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 in 3 128 pixels
AXIS Length Description 1 130 signal 2 13 time in 3 128 pixels