Define "telescope states"

This ADR has been updated 2021-06-22 (after the initial decision) to provide more details.

The  document CS Guidelines provides a general definition of the operational state machine;  analysis is required at each level of monitor and control hierarchy (and for each subsystem and component) to identify which states and state transitions are applicable, what is the meaning of each state and how is the state derived.  There is a need to define the rules for determining the telescope state (and telescope status in general), execution of commands related to state transitions, and interaction between state and mode indicators.   

So far the following has been agreed:

TMC state:

• TMC Central Node derives and reports the overall state of the TMC.
• At this time the roll-up includes: status of the TMC Central Node, Leaf Nodes, and TMC Sub-arrays.  The status of the TANGO DB is also included, if TANGO DB is not available the TMC is unresponsive.
• The roll-up does not include the status of the computing infrastructure.
• After successful initialization, the TMC transitions directly to state=ON.  Justification: States OFF and STANDBY as defined in the SKA Telescopes are related to power (OFF means power is not provided, STANDBY means that the device/subsystem/system uses less then 5% of the total power budget).  Given that the TMC consists of software components which are all  fully activated during initialization there is no need to implement STANDBY state.   This decision may be changed  if the computing platform where TMC is running is required to implement STANDBY state.
• PI11 version: State of the Telescope Alarm Handler, Engineering Data Base and Central Logging Repository is not taken in consideration when deriving the overall state of TMC.  This is a temporary solution and requires further consideration.
• Currently command Off() simply causes transition in the state=OFF where TANGO Device does not accept commands other then Standby() (or On() if STANDBY  is not implemented).  
  • Should Off() cause the TMC software to terminate?  -  this requires further consideration.

Telescope state:

• TMC implements attribute Telescope state and commands that trigger Telescope state transitions.
• TMC implements attributes that indicate availability of the processing modes: imaging, pulsar-search, pulsar-timing and vlbi.
• To determine the overall state of the telescope, TMC takes in consideration:
  • for Mid Telescope: status of the Dishes, CSP and SDP.
  • for Low Telescope: status of the MCCS, CSP and SDP.
• PI11 version implements only rudimentary functionality and does not take in consideration status of: OET, Alarm Handler, EDA, SAT (clocks and frequency reference), RFI monitors, weather station, network and other infrastructure.

Additional indicators will be provided for tracking and reporting availability of resources. For example TMC shall inform users:

How many dishes, stations can be used; how many pulsar beams and pulsar timing beams can be formed and processed; how many VLBI beams can be processed, and more.