Use of new Pointing Products

Introduction

On OD 320 the temperature of the star-tracker (STR) CCD was lowered, to mitigate the effect of hot flickering pixels. As a side effect this change slightly the focal length of the star tracker, hence introducing a shift in the reconstructed astrometry of Herschel maps when the distribution of tracking stars was not homogeneous in the STR field-of-view, up to 7-8 arcsec in the most extreme cases. A new model was uploaded on-board on OD762 to correct for this. For the interim period ODs 320 to OD761 new first order pointing products have been generated at HSC to correct this problem.

Below an example for a star (UZ Tau) in OD684, on the left the current HSA level 2 blue channel (70 microns) maps and in the right processed with teh new pointing product. The absolute astrometry offset is reduced from 7.5 arcsec to 1 arcsec.

UZ_Tau.jpg

The new pointing products are posted on ftp://ftp.sciops.esa.int/pub/msanchez/corrected_pointing_od320_761/

How to use the new pointing product for PACS photometer scan maps

Replace the line extracting the pointing product :
pp = obs.auxiliary.pointing
by:
pp = fitsReader('/my_directory_path/pointing_od_0nnn.fits')
where nnn is the OD number

Not that if you use the SPG pipeline scripts, the pointing product is read twice in L05_phot.py and L1_scanMapPhotProject.py, hence the line must be commented out in the second script.

-- BrunoAltieri - 24 Jul 2012

Topic attachments
I Attachment History Action Size Date Who Comment
JPEGjpg UZ_Tau.jpg r1 manage 22.3 K 2012-07-24 - 16:25 BrunoAltieri UZ Tau new astrometry OD684
Edit | Attach | Watch | Print version | History: r21 | r4 < r3 < r2 < r1 | Backlinks | Raw View | Raw edit | More topic actions...
Topic revision: r2 - 2012-07-26 - BrunoAltieri
 
This site is powered by the TWiki collaboration platform Powered by Perl