Glossary#

This page contains a brief description of commonly used terms in the context of the Constellation control & data acquisition system.

Constellation#: Either the name of the control & data acquisition software, or a group of Satellites.
Satellite#: Central component of a Constellation containing a Finite State Machine as well as communication modules to receive and process commands from Controllers.
Controller#: Component of a Constellation which can send commands to Satellites and thereby control their state. Often controllers also receive Heartbeats from the Constellation in order to show the most up-to-date state information available. Controllers are stateless and can be restarted at any time.
Finite State Machine#: Central component of any Satellite which keeps track of the current state of the satellite and its attached instrument hardware, and which controls which transitions into other states are currently allowed.
Transition#: Change from one state of the Finite State Machine to another state, triggered either by a transition command sent by a Controller or by an autonomous reaction.
Telemetry#: System to send, distribute and receive monitoring information.
Transmitter#: A Satellite which can transmit data to Receiver satellites. These satellites usually control instruments which generate data. They retrieve data from the instrument data acquisition and send them to storage.
Receiver#: A Satellite which can receive data from one or multiple Transmitter satellites. Usually represents a storage note which received instrument data and saves it to disk or to a database.
Listener#: Passive component of a Constellation which can subscribe to Heartbeats, Telemetry or logging information and display them to the operator. Listeners are stateless and can be restarted at any time.
Run#: One individual measurement, characterized by a Finite State Machine transition into and out of the RUN state.
Measurement Queue#: Series of measurement runs mediated through a Controller. Each of these measurements can have a different set of parameters for the participating Satellites, which is passed to them via the reconfiguring Transition.
Heartbeats#: Messages distributed by Satellites in regular intervals to all other components of the Constellation. These heartbeat messages contain the current Finite State Machine state along with some message flags indicating the desired treatment of the sender.