The Science Calibration And Alignment Subsystem (SCAS) provides quantified alignment standards for the Magnetometer (MAG) Subsystem throughout the mission. These standards permit verification of MAG instrument alignment on a routine basis.
The SCAS consists of three interconnected subassemblies: the X-magnetometer alignment coil, the Y-magnetometer alignment coil, and the magnetometer alignment coil electronics. For information on these components, click on their names.
The X-magnetometer alignment coil (X-MAC) is mounted parallel to the magnetometer boom axis in the perimeter of the spacecraft electronics bus Bay 7 outboard shear plate. The coil consists of 179 turns of No. 26 AWG copper magnet wire, and when it is energized with 30-volt d.c. power it generates a magnetic field with a component parallel to the spacecraft X axis at the vector/scalar helium magnetometer location. A platinum resistance transducer is mounted in proximity to the X-MAC to measure the operating temperature of the unit.
The Y-magnetometer alignment coil (Y-MAC) is mounted parallel to the magnetometer boom axis in the perimeter of the spacecraft electronics bus Bay 4 outboard shear plate. This coil consists of 89 turns of No. 29 AWG copper magnet wire, and when it is energized with 30-volt d.c. power it generates a magnetic field with a component parallel to the spacecraft Y axis at the V/SHM location. As with the X-MAC, a platinum resistance transducer is mounted in proximity to the Y-MAC to measure the operating temperature of the unit.
The magnetometer alignment coil electronics (MAC-E) provide the circuitry to switch polarity and to power the X-MAC and Y-MAC alternately when 30-volt d.c. power from the Power and Pyrotechnic Subsystem (PPS) is applied.