Communication

Antenna Deployment

The basic idea

 

The structure of TIsat-1 can accomodate up to four 8mm thick deployables. The deployable hold was designed with antennas in mind, but may be used for any small probe to be exposed in space. In the final implemenetation, after signal strength measurement, only two monopole antennas were used, one for each COMM device.

Ham Radio

TIsat-1 communicates over amateur radio frequencies as most CubeSats do. Frequencies were coordinated with the International Amateur Radio Union (IARU). The coordination process was completed in november 2008.
TIsat-1 is on
  • 437.305 MHz for downlink (beacon, telemetry)

    In the telemetry frames TIsat-1 will periodically identify himself with his unique callsign HB9DE granted by the Swiss Federal Office for Communication (BAKOM).

  • Doubled Radio Subsystem

    TIsat-1 carries two radio devices: a beacon transmitter (entierly developed at SUPSI-DTI) and a commercial FM transceiver.
    The two devices alternate for downlink on even and odd orbits, while an uplink "listen state" is periodically activated via the FM transceiver, regardless of the orbit number.
    For energy balance issues, during eclipse TIsat-1 communicates less data less frequently, solely using the the FM channel.

    OOK Beacon

    437.305MHz; ±2kHz over [-20, +70°]; 400mW.
    The device is qualified to transmit plain Morse characters and NRZ or Manchester encoded binary data at different baudrates.
    During early days of mission the satellite will use slow data rate (i.e. Morse at 15 words-per-minute, WPM), increasing with time up to 110 WPM for enhanced data throughput.
    After ten (Earth's) days the data rate will fall back again to 15 WPM and the sequence is restarted.

    FM transceiver

    300/500 mW; ALINCO DJC-6.
    The FM transceiver is interfaced to both processors of the On Board Computer (OBC). The processors provide binary FSK, AM, PSK (NRZ/Manchester) and plain Morse modulation and demodulation in firmware.
    An integrated DTMF transceiver is also available as alternate communication channel.

    Acknowledgements

    EMC SA, CH-6592 S. Antonino
    Casram SA, CH-6805 Mezzovico
    HB9AUS, HB9MAD, HB9SV and more.

    Documents

    Communication Systems Survey (italian)
    Link Budget