Reprocessing Information

CXC reprocessing consists of three groups. The first part, called REPRO-I (or simply REPRO), is full end-to-end processing of early observational data with significantly improved software and calibration data. The 2nd part, called REPRO-II, is partial processing to resolve specific issues for selected ObsIDs. The third reprocessing of Chandra data (REPRO-III) was started in February 2006 and will cover the entire mission.

Both REPRO-I and REPRO-II were completed with exceptions of a very small number of low-priority, calibration or engineering observations with data-related issues.

REPRO-I

Reprocessed all the observations taken from the launch to 08/15/2000. Intended to replace full data processed earlier with old software and calibration data.
software used: R4CU5UP8 (released on Aug. 25, 2000) or later. R4CU5UP8 was the version of software which was specifically prepared for this reprocessing. For details of software updates and CALDB updates, users can visit http://cxc.harvard.edu/proc_stat/rel_notes/ for software release notes and http://cxc.harvard.edu/caldb/index.html for the CALDB home page.
A few highlights on changes for reprocessing are:
- Accurate position with enhanced algorithm and calibration data
  - Improved centroiding algorithm
  - Applied time-dependent aspect calibration files
- ACIS
  - Applied datamode-dependent bad pixel handling
  - Detect and remove of cosmic ray flaring pixels
  - Revised file formats, particularly for level 2 event file
  - Numerous fixes to good time intervals for multi-chip observations
  - Added background lightcurve to mission time line
- HRC
  - New event validity tests reject background events and eliminates ghosts
  - Revised file formats, particularly for level 2 event files
  - Added background lightcurve to mission time line
- Important CALDB files updated for reprocessing
  - ACIS position-dependent temperature-dependent order-sorting(OSIP)tables
  - ACIS Badpix file
  - ACIS Gain file
  - PCAD CALALIGN (necessary for accurate position)
  - PIXLIB geometry file

REPRO-II

REPRO-II consists of 9 sub-groups with specific issues. The number of ObsIDs involved is 706.

HRC-I
HRC-S (without grating)
HRC-S (with LETG)
HRC-SI (fast timing mode)
ACIS CTI (or ER)
ACIS CC Mode
ACIS Interleave Mode (or alternative exposure)
Cal Alignment (ACIS-I)
CP Only (custom processing)

HRC-I

Nature of Enhancement: De-gap correction + Accurate absolute position
Data to be reprocessed: those processed before Jan. 25, 2001 (or with CALDB earlier than v2.2)
Total number of ObsIDs involved: 258
Processing status: done

Note: 51 ObsIDs which satisfy one of the two following conditions were also corrected for an error in absolution position (< 2"):
AP Date < Nov. 7, 2000 and Obs Date Aug. 15, 2000
REPRO-I Date < Nov, 7, 2000 and Obs Date < Dec. 1, 1999

HRC-S (without grating)

Nature of Enhancement: De-gap correction + Accurate Absolute position
Data to be reprocessed: those processed before Jun. 1, 2001 (or with CALDB earlier than v2.6)
Total number of ObsIDs involved: 106
Processing status : done

Note: 38 ObsIDs which satisfy one of the two following conditions were also corrected for an error in absolution position (< 2"):
AP Date < Nov. 7, 2000 and Obs Date Aug. 15, 2000
REPRO-I Date < Nov, 7, 2000 and Obs Date < Dec. 1, 1999

HRC-S with LETG

Nature of Enhancement: restore incorrectly removed events
Data to be reprocessed: those processed before Jul. 2, 2001 (or with software earlier than DS6.1.0)
Total number of ObsIDs involved: 75
Processing status : done

HRC fast timing mode

Nature of Enhancement: accurate timing correction
Data to be reprocessed: those processed before May 2, 2001 (or with software earlier than DS6.0.1)
Total number of ObsIDs involved: 12
Processing status : done

ACIS CTI (Charge Transfer Inefficiency Test in Engineering Requests)

Nature of Enhancement: Restore L2 events by fixing software bug
Data to be reprocessed: those processed before Mar. 1, 2001 (or with software earlier than R5CU5UPS14.3)
Total number of ObsIDs involved: 148
Processing status : done

ACIS CC mode (continuous clocking mode)

Nature of Enhancement: coordinate updates
Data to be reprocessed: those processed before Dec. 19, 2001 (or with software earlier than DS6.5)
Total number of ObsIDs involved: 55
Processing status : partially done (see note).

Note: Improved timing correction still needs to be applied. A new algorithm is being tested.

ACIS Interleave Mode (or alternative exposure)

Nature of Enhancement: Dead time correction
Data to be reprocessed: those processed before Jul. 2, 2001 (or with software earlier than DS6.1.0)
Total number of ObsIDs involved: 32
Processing Status: done

CAL Alignment (ACIS-I only)

Nature of Enhancement: accurate absolute position
Data to be reprocessed: those reprocessed (in REPRO-I) before Sep. 14, 2000 (or with CALDB earlier than v1.5)
Total number of ObsIDs involved: 7
Processing Status: done

CP Only (CP = custom processing)

Nature of Enhancement: to archive data products in the CXC database
Total number of ObsIDs involved: 13
Processing Status: done

Note: CXC data products delivered to PI were correctly processed by custom processing (CP). The reprocessing is only for the archival purpose.

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Last modified: 04/13/06