9.8 APS-Backup-Antenna-Control

The APS-Backup-Antenna-Control logical device is a project specific extension to the sat-nms software. The device controls the switch over procedure between a backup antenna and a number of operative antennas.

Switching the uplink from an operative antenna to the backup antenna is a 2-step procedure. The first step (preparation) positions the backup antenna to the same satellite as the operative antenna and prepares the waveguide switches at the backup antenna for taking over the signal(s) from the operative antenna.

After the preparation has been completed successfully the final switchover is executed as an independent command. The actual switchover is performed by a APS-Backup-Antenna-Switch logical device located at the operative antenna. This sets the waveguide switches there to route the uplink to the backup antenna instead to the local one. Immediately after the switchover this device also increases the transmit power to compensate for the increased waveguide loss to the backup antenna. At the backup antenna M&C, Proxy devices act in place of the remote APS-Backup-Antenna-Switch devices.

Antenna command and verification

As of version 2.00 the APS-Backup-Antenna-Control device expects the backup antenna to be controlled by a SatService ACU/ODM ( SatService-ACU-ODM device driver). During the switchover preparation phase, the APS-Backup-Antenna-Control device commands a target memory number to the ACU/ODM. The target memory in the ACU contains the center of box coordinates of the satellite and the beacon/tracking parameters stored for the satellite normally tracked by the antenna which is going to be backed up.

The center of box coordinates are stored in the APS-Backup-Antenna-Control device's configuration file as well. After the the antenna has been commanded to move to the target in question, the APS-Backup-Antenna-Control device polls the actual antenna pointing and compared it to the pointing stored in the configuration file. Once the pointing matches within a configurable threshold, the APS-Backup-Antenna-Control device states "position reached" and proceeds to the next step.

With this next step the beacon level threshold fault is monitored. The device waits until there is no beacon level stated by the ACU, then the device assumes the antenna points to the satellite.

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

• --- Shows / commands the signal destination setting.
• --- The faults page.
• --- The device info page.
• --- The maintenance page. The configuration parameters from this page are described below.

Configuration parameters

Most of the configuration parameters of the APS-Backup-Antenna-Control device are defined in a configuration file (see below). At the maintenance page of the device window there are a couple of configuration parameter which concern the local (backup) antenna device.

Fault flags

The device provides three fault flags:

• The 'Configuration file FAULT' is set if the device could not parse it's configuration file on startup.
• The 'Switch combination FAULT' is set if the combination of waveguide switch settings does not match any of the configured combinations. Command a 'prepare', optionally followed by a 'release' to reset this fault.
• The 'Switchover procedure FAULT' is set if a fault occurs during a prepare or switchover procedure. The 'reset' command clears this fault.

Configuration file

The APS-Backup-Antenna-Control device requires to be setup by a configuration file. The file has the name of the device (case sensitive!) extended by the suffix '.txt'. The file must reside in the M&C server's home directory. It defines the number of stations this antenna shall backup, the antenna pointings and all switch setting to be performed during the preparation / switchover.

The file format text based, straight forward and almost self-explaining. This is a short example, taken from the real installation in Munich. Everything right of a '#' character is treated as a comment, in the example below those are used used to describe the file format.

#
#  Example for an APS-Backup-Antenna-Control configuration file
#
#
    S1-2X = A    # WG switch setting for the local operation
    S1-2Y = A    # of the backup antenna. The 'forceLocal' command
    S1-3X = A    # tells the APS-Backup-Antenna-Control to perform
    S1-3Y = A    # these settings
    S2-1X = A
    S2-1Y = A
    S1-AX = B
    S1-AY = B
    S2-AX = B
    S2-AY = B

#  The 'station' statement opens the definition of a antenna / M&C to backup.
#  '1A' is the name of the antenna which appears in the selection box a the 
#  APS-Backup-Antenna-Control's user interface.
#  
station 1A

    S1-2X = B    # The WG switch settings following the 'station' statement
    S1-2Y = B    # are performed when the operator commands to prepare the
    S1-3X = B    # take over for this antenna. They are performed immediately,
    S1-3Y = B    # before the antenna gets moved.

    # The 'antenna' statement tells the device where to point the antenna. It
    # must be followed by the target memory number to be invoked at the
    # antenna controller and the azimuth / elevation reference angles on
    # the same line. 
    # 
    antenna  2  169.958  34.115 

    SU-4X = B    # After the antenna has been pointed to the new satellite and
    SU-4Y = B    # tracking has found the satellite, the WG switch settings
    SU-3X = B    # following the 'antenna' statement are performed. After
    SU-3Y = B    # these settings have been verified successfully, the
    S1-AX = A    # backup antenna is prepared for the switchover.
    S1-AY = A   

    # The 'final' statement closes the definition opened by 'station'. It
    # tells the APS-Backup-Antenna-Control device which proxy device
    # has to be controlled in order to execute the actual switchover at the
    # remote antenna. The proxy device must be configured to act for the
    # APS-Backup-Antenna-Switch device at the M&C of interrest.
    # 
    final ASTRA-1A

#  Here starts the definition of the second station (omitted here). The 
#  APS-Backup-Antenna-Control device is capable to manage an arbitrary number
#  of stations.
#  
station 1B
                        

Variables defined by this device driver