User’s Overview of PlateMaker

PlateMaker is a DESI DOS “Application”, a program started by the DOS Architect that provides its services over a PML interface. It provides get and set utilities for setting and retrieving state and data from the PlateMaker service, plus three user-level functions: nfsproc, gfaproc, and fvcproc. Each functional service takes input either through parameters sent with the PML command, or from state set by the set service. Output from any of these services must be retrieved using the get service. The functional services are:

nfsproc

Takes parameteres provided by the Next-Field-Selector, including fiber coordinates (targets), telescope pointing coordinates (raBore and decBore), and a sequence identifier (seqid), and calculates a revised field center coordinates (center), ADC prism positions, and focal plane coordinates for the positiones (positioner_pos).

gfaproc

Takes a catalog of standard stars provided by the Next-Field-Selector (stdstars), and images from the Guider-Focus-Alignment system (gfa_images), and calculates the pointing correction needed to center the focal plane on the target field (gfa_center) and expected pixel positions in the hypethetical case where the telescope is at the correct pointing (gfa_guide).

fvcproc

Takes a catalogs targets from the Next-Field-Selector (targets) and image coordinates of spots in the Fiber View Camera image (merged_fvc_spots), and calculates corrections for the fiber positions (positioner_corr).

Using PlateMaker through DOS walks through the process of using these services using a python interpreter interacting with PlateMaker over PML.

The following diagram represents the data flow graphically: