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
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.
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.
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.