Glossary

ack: Acknowledgement of command receipt.
ADC: Anti-dispersion corrector.
AO: Adaptive Optics.
AOC: The adaptive optics computer.
APLC: Apodized-Pupil Lyot Coronagraph.
apodizer: The first component of the APLC, residing in a filter wheel at a pupil plane.
assembly: GPI software construct grouping together control of multiple (usually) related mechanisms. Some (notably the PPM and FPM) assemblies only control a single mechanism.
ASU: Artificial Source Unit. The ASU can be deployed into the Gemini f/16 focus (immediately after the ADC, after the OMSS shutter) to provide an internal light source, used for engineering tasks and calibrations. The ASU is equipped with three light sources: the SC and two monochromatic lasers in the visible and IR.
CAL: The Calibration subsystem computer. Also the subsystem itself.
CAL Sphere: Integrating sphere that can be deployed into the light path immediately ahead of the FPM to provide a light source directly to the CAL.
FPM: Focal Plane mask. The second component of the APLC, residing in a filter wheel at a focal plane.
GMB: Global Memory Block. The GMB is shared memory with segments on each of the four GPI computers. It is implemented as a database with key:value pairs, with keys prefixed by the system repsonsible for populating the values.
IFS: The integral field spectrograph computer (also the instrument itself).
IS: Instrument Sequencer. Highest-level software interface between observatory systems and GPI. This exposes GPI commands that can be directly called by the observatory.
Lyot: The third components of the APLC, residing in a filter wheel at a pupil plane.
MCD: Motor Control Device. Also the lowest level of software interfacing with (some) GPI mechanism controllers.
OLM: Open-Loop Model. Multiple components have open loop models intended to automatically correct their settings in response to changes in tempreature and zenith angle (instrument orientation). These changes are only applied when a mechanism is in TRACK.
OMSS: Opto-Mechanical Support Structure. GPI’s skeleton.
oneWire: Device communications bus system for devices employing (unsurprisingly) a single conductor. In GPI, the oneWire assembly includes all temperature, pressure, and humidity sensors other than those inside the IFS and internal to devices (primarily cameras) that have their own sensors.
PnC: Pointing and Centering mirrors. Pairs of mirrors that can be moved to produce pure pointing and/or pure centering changes. GPI has two such pairs: The first is immediately in front of the AO WFS (after the dichroic so only the WFS sees the pointing and centering changes due to these mirrors. The second lies immediately before the CAL exit and is used to steer the beam onto the IFS.
PPM: Pupil-plane Mask. In GPI, this typically refers to the apodizer. The PPM assembly explicitly is for control of the apodizer filter wheel only.
RPC: Remote Procedure Call. The primary mechanism by which commands are sent to and between the GPI subsystems. See also: https://man7.org/linux/man-pages/man3/rpc.3.html
SC: Supercontinuum source. This is a white light laser source with a wavelength range from the visible to just past 2 microns. It can illuminate both the ASU and the CAL Sphere, each of which has an independent attenuator. The SC is chromatic in power setting, and so is always run at 100% power in normal operation. Each attenuator can be set between 2.2 and 60 dB (the latter being the nominal off setting).
SIM: Simulated operation. There exist multiple level of SIMs possible: at the MCD level, at the Assembly level, and at the gpilib2 level. Each of these has different impacts on what actually happens in the system when a command is sent to a simulated component.
TLC: The Top-Level Control computer.
TRACK: Mechanism state where settings changes (in response to an OLM and other inputs) are continuously and automatically applied.
WFS: Wavefront Sensor.