Calibration Access and Data Handbook

Description

The CCF contains three table extensions : ADUCOEFF, OFFSET_GAIN and ENERGY_COMBINE.

ADUCOEFF:

Obsolete, it was supposed to be used by the operational Payload Monitoring Sub-system (PMS) for a rough approximation of energy to PHA conversion.

Attributes:

None.

Columns:

CCD_ID:

CCD index number (1-7).

NODE_ID:

0/1 prime/redundant node.

OFFSET:

One global offset value per CCD.

GAIN:

One global gain value per CCD.

OFFSET_GAIN:

With respect to the SAS, the detailed conversion is provided by the coefficients of this second extension. Three polynomial coefficients for the gain conversions are given for the four different pattern types (mono- (0), bi- (1-4), tri- (5-8) and quad-pixels (9-12) ) and for the seven CCDs: a constant term (OFFSET), linear term (GAIN) and a quadratic term (POLY_TERM).

The polynomial coefficents are at present repeated for the redundant node, but not used in in-orbit operations, so pending necessity to recalibrate the latter.

Accessed by:

• CAL_gainCorrect():

  p=0: $eOut = OFFSET[\_n] + GAIN[\_n] \times eIn + POLY\_TERM[\_n] \times eIN^{2}$

  p=1: $eOut = OFFSET1[\_n] + GAIN1[\_n] \times eIn + POLY\_TERM1[\_n] \times eIN^{2}$

  p=2: $eOut = OFFSET2[\_n] + GAIN2[\_n] \times eIn + POLY\_TERM2[\_n] \times eIN^{2}$

  p=3: $eOut = OFFSET3[\_n] + GAIN3[\_n] \times eIn + POLY\_TERM3[\_n] \times eIN^{2}$

  where _n is the node and p in the range [0,3] is a pattern index computed from event pattern passed to CAL_gainCorrect() as input argument :

  
  

  Pattern ID	Pattern index
  0	0
  1,2,3,4	1
  5,6,7,8	2
  9,10,11,12	3
  13 ...	3

  
  

• CAL_offsetCorrect(): $eOut = eIn - OFFSET[\_node]$. An alternative MOS offset correction could be obtained via CAL_getMOSoffsets(), which makes use of EMOS1/2_DARKFRAME.CCF.

• CAL_piToeV(): $eOut = KEV0 + eIn \times KEV\_P\_PI$.

Attributes:

KEV0:

Constant in linear PI to keV conversion.

KEV_P_PI:

Slope of linear PI to keV conversion.

Columns:

CCD_ID:

CCD index number (1-7).

OFFSET:

vector column of length 2; one offset value for pattern index 0 events, one value per node per chip.

GAIN:

vector column of length 2; one gain value for pattern index 0 events, one value per node per chip.

POLY_TERM:

vector column of length 2; quadratic term for pattern index 0 events, one value per node per chip in gain correction.

OFFSET1/2/3:

vector column of length 2; one offset value for pattern index 1/2/3 events, one value per node per chip.

GAIN1/2/3:

vector column of length 2; one gain value for pattern index 1/2/3 events, one value per node per chip.

POLY_TERM1/2/3:

vector column of length 2; quadratic term for pattern index 1/2/3 events, one value per node per chip in gain correction.

ENERGY_COMBINE:

Accessed by :

• CAL_mosPhaBuild (in package emsalib). This routine combines the four MOS event energies ENERGY_1/2/3/4 into a single PHA value according to an algorithm described in the documentation of package emsalib. The table contains for every event pattern (0-31) a set of four coefficients a1=ENERGY_PARAM[0], a2=ENERGY_PARAM[1], a3=ENERGY_PARAM[2], a4=ENERGY_PARAM[3]; depending on the sign of a4, one of the two schemes is selected :
  • for $a4 > 0$ : $PHA = a1 \times ENERGY\_1 + a2 \times ENERGY\_2 + a3 \times ENERGY\_3 + a4 \times ENERGY\_4 - BKG$, where BKG is a local weighted background value.
  • for $a4 < 0$ the formula is more complicated; see emsaplib documentation for more details.

Attributes:

None.

Columns:

PATTERN_ID:

event pattern ID in valid range [0, 31]

ENERGY_PARAM:

vector column of length 4; four parameters (a1/a2/a3/a4) per PATTERN_ID