HETG Angles Analysis, Sept.'99

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Conclusion The angles of the HEG and MEG spectra on the ACIS-S detector were measured using the 15 A lines seen in the observations of Capella, ObsIDs 1099 and 1235. The new angle values are:

and are in $CALDBaxafcal/hetg/cip/hetgD1999-07-23periodN0003.rdb.

Analysis The angles were measured as the slope of the line connecting the centers of the plus and minus first-order images of the 15 A line; see the IDL script meas_line_angle.pro.

The "oa_AX, oa_AY" event arrays are returned by obs_anal.pro when the /EXPORT option is set. For the measurements here, the AX,AY arrays are the CXCDS Level 1 X,Y values with Y-sign flipped and rotated about zero-order by -1*average(aspect_ROLL) to align the X,Y to detector corrdinates. This alignment is verified by the narrow 1-D projection of the zero-order "streak" events.

Plots of the events and "center" locations as well are text output are available below:

meas_line_angle.pro output:


OBSID 1099
----------

 HEG   15.010 A line,  acisf1099_000N001_evt1.fits

  Plus-side:       2688.91     -247.836
 Minus-side:      -2687.82      244.779
      Angle:      -5.23482

 MEG   15.010 A line,  acisf1099_000N001_evt1.fits

  Plus-side:       1345.40      109.378
 Minus-side:      -1344.70     -112.955
      Angle:       4.72468


OBSID 1235
----------

 HEG   15.010 A line,  acis_f1235_000N002_g02346_evt1a.fits

  Plus-side:       2688.93     -247.056
 Minus-side:      -2687.73      245.617
      Angle:      -5.23551


 MEG   15.010 A line,  acis_f1235_000N002_g02346_evt1a.fits

  Plus-side:       1345.39      110.168
 Minus-side:      -1344.67     -112.212
      Angle:       4.72574




Please send any comments to Dan Dewey at dd@space.mit.edu.