SDSS - getting separate u, g, r, i, z frames from SWARP tool and astropy

I am following this paper to extract the u,g,r,i,z image frames from the SDSS image fits files. I have the fits files downloaded (using the bulk data download option from SDSS) and tried to run the SWARP tool to get the resampled image as output, which I will access through astropy. I am still unclear on the exact parameters that will make up the entire SWARP command. So far I have:

swarp frame-i.fits[0] frame-r.fits[0] frame-g.fits[0] frame-u.fits[0] frame-z.fits[0] -SUBTRACT_BACK N -RESAMPLE Y -RESAMPLING_TYPE LANCZOS3 -IMAGE_SIZE 64,64 -IMAGEOUT_NAME attempt.fits


This is written with the description of it in the paper, which is:

With the command that has been run, I am getting quite noisy images as output that do not relay any sort of information. What am I doing wrong in this process?

What you are telling SWarp to do is something different: combine five individual-filter images into a single "$$u+g+r+i+z$$" image. (People do sometimes do this sort of thing, though with SDSS images they would normally just use the g, r, and i images, since the u and z images are so low-S/N that they mainly just add noise to the result. And in any case this isn't what the paper you're interested in was doing.)
• Thanks for the clarification. I understand that the command that I've entered will not give me what I want. However, I'm new to this and have been using SWARP in many different combinations. I've also tried swarp frame-z.fits[0] -SUBTRACT_BACK N -RESAMPLE Y -RESAMPLING_TYPE LANCZOS3 -IMAGE_SIZE 64,64. It does not give the expected result when extracted through astropy, please view here. Would you know why? Thanks once again. Oct 26 '20 at 10:53
• hdr = astropy.io.fits.getheader("/path/to/image.fits") Nov 11 '20 at 11:42
• cd1_1,cd1_2,cd2_1,cd2_2 = hdr['CD1_1'],hdr['CD1_2'],hdr['CD2_1'],hdr['CD2_2']  Nov 11 '20 at 11:45
• rot = math.degrees(math.atan2(math.radians(cd2_1), math.radians(cd1_1))) Nov 11 '20 at 11:45