Description Parameter: Section 5.2.6 Processing Level: SPD Usage in processing: Section 7.4 in particular Section 7.4.2 File Type: FITS Image Units: Jy for PSDYNAMIC, dimensionless for PSDYNWT File names: PSDYNAMIC, PSDYNWT
The dynamic calibration for staring observations with PHT-S is based
on the assumption that point sources with similar flux densities will
produce identical signal variations as a function of time for each
PHT-S detector array element. With a sufficient number of calibration
stars spanning a large range of flux densities for each detector pixel,
it has been possible to construct two dimensional surfaces where for any
signal of detector pixel
at time
a flux density
in Jy can be assigned
(see Section 5.2.6). The calibration data are
tabulated in PSDYNAMIC.
The SPD processing subdivides a staring measurement into a number of
depending on the number of ramps in the measurement. For
each value of
a value of
can be determined. For small
, the corrections are largest because of the steep initial rise of
the signal transient curve. The flux calibration becomes more accurate
by giving the signals at larger
a relatively higher weight when
averaging the
to obtain the average flux density for a
measurement. The weights are stored in a separate calibration file
PSDYNWT.
Due to the high dynamic range in possible signals and times
, the calibration tables use logarithmic axes for signal and time.
The axes are tabulated as follows:
![]() |
![]() |
![]() |
(14.1) |
![]() |
![]() |
![]() |
(14.2) |
![]() |
![]() |
![]() |
(14.3) |
where is the array index and signal
is in [V/s]. Note that
negative signals can occur.
![]() |
(14.4) |
As a consequence, times smaller than 1 s (and larger than 4096 s) are not handled by the calibration.
For both PSDYNAMIC and PSDYNWT the following FITS keywords are
common:
NAXIS = 3
TYPE = REAL*4
AXIS Length Description 1 130 signal 2 13 time in3 128 pixels
AXIS Length Description 1 130 signal 2 13 time in3 128 pixels