Applying Array Layout Through TMC

Overview

This page provides instructions for applying an Array Layout configuration through the TMC for SKA-Low.

TMC allows operators to specify which Array Layout should be used for observations by providing its reference in the AssignResources command.

When the Array Layout is applied successfully, TMC distributes it automatically to all relevant subsystems during configuration.

How to Apply Array Layout

There are two ways to apply an Array Layout in TMC:

1. Set a Telescope-level Default Layout

   Define a default layout once at telescope level. This layout applies automatically to all subarrays unless a specific layout is later provided. You can set this using the DefaultArrayLayoutURL attribute.

2. Set a Subarray-specific Layout

   Provide a custom layout for a particular subarray using the telmodel section in the AssignResources JSON payload. This overrides the default layout only for that subarray. You can confirm that the ArrayLayoutURL attribute reflects the correct layout reference.

Note

The telmodel section is optional. If it is not included in the AssignResources JSON, the system will use the default Array Layout already configured.

AssignResources Example

The Array Layout can be provided as part of the AssignResources command using the telmodel section.

This feature is supported from schema version "https://schema.skao.int/ska-low-tmc-assignresources/4.3" onwards.

Only this section is new — the rest of the AssignResources JSON remains unchanged.

Example:

{
  "interface": "https://schema.skao.int/ska-low-tmc-assignresources/4.3",
  "transaction_id": "txn-00000-assign-low-4.3",
  "subarray_id": 1,
  "telmodel": {
    "source_uris": [
      "gitlab://gitlab.com/ska-telescope/ska-telmodel-data?main#tmdata"
    ],
    "array_layout_path": "instrument/ska1_low/layout/low-layout.json"
  },
  ...
}

Explanation of the telmodel Section

The telmodel section provides the reference to the Array Layout data stored in the TelModel repository.

• source_uris Specifies the source location of the TelModel data repository. This can be a URI pointing to the repository containing the telescope configuration data. In the example above, it points to the official SKA TelModel data repository.

  Example: "gitlab://gitlab.com/ska-telescope/ska-telmodel-data?main#tmdata" → Fetches layout data from the main branch of the ska-telmodel-data repository, under the tmdata directory.

• array_layout_path Specifies the path within the TelModel data where the layout JSON file is located.

  Example: "instrument/ska1_low/layout/low-layout.json" → Refers to the layout file defining the SKA-Low array configuration.

Behavior Scenarios

This section explains how TMC behaves under different layout assignment conditions.

1. Default layout only

   • If a default layout is set (via DefaultArrayLayoutURL), it applies automatically to all subarrays.

   • No telmodel section is required in the AssignResources payload.

2. Custom layout for a subarray

   • If a telmodel section is provided, that subarray will use the specified layout.

   • Other subarrays continue using the default layout.

3. Multiple AssignResources calls

   • When AssignResources is issued multiple times:

     • If the latest JSON includes a telmodel section, that layout replaces the previous one.

     • If the latest JSON does not include a telmodel section, the last successfully applied layout remains active.

4. Optional use of telmodel section

   • The telmodel block is not mandatory.

   • If omitted, the default or previously applied layout continues to be used.