Requirements Management and the Rosetta Mission

Published by on December 8, 2014 at 9:00 am.

Rosetta probe and comet 67P Churyumov-Gerasimenko - 3D renderThe world’s imagination was captured on November 12th 2014 when the lander for the European Space Agency’s Rosetta mission set down on comet 67P/Chuyumov-Gerasimenko (more simply ‘67P’), the first spacecraft ever to do so. It was a historic mission, and it was only possible through the diligent engineering teams at the European Space Agency (ESA) and a host of other space agencies and organizations around the world, including NASA. In fact, the touchdown – while garnering the lion’s share of the world’s attention – was only the end result to an engineering effort that began long before the actual landing day.

The initial need statement for the mission was ‘To understand the origin of the solar system by determining the composition of a comet through observation and experimentation’. In other words, to obtain samples directly from a comet, and analyze those samples to see what they could tell us about the comet, the formation of our solar system, and possibly whether water and organic molecules first arrived on earth via cometary impacts.

It was a bold mission, and unlike anything that had been attempted before. Unmanned probes have been launched before, of course, to the moon and other planets and even to asteroids and other comets. But the Rosetta spacecraft had the rather unique objective of being launched, traveling through space for 10 years and 310 million miles, and then rendezvous and land on a moving comet. It would need to protect all of its instrumentation during the long trip to meet 67P, taking data from a couple of asteroids it passed on the way. Finally, it would orbit 67P and separate the lander (called ‘Philae’), which would then land on, and attach itself to, the comet. Philae would then take its samples and measurements of 67P, and send those results back to the orbiter.

The ESA systems engineering team, in the original Concept of Operations (CONOPS) document for the program, defined the high-level requirements for the mission. Among those requirements were:

  • Thermal protection – The spacecraft would have to endure the extremely high and low temperatures that it would encounter during the journey, and would need to protect the internal instrumentation during that time. It would also need to keep certain instruments heated, to ensure that they survived the voyage.

  • Autonomous control – The Rosetta spacecraft would pass by a couple of asteroids on its way, and the ESA wanted it to collect data from them as well. However, the craft would need to do this on its own, without any control input from the ESA, in order to conserve power.

  • Weight limit – The spacecraft would need to meet its objectives while operating under a weight limit of 3000 kg at launch, owing to the lift capacity of the Ariane-5 rocket which launched it. Of that weight, more than 50% would need to be propellant.

  • Critical system availability – The critical systems on the spacecraft would need to be redundant and fault-tolerant, to ensure their operation at the right time.

There were, of course, more high-level requirements defined in the CONOPS, but they were mostly all concerned with the same core functions – the spacecraft would need to be small, autonomous, resilient to its environment, able to gather and transmit the right data, and able to work properly when the time came.

From these high-level requirements the system engineers went on to define the lower level and subsystem-level requirements necessary to define what each subsystem would be required to do in order to fulfill their portion of the mission. This ultimately led to the identification of literally hundreds (if not thousands) of requirements, spread not only across teams at the ESA, but also across organizations all over the world.

Its programs like this that highlight the need for solid requirements management and systems engineering. Without these disciplines in place, highly complex projects like the Rosetta mission simply cannot function. But with these functions and systems in place, organizations like NASA and the ESA can achieve mission objectives that would have been unthinkable only a short while ago.

Its with programs like Rosetta in mind that SPEC Innovations built Innoslate, so that mission-critical programs can model, manage and analyze their requirements, collaborate across teams, and visualize the end result, keeping the systems engineering effort on track.

We’d love to talk to you about our approach to modeling and managing systems and their requirements. If you’d like to hear more about SPEC Innovations and Innoslate, please contact us.