alignment concept

Solar-B Data Co-Alignment Plan: 

Solar-B Data Co-Alignment Plan T.Shimizu (NAOJ) Solar-B MO&DA Working Group Meeting @SAO, 2002.7

Background: 

Solar-B Background Co-alignment of data from three telescopes is one of keys for Solar-B sciences Sub arcsec accuracy (~ SOT resolution) is required for Photosphere-Corona Connectivity Studies Telescopes are mounted on “stable” cylindrical optical bench (OBU) However, the pointing of telescopes relative to other telescope is not perfect due to thermal deformation - Rotating barbecue effect (orbital period) - Temperature potential change (maybe seasonal period) OBU

Background: 

Solar-B Background Attitude sensors can provide the data necessary for data co-alignment Attitude sensors are installed in IRU box tower attached to OBU The pointing of sun-sensors relative to telescope is not perfect due to thermal deformation Sun-sensors

Purposes and Required Accuracy: 

Solar-B Purposes and Required Accuracy For what purposes, do we need pointing information? To know where are observed with Solar-B telescopes (Useful for operation planning and database search) Absolute coordinate on the solar disk ~20 arcsec accuracy enough To co-align Solar-B data with data from other observations Other observations: satellites, ground-based Absolute coordinate on the solar disk ~1 arcsec accuracy required To co-align among data from Solar-B telescopes Relative relation among the telescope pointings Sub-arcsec accuracy (~ SOT resolution) required

Solar-B Pointing Information: 

Solar-B Solar-B Pointing Information UFSS (Ultra Fine Sun Sensor) Main sensor + redundancy sensor Position of sun center in 2 axis (X, Y) (arcsec) High resolution IRU (Inertia Reference Unit; Gyro-scope) Main sensor + redundancy sensor Angular velocity in X, Y & Z (arcsec/sec) Highest resolution, but not angle STT (Star Tracker) Position of “Canopus” (a Cen) to control around Z axis Can be used for correcting image rotation. Others NSAS (Non-Spin-type sun aspect sensor) GAS (Geomagnetic sensor)

Where observed?: 

Solar-B Where observed? To know where are observed with Solar-B telescopes (Useful for operation planning and database search) Absolute coordinate on the solar disk ~20 arcsec accuracy enough System requirement Absolute Pointing accuracy (over mission life): 20 arcsec 0-p (X, Y) 145 arcsec 0-p (Z) (from SOT) Without any correction by using attitude data, enough accuracy will be expected for this purpose. To include this information in FITS header But notice that its accuracy is poor for scientific data analysis

Co-Alignment with Non-Solar-B Data: 

Solar-B Co-Alignment with Non-Solar-B Data To co-align Solar-B data with data from other observations Other observations: satellites, ground-based Absolute coordinate on the solar disk ~1 arcsec accuracy required The way to have ~1 arcsec accuracy in absolute coordinate is to use limb position in full- disk images from XRT.

Co-Alignment with Non-Solar-B Data: 

Solar-B Co-Alignment with Non-Solar-B Data Cross-correlation between XRT full-disk images and attitude pointing data will calibrate the attitude data Accumulating the cross-correlation allows us to make a model for the calibration. Longer accumulation will improve the model.

Co-Alignment of Solar-B Data: 

Solar-B Co-Alignment of Solar-B Data To co-align among data from Solar-B telescopes Relative relation among the telescope points Sub-arcsec accuracy (~ SOT resolution) required Example: time How can we have high accuracy in relative coordinate?

Co-Alignment of Solar-B Data: 

Solar-B Co-Alignment of Solar-B Data time XRT and EIS Data To well co-align images along in time, we need to consider ... Satellite jitter is included in image sequences. Attitude (UFSS, IRU) data can be used to remove satellite jitter. Internal mis-alignment XRT: X-ray optical axis and WL aspect sensor axis S/C jitter

Co-Alignment of Solar-B Data: 

Solar-B Co-Alignment of Solar-B Data SOT (Filtergram, Spectro-Polarimeter) Data time To well co-align images along in time, we need to consider ... Satellite jitter is already removed in sequence of SOT images Tip-tilt mirror with correlation tracker removes satellite jitter Internal mis-alignment Filtergram: image shift caused by Filter wedge Spectro-polarimeter: error in scanning mirror positioning

Co-Alignment of Solar-B Data: 

Solar-B Co-Alignment of Solar-B Data time The images with same solar features are used to co-align the data from different telescopes with each other. Sunspots seen in SOT continuum and XRT aspect images QS Network features seen in SOT magnetogram and EIS images

Database for Co-Alignment: 

Solar-B Database for Co-Alignment Requirements for attitude database The database should be convenient for modeling the calibration (temporal evolution) for attitude data Time sequence of attitude data To use IRU (output: angular velocity) data Separated from the image database Need time stamp to identify attitude data at the time when an image is exposed Need other information Orbital phase information Thermal condition (measured temperatures)

Database for Co-Alignment: 

Solar-B Database for Co-Alignment Pointing information in image database Target information in absolute coordinate is useful Need a note about accuracy in analysis guide Accuracy in order of less than 10-20 arcsec in absolute coordinate will need a calibration The calibration is cross-correlation between XRT full- disk images and attitude pointing data Accumulating the cross-correlation allows us to make a model for the calibration. Longer accumulation will improve the model Two ways to obtain more accurate address Update the image header when the calibration is improved (Not recommended) Provide a S/W to calculate (I like) If the calculation should be performed only with image data, the image header should contain attitude data, orbital phase, thermal condition