Updated: 2001 June 29
This page provides basic description of the ANDICAM's CCD and IR detectors, including pixel scales and FOV, orientation, gain and readout noise, and other useful data for observing planning and data analysis. The contents of this page should be considered definitive.
CCD Array Parameters
The CCD for the ANDICAM is a Lick/Loral-3 2048x2048 CCD with 15-micron pixels. The CCD is readout with two amplifiers, one for the each of the left and right halves of the detector.
DATASEC1 [49:1072,1:2048] BIASSEC1 [1:32,1:2048] DATASEC2 [1073:2097,1:2048] BIASSEC2 [2113:2144,1:2048] TRIMSEC [49:2096,1:2048]
DATASEC1 [25:536,1:1024] BIASSEC1 [1:16,1:1024] DATASEC2 [537:1048,1:1024] BIASSEC2 [1057:1072,1:1024] TRIMSEC [25:1048,1:1024]
There are electronics problems that give artifacts (low-level, non-fixed pattern bias) and noise on the left half, so most of the science data has been acquired with the right half of the CCD. The IR channel is centered in the middle of the right half of the CCD.
The horizontal readout registers have 16 extra pixels for each readout amplifier that are read before the data pixels in a line. These constitute "hardware underscan" pixels. After reading each line of data, we readout an additional 32 pixels of "overscan" at the end of each line. These latter are used to measure the DC bias level during the readout of that line on that amplifier, and constitute the traditional "overscan" columns familiar to most CCD observers. Our data-taking system repacks the data and under/overscan pixels so that the non-image pixels are to the outside (left and right) of the data sections. This can make it look like the images have extra overscan. The diagram below should clarify this.
IR Array Parameters
The IR Array for the ANDICAM is a Rockwell 1024x1024 HgCdTe "Hawaii" Array with 18-micron pixels. The array is readout in 4 quadrants.
IR Array Notes
The Hawaii is flat to about 20%, with most of the variation being a gradient towards the right-hand side (North) side of the array.
The 4-second readout time means that the minimum integration time with the array is also about 4 seconds (this is the time necessary to rest, preread, then post-read the array and take the difference). Integration times less than 4 seconds will be 4 seconds long.
The array has one round group of ~300 dead pixels located near the right/middle part of the array (see picture), and ~50 scattered hot and dead pixels across the array. These are generally removed by taking at least 5 images at different dither positions. A dithering mirror throw of 10 units (5 arcseconds) is sufficient to remove most bad pixels.
The IR and CCD channels are parfocal, with the IR field of view currently located in the middle of the right half of the CCD field (see this picture, the red box is the IR FOV).
Updated: 2001 June 29 [rwp/osu]