Before we get into the gist of this article, we first need to know what is a satellite bus. Also known as the spacecraft bus, it’s a general model upon which various satellite bus types are often based. This is considered an essential infrastructure of the spacecraft and is usually used to provide storage space for payloads like space instruments or experiments.
Spacecraft buses are very different from satellites that are produced specifically. Satellite buses can be customized based on the requirements of the customers. For instance, they can be fitted with specialized transponders or sensors to meet the needs of a specific mission.
They are usually used as communications satellites (or geosynchronous satellites). However, they can also be used to accompany low-orbit satellites for various types of missions.
What Is Its History?
One of the first satellite buses developed was the Modular Common Spacecraft Bus (MCSB), a low-cost and fast-developing spacecraft bus platform. The design was kept modular to decrease the lead time, complexity, and cost of the missions by offering a well-characterized and reliable system that can transport various payloads. According to the statement by NASA, this technology could reduce the total cost by a tenth.
Alan Weston was the supervisor for the MCSB and was granted $4 million from the NASA Ames Research Department. With the money, he created the prototype in 2007/2008. Weston utilized cold gas engines and SCUBA air tanks instead of the traditional rocket engine, allowing the team to perform indoor flight tests every 40 minutes instead of waiting for weeks and months.
The system was chosen as the first spacecraft bus for the LADEE Lunar Atmosphere and Dust Environment Explorer mission on the mood. Once the switch to the traditional rocket engine was made, the flight control software was modified with minimum expenses.
This MCSB module received the Popular Mechanics Breakthrough Award in 2014 for the best innovation in technology and science.
How Does It Work?
So, how does a satellite bus work? The bus is primarily used to provide the structural body and locations for the payload. While the payload in each spacecraft can be different, the buses look very similar. As mentioned above, a spacecraft bus is a general model on which various types of such technology are based.
When you open up the element, you will notice that it contains various subsystems, each having a unique purpose. In most cases, the buses will include the following satellite bus details:
- Guidance, navigation, and control (GNC) system
- Attitude control system (ACS)
- Thermal control systems (TCS)
- Propulsion system (PS)
- Electrical power system (EPS)
- Communications system and antennas
- Command and data handling system (C&DH)
- Structures and mechanics subsystems (S&MS)
One of the most critical systems is represented by the structures, and mechanics subsystem, which provides all the required mechanical structures that can handle the load of the payloads during the launch, orbital maneuvers, and even while re-entering the atmosphere. This system is the primary structure of the satellite and supports all the payload instruments and the spacecraft hardware. Depending on the requirement of the mission, the structure can take various forms to minimize the mass and survive the journey.
The electrical power subsystem also plays a vital role in a spacecraft bus. This satellite bus power system provides electrical power and distribution for various other systems in the spacecraft. Apart from the bus, the power system will also power the payload. In most cases, this is achieved using solar panels to convert the solar radiation from the sun to electrical current. However, the panels need to be flexible enough, so they can be folded and then deployed once the satellite is in space.
As you can guess, command and data handling is another important system on the spacecraft bus. You can consider it as the ‘brain’ of the operation. It will command all the electronics and control data flow from one component to another. All the subsystems will send and receive data via the wires routed throughout the body of the bus.
What Are Some Current Technological Trends?
Let us now understand the evolution of satellite buses. Nowadays, all the subsystems mentioned above can now be combined. COTS (commercial-off-the-shelf) assembled satellite buses will enable secondary payloads on the bus, thereby increasing the number of payloads without requiring another spacecraft bus. All these satellite buses offer a modular platform where the payload can be hosted and launched in a relatively short period. These integrated platforms can be utilized for different missions, and these integrated subsystems can operate in various mission and environmental conditions.
Let us take an example. Two trends have emerged in the industry — the developers of CubeSat components with various subsystems offer a package deal. These companies provide engineer services for large platforms that miniaturize their subsystems.
As you can see, while satellite buses are pretty new to the world of space, it is quite an important invention. Since its first launch, spacecraft buses have been through some significant advancements, and it’s safe to say that such elements will soon become a very integral part of all types of satellites, big or small.
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