Memos and specifications

We provide a range of information about pipeline processing, the CXC Data Analysis System, Grating related analysis issues, and general scientific analysis algorithms.

The MIT/CXC team produces different types of documents:

  • spec (specification) Exact specification for the behavior of analysis tools. Look here for a description of the exact algorithm that a CIAO tool should implement.
  • ARD (analysis reference data) Specification for the mormat of CALDB files
  • ICD (Interface control document) Specification of file format produced by tool.
  • memo General documents written to support the development of specs, ARDs, or ICDs. For example, the analysis of a specific detector effect might be documented here. If that analysis leads to specific changes in the algorithm for a tool, then the new algorithm will be included into the revised version of the relevant specs.
  • misc Miscellaneous files including white papers and presentations.

The documents listed on this page are revised over time, some may still be under development, while others may become obsolute when a tool is discontinued, e.g. because its functionality is now integrated into other tools.

Current versions

In this section, we list the most relevant and current documents.

Type Instrument Title
spec ACIS acis_build_badpix
spec ACIS acis_build_mask
spec ACIS acis_find_afterglow
spec ACIS acis_make_bkgd
spec ACIS acis_process_events
spec ACIS computation of TIME for the ACIS tool acisreadcorr
ARD ACIS ACIS ARD (draft, but best available description)
memo ACIS Some keywords in ACIS bias files
spec ACIS Bias parity errors
spec ACIS Bias repair and replacement
spec ACIS Search for cosmic rays in VFAINT mode
spec ACIS Computation of ONTIME, DTCOR, and EXPOSURE
spec ACIS Computation of QUERY_VAL
spec ACIS identify anomalous DELTOCLK values
memo ACIS caveat about FLTGRADE = 255 in Level 1 event files
ARD ACIS Grade file
ICD ACIS ACIS Level 0 ICD
ICD ACIS ACIS Level 1 ICD
spec ACIS makeacisrmf
memo ACIS Tests for self-consistency of ACIS LCI coordinates
spec ACIS S4 streak loss parameter
memo ACIS Status bits in bad-pixel files
memo ACIS Status bits in event files
ARD ACIS time-dependent gain adjustment
spec HETG/LETG Pipeline enhancements to compute grating responses in the archive
spec HETG/LETG Grating/CC-mode enhancements This memo describes changes made to acis_process_events and tg_resolve_events which improve order-sorting through a second pass of processing which uses the HETG-processing-determined CHIPY position to re-do CTI/gain/tgain corrections.
spec HETG/LETG Tests/validation of new HRC-S QE and LETG EEFRAC This memo shows test of the revised HRC-S QE and LETG EEFRAC (in the LSFPARM file). The LETGS effective area should be unchanged. EEFRAC changes were required for custom extractions which can improve a weak lines signal-to-noise ratio.
spec HETG/LETG tgdetect2, tg_choose_method
spec HETG/LETG tg_findzo
ICD HETG/LETG HRC-S Tgain correction (for reduced background); LETG/HRC-S spectral filtering after HRC-S Tgain correction This document describes the HRC-S time-dependent linearized PI computation ("SPI") for background reduction and associated CALDB "t_gmap" file (appropriate for all HRC-S observations), and the associated HRC-S/LETG event filter required for spectral extraction from Tgain-corrected HRC-S events (CALDB "pireg_tgain" file).
spec HETG/LETG LETG+ACIS-S Spurious Rotation Issue
memo HETG/LETG Technical Note: LETG/ACIS-S rotation compensation
ICD HETG/LETG Transmission Grating L1.5 to Archive
ICD HETG/LETG Transmission Grating Level 2 to Archive
spec HETG/LETG Level 1.5 LETG/HESF Region Mask Definitions and Wavelength Determination
spec HETG/LETG Level 1.5: ACIS Continuous-Clocking Mode Processing
memo HETG HETG/ACIS Focal Plane Temperature Analysis
ICD HETG/LETG Grating LSF Library
ICD all PSF Library
memo HETG/LETG LSF library and tools technical reference
memo HETG/LETG FITS keywords to describe data randomization
memo HETG/LETG LSFPARM validation for HETG+ACIS-S, LETG+HRC-S, LETG+ACIS-S, MEG+ACIS-S

Archive

In this section we list all documents including those that are still under development, already outdated, or only of historical interest. For most documents we list the current and a few previous versions. Older versions may be available on request.

CONTENTS

ACIS

acis_build_badpix spec

This document describes the use of the parameters bitflag and usrfile for the tool acis_build_badpix.

Date Version Download
04/28/2017 2.6 PDF, PS, LaTeX source
10/06/2009 2.5 PDF, PS, LaTeX source
04/24/2009 2.4 PDF, PS, LaTeX source
04/01/2009 2.3 PDF, PS, LaTeX source

acis_build_chip_gti spec

Disregard. The acis_build_chip_gti specs are flawed.

This document describes a specification for the ACIS tool acis_build_chip_gti.

Date Version Download
07/15/2014 2.1 PDF PS LaTeX Source
06/22/2014 2.0 PDF PS LaTeX Source
11/08/2004 1.1 PDF PS LaTeX Source

acis_build_mask spec

This document describes a specification for the ACIS tool acis_build_mask.

Date Version Download
04/04/2007 4.0 PDF PS LaTeX Source
08/11/2004 3.10 PDF PS LaTeX Source
04/26/2004 3.9 PDF PS LaTeX Source

acis_detect_hotpix spec

This document describes a specification for the ACIS tool acis_detect_hotpix.

This spec is superseded by the newer acis_find_afterglow spec.
Date Version Download
06/16/2006 1.11 PDF PS LaTeX Source
05/10/2006 1.10 PDF PS LaTeX Source
10/15/2004 1.9 PDF PS LaTeX Source

acis_find_afterglow spec

This document describes a specification for algorithms to find afterglows and hot pixels on ACIS CCDs. This spec supersedes the previous acis_detect_hotpix and hot-pixel detection specs.

Date Version Download
04/28/2017 2.11 PDF PS LaTeX Source
04/11/2012 2.10 PDF PS LaTeX Source
03/02/2012 2.9 PDF PS LaTeX Source
12/09/2011 2.8 PDF PS LaTeX Source

acis_make_bkgd spec

This document describes a specification for the ACIS tool acis_make_bkgd.

Date Version Download
05/11/2006 1.4 PDF PS LaTeX Source
04/08/2005 1.3 PDF PS LaTeX Source
04/01/2008 1.2 PDF PS LaTeX Source
03/16/2005 1.1 PDF PS LaTeX Source
02/18/2005 1.0 PDF PS LaTeX Source

acis_process_events spec

This document describes an incomplete specification for the ACIS tool acis_process_events.

Date Version Download
04/28/2017 4.17 PDF PS LaTeX Source
09/28/2016 4.16 PDF PS LaTeX Source
/07/07/2016 4.15 PDF PS LaTeX Source
06/23/2016 4.14 PDF PS LaTeX Source

acis_process_events: bad-pixel spec

This document describes a specification for the use of bad-pixel files by the ACIS tool acis_process_events.

This spec is still under development.
Date Version Download
01/19/2007 1.0 PDF PS LaTeX Source

acisreadcorr spec

This document describes a specification for the computation of TIME for the ACIS tool acisreadcorr.

Date Version Download
10/01/2002 1.3b PDF PS LaTeX Source

Afterglow detection efficiency

This document describes the afterglow detection efficiency of acis_run_hotpix.

This spec is superseded by the newer acis_find_afterglow spec.
Date Version Download
03/01/2011 1.2 PDF PS LaTeX Source
10/07/2010 1.1 PDF PS LaTeX Source

ACIS Analysis Reference Data Interface Control Document

This document describes the formats of the Analysis Reference Data files used by the ACIS tools.

This spec is still under development.
Date Version Download
03/15/2000 2.1 PDF PS
11/30/1999 2.0 PDF PS
03/12/1999 1.3 PDF PS LaTeX Source

Bias header keywords

This spec describes how to determine the values of some of the keywords in the header of an ACIS bias file.

Date Version Download
09/05/2006 1.0 PDF PS LaTeX Source

Bias-parity error

This spec describes how to handle bias-parity errors when producing a bad-pixel file.

Date Version Download
11/14/2013 1.3 PDF PS LaTeX Source
10/21/2013 1.1 PDF PS LaTeX Source
11/21/2012 1.0 PDF PS LaTeX Source

Bias repair and replacement

This spec describes how to repair or replace a bias for an observation with a suitable bias from another observation.

Date Version Download
05/25/2011 5.5 PDF PS LaTeX Source
05/13/2010 5.4 PDF PS LaTeX Source
05/12/2010 5.3 PDF PS LaTeX Source

Check VFAINT background

This document describes an algorithm that can be used to search for potential cosmic-ray background events in the data for TIMED VFAINT mode observations.

Date Version Download
03/10/2008 1.4 PDF PS LaTeX Source
09/22/2006 1.3 PDF PS LaTeX Source
09/01/2006 1.2 PDF PS LaTeX Source

CTI spec

This document describes how to compute the CTI-adjusted values of PHAS, PHA, ENERGY, PI, FLTGRADE, and GRADE for ACIS event data. The algorithm includes a temperature-dependent scaling factor for the integrated trap-density maps.

Date Version Download
10/27/2010 7.2 PDF PS LaTeX Source
10/10/2010 7.1 PDF PS LaTeX Source
06/08/2010 7.0 PDF PS LaTeX Source
09/01/2009 6.2 PDF PS LaTeX Source

DELTOCLK spec

This document describes the algorithm used to identify anomalous DELTOCLK values.

Date Version Download
02/19/2013 3.2 PDF PS LaTeX Source
02/19/2013 3.1 PDF PS LaTeX Source
02/19/2013 3.0 PDF PS LaTeX Source
04/30/2012 2.0 PDF PS LaTeX Source

Computation of ENERGY and PI

This document describes how to compute ENERGY and PI for ACIS event data.

This spec is superseded by the newer acis_process_events spec.
Date Version Download
07/20/2013 1.0

Computation of FLTGRADE, GRADE, and PHA

This document describes how to compute FLTGRADE, GRADE, and PHA for ACIS event data.

This spec is superseded by the newer acis_process_events spec.
Date Version Download
03/18/2014 1.7
01/08/2007 1.5
05/16/2003 1.4

Computation of ONTIME, DTCOR, and EXPOSURE

This document describes how to compute TIMEDEL, FLSHTIME, ONTIME, DTCOR, and EXPOSURE for ACIS event data.

Date Version Download
09/09/2002 1.2b PDF PS LaTeX Source

Computation of QUERY_VAL

This document describes how to compute QUERY_VAL for ACIS housekeeping data.

Date Version Download
09/09/2002 1.1 PDF PS LaTeX Source
08/26/2002 1.0 PDF PS LaTeX Source

Computation of X, Y, and TIMEs of arrival of CC-mode events

This document describes how to compute the sky coordinates and times of arrival of photons at the detector for CC-mode event data.

This spec is superseded by the newer acis_process_events spec.
Date Version Download
04/04/2006 4.6 PDF PS LaTeX Source
01/14/2005 4.5 PDF PS LaTeX Source
04/25/2003 4.4 PDF PS LaTeX Source

A caveat about FLTGRADE = 255 in Level 1 event files

This document describes why Level 1 event files can contain events that have FLTGRADE = 255.

Date Version Download
02/27/2007 1.0 PDF PS LaTeX Source

Grade ARD spec

This spec describes the grade ARD file structure.

Date Version Download
03/18/2014 1.0 PDF PS LaTeX Source

Hot-pixel spec

This document describes a specification for a hot-pixel detection algorithm.

This spec is superseded by the newer acis_find_afterglow spec.
Date Version Download
01/23/2011 2.3 PDF PS LaTeX Source
10/23/2009 2.2 PDF PS LaTeX Source
07/30/2008 2.1 PDF PS LaTeX Source
07/29/2008 2.0 PDF PS LaTeX Source

ACIS Level 0 Interface Control Document

This document describes the formats of the Level 0 data products.

Date Version Download
10/23/2000 3.2 PDF PS Framemaker source
08/10/2000 3.1 PDF PS Framemaker source
08/18/1999 3.0 PDF PS Framemaker source

ACIS Level 1 Interface Control Document

This document describes the formats of the Level 1 data products.

Date Version Download
10/23/2000 3.2 PDF PS Framemaker source
08/10/2000 3.1 PDF PS Framemaker source
08/18/1999 3.0 PDF PS Framemaker source

Notes about ACIS instrument geometry data memo

This document describes some self-consistency tests of the LSI coordinates of the ACIS CCDs.

Date Version Download
06/08/2005 1.0 PDF PS LaTeX Source

Mean biases

This document describes a specification for computing observation-specific biases from mean biases.

This spec is still under development and does not work in the current form.
Date Version Download
06/12/2007 1.2 PDF PS LaTeX Source
06/04/2007 1.1 PDF PS LaTeX Source
05/30/2007 1.0 PDF PS LaTeX Source

mkacisrmf spec

This document describes a specification for computing an ACIS RMF.

Date Version Download
02/01/2017 1.00 PDF PS LaTeX Source

ACIS pipeline processing caveats memo

This document describes caveats about ACIS pipeline-produced event data.

HTML (07/10/2002)

ACIS pipeline processing tools

This document describes the ACIS pipeline processing tools.

Date Version Download
02/28/2000 2.1 PDF PS
11/01/1999 2.0 PDF PS

S4 streak algorithm

This document describes an algorithm used to identify horizontal, instrumental, streak events on ACIS-S4.

This memo is superceeded by the S4 streak algorithm spec.
Date Version Download
06/07/2013 000801 PDF

S4 streak loss parameter

This document describes a better implementation of the fractional loss parameter of the tool that identifies horizontal, instrumental, streak events on ACIS-S4.

Date Version Download
08/15/2013 2.0 PDF
06/12/2013 1.1 PDF
06/10/2013 1.0 PDF

S4 streak properties

This document describes the properties of the horizontal, instrumental, streak events on ACIS-S4.

This memo is superceeded by the S4 streak algorithm spec.
Date Version Download
06/07/2013 040316 PDF

STATUS bits in bad-pixel files

This document describes the conditions for which the STATUS bits in ACIS bad pixel files are set.

Date Version Download
04/28/2017 1.12 PDF PS LaTeX Source
06/19/2007 1.11 PDF PS LaTeX Source
05/04/2006 1.10 PDF PS LaTeX Source

STATUS bits in event files

This document describes the conditions for which the STATUS bits in ACIS event data files are set.

Date Version Download
05/18/2009 2.3 PDF PS LaTeX Source
01/19/2007 2.2 PDF PS LaTeX Source
04/24/2006/ 2.1 PDF PS LaTeX Source

Sub-pixel event-repositioning and pixel randomization spec

This document is a spec describing the sub-pixel event-repositioning and pixel randomization algorithms.

This spec is superseded by the newer acis_process_events spec.
Date Version Download
09/30/2013 2.4 PDF PS LaTeX Source
08/21/2013 2.3 PDF PS LaTeX Source
06/28/2013 2.2 PDF PS LaTeX Source

Temperature-dependent RMF spec

This document describes how a script could be used to create a temperature-dependent RMF.

This document is still in development.
Date Version Download
03/16/2017 1.01 PDF PS LaTeX Source
02/02/2017 1.00 PDF PS LaTeX Source

Time-dependent gain ARD

This document describes the format of the ARD file used to compute the time-dependent gain adjustment.

Date Version Download
06/04/2003 1.0 PDF PS LaTeX Source

Time-dependent gain spec

This document specifies how to apply the time-dependent gain adjustment.

This spec is superseded by the newer acis_process_events spec.
Date Version Download
06/02/2006 1.6 PDF PS LaTeX Source
04/20/2004 1.5 PDF PS LaTeX Source
09/24/2003 1.4 PDF PS LaTeX Source

New ACIS-S geometry file in 2004

This document specifies the update on ACIS-S CCD chip corner positions and MEG grating period.

Date Version Download
11/15/2004 1.0 PS LaTeX Source

HETG and LETG

Pipeline enhancements to compute grating responses

This memo describes proposed pipeline changes for computation of grating responses (ARFs, RMFs) for the archive

Current version: PDF Ver. 1.0 (10 Aug 2019)

Grating/CC-mode enhancements

This memo describes changes made to acis_process_events and tg_resolve_events which improve order-sorting through a second pass of processing which uses the HETG-processing-determined CHIPY position to re-do CTI/gain/tgain corrections.

Current version: PDF Ver. 1.0 (04 Nov 2015)

Tests/validation of new HRC-S QE and LETG EEFRAC

This memo shows test of the revised HRC-S QE and LETG EEFRAC (in the LSFPARM file). The LETGS effective area should be unchanged. EEFRAC changes were required for custom extractions which can improve a weak lines signal-to-noise ratio.

tg_findzo specifications

Current version: PDF TEX Ver. 1.0 (13 Dec 2012)

Finding Zeroth Order Position

This document describes a new algorithm of detecting zeroth order position.

Download PS or LaTeX source of Ver. 1.4 (04/11/07)

tgdetect2, tg_choose_method specifications

Overview PDF

Current version: PDF TEX Ver. 0.2 (11 Sept 2012)

HRC-S Tgain correction (for reduced background); LETG/HRC-S spectral filtering after HRC-S Tgain correction

This document describes the HRC-S time-dependent linearized PI computation ("SPI") for background reduction and associated CALDB "t_gmap" file (appropriate for all HRC-S observations), and the associated HRC-S/LETG event filter required for spectral extraction from Tgain-corrected HRC-S events (CALDB "pireg_tgain" file).

Current version: PDF Ver. 2.0 (February 2018)

Previous version: PDF Ver. 1.4 (24 November 2009)

Previous version: PDF Ver. 1.3 (8 July 2009)

LETG+ACIS-S Spurious Rotation Issue

This document describes the LETG+ACIS-S spurious rotation issue.

PS or LaTeX source of Ver. 1.0 (11/02/04)

Technical Note: LETG/ACIS-S rotation compensation

Modification to extraction region to compensate for anomalous rotation residuals.

PS (2004 Jun 11)

Transmission Grating L1.5 to Archive Interface Control Document

A detailed description of Grating L1.5 (event diffraction coordinates) data products.

PS LaTeX source Change-Orders (1999 March 27)

Previous version: PS LaTeX source

Transmission Grating Level 2 to Archive Interface Control Document

A description of Grating Level 2 data products (binned spectrum).

PS LaTeX source Change-Orders (1999 May 28)

Previous version: Download PS LaTeX source

Grating Tool Specifications: Level 1.5 LETG/HESF Region Mask Definitions and Wavelength Determination

PS LaTeX source (1999 June 04)

Grating Tool Specifications: Level 1.5: ACIS Continuous-Clocking Mode Processing

PS LaTeX source (1999 Apr 22)

HETG/ACIS Focal Plane Temperature Analysis

Analysis of effects of high focal-plane temperature on HETGS effective area through QE and/or order-sorting.

PDF (2020 June 15)

PSF

ICD for the GRATING LSF LIBRARY

A detailed description of the LSF Library files.

PDF Latex Source (02/04/2021)

Previous version: PS Latex Source (12/28/2001)

PSF TOOL ICD

This ICD is obsolete.

PS Latex Source (10/07/98)

LSF LIBRARY and TOOLS TECHNICAL REFERENCE

The LSF Library and Tools Technical Reference.

PS HTML (02/24/00)

LSF GUIDE

This spec is superseded by a newer analysis from 2003.

PS HTML (12/28/01)

Data Randomization / New Header Keywords

This document describes how we propose to implement additional FITS keywords into Level 1 Event products and higher.

LSFPARM validated for unrandomized datasets

Grating/Detector most recent version Download
HETG+ACIS-S 1.1 (05/03/04) PS LaTeX source
LETG+HRC-S 1.0 (05/03/04) PS LaTeX source
LETG+ACIS-S 1.0 (07/20/04) PS LaTeX source
Update for MEG+ACIS-S 1.0 (01/22/06) PS LaTeX source

Analysis Reference Data

Exposure Maps and Gratings Data Level 1.5 and 2.0 Analysis Reference Data ICD

Interface Control Document describing the reference data read by exposure map and gratings pipelines and tools.

PS LaTeX source LaTeX template for new files. Change-Orders.

ACIS Spatial Contamination (2004.10.13 UPDATE)

ACIS Dead Area (2006.09.14 update)

Spectroscopy Database: Analysis Reference Data ICD

The format of the Spectroscopy Database files to be used in L2 spectral analysis is described here.

This ARD is obsolete.

PS LaTeX source

Exposure Map

Exposure Map Data Products ICD

PDF, PS LaTeX source

Aspect Histogram Processing and Data Products ICD

PDF PS LaTeX source

Introduction to Exposure Maps

PDF PS

Miscellaneous

AXAF Transmission Grating Diffraction Coordinates

Describes the transformation from reported event positions to dispersion coordinates.

PS

CIAO 3 Interactive Analysis Planning

Architecture design for interactive analysis and rapid prototyping.

CIAO is currently in version 4, so this document is obsolete.

Part 1 (PS) Part 2 (PS)

ISIS: Interactive Spectral Interpretation System

Original design requirements for ISIS.

PS