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Information for radio amateurs
This page is dedicated to the amateur radio community and lists information related to the BEESAT pico satellite series with respect to the usage of amateur radio frequency bands and the operating times of selected services.
BEESAT radio link
Up- and downlink with picosatellites of the BEESAT series is established by half-duplex GMSK modulated narrow-band radio at 435.9500 MHz. The standard baudrate is 4800 bps but can be switched to 9800 bps for increased channel capacity at higher elevations. Each transmission at the higher baudrate is announced by a small 4800 bps header to allow for adaptive receiver re-configuration. The output power of the satellites is 27 dBm (0.5 W) using quarter-wave monopole antennas with toroidal radiation pattern.
On the data-link layer - as described by the OSI model - radio link communication makes use of scrambling and interleaving features of the modem device itself, namely the CML CMX909b. Forward error correction is also performed internally.
The transport layer uses individual frame headers for addressing multiple satellites and for handling variable length messages. Additionally, backward error correction adds to data consistency and transmission safety when needed (implemented aboard BEESAT-2 and BEESAT-3 only). Both protocol features are realized by the attached microcontroller of the on-board and groundstation TNC.
BEESAT terminal node controller
Telecommand uplink and telemetry downlink always passes the terminal node controllers which are responsible for failure tolerant communication between the on-board computer and the groundstation's telemetry and telecommand server.
You may find a schematics of the TNC in the download section of this page for reference.
BEESAT-1 telemetry format
In order to decode telemetry data of BEESAT-1, please refer to the telemetry stream format definition in the download section of this page.