dsat.space   I   info@deorbitaldevices.com

a Space Mission by D-Orbit   I

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:

  • to transmit a beacon signal (a Morse signal FM modulated) as tracking signal;

  • to transmit and receive Telemetry and Tele-command;

  • 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

  • Yagi-Uda Antenna

    • Gain = 15.5 dBi

    • 19 elements

  • Azimuth and Elevation Rotators

    • Transmitted Power = 20 W

  • Kenwood TS-2000 amateur radio transceiver

  • PCs with Software Defined Radio and software for satellite prediction

  • Terminal Node Controller: MSK  modem and CSP router

 

SIGNAL's CHARACteristics

BEACON

  • FM Signal @ 437.505 MHz

  • CW tone @800 Hz

  • WPM 20 PARIS alphabet

  • Period 90 sec

 

DATA

  • FM Signal @ 437.505 MHz

  • FSK @4800 bps.

  • Reed-Solomon (223,255)

  • CCSDS Randomization

  • Protocol: CSP

Possible Data Frame are:

  • D-SAT Real Time Telemetry (CSP port 18);

  • D-SAT Reentry Telemetry (CSP port 21/22);

  • 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:

 

  • D-SAT Beacon Morse Decoding

  • D-SAT data decoding

  • MAMES message parsing and printing

  • 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.

During the initial phase of the mission, D-SAT will automatically transmit a beacon signal to help D-Orbit team in the acquisition of the satellite after the launch.

 

The more people will be listening, the better!

 

The mission has launched on Friday, June 23rd. If you could use the forum to let us know every time you acquire signal or data from the satellite, it would greatly help us. Simply copy and paste in the dedicated section of the forum the textual information generated by the D-SAT Decoder Software. The morse text will be shown in the console of the GNU radio software

 

Other useful information to report are: TLE Satellite number, Position of Ground Station used to receive the information, frequency value of the signal, Signal Strength.

satalert experiment

The experiment consists of the generation and transmission of a MAMES ALERT message, from an Earth station to the satellite, which will process and broadcast the received message back to Earth.

 

Multiple Alert Message Encapsulation Protocol Objectives:

 

  • Powerful encapsulation scheme for embed other alerting alert messages (e. g. Common Alert Protocol (CAP, unstructured text, image, paging protocols, DeCas Alert);

  • Provide a multi-semantic representation of the alert, allowing the interpretation by automated devices with low capabilities;

  • Designed to support transmission over satellite also over limited channels;

  • Fit in the main SatCom and SatNav systems.

EARTH TO SATELLITE PATH

During the visibility period, the Earth station sends to the satellite a MAMES message (maximum width of 4KB).

The MAMES Message will be stored in the satellite On-Board Computer memory.

1.

2.

SATELLITE TO EARTH PATH

As a trigger command is sent by the Earth Station,  the MAMES message stored on the satellite will be broadcasted.

MAMES broadcast transmission will be activated in all the available visibility windows.

3.

4.

D-sat re-entry trajectory reception

During the final phase of the mission, immediately after the activation of the decommissioning device, D-SAT will automatically transmit reentry telemetry frames that include the information about D-Sat position and velocity acquired during the reentry trajectory.

The re-enrty telemetry frames will allow D-Orbit team to evaluate the success of the decommissioning maneuver.

Radio HAMs can participate in the reception and de-encapsulation of the MAMES messages. 

how you can help

 

practical information

 

D-SAT OBDH & COM