On 31 May, the last two Galileo satellites of the second tranche were sent to Kourou. What are the predominant emotions? Tense expectation in anticipation of the next launch, or a sense of coolness and routine given that you have already built 22 satellites?
Paetsch: This is, of course, a very special day for us. The first circle is closing. The first major stage has been completed. We have built 22 satellites, and the constellation thus reaches its first nominal completion.
What does that actually mean?
Paetsch: In theory, a constellation has to have at least 24 satellites in 3 orbits, that is, three different planes in space. This means that a coverage of 100 percent is reached; in other words, a signal is provided for every location throughout the world. And this is how positioning becomes possible. A fundamental issue in signal emission is that at least 24 satellites are required to achieve a specific signal coverage at every point on the globe. On top of this, simultaneous contact with four satellites is required to enable positioning. Substitute satellites, so-called spares, are added to ensure coverage should a satellite run into difficulties.
This then is Batch 3. What will happen once the last four satellites from the second tranche are in space?
Paetsch: After the launch there will be a test phase. All told, this phase lasts around half a year. Only then will the satellites go into service operation. At that point, the end of 2018, the constellation will be complete. The production of Badge 3 will work like this: we are planning for the first launch in 2020.
This means that the first of the new Galileo satellites will be built in 2019. When will all twelve be completed?
Paetsch: The first two will be ready at the end of 2020. Thereafter, two additional satellites will follow about every three months until all twelve have been built. But this does not mean that all twelve will be launched immediately. All nominal spares will definitely be launched quickly. And after that, it is also a question of the life span of the satellites. In addition to our 22 FOC satellites there are also the four IOVs, that is, the satellites that were launched into space as In-Orbit Validation satellites to test the technology. Their first launch goes back to 2011. Based on a nominal life time of between ten and twelve years, these satellites will reach the end of their life span around 2023. It remains to be seen whether spares will have to be launched at that time, but from a certain point onwards risk mitigation dictates that these spares be launched into space. We can assume that, starting in 2020, on average two Galileo satellites will be put into space every year
What does this mean for our OHB colleagues who until now took care of Batch 2? Will there be any changes to these teams?
Paetsch: Nothing much will change with regard to the teams. The colleagues who worked on Batch 2 will, so to speak, hurry straight back from the launch pad in Kourou to OHB in Bremen to ensure a seamless transition to the start of Batch 3. So we have actually built up a good head of steam.
Since we are thinking about the future, can we look a little further afield. You mentioned that a good head of steam has been built up and explained that from the mid-2020s onwards it will be relatively easy to predict when the remaining twelve satellites need to be replaced. Are the plans for Batch 4 already being drawn up, and if so, what is happening at OHB?
Paetsch: A little time ago the European Commission charged the European Space Agency with exploring what a next generation of Galileo satellites might look like. Parallel studies were conducted at various firms in Europe, their results have been passed on. The Commission subsequently decided to start the tender for what it calls a “transitional batch”. The process has only just begun. The requirements for this batch are on the table.
What does a “transitional batch” mean?
Paetsch: It refers to satellites that are designed to form the transitional phase from the current to a more developed generation of Galileo satellites.
What changes will there be compared to the previous generation?
Paetsch: We are aiming to improve the signals and services, to optimise operational costs, and to enhance security. The relevant developments will start over the coming months. Beginning with preliminary studies and further studies until a point has been reached when the concept is ready for development. This will then trigger activities of all different kinds across Europe. After about five years the satellites of this batch should then be ready. On the basis of the Commission's plans the development of these satellites will be completed in 2024, by which time the last Batch 3 satellites will be in space and the life span of the first Galileos will have reached its nominal end. So this all fits together very well.
There will be an even greater focus on the benefit to end customers, with even greater signal strength, even more signal security and enhanced accuracy together with faster position determination.
What is the biggest difference between the next generation and the current one?
Paetsch: There will be an even greater focus on the benefit to end customers, with even greater signal strength, even more signal security and enhanced accuracy together with faster position determination. This will prove to be an advantage in urban canyons, in buildings or moving objects, in particular.
Back to the present. So “Anna” and “Ellen” will now follow “Tara” and “Samuel” to Kourou, racing around the globe. What is that like for the engineers at OHB? Will there be a little bit of wistfulness when it comes to saying goodbye?
Paetsch: There certainly will be. After all, our colleagues have invested a considerable amount of time and passion. It will be both a joyful and a sorrowful occasion. Joyful because after many ups and downs this project is coming to a good end. Everyone is really happy about it. And sorrowful because many of our colleagues, including myself, of course, will ask themselves, is it really possible that this chapter is already drawing to a close? The time has gone by far too quickly. But this sorrow will be of short duration. As mentioned earlier, there will be a seamless transition to Batch 3. Nothing tastes as sweet as success - a success we all want to continue. This is what makes the spirit of the group: We want to continue working together as well as we have been.
But is that not also a burden? Everyone now assumes that it will all work. How do you deal with that?
Paetsch: Simply assuming that you will succeed is the greatest enemy of the actual goal. A certain measure of paranoia is helpful. It is only by constantly doubting that you are always on the alert. In batch production, in particular, we always need to make sure that every step is executed as carefully as it was the first time. And that is what we are doing. Towards the end it is even advisable to check two or three times more to make up for the effect of routine.
And what about pride? How proud do you feel about what has been achieved?
Paetsch: There are three things I would like to say in response to this: First of all, we are happy. Secondly, we are happy. Thirdly, we are happy. That’s it in a nutshell. On top of this, most of us will not get another opportunity to build a constellation. Once you become aware of this, you are happy even if something does not work out as planned. So there is always pride and joy, but without drifting into arrogance.
A large number of OHB employees will be in Kourou around the time of the rocket launch and before that, during the test phase. What exactly is their mandate?
Paetsch: Those who accompany the satellites are essentially those who watch over things. Some people are only responsible for security. But there is also always someone on hand who is able to act quickly should something go wrong with the air conditioning in the container on the journey. This sounds trivial, but if anything were to happen, the consequences would be huge. The whole satellite would need to be sent back, a full basic test performed and the whole system put through its paces. So such an event is to be avoided at all cost. Paying attention in all areas is therefore the prime responsibility of OHB employees during transportation!
And what about once you are in Kourou?
Paetsch: On average, between eight and fifteen colleagues will be there. The number will vary depending on the tests that need to be performed. All subsystems will be tested thoroughly, the electronics, the drive system, the sensors, the signals. All basic functions need to work normally. These tests are conducted according to a predefined sequence that has been discussed with all partners. For four satellites, nine weeks are required from the time of their arrival to their mounting atop the rocket.
How many launches have you witnessed?
Paetsch: The next one will be my eighth.
Is it still as exciting?
Paetsch: Of course! I always enjoy being part of it all!