The PLATO instrument module

Bridge clamps Clamps used to join modules

The PLATO instrument module was designed and built by the University of New South Wales during 2007. The instrument module is based on a standard 10 foot shipping container, allowing it to be coupled to the engine module and shipped as an ISO standard 20 foot container. Twenty-foot containers are the standard size for Antarctic sleds, and facilitate convenient shipping via road, rail and sea.

The instrument module contains the core control, communication, computing and power conversion electronics for PLATO. The module is designed as a stand-alone unit designed to take solar power, high voltage DC, and 100-250VAC, efficiently converting it to an internal 28VDC bus. A lead-acid battery bank provides uninterrupted power to the instruments, and allows for multiple restart attempts of the engine module if needed. All the PLATO equipment and experiments are standardised to operate from 28VDC.

The instrument module's primary purpose is to provide all the necessary functions for PLATO's instrument suite. Each instrument is provided with its own customisable power, communication, and thermal control. The module has standardised internal and external roof or wall ports for physically mounting the instruments, depending on the type of observation they need to perform.

Instrument module Instrument module at Dome A: mouse over (Xu Zhou and Zhenxi Zhu: Jan 2008)

PLATO is designed to run unattended for periods of up to one year. To achieve this level of autonomy, multiple-redundant Linux-based supervisor computers, each with their own management electronics and Iridium satellite modem, provide multiple paths of communication with each other and the outside world. The supervisor computers monitor and control the PLATO power distribution, thermal, and engine management subsystems via CAN (control area network) bus, and are able to gracefully handle various failure scenarios. High-bandwidth communication between the instruments and the supervisor computers is provided via Ethernet.

Bulk data are stored in cold-verified flash memory for later retrieval by the PRIC Dome A traverses each summer. The PLATO control system monitors up to 140 analog channels, multiple video sources, and distributes electrical power and heating to 96 current-monitored channels via a priority-based allocation algorithm.

The module is extremely well insulated with 200mm thick polyurethane foam. The internal temperature is can be regulated by microprocessor-controlled fans that prevent large temperature gradients due to stratification from occurring. Small heaters are placed in key points in the module and battery compartment, and a thermal control loop ensures that cold-sensitive items such as the battery bank and cold-sensitive electronics are kept within operating range. The instrument module internal temperature is regulated between –30°C and 15°C depending on the time of the year. During summer, ventilation fans can bring in cold outside air to keep the temperature closely regulated. Perhaps surprisingly, overheating of electronics is potentially an issue at Dome A because the efficiency of convective cooling is reduced in the thin air.