sampinfo

wfc3tools.sampinfo Module

Sampinfo prints information about a WFC3/IR MultiAccum image, including exposure time information for the individual samples (readouts). The global information listed (and the names of the header keywords from which it is retrieved) includes:

  • the total number of image extensions in the file (NEXTEND)

  • the name of the MultiAccum exposure sample sequence (SAMP_SEQ)

  • the total number of samples, including the “zeroth” read (NSAMP)

  • the total exposure time of the observation (EXPTIME)

Information that is listed for each sample is the IMSET number (EXTVER), the sample number (SAMPNUM), the sample time, which is the total accumulated exposure time for a sample (SAMPTIME), and the delta time, which is the additional exposure time accumulated since the previous sample (DELTATIM).

Note that the samples of a MultiAccum exposure are stored in the FITS file in reverse time order. The initial, or “zeroth” read, appears last in the FITS file, with IMSET=NSAMP, SAMPNUM=0, SAMPTIME=0, and DELTATIM=0. The final read of the exposure appears first in the file and has IMSET=1, SAMPNUM=NSAMP-1 (SAMPNUM is zero-indexed), and SAMPTIME=EXPTIME.

>>> from wfc3tools import sampinfo
>>> sampinfo('ibcf02faq_raw.fits')
IMAGE           NEXTEND SAMP_SEQ    NSAMP   EXPTIME
ibcf02faq_raw.fits  80  STEP50      16  499.234009

IMSET   SAMPNUM SAMPTIME    DELTATIM
    1   15  499.234009  50.000412
    2   14  449.233582  50.000412
    3   13  399.233154  50.000412
    4   12  349.232727  50.000412
    5   11  299.2323    50.000412
    6   10  249.231873  50.000412
    7   9   199.231461  50.000412
    8   8   149.231049  50.000412
    9   7   99.230637   50.000412
    10  6   49.230225   25.000511
    11  5   24.229715   12.500551
    12  4   11.729164   2.932291
    13  3   8.796873    2.932291
    14  2   5.864582    2.932291
    15  1   2.932291    2.932291
    16  0   0.0 0.0

Include median:

>>> sampinfo('ibcf02faq_raw.fits', median=True)
IMAGE           NEXTEND SAMP_SEQ    NSAMP   EXPTIME
ibcf02faq_raw.fits  80  STEP50      16  499.234009

IMSET   SAMPNUM SAMPTIME    DELTATIM
    1   15  499.234009  50.000412   MedPixel: 11384.0
    2   14  449.233582  50.000412   MedPixel: 11360.0
    3   13  399.233154  50.000412   MedPixel: 11335.0
    4   12  349.232727  50.000412   MedPixel: 11309.0
    5   11  299.2323    50.000412   MedPixel: 11283.0
    6   10  249.231873  50.000412   MedPixel: 11256.0
    7   9   199.231461  50.000412   MedPixel: 11228.0
    8   8   149.231049  50.000412   MedPixel: 11198.0
    9   7   99.230637   50.000412   MedPixel: 11166.0
    10  6   49.230225   25.000511   MedPixel: 11131.0
    11  5   24.229715   12.500551   MedPixel: 11111.0
    12  4   11.729164   2.932291    MedPixel: 11099.0
    13  3   8.796873    2.932291    MedPixel: 11097.0
    14  2   5.864582    2.932291    MedPixel: 11093.0
    15  1   2.932291    2.932291    MedPixel: 11090.0
    16  0   0.0 0.0 MedPixel: 11087.0

Functions

sampinfo(imagelist[, add_keys, mean, median])

Print information for each sample in the image.