The spacecraft carried various instruments that would perform specific functions. However, along with these instruments, both, the orbiter and the probe were incorporated with some sub systems that not only assist the instruments, but also perform their specific functions.
The Casini orbiter had 12 sub systems. A detailed study of these sub systems follows as below.
- Command and Data Subsystem - this sub system can be termed as the brain of the spacecraft. Its main function is to sote and process the data received from all subsystems, sensors and instruments. It also commands all of the subsystems and instruments.
- Solid State Recorder - this subsystem collects science data regarding the state of the spacecraft. A unique property of this is that there are no movable parts in it.
- Propulsion Module Subsystem- this subsystem provides thrust or “direct impulse” for the spacecraft. This is required for changes in the route and orbit of the spacecraft, and for attitude control.
- Attitude and Articulation Control Subsystem (AACS) - this subsystem has three main functions to be performed. The first is to maintain the attitude control (position along three axes) of the spacecraft. The second function is articulation, while the third function is pointing control of the main propulsion engines relative to the spacecraft.
- Power and Pyrotechnic Subsystem (PPS)- this subsystem is designed to provide 30 Volts regulated DC electrical power to the spacecraft. This power is obtained from the three Radioisotope Thermoelectric Generators (RTGs) onboard.
- Radio Frequency Subsystem (RFS)- this subsystem, along with the antenna subsystem, enable the spacecraft to communicate with Earth.
- Antenna Subsystem (ATM)- The Antenna Subsystem consists of two antennas, the High-Gain Antenna (HGA) and two Low-Gain Antennas (LGA-1 and LGA-2). The main function of the high-gain antenna is to enable communication with Earth, while the low-gain antennas are used for exchanging information with ground controllers.
- Structure Subsystem- this system be termed as the skeleton as the spacecraft. It provides mechanical support and alignment for all flight equipments.
- Mechanical Device Subsystem (DEV)- The Mechanical Device Subsystems supply equipment to the spacecraft that provides non-feedback controlled motion. These subsystems supply a number of mechanisms for separating Cassini from the Centaur launch vehicle.
- Electronic Packaging Subsystem (EPS) - this subsystem can be termed as the “house” of all electric equipment needed by the orbiter.
- Cabling Subsystem- this subsystem provides wiring for all other subsystems. The cabling system of he orbiter is passive, as it contains no active electronic component.
- Temperature Control Subsystem (TEMP)- this subsystem maintains the temperature of the spacecraft within an appropriate range.
Now let us see the subsystems in huygens probe.