The Gigapixel Camera #1 (GPC1) uses Orthogonal Transfer Arrays devices, a concept developed by Tonry et al. (1997). The detectors in GPC1 are CCID58 back-illuminated Orthogonal Transfer Arrays (OTAs), manufactured by Lincoln Labora- tory Tonry et al. (2008, 2006). They have a novel pixel structure with 4 parallel phases per pixel (Tonry et al. 2008) and required the development of a new type of controller, Onaka et al. (2008). GPC1 is actually populated with two different kinds of CCID58s, the CCID58a with a three phase serial register, and the CCID58b which has a two phase serial register (Onaka et al. 2012). For the science data discussed in the Pan-STARRS1 papers and presented in the public data release, the devices were always operated without OT and in a normal readout mode, and none of public Pan-STARRS1 data has OT correction. The detectors are read out using a StarGrasp CCD controller, with a readout time of 8 seconds for a full unbinned image. Performance assessments are presented in Tonry et al. (2008); Onaka et al. (2012)
The focal plane of Pan-STARRS1 comprises a total of 60 CCID58 OTA devices Tonry et al. (2008). Each of these devices consists of an 8 × 8 array of individual addressable CCDs called “cells”. The overall format of a single OTA is a 4846×4868 pixel array with a pixel size of 10μm which subtends 0.258 arcsec Each OTA device is made up of 64 cells where each cell is 590×598 pixels. The cells are separated by a gap between columns, that is 18 “inactive” pixels in size, and a gap between rows that is 12 inactive pixels in size. Thus a single OTA device contains a single piece of silicon with 64 cells in an 8×8 array separated by a grid of 7×7 internal streets. Further more, there is physical gap between the devices as mounted in GPC1. The separation between the OTA devices is 1400 microns (approximately 36 arcsec) in the x direction and 2800 microns ( approximately 70 arcsec) in the y-direction. In practice the devices are not perfectly spaced and can have some small rotation with respect to one another.
Fig 3 from Chambers et al. 2016. Gigapixel Camera 1 focal plane layout and mask. The non-functioning cells are blanked out in white. |