October 24, 2023



On board calculator

The onboard management unit (UGB) has been designed to perform the following hardware functions:

  • Manage power supplied by the PDU (28V) and mainly:
  • Switching PHARAO on and off
  • Thermal control (heaters and Peltier coolers)
  • Data-handling protocols with the ACES XPLC computer using the serial link (time-tagging and synchronization with ACES)
  • Data-handling protocols with PHARAO
  • Control of onboard timing and synchronization (micro-sequencer)
  • TM/TC activities to control analog housekeeping TMs and digital settings

The UGB was developed by EREMS. Its overall dimensions are: 240 x 245 x 120 mm (7.3 l). The unit weighs near 5 kg and the total power consumption is less than 30 W. The computer is composed of five boards connected to a back frame:

  • CPU board
  • Digital sampling board
  • Analog acquisition board
  • Power heater board
  • DC/DC converter boards

Flight Software

The context of the PHARAO project implies two constraints on the flight software, i.e. flexibility and ability to evolve. Therefore, the main aspect of the PHARAO Flight Software is the definition of a software interpreter. It relies on two concepts: an interpreter and science sequences.

The Flight Software comprises three levels of software:

  • Board Support Package: this is the first level of software that is in charge of control and supervises the hardware.
  • Low-Level Software: this is the part of the software that provides a set of primitives to operate the hardware and subsystems.
  • PHARAO Flight Software: this is the part of the software that implements the functional part (TM/TC management, subsystem control and supervision, interpreter and sequences, etc.) using LBN services. It relies on the software interpreter and science sequences. A sequence is a set of software instructions that the flight software has to execute. The sequences are defined by the science and system teams. They control and supervise the subsystems and create TM packages.
PHARAO Flight Software (LV)
Low-Level Software (LBN)
Board Support Package (BSP)
Hardware (ERC32, RAM, etc.)

CS-SI is responsible for developing the PHARAO flight software.