The sun sensor determines the spacecraft body angles with respect to the sun. It accepts configuration commands and outputs digital angles and telemetry over a serial interface to the on-board computer. The unit is powered from unregulated DC power from the spacecraft.

The front surface of the sensor is a mirror with slits cut in the reflective metal. Sunlight passes through these slits and then through an optical filter. Below this is an array of photosensors interfaced to a micro-controller.

The charge on the photosensors are read by the microcontroller, which processes the image and computes the sun vector. The vector and other telemetry is returned to the spacecraft through the serial interface.

The qualification of the Fine Sun Sensor comes from 14 on-orbit sensors on 4 LEO satellites.

FUNCTIONAL CHARACTERISTICS

• Field of view 140°
• Update Rate 5 Hz
• Accuracy <0.1°

PHYSICAL CHARACTERISTICS
Mass:

• 35 grams

Power:

• 7.5mA average, 26mA peak

Size:

• 34mm x 32mm x 21mm

ENVIRONMENTAL SPECIFICATIONS

• Operating temperature -25°C to +50°C
• 25g rms random, 5000g shock
• 20krad total dose (component level)

INTERFACES
Power Supply:

• 28 DC nominal (5V to 50V)

Data interfaces:

• Digital I/F: UART, SPI, I2C, CAN or RS-485/422

FEATURES

• Digital architecture
• High accuracy
• Wide field of view
• Small size and mass
• Low power
• Simple to interface

APPLICATIONS

• Accurate determination of sun-angle
• Four sensors can achieve full sky coverage
• Used in conjunction with a magnetometer
  for simple attitude control
• Can be used as safe-mode sensors on gyro
  or star-mapper controlled systems