Difference: StrSwitchOversAndSvvResets (8 vs. 9)

Revision 92015-12-15 - MiguelSanchez

Line: 1 to 1
 
META TOPICPARENT name="ImprovedPointing"

Periods of anomalous pointing during the Herschel mission due to star-tracker switch-overs and lack of aberration correction.

Line: 11 to 11
 
  1. Switch from the main star-tracker (STR1) to the backup unit (STR2) either driven by the autonomous Failure Detection, Isolation and Recovery (FDIR) or commanded from ground for testing and calibrating the backup unit. This produces an offset of some 15 arcsec between the desired (nominal) and actually commanded coordinates.
  2. Incorrect upload of the Spacecraft Velocity Vector (SVV) to the star-tracker (STR) resulting in a lack of light aberration correction in the coordinates of the STR guide stars. This produces a variable error in the range 0 - 20 arcsec between the desired (nominal) and actually commanded coordinates.
Changed:
<
<
NEW In HCSS 13.0, the auxiliary processor that creates the pointing product was updated to automatically check for those events and apply the corrections whenever appropriate. However, this was only implemented for the "simple-corrected" attitude (column simpleCorrFilterQuat) and not for the "gyro-propagated" one (column filterQuat). Hence, the astrometry of the products retrieved from the archive (processed with the gyro-propagated attitude) are still affected by the problems outlined above. If you want to reprocess the data by your own, you will need to overwrite the column filterQuat of the pointing product with the simpleCorrFilterQuat and then launch the pipeline processing ensuring that you use the new pointing product. However, in case of doubt of if you have observations in one of the ODs referred below and processed with SPG < 13.0, please contact the HSC Helpdesk for more information and support. Please refer to the HSC Helpdesk web link
>
>
NEW In HCSS 13.0, the auxiliary processor that creates the pointing product was updated to automatically check for those events and apply the corrections whenever appropriate. However, this was only implemented for the "simple-corrected" attitude (column simpleCorrFilterQuat) and not for the "gyro-propagated" one (column filterQuat). Hence, the astrometry of the products retrieved from the archive (processed with the gyro-propagated attitude) are still affected by the problems outlined above.
 
Changed:
<
<
NEW The problem has been fully solved in HCSS 14.0. Hence, future HSA products will be free of anomalies.
>
>
<--If you want to reprocess the data by your own, you will need to overwrite the column filterQuat of the pointing product with the simpleCorrFilterQuat and then launch the pipeline processing ensuring that you use the new pointing product.-->

If you have observations in one of the ODs referred below please contact the HSC Helpdesk for more information and support. Please refer to the HSC Helpdesk web link


NEW Contrary to previous statements, the problem with STR switch-overs still persists in HCSS 14.0. It is under investigation.

 

STR switch-overs

Line: 47 to 50
 
1308 2012-12-11T14:41:58.644 2012-12-11T19:56:45.000 5.246
The full list of observations affected by SVV resets, including science, calibration and engineering ones can be found here.
Changed:
<
<

Miguel Sanchez - 2015-11-26
>
>
-- Miguel Sanchez - 2015-12-15
 
META FILEATTACHMENT attachment="SVV_resets_aberration_shift_all_spg_versions.txt" attr="h" comment="" date="1448529955" name="SVV_resets_aberration_shift_all_spg_versions.txt" path="SVV_resets_aberration_shift_all_spg_versions.txt" size="8849" user="MiguelSanchez" version="1"
META FILEATTACHMENT attachment="STR_switch_shift_all_spg_versions.txt" attr="h" comment="" date="1448529955" name="STR_switch_shift_all_spg_versions.txt" path="STR_switch_shift_all_spg_versions.txt" size="78063" user="MiguelSanchez" version="1"
 
This site is powered by the TWiki collaboration platform Powered by Perl