Payload ICD

Introduction

Each subsystem should have an interface control document (ICD). Detail the mechanical, electrical, data, thermal interfaces between this subsystem and other subsystems (what's unique to this project).

Electrical Interface

• PLD receives power from a distributed power bus at unregulated battery voltage (Vbat = 6.4 +/- 0.4V) through distribution load switches that are operated by the Power module controller. 

• Power ON/OFF is controlled by a CAN-Controlled Load Switches and Monitors (CCLSM).

Mechanical Interface

• M3 or M4 fasteners with hex drive: Used for assembly throughout the shell

• 1x hinge: located between the payload reflector and the structure shell

• 1x hinge: located between the payload feed and the structure shell

Data Interface

• Power ON/OFF is controlled by a CAN-Controlled Load Switches and Monitors (CCLSM) through the auxiliary CAN bus, which is commanded and controlled by the Power subsystem

• CAN Bus connection betweeen PLD and CDH

  • Data rate: 250 kbps

• 3 analog connection for thermistor.

• 1 2.92-SMA connection to the antenna.

Payload - CDH

The data interfaces between the Payload and CDH subsystems through the main CAN bus are listed below. This shows the data that can be read or manipulated on Payload by the CDH subsystem. 

Data Read/Write Value Ranges

Calibrate PLD W         True/False (True begins PLD calibration process)

PLD Measure                     W True/False (True begins PLD data measurement)

PLD Voltage Data         R         0.5 ~ 3.3 [V] (measurement raw brightness voltage)

PLD Voltage Calibration                     R                                             0.5 ~ 3.3 [V]  (Calibration voltage data)

PLD Temperature calibration          R                                             T [K]   (Calibration brightness temperature)

PLD Temperature Data                       R                                              T [K]    (Measurement brightness temperature)

PLD Board Temperature                     R                                              T [°C]  

Thermal Interface

• 3 thermistor to measure temperatures at different parts of the PLD 

  • 1 for the noise source

  • 1 for the radiometer RF stage

  • 1 for the ambient temperature of the PLD unit

• Operational temperature range: -40°C to 85°C. 

• Survival temperature range: -40°C to 85°C. 

• The PLD subsystem provides ambient PLD temperature reading to the CDH over CAN

Software

The ArcticSat payload radiometer has its own dedicated software system that interfaces with the ArcticSat's Flight Software (FSW).

calibrate ():
This method is used to run the radiometer calibration sequence. This would be called after ArcticSat has been oriented properly with the payload antenna pointing to deep space. After the calibration measurement is completed, the function returns a Boolean value to indicate whether the measurement was successful. 

getCalibrate ():
This method retrieves the last calibration data and returns both the raw voltage output and brightness temperature measurements, respectively. 

measure ():
This method runs the radiometer measurement sequence and stores the data. This would be called when ArcticSat is over the measurement region. It returns a Boolean to indicate if the measurement was successful.

getRawMeasure ():

Radiometer Algorithm

The radiometer algorithm for calibration and data processing is designed in-house and presented in this section. 

Communication Protocol abd