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ASC Data Products Guide: SDS­1.0
Jonathan McDowell
February 26, 1998
This document is a revision of the material in the data products chapter of the ASC Re­
quirements document, SE03.
1 ASC Data Products
1.1 Standard Data Processing
1.1.1 Standard Data Processing Overview
Standard Data Processing (SDP) performs automated, on­line standard reduction and anal­
yses of data gathered during an X­ray observation to provide data products which are useful,
to the widest possible range of observers, as initial indications of the observation's scientific
content and as bases for more detailed, refined, and customized off­line analysis using the
capabilities specified in section ??. A common set of software tools (section ??) is used for
both the on­line and off­line analysis.
The Standard Data Products are produced at four processing levels -- Level 0 through Level 3.
Level 0 Products consist of Level 0 Telemetry and Ancillary Data (see section ??) applicable
during the observation intervals and are provided to the user upon request. Level 0 Products
preserve all information available in the original data and provide the basis for the higher­
level products. The Level 0­3 Products are summarized in Tables 5.4­4 and ??. Table 5.4­4
shows the data products which are produced for all observations, regardless of the science
instrument used. Table ?? shows, by instrument, the Level 2 products which are produced
in addition to those in Table 5.4­4. Descriptions of each standard product are provided in
glossary form by Table 5.4­5. Details about each product's contents are provided by Tables
5.4­7 through 5.4­9. All quantities derived during standard processing have their uncertain­
ties estimated and are supplied as part of the data. All calibration information used to
perform any corrections during standard processing form an integral part of the Standard
Products. All calibration data is maintained current based on measured spacecraft/SI per­
formance (section ??).
Full data accountability, processing history, and version histories are maintained throughout
all levels of standard processing. The resulting processing logs provide both the user and
the ASC staff with full visibility into each step of the standard reduction and analysis. The
1

logs contain data and version history sufficient to exactly reproduce the original standard
processing at any time in the future. Standard processing is expected to operate under
the routine supervision of an ASC data technician with scientist supervision and review to
handle special problems.
1.1.1.1 Processing Control Overview The ASCDS archives accumulated Level 0
telemetry as the original Merged Telemetry is received. Level 1 processing is performed,
to the extent possible, on the received data intervals. For a given observation, when the
received data intervals sum approximately to the observing time, the ASCDS requests final
Level 1 and Level 2 processing for that observation. If a time interval (nominally one month)
has elapsed prior to collecting all the observation data, the ASCDS automatically requests
Level 1 and Level 2 processing (to the extent possible) for the pointings accumulated so far.
The ASC staff can view telemetry accumulation summaries and manually request SDP of
an observation part (a single pointing or a set of accumulated pointings) at any time for
any observation. Once requested, the processing of a single interval of data will hereafter
be referred to as an SDP job. The ASC staff can, at any time, view the active and pending
SDP jobs and reprioritize, suspend, restart, or cancel
2

Table 5.4­4: Standard AXAF Data Products: All Instruments
Data Product Level Delivery
Observation Description Products
Telemetry Data 0 On Request
Housekeeping and Spacecraft Data
Observation Table 1 Routine
Temporal Status Intervals 1 Routine
Orbital Ephemeris Table 1 Routine
Sun Angle Table 1 On Request
Solar System Ephemeris 1 On Request
Housekeeping Status Changes 1 Routine
Event Rates Table 1 Routine
Aspect Solution Data
Aspect Solution 1 Routine
Aspect Quality 1 Routine
Aspect Solution Histogram 1 Routine
Stable Aspect Intervals 1 Routine
Field Data
Field Source Catalog 1 Routine
Field Diffuse Emission Catalog 1 Routine
Field Multiwaveband Image 1 Routine
Processing Information
Observation Summary 2 Routine
SDP Profile 2 Routine
SDP Log 2 Routine
Aspect Solution Secondary Products
Guide Star Properties 1 On Request
Guide Star Observations 1 On Request
Guide Star Usage 1 On Request
ACA Data 1 On Request
ACA Bad Pixel Map 1 On Request
ACA Flat Field 1 On Request
ACA Dark Current Image 1 On Request
ACA Field Distortion Table 1 On Request
ACA Sub Pixel Response Map 1 On Request
ACA Misalignment 1 On Request
ACA Stellar PSF 1 On Request
3

ACA Fid Light PSF 1 On Request
ACA Read Noise Calibration Table 1 On Request
ACA Color Magnitude Correction Table 1 On Request
Gyro Data 1 On Request
Gyro Calibration Data 1 On Request
Gyro Status History 1 On Request
Gyro Rotation Angles 1 On Request
Fid Light Calibration 1 On Request
ACA Sightings 1 On Request
ACA Kalman Data 1 On Request
ACA Photo Centroids 1 On Request
Image Motion Correction 1 On Request
Reference Aspect Solution 1 On Request
X­ray Data Calibration Products
Vignetting Map 1 Routine
Ancillary Response File 1 Routine
Redistribution Matrix File 1 Routine
QE Uniformity Map 1 Routine
PSF Models 1 Routine
PSF Size Table 1 Routine
Background Model 1 Routine
X­ray Basic Data Products
Level 1 Photon List 1 Routine
For each PI band:
Sky Image 1 Routine
Detector Image 1 Routine
Exposure Map 1 Routine
Effective Exposure Map 1 Routine
Effective Exposure Map 1 Routine
Predicted Background Map 1 Routine
Background Map 2 Routine
Next­In­Line SI Photons 1 On Request
Level 2 Photon List 2 Routine
Source List 2 Routine
Source Detection Processing Summary 2 Routine
Source Analysis Products
4

For each detected source:
Source Photon Filter 2 Routine
Source Properties 2 Routine
Source Flux Table 2 Routine
Source Pulse Height Spectrum 2 Routine
Source Light Curve 2 Routine
Source Light Curve Power Spectrum 2 Routine
Local Background Photon Filter 2 Routine
Local Background Pulse Height Spectrum 2 Routine
Local Background Light Curve 2 Routine
Source Cross­ID Table 2 Routine
Source Ancillary Response File 2 Routine
Source Redistribution Matrix File 2 Routine
Background Photon Filter 2 Routine
Background Pulse Height Spectrum 2 Routine
Background Light Curve 2 Routine
Grating Data Products (HETGS,LETGS only)
TG Vignetting Map 2 Routine
Zero Order Image 2 Routine
Spectrum List 2 Routine
For each detected spectrum:
High­Resolution Spectrum 2 Routine
Spectrum Properties 2 Routine
Spectrum RMF 2 Routine
Spectrum ARF 2 Routine
Spectral Exposure Map 2 Routine
Spectral Effective Exposure Map 2 Routine
Spectral Effective Area Map 2 Routine
Spectrum Local Background 2 Routine
Spectrum Local Background ARF 2 Routine
Spectrum Local Background Exposure Map 2 Routine
Spectrum Local Background Effective Exposure Map 2 Routine
Spectrum Local Background Effective Area Map 2 Routine
Spectral Line Feature Table 2 Routine
Catalog Products
AXAF Observation List 3 On Request
AXAF Pointing Catalog 3 On Request
AXAF Candidate Source Catalog 3 On Request
AXAF Source Catalog 3 On Request
5

AXAF Spectral Catalog 3 On Request
AXAF Source Bibliographic Catalog 3 On Request
AXAF Bibliography 3 On Request
AXAF Identifications and Cross­Ref Catalog 3 On Request
AXAF Object Class List 3 On Request
AXAF Class Catalog 3 On Request
AXAF Images In Region 3 On Request
Sky Coverage Map 3 On Request
Selected Region List 3 On Request
Selected Region File 3 On Request
Selected Region Mosaics 3 On Request
Slew Photon Lists 3 On Request
Diffuse Background Maps 3 On Request
Table 5.4­5: Standard Data Product Glossary
ACA Bad Pixel Map ­ Map of bad pixels in Aspect Camera.
ACA Color Magnitude Correction Table ­ Calibrated corrections to Aspect Camera counts
and positions as a function of guide star color.
ACA Dark Current Image ­ Aspect Camera dark current calibration image.
ACA Data ­ Aspect Camera raw image extracts and calculated centroids for each exposure.
ACA Field Distortion Table ­ Geometric distortion as a function of Aspect Cameral pixel
position.
ACA Flat Field ­ Sensitivity variations across Aspect Camera CCD.
ACA Kalman Data ­ Results of Kalman filter combination of aspect camera and gyro data.
ACA Misalignment ­ Calibration of aspect camera optical misalignments.
ACA Photo Centroids ­ Intermediate star and fid light centroid positions, for ACA exposures
grouped into `photos'.
ACA PSFs, Stellar and Fid Light ­ Point Spread Functions for stars and fiducial lights
imaged by the Aspect Camera, modelled for each star and fid light.
ACA Read Noise Calibration Table ­ Calibration of read Noise versus engineering param­
eters for the Aspect Camera CCD.
ACA Sightings ­ Calibrated Aspect Camera star and fid light centroid positions and magni­
tudes as a function of time.
6

Table 5.4­5: Standard Data Product Glossary (continued)
ACA Sub Pixel Response Map ­ Calibration of sub pixel sensitivity response versus position
for Aspect Camera CCD.
Ancillary Response File (ARF) ­ Multiplicative components of energy response, as a function
of energy, giving effective area normalization.
Aspect Solution ­ Celestial pointing/roll angles and image motion correction (in tangent plane
pixel coordinates) as a function of time.
Aspect Solution Histogram ­ Binned aspect solution as a fraction of the observation livetime,
used to apply detector coordinate calibration maps to the sky image.
AXAF Bibliography ­ Bibliographic references to results based on AXAF observations.
AXAF Candidate Source Catalog ­ List of candidate sources detected by each standard
processing, without matching performed between observations. A rawer product than the AXAF
Source Catalog.
AXAF Class Catalog ­ AXAF sources and upper limits by source class. Example source
classes are: Solar system; Stellar coronal sources; sub­classes O, B, A, F, G, M, K, C, WD;
T Tauri; White dwarf/Neutron star/Black hole systems; Supernovae; Supernovae remnants;
Pulsars; Star formation regions; Galaxies by sub­classes Irr, Sa, Sb, Scd, S0, E, starburst;
Groups, clusters of galaxies; AGN and quasars by sub­classes BL Lacs, Seyferts, + others.
AXAF Identifications and Cross­Reference Catalog ­ AXAF source designations and
upper limits for objects in non­AXAF catalogs. Example catalogs are: IRAS PSF, FSC; 87BG &
PKS extension; SAO (star) catalog; Uppsala/ESO galaxy catalogs; Veron Quasar/AGN catalog;
Abell, Corwin, & Olowin cluster catalogs); source identification information from the literature
via SIMBAD and NED.
AXAF Images in Region ­ Derived data product listing all AXAF data overlapping given
sky region or including given position.
AXAF Object Class List ­ List of the defined source classes.
AXAF Observation List ­ List of all observations made with AXAF. Compilation of data
from all Observation Summaries.
AXAF Pointing Catalog ­ List of all pointings made by AXAF. Serves as a quick reference
for identifying images and exposure time within a designated region of the sky.
AXAF Source Catalog ­ Summary information on all confirmed (high probability) sources
observed by AXAF, including properties. Identifies multiple observations of the same source
and assigns AXAF­unique designations to sources.
AXAF Source BibliograPIc Catalog ­ BibilograPIc information collected by source.
7

Table 5.4­5: Standard Data Product Glossary (continued)
AXAF Spectral Catalog ­ Summary information on all high­resolution spectra produced by
AXAF and their characteristics (fits, line/edge detections, parameter lists).
Background Light Curve ­ Same as Source Light Curve, but for the image background after
source removal.
Background Map ­ Background counts over the image grid after source removal (one for each
image).
Background Model ­ Instrument­internal, solar, galactic, extragalactic, particle, and summed
expected background over the field.
Background Photon Filter ­ Mask for photons corresponding to the image background after
source removal.
Background Pulse Height Spectrum ­ Binned PI spectrum from image background after
source removal.
Detector Image ­ Map of detected photons in PI band versus detector coordinates.
Diffuse Background Maps ­ Maps of composite background, background spectra, etc. gen­
erated from multiple observations.
Effective Area Map ­ Effective sensitivity times collecting area (corrected for instrument
effects and vignetting) as a function of position, energy, within the detector field of view (one
map for each image).
Effective Exposure Map ­ Exposure time (corrected for instrument effects and vignetting)
as a function of position, energy, within the detector field of view (one map for each image).
Event Rates Table ­ Summary of primary and secondary science event count rates, field and
background count rates, versus time.
Exposure Map ­ Exposure time as a function of position, without corrections.
Fid Light Calibration ­ Positions of each Fid Light in SIM table coordinates, and nominal
positions in aspect camera coordinates.
Field Diffuse Emission Catalog ­ Sky survey image maps/values for field: Galactic NH (21
cm), Hff, CO, HI with velocity information.
Field Multiwaveband Image ­ Optical sky survey digitizations of the observed field of view.
POSS/UKS; IRAS­FSS; Radio­87GB; IR cirrus; ROSAT.
Field Source Catalog ­ Lists of cataloged objects in field.
8

Table 5.4­5: Standard Data Product Glossary (continued)
Guide Star Observations ­ Observed properties of guide stars derived from ACA data
processing.
Guide Star Properties ­ Extract from the AXAF Guide Star Catalog giving the relevant
properties of all guide stars used or attempted for this observations.
Guide Star Usage ­ Guide stars used as a function of time.
Gyro Calibration Data ­ Bias and scale factors for each gyro used.
Gyro Data ­ Raw gyro count behaviour versus time.
Gyro Rotation Angles ­ Spacecraft motion solution based on gyro data only.
Gyro Status History ­ Gyros in use as a function of time.
High­Resolution Spectrum ­ Spectrum, region background (both separated by PI bin into
orders for the ACIS), and calibrated spectrum (summed by side and order for the ACIS),
background­subtracted. Calibrated to counts/bin/sec, corrected to energy/wavelength scale,
local quantum efficiency, gain, and (for ACIS) spectral resolution.
Housekeeping Status Changes ­ Changes in housekeeping status parameters for SI and
spacecraft, versus time.
Image Motion Correction ­ Relative motion of sky, X­ray image and aspect camera frames
versus time.
Local Background Light Curve ­ Same as Source Light Curve, but for the local background.
Local Background Photon Filter ­ Photons corresponding to the local background region.
Local Background Pulse Height Spectrum ­ Binned PI local background spectrum.
Observation Summary ­ Target parameters, active detector, FPSI position/focus, active grat­
ing, ACIS operating mode and submode, live time correction factors, number of sources detected,
target detected (yes/no), background rate, center­of­field exposure time, center­of­field upper
limit and threshold number of counts for each energy band, dead time, SI/subsystem anomaly
reports. Plots of image field and summary of sources detected.
Observation Table ­ List of individual pointings making up the observation.
Orbital Ephemeris Table ­ Spacecraft position versus time.
9

Table 5.4­5: Standard Data Product Glossary (continued)
Photon List ­ Photon event file consisting of all photons in the observation. Corrected for
aspect and instrument effects to celestial coordinates. Calibrated for instrument effects to true
energy/pulse height. Identified as to validity and whether received during a ``good'' observing
interval. Good­times are based on standard criteria used to optimize the observation for a
``typical'' observer, e.g., minimize background by avoiding solar fluorescence off the Earth's
atmosphere. Level 1 Photon List contains basic information on all photons. Level 1.5 Photon
List adds information from transmission grating order sorting analysis. Level 2 Photon List
contains only good photons and incorporates some source information from source detection
processing. Next­In­Line SI Photon List contains Level 1 class information on events detected
by the next in line science instrument.
Predicted Background Map ­ Predicted background counts in the PI band versus image
pixel position.
PSF Models ­ Point Spread Function information as a function of energy.
PSF Size Table ­ Single parameter describing size of point spread function, as a function of
detector position and energy.
QE Uniformity Map ­ Map of detector sensitivity as a function of position.
Redistribution Matrix File ­ probability distribution for photon pulse heights as a function
of energy.
Reference Aspect Solution ­ Aspect solution at reference time for each observation interval.
SDP Log ­ Data processing history, software version numbers, bug reports.
SDP Profile ­ Data Processing profile used for this set of data products.
Selected Region File ­ For regions of special interest, definition of the sky extent of the region.
See Selected Region Mosaics.
Selected Region List ­ List of regions of special interest. See Selected Region Mosaics.
Selected Region Mosaics ­ Mosaics of AXAF observations covering particularly interesting
areas on the sky (e.g. M31, Orion, Galactic Center, Virgo).
Sky Coverage Map ­ for statistical population studies. Contains sensitivity as a function of
solid angle covered, extractable for arbitrary sets of AXAF HRC/ACIS observations and regions
within observations.
Sky Image ­ X­ray image for each detector pulse height invariant (PI) band (1 for the HRC,
10 for the ACIS) formed from ``good'' photons (includes strong lines/across edges for the ACIS).
Slew Photon Lists ­ Photons detected while the spacecraft was slewing.
10

Table 5.4­5: Standard Data Product Glossary (continued)
Solar System Ephemeris ­ Position of planets versus time for this observation, used for
barycenter corrections.
Source ARF ­ Source Ancillary Response File. ARF appropriate for source region, derived
from source position and ARF calibration.
Source Cross­ID Data ­ Possible source counterparts from sky surveys. Multi­wavelength
fluxes. Probable source types given L x =L(other), f x =f(other). NED, SIMBAD search
references.
Source Detect Processing Summary ­ Detailed algorithm­specific results of detect process­
ing, giving parameters of detected sources at different cell scales and bands.
Source Flux Table ­ Source fluxes in different bands.
Source Light Curve ­ Binned light curve of source photons.
Source Light Curve Power Spectrum ­ Power spectrum of source light curve.
Source List ­ Summary of detected sources, including detection method, significance, source
and local background regions.
Source Photon Filter ­ Mask for photons corresponding to the source region.
Source Properties ­ Flux, position, extent, colors, hardness ratios, simple spectral fits, vari­
ability, period. Includes photometric results for the target, if available.
Source Pulse Height Spectrum ­ Binned PHA source spectrum.
Spectral Effective Area Map ­ Effective Area Map versus dispersion coordinate for extracted
high resolution spectrum.
Spectral Effective Exposure Map ­ Effective Exposure Map versus dispersion coordinate
for extracted high resolution spectrum.
Spectral Exposure Map ­ Exposure Map versus dispersion coordinate for extracted high
resolution spectrum.
Spectral Line Feature Table ­ Line fits parameters for high resolution spectrum. Line or
edge central energy/wavelength, flux, or fractional rise/fall, width (energy/wavelength, velocity),
shape parameters plus order.
Spectrum ARF ­ ARF for extracted dispersed spectrum, giving effective area components as
a function of energy.
Spectrum Local Background ­ Extracted local background versus dispersion coordinate for
a high resolution spectrum.
Spectrum Local Background ARF ­ ARF for Spectrum background.
Spectrum Local Background Effective Area Map ­ Effective Area versus dispersion coor­
dinate for Spectrum Local Background.
Spectrum Local Background Effective Exposure Map ­ Effective exposure, corrected for
vignetting and QE, for Spectrum Local Background.
11

Table 5.4­5: Standard Data Product Glossary (continued)
Spectrum Local Background Exposure Map ­ Exposure time as a function of dispersion
coordinate for the Spectrum Local Background.
Spectrum Properties, source confusion information, Includes cross dispersion spatial proper­
ties of the spectrum.
Spectrum RMF ­ RMF response matrix for transmission grating spectrum.
Stable Aspect Intervals ­ Binned aspect solution as a function of time, the stable aspect
intervals.
Sun Angle Table ­ Spacecraft to Sun angle versus time.
Telemetry Data ­ Complete processed telemetry for each observation, decommutated, time­
tagged, grouped into a set of time­ordered substreams, and delivered in FITS format.
Temporal Status Intervals ­ List of intervals in which the standard screening criteria changed
their values; definition of standard screening criteria.
TG Vignetting Map ­ Vignetting of telescope as a function of shell and grating order.
Vignetting Map ­ Vignetting of telescope versus energy and position.
Zero Order Image ­ Cumulative counts in spatial bins for zero order photons only, in grating
data.
individual jobs. If two separate jobs are to be linked in some way, so that the outputs of one
are to affect the inputs or the processing parameters for the other, then their relative priority
handles the linking (TBR). For example, if one of the jobs is a calibration observation that
is intended to update calibration information to be used in a later job, then the calibration
observation must have the higher priority.
SDP conducts limit and other TBD in­line checks to verify that the processing is proceeding
satisfactorily. If a job fails TBD in­line checks or hangs in its pipeline, it is automatically
suspended (other actions are TBD and possibly severity­based); the suspension status and
other TBD indicators as to the reason are displayed to the ASC staff. Processing automati­
cally continues with the next­highest priority pending SDP job. The ASC staff can examine
the indicators, processing log, and any results produced from the suspended job. Once the
problem has been identified (see section ??), the ASC staff can modify or substitute the
Processing Profile, restart the job from well­defined points within the sequence (including
the start and others TBD), or cancel the job.
When an SDP job executes, it uses setup and processing parameters expressed in a Pro­
cessing Profile. All science observations are processed using a Standard (default) Profile.
A Processing Profile consists of a ``script'' which defines sequence and configuration of the
processing to execute, links to all necessary calibration models and parameters, the limits
to use in SDP self­checks (TBR), and any other parameters required by each constituent
12

process. All science observations are processed using a Standard (default) Profile. The ASC
staff and the user have the option to request that additional, individualized processing be
performed by specifying a separate Processing Profile for the observation or data interval
(see section 1.1.1.5). Only the ASC staff can view and modify the Standard Profile, though
users have access to copies of it. The Standard Profile configures the automated sequence of
Level 1 through Level 2 processing, the sequence is performed, and the Level 1 and Level 2
Products listed in Tables 5.4­7 and 5.4­8 are produced. If the job completes successfully,
its status is logged and the resulting data products are archived. The overall quality of the
products is evaluated relative to scientific expectations as described in section ??.
Table 5.4­6: AXAF Standard Header Information
Section Data Items
In distributed FITS files, this is included as header information, the AXAF Standard Header Information incorporated in each FITS file primary header.
Processing Keywords:
Processing system version
SDP Profile
Processing number (Number of times processed)
S/C Configuration Keywords:
Mission (AXAF)
Focal Plane Instrument
detector ID
grating
detector modes
focus
SIM Position
Observation keywords:
Observation ID
Target name
Target coordinates
Start and stop date/time
Principal Investigator
Proposal Title
Requested Time
Ontime
Livetime
13

A standard set of observation information (Table 5.4­6) is compiled by the SDP during Level
1 processing and is included in each Level 1 and Level 2 standard product, so that an isolated
standard product is self describing to the extent that it associates the data product with
the AXAF mission, a particular proposal and observations, and the processing configuration
that produced it. This information will include standard multi­mission information to ensure
compatibility with external analysis systems.
14

An Observation Summary containing overview information about the observation and the
processing results is compiled upon SDP completion and forms an integral part of the set of
standard products.
The Observation Summary data product is a document as distinct from a scientific data file.
It contains science data from the other data products, formatted for easy interpretation.
This document takes the place of the paper hardcopy supplied for earlier missions and is
available in at least EPS (Encapsulated Postscript) format.
The Summary contains:
ffl All of the Standard Header information listed above;
ffl A plot (grey scale) of a smoothed version of the Level 1 Image Array in the broad
band, annotated with celestial coordinates and detected sources.
ffl A summary of the Temporal Status Intervals product.
ffl A table summarizing the Observation Table product.
ffl A table summarizing the Source List product.
ffl A grey scale plot of the Optical Field Image annotated with the information in the
Field Catalog.
ffl A copy of the processing profile and processing summary.
An Observation Index data product contains pointers to all the data products for an obser­
vation, allowing user­provided software to identify particular types of data products without
having access to the file naming rules. (This also allows users to construct an Observation
Index for data for other missions which follow different file naming rules). The Observation
Index will map data product types to specific filenames.
1.1.1.2 Level 1 Processing Overview Level 1 Products (Table 5.4­7) are observation
results typically based on data gathered over the entire FPSI field of view and observing
interval. AXAF users will perform substantial analysis work using products from this level.
Principal Level 1 Products are a set of X­ray images (the number of which depends on the
FPSI used), created from photon events detected during ``good time'' subintervals of the total
observing interval, and their corresponding exposure maps. The precision Aspect Solution is
generated and the Mission Timeline (page 39) is updated. Time slices of both corresponding
to the observing intervals are supplied as Level 1 Products. All detected photon events are
supplied. These are corrected for instrument distortions to incident pixel positions and for
aspect motion to celestial positions and barycentric times. All pulse height, timing, uncor­
rected pixel positions, and observation information (e.g. which ACIS CCD chip detected
the event) are retained at this level. Level 1 Products also include non­AXAF information
applicable to the observed field such as N HI (21 cm) information and digitized POSS/UK
Schmidt sky survey images.
15

Level 1 processing is applied to data acquired during all science observations, calibration
observations, and during slew periods between observation pointings. The calibration results
are archived and provided to the Calibration element. Proprietary rights to the slew results
will be governed by AXAF science policies.
Table 5.4­7: Level 1 Standard Data Products
Data Product Data Items
Housekeeping and Spacecraft Data
Observation Table For each observation interval
Observation Interval names
Observation Interval start and stop times
Observation Interval start and stop formatted dates
Observation Interval pointing directions
Observation Interval roll angles
Observation Interval duration, ontime, livetime
Observation Interval number within observation
Temporal Status Intervals Event screening conditions.
For each time a column value changes
Start time of interval
SI at focus
SI NIL
SI temperature code
SI pressure code
SI high voltage step
Grating in path
Datamode
Viewing geometry
Radiation flag
Aspect quality flag
Telemetry problem flag
Orbital Ephemeris Table For every 10 min of data
Time
Solar position vector
Lunar position vector
AXAF position vector
McIlwain parameters
OCC time delay
AXAF long, lat, height
Sun Angle Table For every time angle changes by 10 (TBR) deg
Start, stop time
Angle between Sun and nominal pointing direction
Solar System Ephemeris For each day of observation; plus 2 days either side
Time
Daily Solar position vector
Daily Jovian position vector
Daily Saturnian position vector
16

Table 5.4­7: Level 1 Standard Data Products (continued)
Data Product Data Items
Housekeeping Status Changes For each time any value changes
Time
SI at focus
SI next­in­line
SI temperature step
SI pressure step
SI high voltage
Grating in path
Instrument mode
Event Rates Table For every 10s (TBR)
time
background rates
total event rates
other rates TBD
Field Data
Field Source Catalog
SIMBAD and x­ray catalogs extract
For each astronomical object
Object name
Object RA, Dec and uncertainty
Object magnitudes and fluxes
Object class
Object variability flag
Object extent
Object alternate names
Field Diffuse Emission Catalog
1 value for each quantity
HI column
Reddening
CO
HI velocity histogram
Hff flux
Cirrus code
Field Multiwaveband Image Stack of other images of field
For each other mission image
Image is binned to same grid as X­ray image
Mission
Instrument
Observation ID
Image
Includes:
Optical POSS Image
All X­ray pointed images of field
EUVE image of field
17

Table 5.4­7: Level 1 Standard Data Products (continued)
Data Product Data Items
IRAS 100 micron mosaic
ROSAT RASS mosaic of field (if available)
VLA FIRST survey mosaic of field (if available)
Aspect Solution Data
Aspect solution Pointing vs time
(RA, Dec, roll, on­axis pixel coords, and uncertainty)
Aspect quality Times of good quality aspect:
Start time, stop time
Aspect quality flag
Kalman fit quality flag
Gyro data quality flag
Number of guide stars detected
Centroid fit quality flag
Aspect Solution Histogram Bins of aspect relative to nominal aspect.
Stable Aspect Intervals Binned aspect intervals
one record per period of stable aspect
Start time, stop time
Mean aspect
RMS aspect jitter
In header:
Sky region and pixel size
(detector­dependent)
Aspect Solution Secondary Products
Guide Star Properties For each guide star used
ID, RA, Dec, V mag, colors,
Proper motion, spectral type, multiplicity
Guide Star Observations For each guide star used
Derived RA, Dec
Instrument mag
Spoiler flag
Spoiler distance, angle
Spoiler instrumental mag
Guide Star Usage For each change or loss of guide star
Start time, stop time
IDs of Guide stars in use
ACA Data For every ACA readout
Time [from telem]
Subframe boundaries [from telem]
Subframes (stars and fid lights) [raw and corrected]
Bad pixel maps [from calib]
Camera temperatures [from telem]
PSF tables [from calib]
Raw centroids
Gyro corrected centroids
18

Table 5.4­7: Level 1 Standard Data Products (continued)
Data Product Data Items
Guide star detector positions
Guide star + fid light counts
ACA Bad Pixel Map For every time map changes
Image of bad pixels in ACA [from calib]
Header data:
Valid time range
ACA Flat Field
Image of ACA flat field
Header data:
Valid time range
ACA Dark Current Image
zero­level map[from calib]
Header data:
Valid time range
ACA Field Distortion Table Distortion polynomial coefficients [from calib]
Header data:
Valid time range
ACA Sub Pixel Response Map Coarse grid image of mean sub­pixel response
(10 x 10 or less)
Header data:
Valid time range
ACA Misalignment Coordinate transform
for ACA to HRMA
ACA Stellar PSF
Valid time range
Type: Grid, interpolated, CTI (Charge Transfer
Inefficiency)­corrected
Images of star PSFs [from calib]
Header data:
CTI coefficients used (if applied)
ACA Fid Light PSF
Valid Time range
Images of fiducial lights PSFs [from calib]
ACA Read Noise Calibration Table For each temperature step
Temperature
Read Noise in each quadrant
ACA Color Magnitude Correction
Table
For each calibrated color value
Color
Color magnitude correction
Gyro Data For every set of gyro values
(Gyro­only aspect solution)
Start time, stop time
Gyro count data (4)
19

Table 5.4­7: Level 1 Standard Data Products (continued)
Data Product Data Items
Gyro interpolation flag (4)
Gyro rate data (4)
Gyro axis rotation data (4)
Uncorrected S/C gyro rate
Corrected S/C gyro rate
Header data:
Fit parameters
Noise thresholds
Gyro Calibration Data For each gyro
Start time, stop time
Gyro ID
Alignment
Scale factor
Nominal Bias rate
Gyro noise level
Header data:
Gyro to SC transform matrix
Gyro Status History For each change of gyro used
Start and Stop Time
Active gyro IDs
Gyro Rotation Angles For each entry in the Gyro Data product
Time
Scale factors
Bias rates
S/C rotation angles
Fid Light Calibration For each fid light
Fid light number
Fid light location in STT coords
Nominal brightness
ACA Sightings For each ACA readout
Time
For each image: (star or fid)
Image centroid (pixels)
Image centroid (angle)
Image brightness
Image status (detected or not)
Image fitted background
Image fitted ü 2
for each guide star image only:
Image color flag
Image spoiler flag
ACA Kalman Data For each ACA readout
Time
Forward filter outputs
20

Table 5.4­7: Level 1 Standard Data Products (continued)
Data Product Data Items
(Kalman corrected centroids)
Reversed data
SC attitude estimate
Gyro drift estimate
Kalman covariance
Attitude update quaternion
ACA Photo Centroids For each photo interval
Time (photo reference time)
Reference time
Centroids (stars and fids) at reference time
Star centroids motion
Fid light centroids motion
Fluxes at reference time
Image Motion Correction For each (SAP) time of motion interval
Time
Star field motion
Fid light field motion
Relative field motions (stars to fids)
Corrected centroid positions
Reference Aspect Solution For each observation segment
Used to anchor final aspect solution
Anchor Time
Aspect solution at ACA
Aspect solution at SIM
Fid light solution
Calibration Data
Vignetting Map One map for each mirror shell, and for the sum of
shells. In each map, one set of the following values
for each step in Energy, off axis angle and azimuth.
Step sizes are to be determined after calibration.
Energy
Off axis angle
Azimuth angle
Vignetting factor
Ancillary Response File Definition in Legacy No. 2
Energy response information
Redistribution matrix file Definition in Legacy No. 2
Energy resolution matrix (one per ACIS quadrant)
QE Uniformity Map Array
Relative detector QE sensitivity versus position
PSF Models Point Spread Functions for different detector posi­
tions as a function of energy
21

Table 5.4­7: Level 1 Standard Data Products (continued)
Data Product Data Items
Response as a function of detector position and en­
ergy, either in image format or as analytic model
PSF Size Table
PSF Gaussian Width versus off axis
angle, azimuth and energy
Background Model Model parameters for predicted background, calculated
for considered observation
Composite background model
solar
galactic
extragalactic
particle
internal
X­ray Level 1 Basic Data Products
Level 1 Photon List For each event; includes bad events
X, Y sky pixel coordinates
Tangent plane pixel
Detector pixels
Chip Detector pixels for given chip
Chip id
PHA, PI raw and corrected pulse height
Photon arrival time
Time on UTC scale at spacecraft
Time on TT scale at barycenter for photon
Rise time, spread, grade
Status code (good event)
For the photon list as a whole:
Good Time Intervals, Data Subspace Information,
World Coordinate Systems
Sky Image One for each PI band: event counts vs sky pixel
Detector Image One for each PI band: event counts vs detector pixel
Exposure Map ( Raw Exposure Map Array )
Image of livetime versus sky pixel corrected for obscu­
ration using aspect solution
Effective Exposure Map One for each PI band: Image of exposure time vs sky
pixel, corrected for: instrument quantum efficiency,
filter/window transmission and vignetting.
Effective Area Map One for each PI band: Image of effective area vs sky
pixel, corrected for: instrument quantum efficiency,
filter/window transmission and vignetting.
22

Table 5.4­7: Level 1 Standard Data Products (continued)
Data Product Data Items
Predicted Background Map Array of Expected background counts versus detector
pixel
1.1.1.3 Level 2 Processing Overview Level 2 Products (Table 5.4­8) are typically
results generated for each source and, if applicable, spectrum detected from an observation.
AXAF users would look at these results to gain a first impression as to the observation's sci­
entific content and could do fairly detailed analysis for uncomplicated sources and source re­
gions using these products. Level 2 Products include the photon events determined, through
source detection, to correspond to the source (zero­order spectrum for grating observations),
dispersed spectrum (grating observations), the local background, and to a standard back­
ground. Source properties such as position, count rate, and period are derived directly from
observation and calibration data. Fluxes are derived using additional assumptions about the
source. Standard timing analysis results are supplied for each source (zero­order spectrum),
its local background, and for the standard background.
Level 2 Products include standard spectra and spectral analysis results. Low­resolution spec­
tra, based on the intrinsic pulse­height resolution of the FPSI, are supplied for all sources
(zero­order spectra) and backgrounds. High­resolution spectra are standard spectral analy­
sis results are provided for grating observations. Level 2 Products include non­AXAF infor­
mation applicable to each source (e.g. potential multiwavelength identifications and likely
source type based on fX =f other ratios) or high­resolution spectrum (line/edge identifications).
Table 5.4­8: Level 2 Standard Data Products
Data Product Data Items
X­ray Level 2 Basic Data Products
Level 2 Photon List Photon list updated with re­
sults of level 2 processing and
screened to include `good' pho­
tons only.
For each event
(the Photon List files listed below con­
tain some subset of the information
noted here)
X, Y sky pixel coordinate
Tangent plane pixel
coordinate
Tiled detector pixel coordinate
23

Table 5.4­8: Level 2 Standard Data Products (continued)
Data Product Data Items
Chip Detector pixel
coordinate
Chip id
PHA, PI raw and corrected
pulse height
Photon arrival time
Time on UTC scale at
spacecraft
Time on TT scale at
barycenter
Rise time, spread, grade
Status code (good event)
Source number
Grating order (for grating
data)
Photon energy (for grating
data)
Dispersed grating coordinates
(for grating data)
For the photon list as a whole:
Good Time Intervals, Data
Subspace Information, World
Coordinate Systems
Background Map One for each Level 1 Image.
Background counts in Image
bins, after extracting sources.
Source List For each source
Source number
Source candidate ID
Detection method
Significance (in sigma)
Probability
Dispersed spectrum number
J2000 position, error
Sky pixel position
Broad band count rate
Broad band flux
Source detection processing summary For each band
Band name
Band channel max, min
Threshhold
Background rate
Source Analysis Products
24

Table 5.4­8: Level 2 Standard Data Products (continued)
Data Product Data Items
Source Photon Filter Defines a subset of Level 2
Photon List, containing pho­
tons from the source region ­
1 per source
Local Background Photon Filter Defines subset of Level 2 Pho­
ton List, containing photons
from the local background re­
gion ­ 1 per source
Background Photon Filter Defines subset of Level 2 Pho­
ton List, containing photons
used in the analysis of the field
background properties
Source Properties 1 for each source
Source properties keywords:
Source number in this
observation
Source Name
Alternate source identifica­
tions (HEASARC CATIDn)
Extended flag
Extent size
Variability flag
Number of instrumental colors
PHA range for colors
Colors
Pulse pileup fraction (ACIS
only)
Source detection or back­
ground determination method
Non­AXAF data: Redshift,
velocity, spectral type, Object
class
Source Non­AXAF
identification
Counts per order (Grating
data only)
Integrated fluxes per order
(Grating data only)
Total integrated flux (Grating
data only)
Source Map Image of region around source
omitted for background files
25

Table 5.4­8: Level 2 Standard Data Products (continued)
Data Product Data Items
(This product may be embed­
ded in the Source List.)
Source Flux Table 1 record for each PI band
Band min and max
Count rate and errors
Flux and errors
Source Cross­ID Table Non­AXAF data; For each
reference
NED and SIMBAD references
Light Curve Table 1 per source
For each light curve bin
SCC time
TT barycentered time
Fluxes in each band in time
bin
Error on fluxes
Pulse pileup fraction (ACIS
only)
Light Curve Power Spectrum Power spectrum array of light
curve
Field Background Light Curve Light curve table (as Source
Light Curve)
Local Background Light Curve 1 per source
Light curve table (as Source
Light Curve)
Source PHA Spectrum PHA file for source pulse
height spectrum (1 per source)
Format to support compatibil­
ity with XSPEC and standard
OGIP spectral file.
For each channel
Channel
Counts
Rate
Errors
Include pulse pileup header
keyword for ACIS
Background PHA Spectrum PHA file for field background
Data as for Source PHA
spectrum
Local Background PHA file PHA file for local background
(1 per source)
26

Table 5.4­8: Level 2 Standard Data Products (continued)
Data Product Data Items
Data as for Source PHA
spectrum
Source RMF calibration file Mean spectral response matrix
calibration for source region
Source ARF calibration file Mean spectral efficiency cali­
bration for source region
Grating Data Products
Zero Order Image (Grating only)
Image array of zero order pho­
tons only, with aspect applied
TG Vignetting Map
HRMA vignetting vs wave­
length, shell, and source pos
Averaged over aspect history
Spectrum High Resolution Calibrated
Spectrum
Spectrum coordinate system
Spectrum array (calibrated
counts and flux versus energy).
Spectrum extraction masks.
This product is only generated
for grating data.
Spectrum Background Local background for dispersed
Spectrum
Spectrum coordinate system
Spectrum array (counts, flux)
Spectrum background masks
Spectrum RMF Mean spectral response ma­
trix calibration for source re­
gion; position and blur vs
wavelength
Spectrum ARF Mean spectral efficiency cali­
bration for source region; grat­
ing, mirror, detector. Average
for extraction region.
Spectrum Background ARF Mean spectral efficiency cali­
bration for background region;
grating, mirror, detector. Av­
erage for extraction region.
Spectral Exposure Map
27

Table 5.4­8: Level 2 Standard Data Products (continued)
Data Product Data Items
Exposure time vs. dispersion
coordinate
Spectral effective exposure map
Exposure time vs. dispersion
coordinate corrected for detec­
tor QE, vignetting, gaps
Spectral Effective Area Map
Effective area vs dispersion co­
ordinate, corrected for detec­
tor QE, vignetting, gaps
Spectrum Background Exposure Map
Exposure time vs. dispersion
coordinate
Spectrum Background effective expo­
sure map
Exposure time vs. dispersion
coordinate corrected for detec­
tor QE, vignetting, gaps
Spectrum Background Effective Area
Map
Effective area vs dispersion co­
ordinate, corrected for detec­
tor QE, vignetting, gaps
Spectral Line Feature Table Spectral features ­ only present
for grating data
For each line or edge identified
Continuum counts, flux
Line counts, flux
Wavelength/energy
Edge strength
Line equivalent width, fwhm
ACIS Products (for each source)
Grade Fractions For each split event grade
Grade
Fraction of events in grade
Processing Information
Observation Index For each data product
Data product type
Number within type
Filename
SDP Profile
ASCII SDP Profile file
SDP Log ASCII log file
28

Table 5.4­8: Level 2 Standard Data Products (continued)
Data Product Data Items
1.1.1.4 Level 3 Processing Overview Level 3 Products (Table 5.4­9) are catalog sum­
mary products and the results of aggregate analysis. AXAF users would begin browsing the
AXAF data holdings at this level to find answers to questions such as ``was this particular
source observed by AXAF?'' or ``how many pulsars has AXAF looked at?''. The answers
guide the users in the retrieval, if desired, of the relevant Level 2 Products for further anal­
ysis and/or Level 1 Products for in­depth analysis. Also see Search and Retrieval, section ??.
Level 3 products are created only from non­proprietary data. Certain Level 3 Products
are updated automatically as observation data becomes public, specifically the AXAF Ob­
servation, Image, Source, and Spectrum Lists. Update of the Bibliographic, Object, and
Identification and Cross­Reference Catalogs is performed, at ASC staff request, when pub­
lications based on data obtained with AXAF become available. Other Level 3 Products are
created upon ASC staff request either when a sufficient amount of data on interesting objects
is accumulated or otherwise as specified by AXAF science policies. Update of all Level 3
Products is initiated only through ASC staff request.
Table 5.4­9: Level 3 Standard Data Products
Data Product Data Items
Global Catalogs ­ to be maintained up to date
AXAF Observation
List
List of all observations made with all instruments.
All entries are derived from Observation Sum­
mary products.
Observation ID
Processing System Version (most recent
processing)
SDP Profile (most recent processing)
Processing Number (most recent processing)
Detector ID
Grating
Detector Mode
Focus
SIM Position
Next­In­Line Detector
NIL Detector Mode
Observation ID
29

Table 5.4­9: Level 3 Standard Data Products (continued)
Data Product Data Items
Target Name
Target Coordinates
Start and stop date/time
Principal Investigator
Proposal Title
Requested Time
Number of detected sources
Number of good events
Ontime
Livetime
Public Date
Note: These quantities are distinct from those
in the OCAT, in that they represent the post­
observation actual values derived from the pro­
cessing of the data and reflecting unplanned on­
board events and commanding, rather than the
pre­observation intended (planned) values.
AXAF Pointing
Catalog
List of all pointings made by AXAF. An observa­
tion is made up of several pointings. This list is
needed to determine precise sky coverage. Derived
from Observation Table products.
Observation interval name
observation ID
Observation interval number within observation
Start and stop time
Detector ID
Pointing direction
roll angle
livetime
AXAF Candidate
Source Catalog
Summarized information on all sources found by
standard data processing. Provides summary of
source properties derived in Level 2 Processing.
Does not identify multiple observations of the
same source.
Candidate source ID
observation ID(s)
extended source flag, extent size
variability flag, range; period flag, number of pe­
riods, period values
For each PI band: count rates, fluxes, colors
significance
Low resolution spectral fit info
Public date
30

Table 5.4­9: Level 3 Standard Data Products (continued)
Data Product Data Items
AXAF Source Catalog Summarized information on all sources detected
by AXAF above a fixed (3.5 sigma TBR) signifi­
cance level. Provides summary of source proper­
ties. Identifies multiple observations of the same
source and assigns unique designations to sources.
source ID
candidate source ID(s)
observation ID(s)
source name
source class
extended source flag, extent size
revised variability/period info: flags, variability
range, number of periods, period values
for each PI band: mean count rates, fluxes, colors
spectral fit info for low resolution spectra (param­
eter vector values)
Public date (of most recent observation)
AXAF Spectral
Catalog
Summarized information on all high resolution
spectra produced by AXAF.
candidate source ID
source ID
source name
observation ID
detector configuration
continuum fit
observed lines/edges IDs
line/edge strengths
other TBD
Public date
Source Bibliographic
Catalog
Primary goal of this catalog is to provide ref­
erences to published literature for user specified
AXAF sources/source classes/keywords. At a
minimum catalog includes:
source ID
source class (same as in Object Catalog, see Level
3 Processing Overview)
bibliographic ID
bibliographic reference
keywords
abstract
other TBD
AXAF Bibliography Complete list of AXAF related publications. In­
cludes papers on calibration and instrumentation
as well as observations.
31

Table 5.4­9: Level 3 Standard Data Products (continued)
Data Product Data Items
Bibliography ID
bibliographic reference
title
keywords
abstract
AXAF Identifications
and Cross­Reference
Catalog (AICRC)
For sources from other catalogs, it lists their X­
ray properties as observed by AXAF.
non­AXAF source ID
AXAF observation ID(s)
detector configuration
AXAF detection flag
AXAF source ID
AXAF flux/upper limit
information from astronomical databases (e.g.
NED, Simbad)
other TBD
List of Classes List of the types of source class (quasar, white
dwarf, etc.) used in the database. Identifies the
subset of classes for which Class Catalogs are
maintained.
Source class code
Source class name
Class Catalog name (or blank)
Class Catalog Catalog of AXAF sources by type of object. Subset
of Source Catalog.
Other Data Products
AXAF Images In
Region
List of all images produced by AXAF in a given
sky region (or including a given position). It pri­
marily serves as a quick reference for identifying
images containing user specified region of the sky.
Product filename
observation ID
detector ID
image center position and roll angle
image region description
livetime
Observation date start/stop
Public date
Selected Region List List of particularly interesting areas on the sky
(e.g. M31, Orion, Galactic Center, Virgo, etc.)
Name of region
Region ID (filename to use)
32

Table 5.4­9: Level 3 Standard Data Products (continued)
Data Product Data Items
Region specification file
Selected Region File Standard region data product for each selected
region
REGION table:
set of region specifier strings
Slew Photon Lists These are standard photon list files, see Level 1
products
Level 3 Map products
Selected Region
Mosaics
mosaics of AXAF observations covering regions in
Selected Region List
Diffuse Background
Maps
maps of background, background spectra, etc.
Diffuse Background
Model
all­sky maps of components of diffuse background
model
Sky Coverage Map Map of region of sky covered by AXAF obser­
vations. Generated from Pointing Catalog or
OCAT.
Ancillary Databases
Ephemeris For every 10 min of mission
Time
Solar position vector
Lunar position vector
AXAF position vector
McIlwain parameters
OCC time delay
AXAF long, lat, height
Solar System
Ephemeris
For each day
Time
Daily Solar position vector
Daily Jovian position vector
Daily Saturnian position vector
Housekeeping
Database
For every TBD
Time
SI at focus
SI next­in­line
SI temperature step
SI pressure step
SI high voltage
Grating in path
Instrument mode
Event Rate Database For every 10s (TBR)
time
33

Table 5.4­9: Level 3 Standard Data Products (continued)
Data Product Data Items
background rates
total event rates
other rates TBD
Aspect Solution
Database
For each ACA Photo
Time
Aspect Solution (RA, Dec, Roll, Offsets)
Screening Database For each Temporal Status Interval
Time
SI at focus
SI NIL
Temperature code
Pressure code
HV step
Grating
Data mode
Viewing geometry
Radiation flag
Aspect quality flag
Telemetry problem flag
1.1.1.5 Special/Calibration Processing Overview Any observer­requested special
processing for a science observation is performed subsequent to the standard processing
as a separate SDP job under the control of a Special Processing Profile supplied by the
observer (with the proposal or via other TBD interface with the ASCDS). Any Special
Products are then produced and archived in addition to the Standard Products. The format
of the Special Profile is no different than the Standard, but in this case sets up a processing
configuration and provides the necessary models and parameters required to produce the
special products desired. Any Standard Products which are unchanged and can be utilized
during the special processing are not recreated. The ASC staff (and the user TBD) can view
and modify the Special Profile associated with the observation prior to processing execution.
Processing of calibration observations is handled as a variant to this same mechanism, where
each calibration observation is linked to a (possibly unique) Calibration Processing Profile
as determined by the ASC staff. A Calibration Profile allows the option to first perform
processing according to the Standard Profile, to a designated depth, and then the processing
according to the Calibration Profile itself. The ASC staff can copy, input, modify, or delete
Special and Calibration Profiles, as well as associate them to observations.
1.1.1.6 Reprocessing Overview Reprocessing is performed identically to the standard
processing of original data except that the products are intended to replace, as opposed to
add to, existing archived products. Reprocessing is always initiated by the ASC staff. The
reason for reprocessing might be improved calibrations, an improved aspect solution, or
34

an improved/additional processing algorithm (e.g. source detection). A Processing Profile
distinct from the Standard is provided by the ASC staff with the reprocessing request.
Reprocessing can be requested for an observation part, a full observation, a few observations,
or days, weeks, months, or even years of accumulated observations. The ASC staff can select
the observations to be reprocessed according to list or time interval criteria, or criteria
which can be translated to time intervals. Reprocessing can be requested to replace a single
product, an entire Level, or multiple Levels of existing products. Reprocessing can therefore
be requested to start from and stop at any point within the Level 0 through Level 3 sequence.
Reprocessing from raw telemetry through Level 0 is specified in section ??. Reprocessing
from Level 0 through Level 1 is expected to be performed several times during the course
of the mission to reflect improved understanding of the performance of AXAF. As with
Special Processing, any existing products which are not to be modified are utilized by the
reprocessing as necessary, but not recreated. Data products made obsolete by reprocessing
are retained in the archive for reference, subject to AXAF science policies. The changes
implemented by the reprocessing and the reasons for them are recorded with the reprocessed
products.
1.1.2 Standard Data Processing Functional Requirements
1. The ASCDS standard processing shall be performed using an automated, on­line pro­
cessing system (1854 3.2.5[3]).
2. The ASCDS standard processing shall be performed on the same type of computer
hardware and under the same operating system as the ASCDS Data Analysis capability
(section ??) (1854 3.4[3]).
3. The ASCDS shall apply the standard processing to all science observations (1854
3.2.5[1]). All observer­requested special processing is to be in addition to the stan­
dard processing.
4. The ASCDS standard processing shall be constituted of a sequence of the Data Analysis
Tools as described in section ?? configured as designated by the Standard Processing
Profile using the scripting mechanism described in section ?? (1854 3.4[3]).
5. The format for the Standard Data Products listed in Tables 5.4­7, 5.4­8, and 5.4­9 shall
be consistent across all AXAF detector systems. This means that, at a minimum:
(a) all Standard Data Products shall include a standard set of information about the
observation, the Observation Information.
(b) all sky coordinates shall be in the same system
(c) all image/spectrum field origins shall be in the same location
(d) all PHA channel numberings shall begin at 0
(e) all energies corresponding to a PHA channel shall apply to the linear arithmetic
midpoint of the channel
(f) all AXAF sources shall be named using the IAU convention
35

(g) all live time, effective area, and background maps shall use the same grid as
corresponding image
(h) others TBD
1.1.2.1 Processing Control
1. The ASCDS shall perform Level 1 processing, creating/updating the corresponding
products, as intervals of Level 0 Telemetry become available.
2. When sufficient Level 0 Telemetry for an observation has been collected (with TBD
of the observing time), the ASCDS shall initiate the final Level 1 and the Level 2
processing of that observation (1854 3.4[9]).
3. If sufficient Level 0 Telemetry has not been accumulated for an observation and more
than 1 month (SAP) has elapsed since the reception of the earliest data, the ASCDS
shall initiate standard processing of the completed pointings accumulated so far. For
any given observation, this shall be performed no more often than once per SAP (same
SAP as above). (1854 3.2[4]).
4. The ASCDS shall provide the capability for the ASC staff to initiate SDP for a desig­
nated observation, observation part (set of complete pointings) or set of observations
(1854 3.2[5], 3.4[9]).
5. The ASCDS shall allow the ASC staff to view essential data about each SDP job,
including its status (TBD) and linkage to the applicable Processing Profile.
6. The ASCDS shall provide the ASC staff with the capability to (re­)prioritize, sus­
pend, restart, and cancel SDP jobs. Allowable restart points include the start of the
processing sequence and others TBD.
7. The ASCDS shall provide error handling and, where possible, automatic recovery from
processing faults. The types and severity classes of processing faults which determine
subsequent recovery actions are TBD.
8. The ASCDS shall automatically suspend an SDP job that fails one of TBD in­line
checks or has not completed within a Profile­specified interval.
9. Upon automatic suspension of any SDP job, the ASCDS shall provide an alert to the
ASC staff with an indication of the reason.
10. The ASCDS shall configure the standard processing and use any necessary parameters
and models only as directed by the Standard Processing Profile.
11. The ASCDS shall accept and document in the Processing Log (TBR) ASC staff input
of and modifications to the standard (default) processing setup and any necessary
models and parameters contained within (or indicated by) the Standard Processing
Profile (1854 3.4[10]).
36

12. The ASCDS shall provide TBD processing summaries, processing start, stop, and
elapsed times, and SDP job status (at a minimum pending, active, suspended) for
display to the ASC staff.
13. The ASCDS shall log TBD processing summary data, SDP job status changes, fault
indications, recovery actions (whether automatic or manual), and accounting data.
This accounting data shall include, at a minimum, for each pointing (1854 3.2.6[1]):
(a) Data time interval (UT)
(b) Spacecraft ID
(c) Observation ID
(d) Pointing ID
(e) SDP Job ID
(f) Time of processing initiation
(g) Time of processing completion
(h) Software version(s) used
(i) Location of products in archival storage
(j) ID of the calibration models/parameters used
(k) ID of the Processing Profile used
(l) Description of SI configuration used
(m) A TBD summary of processing results
(n) Other TBD information necessary for accurate processing accounting
14. The ASCDS shall provide Processing Status (TBD) for each observation or observation
part processed. This forms a component of the overall Observation Status which is
maintained in the Observing Catalog (1854 3.1.6.1[10]).
15. The ASCDS shall generate an Observation Summary (Table ??) as a Standard Product.
16. The ASCDS shall accept a unique Special Processing Profile for any science observation
to accommodate those observers who wish to specify the type of non­standard (Special)
processing to be performed on the gathered data (1854 3.2[8]).
17. The ASCDS shall accept a unique Calibration Processing Profile from the ASC staff
for each calibration observation.
18. If a Special Profile is supplied by the observer as part of a science observation, the
ASCDS shall first process to completion the gathered data according to the Standard
Profile and then perform the special processing according to the Special Profile.
19. The ASCDS shall first process data gathered from calibration observations according
to the Standard Profile, if so indicated in the Calibration Profile, to the depth specified
in the Calibration Profile and then perform the processing indicated by the Calibration
Profile.
37

20. The ASCDS shall provide the capability for the ASC staff (and the user TBD) to input,
modify, copy, replace, and link Special Processing Profiles.
21. The ASCDS shall provide the capability for the ASC staff to input, modify, copy,
replace, and link Calibration Processing Profiles.
22. The ASCDS shall lock out modifications or replacements to any Processing Profile
while it is in use by any active SDP job.
23. The ASCDS shall provide the capability for the ASC staff to initiate reprocessing using
a designated Reprocessing Profile for a designated observation span. An observation
span can encompass a single observation, an observation part, a set of observations
(possibly with multiple instruments), or the set of complete observations contained
within a designated time interval (1854 3.2[7]). The observation span can be designated
as a single observation or pointing, a list of observations or pointings, or as a time
interval or list of time intervals encompassing a set(s) of observations or pointings.
24. The ASCDS shall provide the capability for the ASC staff to designate the scope of a
reprocessing request. The scope can be designated as an individual Standard Product,
a set of Standard Products, a Level of Standard Products, or a set of Product Levels
(1854 3.2[7]).
25. Upon ASC staff request, the ASCDS shall replace the corresponding products in the
archive with the reprocessed products. Obsolete versions of the products will be re­
tained for reference.
26. The ASCDS shall automatically determine, from information supplied in the Standard
Profile and that designated for special or reprocessing, which intermediate products do
not have to be recreated in order to satisfy the special or reprocessing request.
1.1.2.2 Level 1 Processing
1. The ASCDS shall automatically configure the Level 1 processing sequence from the
appropriate subsets and substitutions of the Data Analysis Tools (Appendix C) as
designated in the Standard Processing Profile.
2. For each observation, the ASCDS shall produce and archive the Level 1 Products,
suitable for further scientific analysis, that are specified in Table 5.4­7 (1854 3.2.5[4]).
3. If requested by a observer­supplied Special Profile, the ASCDS shall automatically
configure an auxiliary Level 1 processing sequence from the appropriate subsets and
substitutions of the Data Analysis Tools (Appendix C) as designated in the Special
Profile to produce and archive the observer­requested Special Level 1 Products.
4. The ASCDS shall accept from the ASC staff a request to re­Level 1 process the Level 0
Products of a span of observations according to a staff­supplied Reprocessing Profile.
The observation span can be designated as a single observation or pointing, a list of
observations or pointings, or as a time interval or list of time intervals encompassing a
set(s) of observations or pointings.
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5. The ASCDS shall derive an ex post facto Aspect Solution for observations made with
the AXAF­I observatory which utilizes data from the on­board star camera, fiducial
lights, and inertial reference systems together with the AXAF Star Catalog (1854
3.2.3[2], 3.4.1[14]).
6. Any ASCDS­derived Aspect Solution shall include the estimated accuracy (uncer­
tainty) of the solution at each aspect point.
7. The ASCDS­derived aspect solution algorithms shall provide for contingencies such as
missed acquisition of an aspect star, loss of accurate star data when pointing near the
sunlit earth, and others TBD (1854 3.2.3[3]) using the sun and earth sensors and other
TBD subsystems.
8. For each observation, the ASCDS shall transform the telemetered FPSI readout, cor­
recting for instrument response and aspect motion, to a complete set of photon events
gathered over the the entire FPSI field­of­view during the entire observing interval
(1854 3.2.4[2], 3.2.5[1],[2]). Events determined to be invalid shall be identified as such
and included in this set.
9. The ASCDS shall produce and archive a Mission Timeline. The Mission Timeline is a
time­aligned series over the mission lifetime of TBD ancillary, spacecraft, environmen­
tal, and on­board data and events which shall include, at a minimum, the following:
ffl Spacecraft state vector
ffl Spacecraft altitude
ffl Spacecraft celestial pointing angle
ffl Spacecraft pointing angle relative to the sun
ffl Spacecraft pointing angle relative to the moon
ffl Spacecraft pointing angle relative to the spacecraft velocity vector (ram vector)
ffl Bright object detector readout
ffl Background monitor readout
ffl Sun sensor readout
ffl Earth sensor readout
ffl Spacecraft attitude
ffl Spacecraft attitude rates
ffl PCAD mode (slew, gyro­only fixed, star tracking. etc.)
ffl Aspect Solution quality
10. The ASCDS shall provide a capability to filter photon events based on logical combina­
tions of criteria which reference the Mission Timeline, the Aspect Solution, and others
TBD. These Filtering Criteria are a component of the Processing Profile. Filtering for
this purpose means annotation for possible elimination from downstream processing,
not the elimination of any actual data (1854 3.2.4[1],[3]).
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11. The ASCDS shall produce Images from photon events gathered during intervals which
have been determined to be ``good'' per the Filtering Criteria defined in the Standard
Profile (1854 3.2.4[3]).
12. The ASCDS shall archive Images and related data in FITS format (1854 3.2.8[4]).
13. The ASCDS shall, upon ASC staff request, recreate the designated Level 1 Products
from the Level 0 Products of a designated span of observations according to a staff­
supplied Reprocessing Profile. The observation span can be designated as a single
observation or pointing, a list of observations or pointings, or as a time interval or list
of time intervals encompassing a set(s) of observations or pointings.
1.1.2.3 Level 2 Processing
1. The ASCDS shall automatically configure the Level 2 processing sequence from the
appropriate subsets and substitutions of the Data Analysis Tools (Appendix C) as
designated in the Standard Processing Profile.
2. For each observation, the ASCDS shall produce and archive the Level 2 Products,
suitable for further scientific analysis, that are specified in Table 5.4­8 in order to
provide initial information as to scientific content and to guide further off­line analysis
(1854 3.2.5[4],[5]).
3. If requested by an observer­supplied Special Profile, the ASCDS shall automatically
configure an auxiliary Level 2 processing sequence from the appropriate subsets and
substitutions of the Data Analysis Tools (Appendix C) as designated in the Special
Profile to produce and archive the observer­requested Special Level 2 Products.
4. The ASCDS shall, upon request from the ASC staff or the active Reprocessing Profile,
recreate the designated Level 2 Products from the designated Level 1 Products of
a set of observations according to the staff­supplied or active Reprocessing Profile.
The observation span can be designated as a single observation or pointing, a list of
observations or pointings, a time interval or list of time intervals encompassing a set(s)
of observations or pointings, an instrument or instrument mode, or as TBD.
1.1.2.4 Level 3 Processing
1. The ASCDS shall automatically update and rearchive the AXAF Observation, Image,
Source, and Spectrum List Level 3 Products (Table 5.4­9) when the antecedent data
products become public.
2. The ASCDS shall, upon ASC staff request, update and rearchive the requested Level 3
Products based on the accumulated Level 1 and/or Level 2 Products that have been
created and have become public since the last update of each requested Level 3 Product
(1854 3.3.2[6], 3.4.5[5]).
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1.1.3 Standard Data Processing Performance Requirements
1. The ASCDS shall standard process one week's worth of observations in less than 40
hours (1854 3.2[6]).
2. The ASCDS shall send to the observer a copy of the standard processed data within 1
week of observation completion (1854 3.2[2]).
3. If an observation is not complete within one month and the observer so requests, the
ASCDS shall provide the standard processed partial data set within 1 week of data
receipt from the most recent complete pointing (1854 3.2[4]).
4. The ASCDS shall standard process a section of observation data (a set of complete
pointings) within 24 hours of data receipt from the most recent complete pointing
(1854 3.2[5]).
5. The quality of the ASCDS­derived aspect solution shall be such that, under normal
conditions (TBR) and the assumptions of perfect HRMA and SI resolution, the re­
constructed image of an X­ray point­like source has a spread diameter of less than 0.5
arcsec rms within the central 5 arcmin radius (1854 3.2.3[1]).
6. The accuracy of the ASCDS­derived aspect solution shall be such that, under normal
conditions (TBR) and the assumptions of perfect HRMA and SI resolution, any pixel
of the reconstructed image can be positioned on the sky to within 1.0 arcsec rms of
the true position (1854 3.2.3[1]).
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