Swayam

Swayam is a 1-U picosatellite (CubeSat) developed by the undergraduate students of College of Engineering, Pune.[1] With size constraints of 1-U standards and weight 1Kg, they have successfully completed assembly of their flight model under the guidance of Indian Space Research Organisation (ISRO). The Satellite will be launched by ISRO in the 4th week of April along with Cartosat - 2C by Polar Satellite Launch Vehicle C-34.[2] The satellite is to be placed in low earth orbit (LEO) around the Earth at a height of 500–800 km.[3]

Payload of the Satellite is point to point packet communication with which a user can send/receive messages from one point to other point on the earth. Scientific objective of the satellite is to demonstrate passive attitude control of the satellite, this is India's first satellite to do so. Without consuming any power the satellite will stabilise in the orbit. Another prominent mission objective is to provide Low earth orbit channel characterization in UHF ham band.

About the programme

Mission Swayam is the first satellite project of COEP Student's Satellite Initiative under the CSAT programme. The team has its members spread over all the years and disciplines of engineering establishing itself as a truly interdisciplinary project.

Timeline

This programme was initiated by a group of few students in late 2008. Then in early 2009 this project was approved officially by the Institute and the team expanded. Team cleared the preliminary design review of mission Swayam in September 2010. Development of ground station was done by October 2012 and is functional there after. College established a Class 10000 cleanroom. Qualification model along with the Environmental tests was completed in May 2014. Flight model along with all the environmental tests completed in February 2015.

Subsystems

The Satellite team is divided broadly into five subsystems.

Attitude Control System

Attitude Control System (ACS) controls the dynamic behavior of satellite like orientation and motion of satellite. In Swayam, the unique technique of Passive Magnetic Attitude Control (PMACS) is implemented for the first time on an Indian satellte.[4] The uniqueness of the technique is that it controls the orientation of satellite without any power consumption with reasonable accuracy for communication. It is the scientific mission of the Satellite to prove that PMACS is a robust and cost effective solution for attitude control.

The primary objective of the ACS is to attain a favourable configuration suitable for communication payload. Earth's magnetic field will be used for achieving this. Components of ACS include permanent magnets to provide pointing direction to the antenna of the satellite and hysteresis rods (soft magnetic materials) to damp the angular velocity and angular oscillations of the satellite.

To evaluate the attitude behavior of the satellite in the orbit, the space conditions and dynamic behavior of the satellite have been simulated through a C Code. From the simulation results it has been observed that, the stabilization of the satellite to the prescribed orientation i.e. antenna along Earth’s magnetic field, takes around 15 to 20 days.

It also has an onboard MEMS gyroscope for stabilisation detection. Using the data from gyro sensor On-Board Computer declares stability of the satellite.

Communication

The Communication subsystem is responsible for enabling half-duplex communication of the satellite with various ground stations in the HAM band of 434-438 MHz which is used both for up-linking and down-linking data.[5] The frequency used by satellite will be 437.025 MHz.[6] Communication subsystem can be subdivided further into two parts:

Spacecraft

The subsystem consists of:

Ground station segment

The team has established a fully functional Ground Station in the premises with uplink and downlink capability in both the 435 MHz as well as the 145 MHz bands.[7] The team has successfully received signals from various analog and digital satellites and the data has been verified from the respective satellite teams.The Ground Segment includes an array of 2 crossed Yagi antennas for the 434-438 MHz band and a simple Yagi Uda and Potato Masher antenna for the 144-148 MHz range.

Onboard computer

The onboard computer subsystem is a fault tolerant microcontroller based system.[8] Over the course of mission, OC collects crucial data about the health of the various systems within the satellite and stores it in a non-volatile memory, only to be sent to the ground station on request. The major role of OC relies in handling the set of commands received from the ground stations through the communication system.

Power

The power subsystem is completely analog in nature and also fully autonomous in its functioning, being the first subsystem to start up after the launch. It provides power to all the electrical systems on board the satellite and protects them from electrical faults. DC-DC converters are used for regulation and conditioning of power. Load protection circuits designed have triple redundancy with On-board computer's and terminal node controller's control. The Power system is responsible for the deployment of the antenna for the communication system through a surge of current. Li-ion battery is used for energy storage. It has on-board voltage/current and temperature sensors which form a part of health monitoring data (HMD) for monitoring electrical and thermal status of the satellite.[9]

Structure

The structure subsystem is responsible for providing a robust body for the satellite which can house all the components and protect them from the harsh conditions of space.[10] Comparative studies of different materials revealed that Al 6061-T6 is better suited. Hence it has been used for the main frame of the satellite. Other materials like ABS, FR4 have also been used as per the specific requirements. All these materials were first tested for their properties before being put into use. The main structure of the satellite consists of four rails and two frames. Three PCB’s are arranged in a U deck, with the battery pack in the middle.

Vibration Analysis: During launch, the satellite undergoes intense vibrations. It must be able to sustain these. For the same, simulations have been run and validated by performing tests on both the qualification and flight models.

Thermal Management and Control: Temperature of the satellite has to be maintained within a particular range in order to ensure proper functioning. A passive thermal system has been employed in Swayam. Insulating materials like kapton, white paint, low emittance tape, black tape and optical solar reflector are used. The thermal system has been put to test in the thermo vacuum test (on QM and FM) and hot and cold test (on QM).

Achievements

The team has published and presented various papers in various conferences.[11]

References

  1. ↑ Mission Swayam, Official Website. "Mission Swayam". Official Website. Team Swayam, COEP. Retrieved 10 January 2016.
  2. ↑ Press Information Bureau, Department of Space. "Launch of Satellites Designed by Students". Press Information Bureau Govt. of India. Retrieved 2 December 2015.
  3. ↑ The COEP Satellite, SWAYAM, Amsat India. "Swayam". AMSAT India. Retrieved 10 January 2016.
  4. ↑ Attitude Control System, Mission Swayam. "Attitude Control System". Team Swayam, COEP. Retrieved 10 January 2016.
  5. ↑ Communication System, Mission Swayam. "Communication System". Team Swayam, COEP. Retrieved 10 January 2016.
  6. ↑ AMSAT-UK, IARU Satellite Database. "IARU Amateur Satellite Frequency Coordination". AMSAT-UK. Retrieved 10 January 2016.
  7. ↑ Mission Swayam, Ground Segment. "Ground Segment". Team Swayam, COEP. Retrieved 10 January 2016.
  8. ↑ On-board Computer System, Mission Swayam. "On-board Computer System". Team Swayam, COEP. Retrieved 10 January 2016.
  9. ↑ Power System, Mission Swayam. "Power System". Team Swayam, COEP. Retrieved 10 January 2016.
  10. ↑ Structure System, Mission Swayam. "Structure System". Team Swayam, COEP. Retrieved 10 January 2016.
  11. ↑ Achievements, Mission Swayam. "Achievements, Mission Swayam". Team Swayam, COEP. Retrieved 10 January 2016.

External links

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