HAP Parameters

Shown below are the parameters that are used by the Hubble Advanced Products. We include the parameter, the default value for WFC3 processing, and a description of that parameter.

Initialize HAP

_mdriztab_btn_: str (default=Update From MDRIZTAB)

Immediately read and use the values from the MDRIZTAB.

runfile: str (default=”astrodrizzle.log”)

File for logging the processing.

wcskey: str (default=””)

WCS version to use in processing

proc_unit: str (default=”native”)

Units used during processing: “native”, “electrons”

coeffs: bool (default=True)

Use header-based distortion coefficients?

context: bool (default=True)

Create context image during final drizzle?

group: str (default=””)

Single extension or group to be combined/cleaned.

build: bool (default=True)

Create multi-extension output file for final drizzle?

crbit: int (default=4096)

Bit value for CR ident. in DQ array.

stepsize: int (default=10)

Step size for drizzle coordinate computation.

resetbits: int (default=”4096”)

Bit values to reset in all input DQ arrays.

num_cores: int (default=1)

Max CPU cores to use (n<2 disables, None = auto-decide).

in_memory: bool (default=False)

Process everything in memory to minimize disk I/O?

Instrument Parameters

gnkeyword: str (default=”ATODGNA,ATODGNB,ATODGNC,ATODGND”)

rnkeyword: str (default=”READNSEA,READNSEB,READNSEC,READNSED”)

Keyword used to specify a value, which is used to override the instrument specific default readnoise values. The value is assumed to be in units of electrons. This parameter should not be populated if the rdnoise parameter is in use.

expkeyword: str (default=”EXPTIME”)

Keyword used to specify a value, which is used to override the default exposure time image header values. The value is assumed to be in units of seconds. This parameter should not be populated if the exptime parameter is in use.

gain: str (default=””)

Value used to override instrument specific default gain values. The value is assumed to be in units of electrons/count. This parameter should not be populated if the gainkeyword parameter is in use.

rdnoise: str (default=””)

Value used to override instrument specific default readnoise values. The value is assumed to be in units of electrons. This parameter should not be populated if the rnkeyword parameter is in use.

exptime: str (default=””)

State of input files

restore: bool (default=False)

Copy input files FROM archive directory for processing?

preserve: bool (default=False)

Copy input files to archive directory, if not already archived?

overwrite: bool (default=False)

Copy input files into archive, overwriting if required?

clean: bool (default=True)

Delete temporary files after completion?

Step 1: Static mask

static: bool (default=True)

Create static bad-pixel mask from the data?

static_sig: float (default=4.0)

Sigma*rms below mode to clip for static mask

Step 2: Sky Subtraction

skysub: bool (default=False)

Turn on or off sky subtraction on the input data. When skysub is set to no, then skyuser field will be enabled and if user specifies a header keyword showing the sky value in the image, then that value will be used for CR-rejection but it will not be subtracted from the (drizzled) image data. If user sets skysub to yes then skyuser field will be disabled (and if it is not empty - it will be ignored) and user can use one of the methods available through the skymethod parameter to compute the sky or provide a file (see skyfile parameter) with values that should be subtracted from (single) drizzled images.

skymethod: str (default=”match”)

Sky computation method: “globalmin+match”,”localmin”, “globalmin”, “match”. See astrodrizzle.help for more details.

skystat: str (default=”median”)

Statistical method for determining the sky value from the image pixel values: “median”,”mode”,”mean”.

skywidth: float (default=0.1)

Bin width of histogram for sampling sky statistics (in sigma)

skylower: float (default=-100.0)

Lower limit of usable data for sky (always in electrons)

sky_bits: int (default=”16”)

nteger mask bit values considered good pixels in DQ array

skyupper: int or null (default=null)

Upper limit of usable data for sky (always in electrons)

skyclip: int (default=5)

Number of clipping iterations

skylsigma: float (default=4.0)

Lower side clipping factor (in sigma)

skyusigma: float (default=4.0)

Upper side clipping factor (in sigma)

skymask_cat: str (default=””)

Catalog file listing image masks

use_static: bool (default=True)

Use static mask for skymatch computations?

skyfile: str (default””)

Name of file with user-computed sky values to be subtracted

skyuser: str (default””)

KEYWORD indicating a sky subtraction value if done by user

Step 3: Drizzle Separate images

driz_separatebool (default=False)

This parameter specifies whether or not to drizzle each input image onto separate output images. The separate output images will all have the same WCS as the final combined output frame. These images are used to create the median image, needed for cosmic ray rejection.

driz_sep_bits: int (default=”16”)

Integer sum of all the DQ bit values from the input image’s DQ array that should be considered ‘good’ when building the weighting mask. This can also be used to reset pixels to good if they had been flagged as cosmic rays during a previous run of AstroDrizzle, by adding the value 4096 for ACS and WFPC2 data. Please see the section on Selecting the Bits Parameter for a more detailed discussion.

driz_sep_kernel: str (default=”turbo”)

Used for the initial separate drizzling operation only, this parameter specifies the form of the kernel function used to distribute flux onto the separate output images. The current options are: ‘square’, ‘point’, ‘turbo’, ‘gaussian’, and ‘lanczos3’. The latter two options (‘gaussian’ and ‘lanczos3’) are not guaranteed to conserve flux, but may produce reasonable results; understand the effects of these kernels before using them. A former option ‘tophat’ has been removed as it was found to produce poor results. See adrizzle.help for more details.

driz_sep_wt_scl: float (default=exposure time (from image header))

This parameter specifies the weighting factor for input image. If driz_sep_wt_scl=exptime, then the scaling value will be set equal to the exposure time found in the image header. The use of the default value is recommended for producing optimal behavior for most scenarious. It is possible to set wt_scl=‘expsq’ for weighting by the square of the exposure time, which is optimal for read-noise dominated images.

driz_sep_pixfrac: float (default=1.0)

Fraction by which input pixels are “shrunk” before being drizzled onto the output image grid, given as a real number between 0 and 1. This specifies the size of the footprint, or “dropsize”, of a pixel in units of the input pixel size. If pixfrac is set to less than 0.001, the kernel parameter will be reset to ‘point’ for more efficient processing. In the step of drizzling each input image onto a separate output image, the default value of 1.0 is best in order to ensure that each output drizzled image is fully populated with pixels from the input image. For more information, see the help for the drizzle task.

driz_sep_fillval: int or INDEF (default = null)

Value to be assigned to output pixels that have zero weight, or that receive flux from any input pixels during drizzling. This parameter corresponds to the fillval parameter of the drizzle task. If the default of INDEF is used, and if the weight in both the input and output images for a given pixel are zero, then the output pixel will be set to the value it would have had if the input had a non-zero weight. Otherwise, if a numerical value is provided (e.g. 0), then these pixels will be set to that value.

driz_sep_compress: bool (default=False)

Whether to use compression when writing out product.

Step 3a: Custom WCS for Separate Outputs

driz_sep_wcs: bool (default=False)

Define custom WCS for seperate output images?

driz_sep_refimage: str (default=””)

Reference image from which a WCS solution can be obtained.

driz_sep_rotfloat or null (default=null)

Position Angle of output image’s Y-axis relative to North. A value of 0.0 would orient the final output image to be North up. The default of INDEF specifies that the images will not be rotated, but will instead be drizzled in the default orientation for the camera with the x and y axes of the drizzled image corresponding approximately to the detector axes. This conserves disk space, as these single drizzled images are only used in the intermediate step of creating a median image.

driz_sep_scalefloat or null (default=null)

Linear size of the output pixels in arcseconds/pixel for each separate drizzled image (used in creating the median for cosmic ray rejection). The default value of INDEF specifies that the undistorted pixel scale for the first input image will be used as the pixel scale for all the output images.

driz_sep_outnxint or null (default=null)

Size, in pixels, of the X axis in the output images that each input will be drizzled onto. If no value is specified, the smallest size that can accommodate the full dithered field will be used.

driz_sep_outnyint or null (default=null)

Size, in pixels, of the Y axis in the output images that each input will be drizzled onto. If no value is specified, the smallest size that can accommodate the full dithered field will be used.

driz_sep_rafloat or null (default=null)

Right ascension (in decimal degrees) specifying the center of the output image. If this value is not designated, the center will automatically be calculated based on the distribution of image dither positions.

driz_sep_decfloat or null (default=null)

Declination (in decimal degrees) specifying the center of the output image. If this value is not designated, the center will automatically be calculated based on the distribution of image dither positions.

driz_sep_crpix1: float or null (default=null)

Reference pixel X position on output (CRPIX1).

driz_sep_crpix2: float or null (default=null)

Reference pixel Y position on output (CRPIX2).

Step 4: Create Median Image

median: bool (default=False)

Create a median image?

median_newmasks: bool (default=True)

Create new masks when doing the median?

combine_type: str (default=”minmed”)

Type of combine operation. “minmed”,”iminmed”,”median”,”mean”,”imedian”,”imean”,”sum”.

combine_nlow: int (default=0)

Minmxa, number of low pixels to reject.

combine_nhigh: int (default=1)

Minmxa, number of high pixels to reject.

combine_maskpt: float (default=0.3)

Percentage of weight image value below which it is flagged as a bad pixel.

combine_nsigma: str (default=”4 3”)

Significance for accepting minimum instead of median.

combine_lthresh: ??? (default=null)

Lower threshold for clipping input pixel values.

combine_hthresh: ??? (default=null)

Upper threshold for clipping input pixel values.

combine_grow: int (default=1)

Radius (pixels) for neighbor rejection.

combine_bufsize: ??? (default=null)

Size of buffer(in Mb) for each input image.

Step 5: Blot back the median image

blot: bool (default=False)

Blot the median back to the input frame?

blot_interp: str (default=”poly5”)

Interpolant (nearest,linear,poly3,poly5,sinc)

blot_sinscl: float (default=1.0)

Scale for sinc interpolation kernel

blot_addsky: bool (default=True)

Add sky using MDRIZSKY value from header?

blot_skyval: float (default=0.0)

Custom sky value to be added to blot image

Step 6: Remove cosmic rays with deriv, driz_cr

driz_cr: bool (default=False)

Perform CR rejection with deriv and driz_cr?

driz_cr_snr: str (default=”5.0 4.0”)

Driz_cr.SNR parameter*

driz_cr_grow: int (default=1)

Driz_cr_grow parameter

driz_cr_ctegrow: int (default=0)

Driz_cr_ctegrow parameter

driz_cr_scale: str (default=”3.0 2.4”)

Driz_cr.scale parameter

driz_cr_corr: bool (default=False)

Create CR cleaned _crclean file and a _crmask file?

Step 7: Drizzle final combined image

driz_combine: bool (default=True)

Perform final drizzle image combination?

final_pixfrac: float (default=1.0)

Linear size of drop in input pixels

final_fillval: int (default=null)

Value to be assigned to undefined output points

final_bits: str (default=”65535”)

Integer mask bit values considered good

final_maskval: ??? (default=null)

Value to be assigned to regions outside SCI image

final_wht_type: str (default=”EXP”)

Type of weighting for final drizzle

final_kernel: str (default=”square”)

Shape of kernel function

final_wt_scl: str (default=”exptime”)

Weighting factor for input data image

final_units: str (default=”cps”)

Units for final drizzle image (counts or cps)

Step 7a: Custom WCS for final output

final_wcs: bool (default=True)

Define custom WCS for final output image?

final_rot: float (default=0.0)

Position Angle of drizzled image’s Y-axis w.r.t. North (degrees)

final_refimage: str (default=””)

Reference image from which to obtain a WCS

final_scale: int (default=null)

Absolute size of output pixels in arcsec/pixel

final_outnx: int (default=null)

Size of FINAL output frame X-axis (pixels)

final_outny: int (default=null)

Size of FINAL output frame Y-axis (pixels)

final_ra: float (default=null)

right ascension output frame center in decimal degrees

final_dec: float (default=null)

declination output frame center in decimal degrees

final_crpix1: ??? (default=null)

Reference pixel X position on output (CRPIX1)

final_crpix2: ??? (default=null)

Reference pixel Y position on output (CRPIX2)