The MERLIS satellite is an amateur radio satellite currently under development by the Amateur Radio Club of the University of Science and Technology of China.
DOC VERSION: 1 @ MAR 28, 2025
Functional Description of Satellite Sub-systems
Satellite Platform
A standardized 12U CubeSat platform will be utilized, incorporating subsystems for power supply, attitude determination & control (ADCS), and thermal management.
UHF/VHF Transceiver
This low-IF software-defined transceiver adopts a LilacSat-2-like architecture. Operating at 146 MHz uplink and 436 MHz downlink. It supports FM voice repeat for radio hams, telemetry downlink, telecommand uplink, and over-the-air (OTA) firmware updates.
47 GHz Transceiver
A software-defined radio (SDR) transceiver operating in the 47 GHz band. It features dual operational modes with different data rates, to match different kinds and levels of ground station:
- High-speed DVB-S2(X)-compliant downlink transmitter for UHD video and payload data,
- DVB-S2(X)-based regenerative transponder for video streams/data packets.
Its primary objectives are:
- Provide high-speed data downlink support for payloads,
- Validate mmWave wideband/high-spectral-efficiency communications on CubeSats,
- Characterize Q-band satellite-ground channel properties,
- Enable amateur radio enthusiasts/youth to experiment with advanced communication technologies.
Video Camera
Equipped with an UHD CMOS sensor, wide-angle lens, and multi-bandpass filters. Designed for atmospheric luminous phenomena observation, with emphasis on transient luminous events (TLEs) such as sprite lightning.
Light Beacon
High-intensity LED array featuring:
- > 2,000 lumens output, peak apparent magnitude + 7,
- Naked-eye visibility in low-speed Morse-coded blinking mode,
- ~ 100 kSps maximum modulation rate for optical communication verification,
- Optical tracking beacon for precision orbit determination.
Payload for Children
Student-developed subsystem created by affiliated secondary school teams, to focus on simple, inspirational programs. Utilizes the 47 GHz downlink channel for experimental data transmission.
Electrical Power budget
The satellite employs triple-junction GaAs solar panels with 30 % efficiency. Forty solar cells (80 mm × 40 mm each) are sun-facing, generating ~ 40 W peak power. Accounting for 50 % orbital time in Earth’s shadow, average power generation stabilizes at ~20 W.The operational power budget demonstrates a ~2W margin under nominal duty cycles.
To align with thermal constraints and mission objectives, most payloads activate during shadow periods. Full payload activation in eclipse results in 99 W power dissipation.
The eclipse duration is about 50 minutes, and total energy demand is about 82.5 Wh, which requires nine 18650 Li-ion batteries (3.7 V nominal voltage, 2600 mAh capacity each).
| Parts | Max Power Dissaption (W) | Duty Rate | Avg Power Dissaption (W) |
|---|---|---|---|
| Satellite Platform | 5 | 1 | 5 |
| U/V Transceiver Rx | 2 | 1 | 2 |
| U/V Transceiver Tx | 3 | 0.3 | 0.9 |
| 47GHz Transceiver Rx | 10 | 0.05 | 0.5 |
| 47GHz Transceiver Tx | 50 | 0.05 | 2.5 |
| 8K UHD Camera | 12 | 0.4 | 4.8 |
| Light Beacon | 15 | 0.03 | 0.45 |
| Payload For Children | 2 | 1 | 2 |
| Total | 99 | 18.15 |
Attitude Stabilization
The satellite employs a multi-sensor attitude determination suite comprising:
- Infrared Earth sensors
- Sun sensors
- Magnetometers
- Gyroscopes
A dedicated data fusion algorithm processes sensor inputs to derive high-precision attitude solutions.
For attitude actuation, the system combines:
- Momentum wheels - Primary actuators for routine attitude control
- Magnetic torquers - Secondary actuators for momentum wheel desaturation
This hybrid configuration maintains attitude stability while managing angular momentum accumulation through periodic magnetic desaturation maneuvers.
Radio Link budget
Telecommand
| Name | Value | Unit |
|---|---|---|
| Baud Rate | 9600 | baud |
| Modulation | GMSK | |
| Bandwidth | 4.8 | kHz |
| BER Threshold | 1E-06 | |
| SNR Threshold | 10.57 | dB |
| Frequency | 146 | MHz |
| Distance | 2000 | km |
| Free Space Loss | 141.76 | dB |
| Ground Station Tx Power | 37 | dBm |
| Ground Station Antenna Gain | 3 | dBi |
| Satellite Rx Antenna Gain | -2 | dBi |
| Satellite Rx Power | -103.76 | dB |
| Satellite Rx Noise Temprature | 3000 | K |
| Satellite Rx Noise Power | -127.19 | dBm |
| Satellite Rx SNR | 23.43 | dB |
| Link Margin | 12.86 | dB |
Key Notes:
- Forward Error Correction (FEC):
- Budget excludes FEC gains
- Achievable BER of 1e-6 enables near-error-free decoding with FEC implementation
- Demodulation Scheme:
- Assumes non-coherent demodulation
- Operational Flexibility:
- Maximum downlink rate: 9600 baud
- Supports reduced-speed modes under degraded link conditions
47GHz Uplink
| Name | Mode 1 | Mode 2 | Mode 3 | Mode 4 | Mode 5 | Mode 6 | Unit |
|---|---|---|---|---|---|---|---|
| Modulation | QPSK | QPSK | QPSK | 16APSK | 256APSK | BPSK | |
| FEC Code | 3/5 | 1/4 | 1/4 | 2/3 | 3/4 | 1/5 | |
| Spectrum Efficiency | 1.18 | 0.49 | 0.49 | 2.63 | 5.9 | 0.16 | bps/Hz |
| Es/N0 Threshold | 2.23 | -2.35 | -2.35 | 8.97 | 19.57 | -6.1 | dB |
| Frame Length | 64800 | 64800 | 64800 | 64800 | 64800 | 64800 | |
| Symbol Rate | 62.5 | 10 | 2 | 4 | 0.2 | 4 | Msps |
| Max Data Rate | 73.75 | 4.90 | 0.98 | 10.52 | 1.18 | 0.64 | Mbps |
| Roll Off Factor | 0.35 | 0.35 | 0.35 | 0.35 | 0.35 | 0.35 | |
| RF Bandwidth | 84.38 | 13.50 | 2.70 | 5.40 | 0.27 | 5.40 | MHz |
| Distance | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | km |
| Free Space Loss | 185.89 | 185.89 | 185.89 | 185.89 | 185.89 | 185.89 | dB |
| Atmosphere Absorption | 3 | 3 | 3 | 3 | 3 | 3 | dB |
| Total Loss | 188.89 | 188.89 | 188.89 | 188.89 | 188.89 | 188.89 | dB |
| Satellite Rx G/T | -18 | -18 | -18 | -18 | -18 | -18 | dB/K |
| Ground Station Diameter | 5 | 1 | 1 | 3 | 5 | 0.5 | m |
| Aperture Efficiency | 0.6 | 0.6 | 0.6 | 0.6 | 0.7 | 0.6 | |
| Tx Power | 33 | 27 | 18 | 33 | 33 | 18 | dBm |
| Gain | 65.05 | 51.07 | 51.07 | 60.62 | 65.72 | 45.05 | dBi |
| Ground Station Tx EIRP | 98.05 | 78.07 | 69.07 | 93.62 | 98.72 | 63.05 | dBm |
| Satellite Rx SNR | 11.09 | 2.88 | 0.87 | 15.11 | 29.71 | -3.30 | dB |
| Uplink Margin | 8.86 | 5.23 | 3.22 | 6.14 | 10.14 | 2.80 | dB |
VHF FM Voice Uplink
| Name | Value | Unit |
|---|---|---|
| Voice Bandwidth | 4 | kHz |
| Modulate Frequency Delta | 2 | kHz |
| Modulate Index | 0.5 | |
| RF Bandwidth | 12 | |
| RF SNR Threshold at 10dB Output SNR | 9.49 | dB |
| Frequency | 146 | MHz |
| Distance | 2000 | km |
| Free Space Loss | 141.76 | dB |
| Ground Station Tx Power | 37 | dBm |
| Ground Station Antenna Gain | 3 | dBi |
| Satellite Rx Antenna Gain | -2 | dBi |
| Satellite Rx Power | -101.76 | dB |
| Satellite Rx Noise Temprature | 3000 | K |
| Satellite Rx Noise Power | -123.21 | dBm |
| Satellite Rx SNR | 21.45 | dB |
| Link Margin | 11.96 | dB |
Telemetry
| Name | Value | Unit |
|---|---|---|
| Baud Rate | 9600 | baud |
| Modulation | GMSK | |
| Bandwidth | 4.8 | kHz |
| BER Threshold | 1E-06 | |
| SNR Threshold | 10.57 | dB |
| Frequency | 436 | MHz |
| Distance | 2000 | km |
| Free Space Loss | 151.26 | dB |
| Satellite Tx Power | 30 | dBm |
| Satellite Antenna Gain | 0 | dBi |
| Ground Station Rx Antenna Gain | 8 | dBi |
| Ground Station Rx Power | -113.26 | dB |
| Ground Station Rx Noise Temprature | 3000 | K |
| Ground Station Rx Noise Power | -127.19 | dBm |
| Ground Station Rx SNR | 13.93 | dB |
| Link Margin | 3.36 | dB |
Key Notes:
- Forward Error Correction (FEC):
- Budget excludes FEC gains
- Achievable BER of 1e-6 enables near-error-free decoding with FEC implementation
- Demodulation Scheme:
- Assumes non-coherent demodulation
- Operational Flexibility:
- Maximum downlink rate: 9600 baud
- Supports reduced-speed modes under degraded link conditions
47 GHz Downlink
| Name | Mode 1 | Mode 2 | Mode 3 | Mode 4 | Mode 5 | Mode 6 | Unit |
|---|---|---|---|---|---|---|---|
| Modulation | QPSK | QPSK | QPSK | 16APSK | 256APSK | BPSK | |
| FEC Code | 3/5 | 1/4 | 1/4 | 2/3 | 3/4 | 1/5 | |
| Spectrum Efficiency | 1.18 | 0.49 | 0.49 | 2.63 | 5.9 | 0.16 | bps/Hz |
| Es/N0 Threshold | 2.23 | -2.35 | -2.35 | 8.97 | 19.57 | -6.10 | dB |
| Frame Length | 64800 | 64800 | 64800 | 64800 | 64800 | 64800 | |
| Symbol Rate | 62.5 | 10 | 2 | 4 | 0.2 | 4 | Msps |
| Max Data Rate | 73.75 | 4.9 | 0.98 | 10.52 | 1.18 | 0.64 | Mbps |
| Roll Off Factor | 0.35 | 0.35 | 0.35 | 0.35 | 0.35 | 0.35 | |
| RF Bandwidth | 84.375 | 13.5 | 2.7 | 5.4 | 0.27 | 5.4 | MHz |
| Distance | 1000 | 1000 | 1000 | 1000 | 1000 | 1000 | km |
| Free Space Loss | 185.89 | 185.89 | 185.89 | 185.89 | 185.89 | 185.89 | dB |
| Atmosphere Absorption | 3 | 3 | 3 | 3 | 3 | 3 | dB |
| Total Loss | 188.89 | 188.89 | 188.89 | 188.89 | 188.89 | 188.89 | dB |
| Satellite Tx EIRP | 42 | 42 | 42 | 39.5 | 33 | 42 | dBm |
| Ground Station Diameter | 5 | 1 | 1 | 3 | 5 | 0.5 | m |
| Aperture Efficiency | 0.6 | 0.6 | 0.6 | 0.6 | 0.7 | 0.6 | |
| Tx Power | 33 | 27 | 18 | 33 | 33 | 18 | dBm |
| Rx Noise Temprature | 600 | 600 | 600 | 600 | 300 | 600 | K |
| Gain | 65.05 | 51.07 | 51.07 | 60.62 | 65.72 | 45.05 | dBi |
| Ground Station G/T | 37.27 | 23.29 | 23.29 | 32.83 | 40.95 | 17.27 | dB/K |
| Ground Station Rx SNR | 10.30 | 8.10 | 15.09 | 11.82 | 22.94 | 10.92 | dB |
| Downlink Margin | 8.07 | 10.45 | 17.44 | 2.85 | 3.37 | 17.02 | dB |
UHF FM Voice Downlink
| Name | Value | Unit |
|---|---|---|
| Voice Bandwidth | 4 | kHz |
| Modulate Frequency Delta | 2 | kHz |
| Modulate Index | 0.5 | |
| RF Bandwidth | 12 | |
| RF SNR Threshold at 10dB Output SNR | 9.49 | dB |
| Frequency | 436 | MHz |
| Distance | 2000 | km |
| Free Space Loss | 151.26 | dB |
| Satellite Tx Power | 30 | dBm |
| Satellite Antenna Gain | 0 | dBi |
| Ground Station Rx Antenna Gain | 8 | dBi |
| Ground Station Rx Power | -113.26 | dB |
| Ground Station Rx Noise Temprature | 1500 | K |
| Ground Station Rx Noise Power | -126.22 | dBm |
| Ground Station Rx SNR | 12.96 | dB |
| Link Margin | 3.47 | dB |
Transmission Formats
Modulation Modes & Data Rates (Physical Layer)
- High-speed link: GMSK-FM @ 9600 baud
- Low-speed link: GMSK-FM @ 1200 baud
Attached Sync Marker (Link Layer)
- CCSDS Standard ASM: 0x1ACFFC1D
Data Frame Length (Link Layer)
- Fixed-length frames: 255 bytes
- Short frames padded with 0xC0 values
Data Frame Structure (Link Layer)
Reference Standard:
- CCSDS 131.0-B (TM Synchronization and Channel Coding)
Frame Composition:
- Transmission Frame Header
- Data Field
- Validity Check Field
- Frame Error Control Field
Transmission Frame Header Fields
| FIELD | LENGTH | DESCRIPTION |
|---|---|---|
| Satellite Callsign | 5 bytes | To be determined |
| Timestamp | 5 bytes | Composite field: |
| ├── Seconds | 1 byte | |
| ├── Minutes | 1 byte | |
| ├── Hours | 1 byte | |
| └── Days | 2 bytes | |
| Frame Counter | 1 byte | Increments 00→FF, cyclic reset |
| Frame Type Indicator | 1 byte | To be determined |
| Reserved Bits | 4 bytes | To be determined |
Data Field
- Structure defined at network layer (TBD)
Validity Check Field
- RSA 4-byte truncated signature for data integrity/authenticity
Scrambling (Pseudo-Randomization)
- CCSDS-standard scrambler applied pre-channel encoding
Channel Error Correction Coding
Concatenated coding scheme:
- Inner code: (1/2, 7) convolutional code
- Outer code: (255, 223) Reed-Solomon code
