CalDB 4.8.0.1 Public Release Notes

I. INTRODUCTION

CalDB 4.8.0.1 is an upgrade to the Chandra CalDB, which includes the following items:

• PCAD IRU Characteristics (IRU_CHAR) File Addition

NOTE: Because the aspect software pipeline is not available to CIAO users, the PCAD IRU Characteristics (IRU_CHAR) File Addition upgrade has not been publicly released. It does not affect CIAO users, and so will not be included in the public CalDB releases until a later, cumulative public release.

II. SUMMARY OF CHANGES

A. PCAD IRU Characteristics (IRU_CHAR) File Addition

Location:	$CALDB/data/chandra/pcad/iru_char/
Filename:	iruD2018-10-17charN0001.fits

NOTICE: This information is provided for completeness in the CalDB Release Notes; users will not find it useful, because they do not have access to the ASPECT pipeline software in CIAO.

The Safe-mode transition of 2018-10-10 occurred as a result of a glitch in in one of Chandra's gyroscopes resulting in a 3-second period of bad data. The ASPECT team and FDB have agreed that the best action to take is a mixed-gyro configuration, activating IRU-A GYRO #2, with the necessary downstream Standard Data Processing (SDP) fixes to the ASPECT L1 pipeline, in the form of an adjustment to the IRU Characteristics file in the CalDB. The subject of this ECR is that update to the IRU_CHAR file in CalDB.

The ASPECT group has provided the DS with the necessary changes to the existing IRU_CHAR file in order to generate the new one. See the DATA VALUE VERIFICATION section below for specific value changes to be implemented.

Since there is a need to preserve the previous state of affairs, a new file will be added with the new characteristics values, to be effective as of (UTC) 2018-10-16T23:00:00, with the existing IRU_CHAR file remaining effective for all observation dates before that.

PIPELINES/TOOLS AFFECTED:

ASPECT Level 1 Pipeline Tool asp_get_calib

THREADS AFFECTED: NONE.

III. TECHNICAL DETAILS

A. PCAD IRU Characteristics (IRU_CHAR) File Addition

MCD generated the new file using the DS Release tool "prism", from the existing IRU_CHAR file named in DESCRIPTION of CHANGE above. Five numerical changes were made to the table to produce the new file:

• The config_curr single-valued column was changed from 1 to 0.
• The config1_chan[4] column vector was changed from [1,0,3,2] to [3,2,5,4].
• The CVSD0001 header keyword was set to 2018-10-16T23:00:00.
• The CVST0001 keyword has been set to 23:00:00.

All other values to the remaining columns/vectors in the binary table remain unchanged in the new file.