BIRDS-2S Project

Maya 1.1 & Maya 1.2

Overview

Maya-1.1 and Maya-1.2 are the first Philippine-homemade satellites developed by the first batch of STeP-UP scholars under DOST’s STAMINA4Space Program. The project aims to gain and extend locally the knowledge and skills on satellite development acquired from foreign schooling and utilize the domestic capabilities for satellite development.

Through the STeP-UP Project, the BIRDS-2S is also a collaboration between the University of the Philippines Diliman and Kyushu Institute of Technology. BIRDS-2S is also guided by the expertise by members of the Joint Global Multi-Nation Birds Project, a cross-border interdisciplinary satellite project that aids non-space faring countries in satellite development and where the Philippines has taken part during its second (BIRDS-2) and fourth (BIRDS-4) iterations. Currently, the knowledge and hands-on experience on satellite development are locally being shared and done under BIRDS-2S to further build capacities and expand the knowledge base on space science and technology in the country.

Mission

The Maya-1.1 and Maya-1.2 cube satellites (or CubeSats) share the same bus, which is based on Maya-1. However, they differ when it comes to the payload. Their missions are as follows:

  1. Automatic Packet Reporting System - Digipeater (APRS-DP) provides digital message relay service to the amateur radio community by means of an APRS digipeater onboard.The APRS digipeater will receive from and digipeat an APRS message/packet to any licensed ham on footprint with APRS-capable handheld or station radio. (Maya-1.1 & Maya-1.2)
  2. Store and Forward (S&F) collects data from remote ground sensors such as temperature, humidity, wind speed, etc, stores them onboard and download them to BIRDS-2S ground stations using VHF amateur band. (Maya-1.1 & Maya-1.2)
  3. 5MP visual camera that will take photos and/or videos of the country. (Maya-1.1)
  4. Near-infrared camera and thermal camera for taking images of the Philippines. (Maya-1.2)

Structure and Functional Description


1. Structure

BIRDS-2S cube satellites measure 10x10x11.35 cm with an estimated mass of 1.1kg. Both satellites feature two (2) deployable UHF and VHF antennas, solar array panels, GPS patch antenna, and lever switch. Maya-1.1 carries two 5MP visual camera to support one of its missions. While, Maya-1.2 is equipped with a near infrared and thermal camera. The satellites' attitudes are passively stabilized by permanent magnets and hysteresis dampers.

2. Command and Data Handling

The On-Board Computer (OBC) is the heart of the cube satellite. It consists of two (2) microcontrollers which are responsible for starting mission, storing data, forwarding data to the ground stations, and resetting the system.

Generally, the main task of the OBC is managing all the functions of the satellite. Specifically it covers the following tasks:

  1. Send CW (Morse) through the Communication (COM) subsystem every time it passes to the ground station;
  2. Receive the Tele-command from ground station through COM sub-system;
  3. Verify the commands from the ground station and send an acknowledgement;
  4. Execute the received commands;
  5. Manage (collect, process and store) Housekeeping data and Mission Data;
  6. Send Housekeeping data and Mission data to ground station thru COM subsystem; and
  7. Monitor the satellite health parameters.

3. Communication

Maya-1.1 and Maya-1.2 cube satellites will receive uplink commands thru UHF receiver. The Command signals from the ground station will be received by a UHF dipole antenna, demodulated and then decoded and executed by the OBC. Telemetry and mission downlinks will be performed by the UHF transmitter. Finally, Morse-coded beacon will be sent to ground at 20 words/minute by the CW transmitter.

Table 1: Link Budget

Mission Downlink
Center Frequency437.375 MHz
Mean Orbital Altitude400 km
ParametersElevation Angle
10 deg80 deg
SC RF Transmit Power (W)0.80.8
SC RF Transmit Power (dBm) 29.03 29.03
SC Transmission Line Loss (db) 0.13 0.13
SC Antenna gain (dBi) 2.14 2.14
SC EIRP (dBm) 30.93 30.93
GS pointing loss (dB) 3 3
Polarization Loss (dB) 3 3
Atmospheric + Ionospheric Loss (dB) 1.4 1.4
Free Space Path Loss (dB) 148.42 137.42
Isotropic received signal level (dBm) -124.89 113.89
GS Antenna Gain (dB) 11.10 11.10
GS Transmission Line Loss (dB) 1.31 1.31
GS Antenna Noise Temperature (K) 270 270
GS Receiver Noise Temperature (K) 300 300
GS Transmission Line Temperature (K) 290 290
GS Effective System Noise Temperature (K) 784.37 784.37
GS Figure of Merit G/T (dB/K) -17.85 -17.85
GS Receiver Sensitivity (dBm) -121 -121
GS Signal to Noise Ratio (S/N)(dB) 10.37 21.37
Link Margin (SNR Method) 0.37 11.37
Command Uplink
UL Frequency435 - 437 MHz
Mean Orbital Altitude400 km
ParametersElevation Angle
10 deg80 deg
GS RF Transmit Power (W)55
GS RF Transmit Power (dBm)36.9936.99
GS Transmission Line Loss (db)1.311.31
GS Antenna gain (dBi)11.1011.10
GS EIRP (dBm)46.7446.74
GS pointing loss (dB)33
Polarization Loss (dB)33
Atmospheric + Ionospheric Loss (dB)1.41.4
Free Space Path Loss (dB)148.38148.38
Isotropic received signal level (dBm)-109.04-109.04
SC Antenna Gain (dB)2.142.14
SC Transmission Line Loss (dB)0.130.13
SC Antenna Noise Temperature (K)290290
SC Receiver Noise Temperature (K)870870
SC Antenna Noise Temperature290290
SC Receiver Noise Temperature (K)870870
SC Effective System Noise Temperature (K)11601160
SC Figure of Merit G/T (dB/K)-28.5-28.5
SC Receiver Sensitivity (dBm)-120-120
SC Signal to Noise Ratio (S/N)(dB)16.6716.67
Link Margin (SNR Method)6.6717.67

4. Power

This system is composed of a battery pack, a microcontroller, and solar array panels responsible in providing power to different subsystems of the satellite.

4.1. Power Budget for Maya 1.2

This system is composed of a battery pack, a microcontroller, and solar array panels responsible in providing power to different subsystems of the satellite.


SubsystemCMD U/L & BeaconCapture Image (Target Mode)Capture Image (Normal Mode)Image D/LS&F (Rx) / DigipeatS&F (Tx)
Payload
Camera (FLIR)0.0270.027
Camera (NIR)0.1670.167
Bus
Communications (ADDNICS & APRS-S&F)
UHF Tx (CW/Beacon-OFF/Standby)0.051
UHF Tx (CW/Beacon-ON)0.217
UHF Tx (Image/Sensor Data Link)0.8960.711
UHF Rx (Uplink)0.1930.1930.193 0.193
VHF Tx (Amateur Packet Data)0.513
VHF Rx (Sensor Data & Amateur Packet Data)0.108
ADCS
ADCS Board/MCU0.0420.042
GPS0.050
On-Board Data Handling
OBC0.330.330.330.330.330.33
TOTAL0.7911.0521.0021.2261.1441.041
4.2 Power Generation Estimation

Each satellite, Maya 1.1 and Maya 1.2, has five solar array panels connected in parallel with 2 solar cells in series. As the cube satellite freely tumbles while in its orbit, it collects solar energy through the solar panels and transforms it into electrical energy and stored in the battery pack onboard the satellite. This provides continuous electrical power to the satellite even during eclipse period or the absence of sunlight. The table below shows an estimate of the power generation for each orbit of 1.5 hours using the solar panels of the satellite and following the movement of the cubesat which is not permanently and steadily facing the sun.

4.3 SEL Protection

Each satellite, Maya 1.1 and Maya 1.2, has five solar array panels connected in parallel with 2 solar cells in series. As the cube satellite freely tumbles while in its orbit, it collects solar energy through the solar panels and transforms it into electrical energy and stored in the battery pack onboard the satellite. This provides continuous electrical power to the satellite even during eclipse period or the absence of sunlight. The table below shows an estimate of the power generation for each orbit of 1.5 hours using the solar panels of the satellite and following the movement of the cubesat which is not permanently and steadily facing the sun.

5. Attitude Determination Control System (ADCS)

Maya-1.1 and Maya-1.2 cube satellites will be stabilized passively using permanent magnets and hysteresis dampers. Attitude determination will be done using gyro sensor and AMR magnetometer. Solar cells will aid in sun detection. Position determination will be done by a COTS GPS chip.

Telemetry Format


aaaaaa maya11 ABCDEFGHIJKLMNOPQRST


Formataaaaaa-maya11-ABCDEFGHIJKLMNOPQRST
Examplejg6aaa-birdph-d0882731369a50101010

Data Format & No. of CharactersDescription
aaaaaaAlphanumeric, 6Callsign of Satellite
_Alphanumeric, 1Spacer
maya11Alphanumeric, 6Name of Satellite
_Alphanumeric, 1Spacer
ABHex, 2Battery Voltage
(2.5*return_data*16/4096)*2000 mV
CDHex, 2Battery Current
((2.5*return_data*16/4096)*1000 -1250)*2 mA
EFHex, 2
If return_data <= 128   
{
  Battery Temp = +(return_data*16/4) °C  
}
Else    
{    
  Battery Temp = -(4096-return_data*16)/4) °C    
}
GHHex, 2
If return_data > 163    
{   
  OBC Temp = +(return_data/2) °C   
}
  Else     
{     
  OBC Temp = -(255-return_data/2) °C    
}
IJHex, 2
If return_data > 163   
{   
  Backplane Temp = +(return_data/2) °C   
}
Else    
{      
  Backplane Temp = -(255-return_data/2) °C     
}
KLHex, 2COM96 TRX Board Temp = (200*(2.5*return_data/256-1.491) + 25 ) °C
MNHex, 2COM-2 TRX Board Temp = (100*(2.5*return_data/256) - 50 ) °C
OPHex, 2Mission Board Temp = (100*(2.5*return_data/256) - 50 ) °C
QRSTBinary
Battery Heater ----->  Disabled:1 Enabled:0
Reservation command --> Reserve:1 Nothing:0
Operation mode --> Mission:1 Normal:0
Kill Switch_Main -----> Normal:1 Kill:0
Kill Switch_COM -----> Normal:1 Kill:0
Antenna Deployment Retrial Status -->  Success: 1 Unsuccess: 0
Solar cell X  -----> Sunshinel:1 Shadow:0
Solar cell -X -----> Sunshinel:1 Shadow:0
Solar cell -Y -----> Sunshinel:1 Shadow:0
Solar cell -Z -----> Sunshinel:1 Shadow:0
Solar cell +Z -----> Sunshinel:1 Shadow:0
Antenna Deploy Status --> Success: 1 Unsuccess: 0
Time after last reset (number of hours)