[SANOSAT-1] NEPAL-PQ1

SANOSAT-1 is a pico-satellite based on the PocketQube form factor. A PocketQube is a common standard of picosatellite with dimensions of 5*5*5 cm3 and weighs less than 250gm. It was first proposed in 2009, from an idea of professor Robert J. Twiggs, as a result of collaboration between Morehead State University (MSU) and Kentucky Space.

SANOSAT-1 is currently being developed by ORION Space in Nepal in collaboration with AMSAT-Nepal and AMSAT-EA. ORION Space is a Nepal based satellite company founded in 2017 with an aim of promoting space education in Nepal and also developing pico/nano satellites in Nepal.

The primary mission of SANOSAT-1 is to measure the radiation dose rate in the orbit. Since, Nepal is new to space technology and involving students/engineers within the country to provide space education is also one of the objectives of SANOSAT-1. Furthermore, encouraging students/engineers to work in the field of space technology, by making the satellite open source and involving amateurs is also the objective of SANOSAT-1. Figure 1 is the 3D model of SANOSAT-1.

Structural Subsystem

Structural subsystem provides support to the other subsystems or components. It also provides thermal isolation and radiation shielding for the satellite. Aluminium alloy Al-6061-T6 was selected as the material for the structure because of its low cost, easy machinability and high strength.

Internal structure contains PCB layers made of FR-4 materials, Connection harness and standoffs to hold the PCBs.

Electrical Power Subsystem: Electrical Power Subsystem is responsible for providing the power to the satellite and utilizing the available power in the efficient manner. This subsystem contains Battery, Maximum Power Point Tracking (MPPT) based Battery chargers, Solar cells, Low Dropout Regulators, Power monitoring devices and Current limiters. Five faces of the satellite contain solar cell with open circuit voltage of 2.5V and short circuit current of 250mA each at AM0. Solar cells from azurspace are cut using laser cutting technology to fit the solar cell on the sides of SANOSAT-1 as in Figure 6.

The output of solar cells is connected to the MPPT based battery charger which charges the 3.7V, 1100 mAh Li-Ion Battery. Power monitoring device consists of current and voltage monitoring circuit which monitors the charging current and voltage of the battery. Low Dropout Voltage Regulators (LDO) converts the battery voltage to 3.3V since the system works on 3.3V logic. Figure 5 is the EPS board of SANOSAT-1.

On Board Computer: The On Board Computer (OBC) is based on the ATMEGA328 microcontroller. It performs the tasks of data handling and control of the PocketQube. It also consists of Watchdog to monitor the program flow and restarts the satellite if any corruptions are found in the program flow. The Board is protected by current limiter for Latch-Up protections. Figure 7 is the Top View of OBC and Communication Board of SANOSAT-1.

Communication: Communication Subsystem is responsible for transmitting the available data to the ground station and receiving the data from ground station. Transmitting and receiving of data is done in half-duplex mode. The communication chip is based on Silicon Labs’ Si4463. It transmits the data in CW Morse Beacon, Radio Tele-Type (RTTY) and GFSK Modulations whereas the uplink is done only by GFSK Modulation. The maximum downlink transmission power is +20 dBm.  The housekeeping data is sent using CW Morse/ RTTY.

Ground Station: SANOSAT-1 has two kinds of Ground Station. The main ground station based on SatNOGS which is a network of open source ground station.

Payload: The primary payload of SANOSAT-1 is a radiation sensor. Initially, SANOSAT-1 developers were looking for a payload which is simple to implement and which does not require a pointing mechanism. So, an ultra-low power Radiation sensor (3.3V, 25uA) BG51SM was selected. The sensor measures the alpha, beta and gamma radiation dose rate around it and transmits the data to the ground station. The intensity of radiation can be used to plot the radiation map, calculate the thickness for radiation shielding materials, identification of solar flare, etc.

Currently, SANOSAT-1 is in the process of Engineering Model assembly. After the Engineering Model is assembled, environmental testing needs to be done. Environmental Testing is the process of testing the satellite to make sure that it operates in space. Some of the testing planned to be done are vibration and thermal vacuum testing. After the testing, Flight model is assembled which is going to be launched in the space. The planned launch date is Second Half 2020 and the planned orbit is Sun Synchronous Polar – Low Earth Orbit.

The transmission protocols will be uploaded here soon.