Page 41 - SATELLITE AND RADAR COMMUNICATION SYSTEM

2. Power subsystem

The satellite present in an orbit should be operated continuously during
its life span. So, the satellite requires internal power in order to operate

various electronic systems and communications payload that are present
in it. Power system is a vital subsystem, which provides the power
required for working of a satellite. Mainly, the solar cells (or panels) and

rechargeable batteries are used in these systems.

Solar Cells
Basically, the solar cells produce electrical power (current) from incident

sunlight. Therefore, solar cells are used primarily in order to provide
power to other subsystems of satellite. The individual solar cells generate
very less power. So, in order to generate more power, group of cells that

are present in an array form can be used.

Solar Arrays

There are two types of solar arrays that are used in satellites. Those are
cylindrical solar arrays and rectangular solar arrays or solar sail. Cylindrical

solar arrays are used in spinning satellites. Only part of the cylindrical
array will be covered under sunshine at any given time. Due to this,

electric power gets generated from the partial solar array. This is the
drawback of this type.

The drawback of cylindrical solar arrays is overcome with Solar sail. This
one produce more power because all solar cells of solar sail are exposed
to sun light.

Rechargeable Batteries
During eclipses time, it is difficult to get the power from sun light. So, in

that situation the other subsystems get the power from rechargeable
batteries. These batteries produce power to other subsystems during

launching of satellite also. In general, these batteries charge due to excess
current, which is generated by solar cells in the presence of sun light.

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Satellite System Elements