Reset-subtraction test 21 Dec 1999 Test to determine if online processing done by PixCel (reset correction, rotate, and assembly) is working correctly. The test data were taken by rgm/aef at Las Campanas on 15 Dec 1999 (the data were obtained by ftp to rigel.lco.cl in /data1/19991215/ioa/irx*fits). Run 9137: Raw data with no on the fly processing One 1024x512 image per chip quadrant containing reset and data portions RRR mode assemble off rotate off subtract off read 000 contains the reset for read 001 read 001 contains the reset for read 002 etc. Run 9138: As above assembled in chips and with reset subraction RRR mode assemble on rotate off subtract on Run 9135: Same as above except that data has been also rotated on the fly so that all datasets are coaligned NS. This is our standard observing mode. RRR mode assemble ON rotate ON subtract ON Test: Assemble and reset-correct run 9137 and make sure this agrees with run 9138. Rotate the assembled/corrected run 9137 and make sure the output agrees with run 9135. The rotations applied to 9137 were 270, 0, 90, and 180 degrees for chip1, chip2, chip3, and chip4 respectively (as specified in the pixcel.ini file). Assembly was done by arranging the quadrants in the image like this: q4 q3 q1 q2 Procedure: IDL> subtract IDL> assemble IDL> diff IDL> rotdiff see programs in /data/cass60d/sabbey/reset/*.pro Result: The difference images (9138-9137 and 9135-9137) are perfectly flat noise images for all loops (difference images and original data are available in /data/cass60d/sabbey/reset). However, a few minor comments: 1) the reset level (mean signal level in the reset portion of the frame) typcically varied between loop 0 and loop 1 but was constant between later loops. For example: cl> imstat irx_09137_c1q1*fits[1:512,*] IMAGE MIDPT MODE STDDEV irx_09137_c1q1_000.fits[1:512,*] 4531. 4516. 260.9 irx_09137_c1q1_001.fits[1:512,*] 4471. 4392. 371.6 irx_09137_c1q1_002.fits[1:512,*] 4472. 4389. 370.9 irx_09137_c1q1_003.fits[1:512,*] 4472. 4389. 369.4 irx_09137_c1q1_004.fits[1:512,*] 4471. 4387. 369.4 2) the difference images do not have a median signal level of 0, especially for loop 1 and loop 2 which have +/- tens of counts. with the reset level known to vary during the first couple of loops, this is possibly not surprising but should probably be looked into more. cl> imstat irx.9135-9137.c3.00?.fits IMAGE MIDPT MODE STDDEV irx.9135-9137.c3.001.fits -19.20 -23.52 66.7 irx.9135-9137.c3.002.fits -29.68 -32.08 67.0 irx.9135-9137.c3.003.fits -2.85 -3.42 64.6 irx.9135-9137.c3.004.fits -7.42 -1.44 66.2 cl> imstat irx.9138-9137.c3.00?.fits IMAGE MIDPT MODE STDDEV irx.9138-9137.c3.001.fits -16.15 -20.62 66.58 irx.9138-9137.c3.002.fits -29.70 -29.61 66.38 irx.9138-9137.c3.003.fits -1.57 -7.22 65.76 irx.9138-9137.c3.004.fits -1.40 2.81 65.86 3) the cross of bad columns/rows at the borders between quadrants sometimes leaves a significant residual in the difference frames. 4) it appears that a dust speck moved between observations leaving a noticeable residual speck in one of the difference frames.