needed. • No particular personnel required.

14. Image Quality: Image scale • Purpose • Determine the absolute image scale. • Requirements • The image scale should be between 0.494”/pixel and 0.505”/pixel. • Description • Take images of Sun. Determine diameter and compare to ephemeris. • Test configuration • Sun from heliostat. • Test plan • Take solar images at each focus position. • Data analysis • Determine solar image diameter. Look up diameter in ” in ephemeris. Divide numbers. • Code exists. • Procedure • STOL status: Exists. • Shop order status: Does not exist • The test timeline: Data already taken for other tests. • No particular personnel required.

15. Contamination • Purpose • Determine if any large particles are present in the optical path. • Requirements • Any contaminants should not be large enough to degrade science. • Description • Using a “pinhole” camera mode look for shadows from contaminants and determine their position in the optical path by determining motion when moving pinhole. • Test configuration • Stimulus telescope with lamp or Sun and direct sunlight. PCU with hole plate. • Laser in stimulus telescope with leg offsets. • Test plan • For each hole position or each leg offset take image in obs and cal mode. • Also rotate each HCM at one or more hole and leg positions. • Data analysis • Offset images proportional to pinhole offset. Look for shadows coming into focus. Determine position in optical path from raytrace and proportionality constant used for shifting. • For HCM rotations look for moving shadows. • Codes exists for MDI. • Procedure • STOL status: Does not exist • Shop order status: Does not exist • The test timeline: About 100 images each series. A few hours total. • Personnel qualified to change PCU configuration needed.

16. Polarization calibration • Purpose • Determine intsrument polarization matrix. • Requirements • See IPD. • Description • Using light with well determined polarization determine instrument response. • Test configuration • Stimulus telescope with lamp or Sun and sunlight from heliostat. • Test plan • Using PCU take series of images with various PCU and instrument settings. • Data analysis • Too complicated to describe here. • Codes are ready. • Procedure • STOL status: Does not exist • Shop order status: Does not exist • The test timeline: 50-100 images in obs and calmode required for Sun and lamp. Total one day. • No particular personnel required.