ICD

Introduction

This page will act as the Interface Control Document for the ADCS subsystem. It details the electrical, data, mechanical, and thermal interfaces between ADCS and the rest of the spacecraft.

System Interfaces

Electrical Interfaces

The electrical interfaces for the subsystem components can be found in the figure below. The majority of components connect to voltage regulators located on the AODC board, which receives power at the common bus voltage. Two exceptions are the thruster, which receives power at the common bus voltage, and the star tracker, which connects to a voltage booster on the communications board.

Data Interfaces

The components that are contained in the subsystem, and the data interface they use to connect to the spacecraft is shown in the figure below.  

The CDH subsystem will communicate to the AODCS control board via Serial Peripheral Interface (SPI) denoted as SPI 1. The reaction wheel cluster will also connect to the SPI 1 bus. The sun sensors will interface to the AODC board on their own SPI bus, denoted SPI 2. The magnetorquers will interface to the AODC board using PWM. The 3-axis gyroscope and magnetometer on the IMU will interface using I2C. The thruster will interface to the AODC board using an RS232 serial connection. Finally, the GNSS receiver and star tracker will connect to the CAN bus to be used by CDH.

Mechanical Interfaces

See the individual components below for info on their mechanical interfaces.

Thermal Interfaces

See the individual components below for info on their thermal interfaces.

AODC Board (UMS-0054) ICD

The schematics for the AODC Board are shown in the figures below. Interface information can be found below that.

Electrical Interfaces

The AODC board receives power at the common bus voltage, which typically ranges from approximately 6.5 to 7.2 Volts. 

Most AODCS components connect to the AODC board for power. They are listed as follows:

• The GNSS receiver, gyroscope, magnetometer, and sun sensors all use a 3.3 V connection.

• The magnetorquers use a 5 V connection.

Data Interfaces

The ADCS board connects to the CDH subsystem via SPI. This will be used to send telemetery and sensor readings to CDH, and receive commands. 

The majority of the ADCS components have data interfaces with the ADC board. They are listed as follows:

• The gyroscope and magnetometer via I2C. 

• The sun sensors connect to an SPI bus separate from the one between ADCS and CDH. 

• The magnetorquers will receive PWM signals from the board to generate dipoles. 

Mechanical Interfaces

Embedded below is the base dimension suite for the Iris ADCS control board (LOTAD). While the LI Bus AODCS board will not have the same circuitry shown, the dimensions remain the same.

Thermal Interfaces

All components on the board satisfy the thermal requirement of -20 to +50 deg C.

GNSS Antenna - Antcom 1.2G-Mini-GNSS-AS4  (UMS-0651) ICD

Electrical Interface

The GNSS antenna connects to the GNSS receiver using a +5.0 Volt DC connection.

Data Interface

The antenna will connect to the receiver using an SMA connector.

Mechanical Interface

The engineering drawing for the 1.2G-Mini-GNSS-AS4  is found below. Dimensions are in inches. Takes No. 5 fasteners.

Thermal Interface

GNSS Receiver - Novatel OEM719 (UMS-0631/0632) ICD

Electrical Interface

Electrical interfaces come from the OEM719 Electrical and Environmental Specifications. The model on LI Bus uses GPS and GLONASS, so will have a typical power consumption of 1.3 W.

The antenna will connect to the receiver via MCX connection.

Data Interface

The GNSS receiver is one of the few components that does not have a data interface with the AODC board. Instead, it connects to the CAN bus to provide CDH and the payload with data directly. The table below comes from the OEM719 Data Communication Specifications.

Mechanical Interface

The drawing for the OEM719 can be found below or in the product's Mechanical Specifications. The receiver will mount to the structure using four M3 screws.

Thermal Interface

Gyroscope - STMicroelectronics A3G4250D

Electrical Interface

Data Interface

Mechanical Interface

Thermal Interface

From the tables given in the electrical interface, the gyroscope's operating temperature range is -40 to +85 degrees Celsius, and the survival temperature is given as -40 to +125 degrees Celsius.

Magnetometer - Memsic MMC5983MA ICD

Electrical Interface

Data Interface

Mechanical Interface

Thermal Interface

Magnetorquer - UMS-0053 ICD

Electrical Interface

The magnetorquers will connect to the AODC board using a 5 V connection. This results in a maximum power consumption of 0.2 Watts per magnetorquer.

Data Interface

The magnetorquers will be controlled using pulse-width modulation (PWM) signals.

Thermal Interface

The table below outlines the thermal performance of both the magnetorquers and the h-bridges.

Sun Sensor - York Univeristy MOLTRES (UMS-0381) ICD

Electrical Interface

The sun sensors will use a 3.3V power connection supplied from the AODCS board. Electrical documentation for MOLTRES can be found below.

Data Interface

The sun sensors will send data to the AODCS board via SPI. The Melexis MLX75306 linear optical array sensor is capable of 100 Hz operation.

Mechanical Interface

The sun sensor PCB connects to the mask using M1 bolts. The mask connects to the spacecraft structure using M2 bolts. 

Thermal Interface