coor.calc: Calculate World Coordinates from Pixel Coordinates

In esplint/IRACpm: Apply Distortion Correction to SPITZER IRAC Data

Description

Basic calculator of world coordinates from pixel coordinates using a specified pixel bias corrector and optical distortion correction given the central world coordinates of the chips central pixel and rotation angle. Generally these latter variables will be measured by CD.solver.

Usage

coor.calc(pix, pars, crsa, u, v, data, ch)

Arguments

pix	Pixel bias correction polynomial - only cryogenic [3.6] observations need this parameter (ca_pix1 for [3.6]). If calculating post cryogenic data coordinates enter NA
pars	Optical distortion correction polynomial: [3.6] = wa_pars1; [4.5] = wa_pars2
crsa	Vector of world coordinates of the chips central pixel and rotation angle c(RA, DEC, angle). If calculating world coordinates for multiple detections, then rbind the respective c(RA, DEC, angle) for each detection.
u	x pixel coordinate with central pixel set to 0 (i.e., a range of -128 to 128)
v	y pixel coordinate with central pixel set to 0 (i.e., a range of -128 to 128)
data	output of read.in.data for the current dataset or a 2 element vector.
ch	integer value of which channel coordinates are being calculated for: [3.6] = 1; [4.5] = 2.

Details

Function first corrects for pixel bias, then optical distortion, and finally projects the pixel coordinates into world coordinates using the gnomonic projection. Other functions linked to this help page are internal to the coor.calc and should not be used by the user.

If data is the output of read.in.data, the function estimates the time-dependent scale factor using the observation dates recorded in the image headers. If data is a two element vector it assumes that the two numbers are the [3.6] and [4.5] scale-factor-correcting ratios measured independently (from CD.solver3 or CD.solver4).

Value

Returns matrix of calculated RA and DEC (alpha and delta)

Author(s)

Taran Esplin

Examples

data(CD1,ca_pix1,wa_pars1,data1)
options(digits=10)
#using a measured scale factor
coor.calc(ca_pix1,wa_pars1,CD1[[1]][1,],-100,104,CD1[[2]],1)
#estimating a scale factor from HMJD.
coor.calc(ca_pix1,wa_pars1,CD1[[1]][1,],-100,104,data1,1)
#the difference for this point in the array is ~2 mas

esplint/IRACpm documentation built on May 16, 2019, 8:52 a.m.