Spitzer Documentation & Tools

IRAC High Precision Photometry

PCRS Peak-Up Results

PCRS peak up is an adaptive positioning technique on board Spitzer that uses the Spitzer Pointing Calibration and Reference Sensor (PCRS) to enhance the precision of positioning a source on a designated sub-pixel location.  The PCRS operates in the visual part of the spectrum (505-595 nm) and its main function is to calibrate and remove the optical offset between the star trackers and the telescope.  It can measure centroids of stars in the 7.0 mag < V < 12.1 mag range to within 0.14″ (1σ radial) and feed these data, in the form of a pointing correction, to the spacecraft pointing control system (PCS).  The PCRS was frequently used in the Spitzer cryogenic mission with the Infrared Spectrograph (IRS).  

As we show below, PCRS Peak-Up allows us to repeatedly place a target within a preselected 0.5 x 0.5 pixel region of the IRAC arrays (the "Sweet Spot"; see Repeatable Pointing) in 98% of trials. To optimize your choice of guide stars, see Effective Use of the PCRS Peak-Up Catalog.  

Peak-Up mode was enabled for general IRAC users in January 2012.  Between that date and April 2014, observers used Peak-Up in 556 CH1 851 CH 2 AORs 


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