sampinfo

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.

Options

This version will accept a single image name or a python list of images. The list of images should be a python style list, such as:

imagelist = ["image1.fits", "image2.fits"]

add_keys=list(): You can also supply a supplimental list of keywords to print for each sample, if the key isn’t found in the sample the global header will be checked.If a key is not found the “NA” string will be printed. Additionally you can ask for the median or mean of the datavalues for each sample using the appropriate switch.

median=False: Set to True in order to report the median pixel value for each sample

mean=False: Set to True in order to report the mean pixel value for each sample (as measured with np.min and np.max)

Usage

from wfc3tools import sampinfo
sampinfo(imagename)

Where imagename can be a single filename or a python list() of names

To get the median value for each sample:
sampinfo.sampinfo(imagename, median=True)
To print additional keys for information:
sampinfo.sampinfo(imagename,add_keys=[“DETECTOR”])
To get the average balue for each sample:
sampinfo.sampinfo(imagename, mean=True)

Example Output

Default output:

In [3]: wfc3tools.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

with median=True:

In [4]: wfc3tools.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