April 8/9, 2003 Green Bank GBT PTCS Conceptual Design Review Overview of the High Frequency Observing System Richard Prestage

GBT PTCS Conceptual Design Review – April 8/9, Overview of talk Precise control of the antenna is a necessary but not sufficient condition to produce high-quality 3mm science. Will not discuss details of observation control – see PTCS/SN/5! The division of responsibilities between “antenna control” (PTCS) and “everything else” will remain the same as now. We need to add facilities to the “everything else”.

GBT PTCS Conceptual Design Review – April 8/9, High Frequency Observing System The core of the PTCS project is the PTCS itself => This is the focus of the vast majority of our work. The PTCS must be integrated into the remainder of the Observing System. A number of other capabilities will also be required for 3mm operation (e.g. atmospheric monitoring). These features will be provided as incremental upgrades to the existing Observing System. We refer to the combination of all of these facilities as the High Frequency Observing System.

GBT PTCS Conceptual Design Review – April 8/9, Role of HFOS Provides Observer’s User Interface (i.e. for astronomy) Provides configuration layer – selection of appropriate devices (receiver, backend), configuration of all of these. Devices are independent state machines – synchronized through IRIG, 1PPS and hardware switching signals. HFOS provides observing procedures, and synchronization of data acquisition via the Scan Coordinator. PTCS then controls the antenna to provide the requested optical alignment and trajectory on the sky

GBT PTCS Conceptual Design Review – April 8/9, Interface to the PTCS The PTCS will present a similar interface to the higher-level Observing System as the current Antenna Control Unit. The concept of “scans” and “observations” will remain unchanged. Specification of desired trajectory of primary, subreflector and prime focus axes will continue to be via the “commanded track”. Specification of control strategy (e.g. focus-tracking algorithms) and ancillary information will need to be considerably expanded.

GBT PTCS Conceptual Design Review – April 8/9, Trajectory Specification a list of piecewise parabolic curves (position, velocity, acceleration) each valid over a specified interval of time. “track” and “offset” for primary drives “track” for subreflector e.g. track: single fixed J2000 (ra,dec) position offset: (az,el) starting offset position and fixed velocity to perform a “peak” about a source position Commanded track and offset derived by the HFOS from simple astronomical input (e.g. SOURCE MOON).

GBT PTCS Conceptual Design Review – April 8/9, Additional (non-PTCS) functionality ComponentResponsibilityReq./Goal Dynamic SchedulingExternalGoal Observation Control (spiral scan)CollaborationRequirement R/T monitoring atmos. conditionsExternalGoal R/T monitoring tel. performancePTCS ProjectGoal Antenna trend monitoringPTCS ProjectRequirement Calibration toolsCollaborationRequirement Antenna calibrationPTCS ProjectRequirement Pointing and flux calibratorsPTCS ProjectRequirement Anomalous refraction correctionsCollaborationGoal

GBT PTCS Conceptual Design Review – April 8/9, Supplemental Material

GBT PTCS Conceptual Design Review – April 8/9, Architecture of current GBT Observing System

GBT PTCS Conceptual Design Review – April 8/9, Executing an observation

GBT PTCS Conceptual Design Review – April 8/9, Architecture of HFOS