Abstract
A satellite spacecraft is generally composed of a central Control and Data Management Unit (CDMU) and several instruments, each one locally controlled by its Instrument Control Unit (ICU). Inside each ICU, the embedded boot software (BSW) is the very first piece of software executed after power-up or reset. The ICU BSW is a nonpatchable, stand-alone, real-time software package that initializes the ICU HW, performs self-tests, and waits for CDMU commands to maintain on-board memory and ultimately start a patchable application software (ASW), which is responsible for execution of the nominal tasks assigned to the ICU (control of the satellite instrument being the most important one). The BSW is a relatively small but critical software item, since an unexpected behaviour can cause or contribute to a system failure resulting in fatal consequences such as the satellite mission loss. The development of this kind of embedded software is special in many senses, primarily due to its criticality, real-time expected performance, and the constrained size of program and data memories. This paper presents the lessons learned in the development and HW/SW integration phases of a satellite ICU BSW designed for a European Space Agency mission.
Highlights
In a satellite spacecraft, an Instrument Control Unit (ICU) is a box in charge of control and monitoring one of the satellite instruments
We introduce some major problems occurring during the boot software (BSW) development and HW integration of a real spacecraft ICU [3], to be utilized in a European Space Agency mission related to the study of the dark matter and dark energy in the Universe [4,5,6,7,8,9]
It is in charge of initializing and testing the ICU processor module, as well as launching the execution of the application software (ASW) after copying it from a nonvolatile memory area (CDPU EEPROM) into the processing SRAM
Summary
An Instrument Control Unit (ICU) is a box in charge of control and monitoring one of the satellite instruments. The ICU will generally communicate with other elements of the instrument, as well as the spacecraft main Control and Management Unit (CDMU), by means of different buses [1] (e.g., Milbus 1553, SpaceWire, high-speed serial lines). A typical ICU is in charge of receiving telecommands (TCs) from the CDMU and carrying out several housekeeping duties, performing the mechanical and thermal control of the instrument itself. These tasks are accomplished by means of radiation-hardened CPUs and FPGAs, including the necessary interface controllers. ASW [2] is devoted to manage all functionalities related to instrument command and control
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