GSAT-7: Enhancing Strategic Communication Capabilities for India's Defense Forces

Have you ever wondered about how easy it is for us to get a network connection or signal around here? Well yes, it’s rather easy with all the technology we have incorporated into our daily lives. But, have you ever thought about how the people who fight for our country communicate with little to no ability to get a phone connection? Well, in this article, we are going to understand the means of communication between the people of a country, specifically India’s military and how they are able to communicate between one another.

The GSAT-7 satellite of India is a vital component of India’s military. It’s a multi-band military communications satellite, developed by the ISRO, also known as Indian Space Research Organization. The ISRO developed the communication and defense satellite to ensure that India’s military was completely independent as it was first relying on foreign satellites like Inmarsat, a British satellite telecommunications company that provides telephone and data services to users worldwide. In this context, the Inmarsat provided communication services to the Indian Navy and Coast Guard. 

Now to look at the satellite itself, it was named Rukmini. It carries the payloads in UHF, C band and K_u, for context, these bands are electromagnetic wavelengths in which radio frequencies are able to travel in. Going back to GSAT-7 (Rukmini), it is the first dedicated military satellite that was made specifically by the ISRO for communication purposes instead of other satellites that were made for dual uses. It was to provide service for the Indian Armed Forces, and the main user is the Indian Navy as they have been using it as a means for communication between ships and submarines, providing them with state of the art GPS tracking and telecom radios. The procured launch cost was all the way up at 480 crore Rupees with the satellite alone costing about 185 crore Rupees and the cost of the whole project was at 950 crore Rupees. 

The satellite is exclusive to communications across all sectors of the Indian Armed Forces, used in communication that happens real time among warships, submarines, air crafts and all land systems. The liftoff mass of GSAT-7 with its main rockets, boosters, propellant and payload was at 2650 kilograms, which is about 5840 lb. The flight was about 34 minutes before the satellite was injected into a geosynchronous transfer orbit (GTO). It has entered with a perigee of 249 kilometers, an apogee of 35929 kilometers and at an inclination of 3.5 degrees with respect to the equator.

Now that we have understood the basic information on GSAT-7, we can look at the mechanical components of it and how it functions. 

The GSAT-7’s mechanical components can be separated into 7 sectors. These sectors all account for different purposes and requirements that the satellite needs to fulfill. These sectors include:

1. Structural Components
2. Propulsion System
3. Power Generation System
4. Thermal Control System
5. Antenna and Communication Systems
6. Attitude and orbit Control System
7. Payload and Data Handling System
8. Onboard Software
9. Sensors and Telemetry System
10. Payload and Service Module Separation Mechanism

Structural Components

The structural components are one of the most important components within the satellite. It provides a mechanical structure for the satellite. It is built with heavy-duty materials like aluminum and composite materials that are built to withstand the intense conditions during launch, the vacuum of space and the harsh space environment. It is made of the spacecraft bus, the frame and thermal insulation. The spacecraft bus is the central structure that all the other components are based and fitted around. It houses and supports the payload and most of the other subsystems. It’s purposely designed for durability and to keep the overall weight of the satellite to a minimum. The frame, which is made from light-weight materials to minimize the overall weight of the aircraft, is made to support other components such as: the solar arrays, payloads, propulsion systems and the antennas. It ensures the stability of the satellite in space. The thermal insulation within the satellite keeps the satellite safe from the extreme temperatures within space. It protects the aircraft from the extreme heat when the sun’s ways are unblocked and the extreme cold when the sun’s rays are being blocked. All the structural components are covered with thermal blankets in order to keep a balanced and consistent temperature to prevent any damage or weathering of the components of the satellite.

Propulsion System

The propulsion system within GSAT-7 is extremely important to positioning and the orientation of the satellite. It is critical for maintaining the satellite’s orbit. It consists of a Bi-propellant engine and a reaction control system (RCS). The Bi-propellant engine within the GSAT-7 satellite utilizes a liquid propellant rocket to propel itself and to move. The GSAT-7 utilizes a combination of monomethyl hydrazine and nitrogen tetroxide, which provides high thrust for orbit correction and attitude control. This is especially important when the satellite needs to have its position or path corrected or diverted. The reaction control system built into the satellite helps in controlling the attitude like correcting or adjusting the satellite’s orientation in space.

Power Generation System

The power generation system is responsible for generating and distributing electrical power to the satellite. To support the power generation system utilizes solar arrays, batteries and power distribution systems to generate and distribute power around the satellite. The solar arrays within the satellite are equipped with solar panels to convert the thermal energy of the sun into electrical power that can later be distributed around the satellite into electricity. The solar panels are multi-junction Gallium Arsenide (GsAs) solar cells that can generate approximately 2900 watts of electrical power. In order to generate power that can successfully power the entire satellite in all kinds of situations, the GSAT-7 is equipped with 108 Ampere-Hour Lithium-Ion Batteries that provide power during situations when the satellite is in Earth’s shadow, causing a difficulty to get the sun’s heat and thermal energy in order to power it. This source of power is mainly used during eclipse times. 

Thermal Control System

The thermal control system maintains optimal temperature for all the satellite components, ergo protecting them from the intense and harsh temperatures of space. The main components of the thermal control system include thermal blankets for the insulation of heat and heat pipes and radiators. Thermal blankets are draped over the satellite’s internal components and areas in order to bring heat loss to an absolute minimum, it also does to effectively protect specific components that are sensitive to temperature fluctuations. The thermal control system also consists of heat pipes and radiators that utilize pipes by circulating heated water around pipe systems (this can also be done with steam). The hot fluids/steam then flow through a radiator and are then transferred to the environment (as heated air), this causes the air to expand and rise, and this creates a flow of warm air that circulates around the satellite, keeping a constant temperature within. 

Antenna and Communication Systems

The function of the antenna and communication systems is to provide secure and reliable communication links between the different sectors of the military. The main components are composed of the transponders and deployable antennas. The transponders within the satellite are able to operate on multiple frequency bands as they are able to handle diverse communication requirements. The deployable antennas are designed for specific frequency bands, allowing for optimal signal transmission and reception for the receiver and caller. 

Attitude and Orbit Control System (AOCS)

The attitude and orbit control systems equipped on the satellite constantly monitor and control the orientation and position of the satellite, making sure it remains correctly and that it is stationed in its geostationary orbit (Check the mini glossary to familiarize yourself with the term) and that it is aligned in the right position. The main components that make up the attitude and orbit control system are the sensors and actuators that the satellite is equipped with. The sensors, that include sun sensors, star trackers and gyroscopes provide data on the satellite’s orientations constantly. The actuators that the satellite is equipped with come with reaction wheels and magnetic torquers that adjust the satellite’s orientation and position based on the information provided by the sensors. 

Payload and Data Handling System

The function of the payload and data handling system is to process, store and transfer the data between the satellite and the ground stations. This is where explicit communication occurs between the satellite and the Indian Armed Forces. The payload and data handling systems are what allow communication to be possible between the Indian Armed Forces and this is an extremely important mechanical component of the satellite. It consists of multiple onboard processors, data storage units and telemetry and command units. The onboard processors handle data processing tasks and they efficiently manage the communication payloads and all the components within the satellite. The data storage units store the data temporarily before it is transferred to the ground stations. The telemetry and command units facilitate the exchange of operational data and commands between the satellite and mission control. 

Onboard Software

The function of the onboard software is to control and coordinate all satellite operations, from payload management to all the system diagnostics. The main components that the onboard software consists of includes the operating system, control algorithms and diagnostic tools. The operating systems provide a foundational platform for all the software operations. It’s the same as a computer you use in your daily lives, all technology has to have an operating system to work on. Some operating systems you might use in your daily lives might include: Windows, Linux and even MacOS. Recognize these? They are the 3 most popular operating systems and maybe even your laptop runs on these. Next off, the control algorithms manage the functions such as attitude control, orbit maintenance and thermal regulation. The diagnostic tools monitor system health and performance constantly, this enables autonomous fault detection and eventually, the system itself, corrects the error. 

Sensors and Telemetry System

The function of this is to constantly monitor the satellite’s environment and internal conditions. The same system transmits this data to ground control in order to conduct analysis. The main components that make up this system include the environmental sensors, internal sensors and telemetry transmitters. The environmental sensors are what measure the external conditions such as the radiation levels and micrometeoroid impacts. They collect the data on these areas of information. The internal sensors measure and monitor parameters like temperature, battery health and fuel levels. The telemetry transmitters send all this collected data back to ground stations for the analysis and monitoring of the satellite. 

Payload and Service Module Separation Mechanism

The function of this is to ensure the safe deployment of the satellite into its designated orbit by separating it from the launch vehicle. The main components that make up this mechanism include the separation mechanisms and sensors and timers. The separation mechanisms utilize devices such as pyrotechnic bolts or spring loaded systems which facilitate the physical detachment of the satellite from the launch vehicle. The sensors and timers ensure the separation occurs at the precise moment during the launch sequence.

GSAT-7 satellite, also called Rukmini, is instrumental in giving the Indian military, particularly the Indian Navy, secure and stable communication. The satellite, developed and constructed by ISRO, is a significant step towards self-reliance, brushing away reliance on foreign communication services. The satellite's cutting-edge structure, propulsion system, thermal control system, and communication system enable impeccable real-time connectivity between warships, submarines, and aircraft of the Navy. Equipped with cutting-edge onboard software, sensors, and telemetry systems, GSAT-7 is a valuable resource for national defense, augmenting India's strategic capabilities. With ongoing developments in space technology, India persistently enhances its military communication network, guaranteeing security and operational effectiveness in hostile environments.