In 2029, the European Space Agency’s (ESA’s) Ariel spacecraft will be launched to study the atmospheres of exoplanets orbiting distant stars in our galaxy. In common with other one-off space missions, it will have a unique design, requiring years of work to specify, develop and build both the spacecraft itself and the onboard instruments.
ESA’s Ludovic Puig, Ariel Project Payload & Performance Manager, describes how Starion’s CDP4-COMET platform is contributing to Ariel’s development by serving as the mission parameter database. He also explains why CDP4-COMET was chosen, given that it is more typically used to support the early stage design of complex projects.
About Ariel
- Name: Atmospheric Remote-sensing Infrared Exoplanet Large-survey (Ariel)
- Mission details: The fourth medium (M-class) mission in ESA’s Cosmic Vision 2015-2025 plan. (Other M-class missions include Solar Orbiter, Euclid, Mars Express and Plato.)
- Objective: Performing a chemical census of a large and diverse sample of exoplanets by analysing their atmospheres.
- Payloads: A telescope assembly plus two instruments – the Ariel InfraRed Spectrometer (AIRS) and the Fine Guidance System (FGS).
- Planned launch: 2029
What is a mission parameter database?
At ESA, when we’re designing and building a spacecraft, we must undertake a lot of verification tasks to ensure the spacecraft will fulfil the mission’s needs, including its scientific objectives. This involves many tests and analyses, and the parameters we use in those analyses need to be representative of what we’re actually building. Otherwise the results will make no sense – as they say: “Garbage in, garbage out”.
That’s where the mission parameter database comes in. For us, it’s the single repository where all the design and engineering parameters of the Ariel payloads are stored. When the engineers and scientists do their tests to demonstrate that what we’re building will fulfil the mission’s needs, they use that database. We then have peace of mind, knowing that because they have been using good inputs, we can trust the outputs.
It’s important to have a single tool for this because the Ariel mission is a large endeavour across many European Member States. With engineers and scientists from many countries working on different subsystems to build the instruments, we need an effective way to share all this information in one controlled place – that way, we’re all working with concurrent data.
Why was CDP4-COMET chosen to be Ariel’s mission parameter database?
We conducted a survey across various missions to check what tools they used, identifying old tools that were good, but effectively obsolete and hard for us to reuse, whereas CDP4-COMET was the most readily available tool that we could use immediately with little modification. There are other MBSE [model-based system engineering] tools that are very powerful, but they’re complicated, hard to learn and master, and require significant maintenance, whereas CDP4-COMET is very straightforward with a friendly user interface, making it easy to learn to use.
Ariel isn’t the first mission to use CDP4-COMET as its mission parameter database. The first was Plato. When I discussed this with the Plato team a few years ago, the feedback was good, so in 2022 we decided to adopt the same approach. They’re still using it now and are still happy with it.
For now, we are only using CDP4-COMET for payload performance parameters. However, in future there is the potential to expand it to include the spacecraft engineering parameters too.
How does CDP4-COMET let you deal with changes during development?
For testing purposes, several ‘models’ of the spacecraft are built during its development. These include a structural model to test the structure, an engineering model to test the functions and performance, and then the flight model. In the mission parameter database, each parameter can have different ‘instances’, allowing us to store the values for each of the models; these are filled in as we progress.
Inevitably things change as a spacecraft is developed. Using CDP4-COMET, we can track the evolution over time, starting with the initial required values, then adding the values agreed during the design phase and finally the values measured once it’s built.
Who can access the database? And how?
Our scientists have tools to interface with the database and extract whatever parameter values they need to run their analyses. There are plenty of ways to interface with CDP4-COMET, which is one of the reasons we selected it.
CDP4-COMET lets us apply different access rights according to an individual’s needs, from parameter owners who can edit the model to change the values, through to those who can’t change anything but can access the values they need for their analyses.
How long will you keep using CDP4-COMET?
The tool is running well for us: we’re making good use of it and our scientists are happy to continue using it. We now plan to extend its use into the operations phase because then the scientists working with Ariel’s raw observation data will need these values to calibrate that data.
This database isn’t currently available to the public; it’s purely for us and the scientists within the Ariel consortium. Once Ariel moves into the operational phase, all the science data produced will be made available via the science archive at ESA’s European Space Astronomy Centre (ESAC) in Madrid. But we will still keep the CDP4-COMET database for reference.
All images © ESA
