Science Run Archive

ATICA organized the events it extracted in the same way that the flight software organizes science data - by science runs which are defined in [Ford and Francis1997]. ATICA creates a directory for each science run, named for the mode and start time of the run, e.g. the run tefwb_111:07:17 was a Timed Exposure Faint With Bias run that started at IRIG time 111:07:17. Within that directory the event list is arbitrarily divided into files of about 100,000 events each. ATICA was not able to organize the data by TRW ID because the flight software and thus the telemetry knew nothing about that concept. Unfortunately it was necessary to schedule multiple TRW ID's within one ACIS science run so a single ATICA output directory will contain data from several TRW ID's.

The FITS binary tables used to store the event lists consist of the following columns.

• TIME: A timestamp for the CCD frame, expressed as an IRIG time in seconds, i.e. the number of seconds since 1997.0.
• CHIPX/CHIPY: The 1-based position of the event. Note that the flight software telemeters event positions in a 0-based system.
• DETX/DETY: The position of the event in the ``tiled coordinate system AXAF-ACIS-2.2'' defined by Jonathan McDowell at the ASC [McDowell1997].
• CCD_ID: The CCD that detected the event. (See Table 3.1.)

  
  

   

  CCD_ID Chip CCD_ID Chip CCD_ID Chip

  0 I0 4 S0 8 S4

  1 I1 5 S1 9 S5

  2 I2 6 S2

  3 I3 7 S3

  
  

  
  

• AMP_ID: The amplifier, numbered 0..3, associated with the central pixel of the event.
• EXPOSURE: The exposure sequence number as telemetered by the flight software.
• PHAS: For most modes this is a 9 element vector containing the event island pixel values NOT corrected for bias. The relationship between this 9-vector and the 3x3 event island is shown in Figure 3.1.

  
  

    

  Figure 3.1: Ordering of PHAS and BIAS Vectors

  
  
  
• BIAS: A vector of the same form as PHAS, containing the BIAS values used for processing this event.
• OVRCLK: The overclock value associated with the amp in AMP_ID for this exposure.

Footnotes

...exposure.

A bias-corrected event island would be computed as PHAS - BIAS - OVRCLK.