By Paul Parkinson
Congratulations to the ESA Rosetta team on a successful landing of Rosetta’s lander Philae on Comet 67P/Churyumov–Gerasimenko after an incredible 10 year+ journey through space!
I first learned about the Rosetta mission during my early years at Wind River, long before the launch on 2nd March 2004, as Wind River had acquired the Virtuoso™ RTOS for digital signal processors (DSP) through acquisition of Eonic Systems (and subsequently renamed Virtuoso as VSPWorksTM).
I remember being awestruck at the time by the ambition of the ESA mission to send a probe billions of kilometres across space chasing a comet travelling at incredible speed (kilometres per second), and after travelling 6.5 billon kilometres over 10.5 years to land on a target only 4 kilometres wide.
The journey itself is an incredible achievement of science (and navigation), but the engineering undertaken to support the mission is also truly inspiring. The Rosetta probe is solar-powered (rather than nuclear-powered), which means that it has to conserve power when orbiting at 800 million kilometres from the sun, where it only receives 4% of the solar energy available on earth. This meant that Rosetta’s on-board systems had to be designed to go into deep hibernation on 8th June 2011 in order to conserve power, and be able to reawaken 31 months later on 20th January 2014.
These challenging requirements place enormous demands on the hardware and software in Rosetta’s on-board systems, in terms of extreme reliability, and minimizing software footprint to reduce computing requirements and therefore power consumption. To achieve this, a number of Rosetta’s systems use Virtuoso RTOS which provides a very small scalable microkernel architecture, enabling it to run on processors with minimal resources; and a Virtual Single Processor (VSP) system-level design model which enables an application to run seamlessly in a multiprocessor DSP environment, including radiation-hardened DSPs designed withstand cosmic radiation in deep space.
The systems include Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA, for an overview visit the ESA website, or for technical details of the hardware & software architecture refer to the ROSINA User’s Manual); and Visible and Infrared Thermal Imaging Spectrometer (VIRTIS, for an overview visit the ESA website, or for technical details refer to VIRTIS conference paper).
It’s also interesting to note how processor architectures have evolved while Rosetta has been on its incredible journey through space. In the late nineties and early 2000’s, a number of digital signal processors architectures provided multiple off-processor communication ports, which enabled the design of large multiprocessor DSP systems. This was in contrast to 32-bit general purpose processors which were generally single-core devices. In the intervening period, there has been a disruptive technology change, and many 32-bit general purpose processors contain multiple cores (some even with DSP functionality), providing the potential to be used in many different types of applications.
The challenge with multicore, is of course, to be able to exploit its potential efficiently in software, and Wind River’s VxWorks RTOS has provided the ability to on 32-bit multicore processor architectures in either asymmetric multiprocessing (AMP) and symmetric multiprocessing (SMP) configurations for a number of years. However, Wind River has recently expanded the potential options available to system architects by providing the VxWorks 7 Microkernel Profile, which brings DSP RTOS levels of extreme scalability to general purpose processors – enabling an application to be scaled to a footprint as small as 20kbytes, which can be used to achieve extremely fast boot times and operate in extremely resource-constrained environments for applications on earth and in deep space.
One final thought, if you find the vast distances of Rosetta’s journey hard to visualize, there’s a really excellent interactive animation on the ESA website.
You can also visit Wind River’s space website for more information on the role our technology plays in some of the most significant space missions in history.