D-SAT OBDH & COM
On-Board data protocol based on Cubesat Space Protocol, a small network-layer delivery protocol designed for Cubesats. The protocol is based on a 32-bit header containing both network and transport layer information. The layering of CSP corresponds to the same layers as the TCP/IP model.
D-Sat main addresses are: 1 (D-SAT Unit 1 OBC) and 4 (D-SAT Unit2 OBC).
The communication system is composed of a turnstile omnidirectional antenna circularly polarized and a UHF transceiver module able to transmit up to 1 Watt.
The UHF communication subsystem has three main functions:
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to transmit a beacon signal (a Morse signal FM modulated) as tracking signal;
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to transmit and receive Telemetry and Tele-command;
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to transmit and receive experiment data.
The link frequency value is 437.505 MHz.
The transceiver uses a FSK modulation over FM signal at a baud rate of 4800 bps.
The data are coded with a Reed-Solomon (255,223) coding and randomized according to CCSDS standard.

D-ORBIT GROUND station
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Yagi-Uda Antenna
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Gain = 15.5 dBi
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19 elements
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Azimuth and Elevation Rotators
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Transmitted Power = 20 W
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Kenwood TS-2000 amateur radio transceiver
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PCs with Software Defined Radio and software for satellite prediction
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Terminal Node Controller: MSK modem and CSP router


practical information
SIGNAL's CHARACteristics
BEACON
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FM Signal @ 437.505 MHz
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CW tone @800 Hz
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WPM 20 PARIS alphabet
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Period 90 sec
DATA
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FM Signal @ 437.505 MHz
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FSK @4800 bps.
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Reed-Solomon (223,255)
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CCSDS Randomization
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Protocol: CSP
Possible Data Frame are:
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D-SAT Real Time Telemetry (CSP port 18);
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D-SAT Reentry Telemetry (CSP port 21/22);
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SatAlert MAMES message (CSP port 29).

WHAT DO YOU NEED TO RECEIVE d-sat
D-Orbit suggests using a directive antenna with a minimum antenna gain of 12 dBi and linear polarization.
The antenna shall be steerable in order to track the satellite during the visibility windows; it’s necessary an Azimuth and Elevation Rotator controlled by a computer.
In order to receive and decode D-SAT signal, it’s enough to connect the antenna to an FM transceiver and the transceiver’s AF output port to a computer soundcard. It’s important to remind that the transceiver shall feature a remotely controllable frequency for Doppler Shif compensation and the FM demodulator shall have a minimum bandwidth of 10 kHz.
The Audio Frequency (AF) signal from the transceiver can be processed by a software provided by D-Orbit or recorded at 48000 sample per second for future post-processing.
An alternative solution for D-SAT signal reception may foresee the use of a Software Defined Radio (e.g. AirSpy Mini) that connects directly the computer with the antenna.
D-Orbit will provide a software based on GNU radio for D-SAT signal decoding able to handle different sources like as: pre-recorded audio files stored on the computer at 48ksps, soundcard input, Airspy Mini SDR and RTL-SDR. The software runs on Ubuntu 14.04 and includes the following main features:
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D-SAT Beacon Morse Decoding
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D-SAT data decoding
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MAMES message parsing and printing
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D-SAT data upload to dedicated database
Please note that D-Orbit shall not be considered responsible for any malfunctioning or damages due to activities presented on this page.