Tel.: +7 4712 50-48-20, Fax: +7 4712 50-48-00

E-mail: rector@swsu.ru

 

The Southwest State University is located in Kursk, Central Russia

Space activity

Autonomous intellectual grouping of CubeSats

 

Mission: Designing interfaces and protocols for peer-to-peer communication networks for the self-organization of an intellectual grouping of small satellites

 

Purpose: Development of functioning algorithms and production of hardware and software for the implementation of communication channels and the exchange of satellite data with each other, and satellites with a ground station.

 

The composition of the grouping:

The CubeSat Tanusha-SWSU-1, the RS6S call sign,

The CubeSat Tanusha-SWSU-2, the RS7S call sign.

 

Parameters of the transmitted signal: operating frequency 437.05 MHz, FM modulation type, channel bandwidth 25 kHz, analog-audio (mono) modulating signal.

Protocol telemetry: analog protocol AX.25, the data rate of 9600 bps.

 

Brief description of the experiment.

Two satellites will be deployed by hand. The transceivers will turn on 10 minutes after the power is turned on. The main task of the two satellites is to create a peer-to-peer information network that allows the addressing of newly arrived satellites and eliminating failed ones without remote control. The information network will be able to exist longer than a single satellite, as long as there is at least one working satellite in orbit. Inside the network, a retransmission and parallel transmission to a ground monitoring station will be established. The task will be considered successful, if at the ground monitoring station it will be possible to receive telemetry from each satellite in conjunction with the retransmitted telemetry of the remote satellite.

 

Composition CubeSat Tanusha-SWSU

cosmos_2

Each satellite has an inertial navigation system for determining the angles of rotation in three axes: yaw, pitch and rotation.

 

This can be used to monitor the position of the satellite relative to the axis of movement. Each satellite has a vacuum meter that measures the density of vacuum by calculating the concentration of neutral and charged particles.

Each satellite transmits telemetry and a voice greeting in four languages: Russian, Spanish, English and Chinese. The period for sending voice messages is 3 minutes.

To arrange reception of data for radio amateurs, it is recommended to study the algorithm-cyclogram of reception.

 

The reception of signals is available to all radio amateurs and is not encrypted. The satellites are controlled via a closed encrypted uplink and occur only in abnormal situations. The grouping of satellites is autonomous and transmits telemetry according to the protocol given in the table.

 

Telemetry of a CubeSat Tanusha-SWSU in the format of the AX25 protocol

Characteristic Parameter The starting position in the package Data type Range Unit of measurement
Package header 0 Hexadecimal number 0xEA23
Satellite ID 16 Symbol P or V P – Tanusha-SWSU_1

V – Tanusha-SWSU_2

Time elapsed since the launch 32 Natural number

and 0

0 … 4294967295 Секунда
State of the solar panels of the channel_1 Input voltage of the converter (output for solar panel) 64 Natural number

and 0

0 … 65 535 Millivolt
Input current of the converter (output for the solar panel) 80 Natural number

and 0

0 … 65 535 Milliampere
State of the solar panels of the channel_2

 

Input voltage of the converter (output for solar panel) 96 Natural number

and 0

0 … 65 535 Millivolt
Input current of the converter (output for the solar panel) 112 Natural number

and 0

0 … 65 535 Milliampere
Battery status_1 Voltage of the 1st battery 128 Natural number

and 0

0 … 65 535 Millivolt
Voltage of the 2nd battery 144 Natural number

and 0

0 … 65 535 Millivolt
Battery current, positive charge, negative discharge 160 Integer -32 768 … 32 767 Milliampere
Battery status _2 Voltage of the 1st battery 186 Natural number

and 0

0 … 65 535 Millivolt
Voltage of the 2nd battery 192 Natural number

and 0

0 … 65 535 Millivolt
Battery current, positive charge, negative discharge 208 Integer -32 768 … 32 767 Milliampere
Current in main power supply 224 Natural number

and 0

0 … 65 535 Milliampere
Temperature Battery temperature 1, bank 1 240 Integer -128…127 Degrees Celsius
Battery temperature 1, bank 2 248 Integer -128…127 Degrees Celsius
Battery temperature 2, bank 1 256 Integer -128…127 Degrees Celsius
Battery temperature 2, bank 2 264 Integer -128…127 Degrees Celsius
Temperature of the power board 272 Integer -128…127 Degrees Celsius
Temperature of the transmitter board 280 Integer -128…127 Degrees Celsius
Temperature of the power amplifier module 288 Integer -128…127 Degrees Celsius
Transceiver temperature 296 Integer -128…127 Degrees Celsius
Transceiver Signal Strength The signal strength of the last packet of an autonomous network 304 Integer -128…127 Decibel for 1 milliwatts
The signal strength of the last packet AX25 312 Integer -128…127 Decibel for 1 milliwatts
Experimental data Inertial system: roll 320 Natural number

and 0

0…1799 Degrees multiplied by 10
Inertial system: yaw 336 Natural number

and 0

0…3599 Degrees multiplied by 10
Inertial system: pitch 352 Natural number

and 0

0…1799 Degrees multiplied by 10
Vacuum meter: ADC gain 376 Natural number

and 0

1…128 Reinforcement times
Vacuum meter: current-voltage converter 384 Natural number

and 0

0…3 Resistor number
Vacuum meter: temperature 392 Integer -128…127 Degrees Celsius
Vacuum meter:

Sensor supply voltage

408 Natural number

and 0

0 … 65 535 ADC count
Check sum 376 Hexadecimal number Using the CRC8 algorithm

 

 

To convert the received demodulated audio signal, you can use the line input of the PC sound card (if your transceiver does not decode AX.25). We use the open MixW program.

cosmos_3

The figure shows an example of successful decoding of AX.25 messages. We provide amateur radio project with an open source project for displaying telemetry parameters. The program is written in Microsoft Visual Studio in C # and can be run in Windows 7 or higher.

cosmos_4

If the synchronization is successful, both satellites will transmit each other's telemetry, as shown in the figures. The inscription in the lower figure "Link state is SINC" of green means successful synchronization of two satellites. The presence of packets to the right corresponds to the received telemetry from RS6S and RS7S at the specified time.