 I'm going to give you an introduction to spacecraft control under the title of Space Ops 101. Okay, thank you very much for the kind introduction. Hello and welcome to Space Ops 101. My name is Den Prüfer. I'm a mission planning engineer at the German Space Operations Center, which is a part of the Gorgeous Centrum in the Lüftelhorn Park. And I will give you a slightly biased introduction to spacecraft control. It's quite biased because, first of all, I'm working for a particular space agency. And secondly, because we will look at... First of all, of course, I work for a certain space agency. And second of all, of course, that's the lens of the mission planning engineering. Unfortunately, the topic is pretty big, so we won't be able to talk about everything. In particular, we won't talk about the start. The start is pretty great. I would really like to see one in real life. But I can't go into so many details because it's a very special topic. We won't talk much about human space travel and also not about the return and landing of the planet. Of course, the combination of this and the human space travel is very great to see. But I can't talk about it right now. So, instead of that, we will talk about one of the main segments of Mission Operations. In total, you have three parts. The world space segment. That's everything that actually flies into the world space. Athletes, space vehicles and even their payloads. So everything that's done up there. Then the transfer segment. And that's the start. And then the ground segment. We will mainly talk about the ground segment. That's what happens on Earth so that space vehicles can be controlled or used in the world. So, the ground segment consists of individual sub-systems. One of them plays the main role when you actually want to talk to a space vehicle. The ground segment. Then we have to know where our space vehicle is and where it goes. That's done by aerodynamic dynamics. Third, the space segment is very cold and very hot at the same time. So there are electricity and heat sub-systems. Then there is equipment and railway control. They tell the space vehicle where it should go and where it should look. Then we talk to the space vehicle. That's the reception and interpretation of data. That's TMTC. And last but not least, the mission planning. This is responsible to determine when and what happens to the space vehicle. So, the talk follows the life cycle of a space vehicle. We start with the start and the early operating phase, Kursliop. That means aerodynamic dynamics and how we actually talk to the space vehicle. Then it's about testing our space vehicle to validate. And then it goes into the routine phase where we do that with the space vehicle, where it was originally built. Including data analysis, telemetry, TMTC and the mission planning. And then at the end, the end of the mission. Whatever we do with the thing, if we want to start at the end. So, everything starts with the start. No, not quite. Before that, the preparation phase. It's a pretty long preparation phase. I don't want to talk about it right now. But it can take two years before the start. Until everything is prepared, so everything runs smoothly and smoothly. Then the space vehicle is attached to the rocket, flew into the space room and separated from the rocket. From this moment on, the space vehicle flies for itself and we have to control it. However, we don't know exactly where the company that answered the start has the space vehicle going. So either on its final runway or a transfer runway which is allowed to arrive in its final runway. During this start, there is a second control center and that's the space vehicle. This is the control room K1 of the German Space Operations Center. And it looks like you're waiting for a short-term control room. There are many large image screens. Everyone has four. There are large image screens where you can see what's supposed to happen. And many small yellow signs. These yellow signs show the position of the operator and engineer who are sitting there. In the back, in the middle, you see a position called the Flight Director. The Flight Director has the saying. If someone makes a decision, he is the one who confirms this decision and orders the operation. Directly after the space vehicle was separated from its start center, this control room is taken over. There are always some small subtleties. Directly after the separation, the space vehicle is somewhere. We know roughly where it is. We have planned this. But we don't know the exact position. We first have to turn on the signal, find the thing in the room and create a connection. For this, we have to talk about orbital mechanics first. So why doesn't a space vehicle fall down? If you look at the ISS, it flies at a altitude of about 3 to 400 kilometers. There, the gravity of the earth is approximately 90 percent on the surface. In other words, you need a certain horizontal speed to not fall on the earth. Approximately 7.9 kilometers per second is needed at the altitude. If you are a little bit higher on a higher runway, you need less speed. So we have to move very quickly. Second, we have to know in which distance our space vehicle flies. This is obviously the earth. The following picture is actually roughly a space vehicle. A possible place is the low-earth runway. This is the region under approximately 2,000 kilometers. But that's already a bit higher. More often, the altitude is between 5,000 to 700 kilometers. Here is mainly scientific city, especially the observation of the earth. We have many, many athletes, who try to make pictures with different frequencies. And here is also observation, in the military sense. Then there is the middle-earth runway. The circle here is at 20,000 kilometers high. And this height range is mainly for navigation and satellite use, so GWS or Galileo, the Euro version of it. Then there is the geostationary orbit. It is at 35,786 kilometers. And that's why it was chosen, because the orbital period, i.e. the time until the satellite flies around the earth is exactly 24 hours. That has the advantage that the satellite moves synchronously with the earth, so that the satellite always seems to be in the same position as the earth. That's particularly important for television athletes, because, well, imagine, you always have to carry out your satellite antenna all the time, because the satellite moves. So you have to fix it all at once, and then it fits. And that's what communication athletes think of the same reason, because we want to fix a fixed position on which we set our antennas. Then there is an entry to get there. Can it be that the launch provider puts us on a transfer orbit? It doesn't look like a circle, but rather like an ellipse. And in this case, we still have to fly in the maneuver. We are on the red circle, we fly outside, and at some point we touch the geostationary orbit, i.e. the black one. But in order to fly back to the earth, we have to accelerate as a maneuver that we have to fill out at the beginning of the mission. The department that takes care of it is Flight Dynamics, whose tasks are the fixed position of the actual orbit. Often you can ask the satellite where it is, because it has GPS on board, or Galileo. In the low Earth orbit, the satellite knows where it is. Or you can do the whole thing with distance measurement. If you have the orbit, you know where it will be in the future. So the orbit will continue to be calculated in the future. Now we have to perform maneuver calculations to calculate where we are and in which direction you have to accelerate so that you can reach the right orbit. You also have to see the satellites to be able to talk to them. Flight Dynamics can calculate the times and positions or respectively the directions where the satellite will be. As you can see, all these tasks are very mathematical. This means that you need some tools, which are also, let's say, tested for battle. This is one of the most commonly used programming languages. This is very good, it works very well, and nobody wants to use anything else. Let's go back to the control room. We have talked to Flight Dynamics. They told us that the satellite will be at a certain time in a certain place. We don't take it in any case. Then we have to communicate with the satellite to make contact with the satellite. We need a ground station for this. The picture you see here is a ground station in Weilheim, in Bavaria. This is basically our main ground station. They know where the satellite should be at a certain time over the horizon and then try to make contact. This first contact recording is called First Contact and this is of course a very important moment. As soon as this connection has been made, various things will be carried out. First, there is a download or a download of data, i.e. telemetry data. This is the current status of the space vehicle. We want to make sure that the space vehicle works according to the start and later the payload data is downloaded, e.g. pictures or whatever the satellite should measure or do. Then there is also a link, i.e. the upload of data, e.g. commands what the satellite should do, but this can also be kept as a software update. The other thing that the ground station should do is ranging. That means you send a packet, a data packet to the satellite. The satellite will answer and these two signals go with the light speed and if you know exactly how long the satellite needs to process the answer, then you can calculate how far away the ground station is. When you do this several times, you can see a distance profile and from this you can calculate the payload. So, let's take a look at this again from the ground. On this picture you can see a ground station and we have a satellite which is not measured. This satellite now flies 600 km over the ground. You can scale it like this. The signals of the ground station have to be dampened by the atmosphere and we only have one final area where the ground station can reach the satellites. The animal is drawn in red and this is only given to a certain part of the runway. In numbers this means when we have a satellite at 600 km altitude, it takes about 90 minutes to round the earth and you can communicate for about 10 minutes with a certain ground station with this satellite. That means we can see all the 90 minutes for the 10 minutes. At this time we have to do all the data transfer, downlink, coupling. Unfortunately it is a bit more complicated because the earth rotates. This map shows the projectile where the satellite flies through. This is the red line. After 90 minutes the satellite is at the same place but the earth rotates a bit. That is why you can see this pattern and it is not a closed circle after 90 minutes. In Europe you can see the VHM with this black line. You can see that you have two contact possibilities per satellite per roundup, per period. The third part of the satellite would be outside of this area. You can see the same picture from the North Pole. These are actually circles. That is only the projection. That is why it did not look like this before. This is what it looks like when you look at it from the air. The others are typical maps that you typically see. Now we have found our space vehicle. We would like to talk about it. What frequencies can we use? First of all we can see that it has, among other things, water vapor in the atmosphere and it absorbs a part of the frequency spectrum. At 2.4 GHz there is a peak and that means that we want to limit our frequencies to smaller frequencies. For example we would have a higher range but less data. For space vehicles the lower part of the graph may be even lower than it is here. So below 10 GHz. For example we can use UHF, which is 430 MHz. That is a typical amateur frequency. The L-band is 1-2 GHz. That is the main frequency of the GPS satellites. The S-band is a typical frequency for 2-4 GHz, which is used for telemetry and T-befaces. That is very important for us. The X-band is a higher frequency, suitable for higher data rates. It is used for large payloads, for example for images and so on. It is also used for missions in deep space. There is also the KU-band for TV satellites and the KA-band, which is a bit above the water vapor absorption maximum. It is used for various applications with higher data rates but it is mechanically difficult because of the directive antenna. It is not trivial and it is used for money. When we have fixed its frequency, of course you have to modulate a signal to send it to the satellite. That also requires a certain level of field correction, but we do not look at that in detail. But there is a very specific standard which is used, which makes this field correction. We are very happy in the control room. We have made our first acquisition. That is what happens when people always listen to applause. And now there are a few things that are still to be done. Now the work starts. For example, the satellite is running on batteries during the start and after that. But of course it only needs a current and that is why you have to fold solar panels. That is done in the value of the LIOVS. The same applies for antennas. I have shown you various frequencies and normally satellites have several antennas and use several bands for different tasks. For example, commands can be transmitted as an S-band, but the data downlink, the user load, may be made as an S-band. That has to work out. That is what happens when we do the transfer maneuver to get to the final orbit. And other parts are switched on. For example, start checkers. Start checkers are cameras that take pictures of the sky, of the stars and compare them with a data bank of the known star position on the vehicle. That is how the space vehicle can find out in which direction this camera is pointing. Now we know how a start tracker, if it is known how the start tracker is mounted on the space vehicle, you also know how the space vehicle is mounted. That is good if you want to make pictures, because then you know what you actually have in front of the lens. Something else that is now turned on or brought to speed are reaction wheels. They are basically circles that turn very quickly. You turn them up and that stabilizes the space vehicle. Because you want to control the rotation of the space vehicle in most cases. So now we hope that everything worked out wonderfully. We started the thing. But it doesn't always work as it should. So an example. That is TV Set One. Well, I don't have a picture, but it was a German television song from 1987. Everything worked as we said. So first acquisition, telemetry. But the solar panels were partly out of place. And the problem had to be diagnosed and repaired as quickly as possible. So the first thing we have to know is that we can't get all the data we get. We have to somehow confirm that what we actually see is true. For example, in the case of such a solar array, we can check how much energy comes out of it. It is significantly less than expected when it has worked out quite well. It shows up, yes, we don't have enough power. Second, now you can give a manual order to unfold. It can be that the automatic unfolding doesn't work. We just tried it again. Unfortunately, it didn't work. So it still worked. Now you think, what are we going to do now? And you ask the manufacturer of the satellite for the first time. The manufacturer even sits in the control room during the Liop phase. Then there will be a lot of questions and then you need someone on site. You or the people who served in the satellite have made different tests to find out what's going on with the satellites. There are two things we could try. Either orient the satellites so that they are at a 35-45 degree angle to the sun and then start turning it. If you do that carefully and miss the current output of the solar array, then you can guess the angle in which the solar panels are unfolded relatively well. We did it and we found out that it didn't work at all. Less than 2 degrees. That's a problem. Then they did different other tests and came to a possible problem. The black box here that the array has been holding on to for a while during the start could still be there. In fact, it should have been removed or fallen and then the solar array would have worked out. But it looked like it was still there. One thing you can try is to rotate the satellites again and that is to throw a little shadow on the solar array. That would reduce the energy output even further and a little bit, which you can maybe measure. That way you can confirm that they are still there. Imagine that it wasn't really good to measure, so it didn't work. But they were still there. They were the clowns. If the problem was diagnosed once, then you can solve it. How do we solve it? Here you can just follow your creativity and develop all kinds of solutions that you unfortunately can't get out of. One problem is that we increase the voltage rate so that we have a very high centrifugal force and so maybe solve the clowns. Another possibility is to speed up the space vehicle with the main power plant, pulsing in order to apply such a resonance in the corresponding parts. Hopefully you will solve it. Another possibility is to stop or cool the space vehicle by commanding it and so to solve the connection between the clowns and the clowns. Another possibility is... Well... Why don't we overdo it? We unfold my antenna and in this case it was the main antenna that was stuck under the solar panel and we tried to open it and we hoped that it would be able to activate the solar array with different power. Unfortunately, nothing worked. We tried to calculate these satellites but they weren't successful. Our main problem was that it was a TV satellite that really needed the main antenna and of course the antenna couldn't get out because the fixed solar panel was blocked. In this case it didn't work but mostly it worked. There are sometimes very interesting, very creative solutions to a real problem so that everything works out. If we have our space vehicle in a stable and secure status we will end up with Liob and test the properties of the space vehicle. It's called commissioning or on-orbit testing. This is generally longer than Liob. It can take several months depending on what kind of mission it is. In this case this is the phase in which you actually use it and verify if it works as you expected. In the world you see a geostationary communication satellite. Its hope is the communication arrays i.e. the antennas. Here you can simply check if the antennas work properly. When it starts, of course they are shifted through. It's pretty hard. So it's better to make sure that they work properly. One thing you can do is to calculate the satellites on the station and move them and measure the signal. This way you get a kind of pattern of the radiation of the antenna. It's a property of this particular antenna that you can use later. The other thing you do is to check the redundant components. So with an earth observation mission you have to know where to look. You need a GPS or a start checker. If that's wrong, you obviously have a big problem because you don't know where your satellite is taking pictures or pictures. In general there are a lot of redundancies on satellites. There are two GPS receivers that are switched on and off and in this phase it's checked that they work properly. So we have done this and everything works as it should. Then we start with the routine phase. The routine phase is the main phase of the operation. This is when the experiments take place or the communication satellites are offered or whatever it is that you have in mind. This picture is one of the Terrasat Tandem X mission. These are two radar satellites that fly in the low earth orbit. And they can make three-dimensional maps of the ground by setting the signal and receiving it again. Because they fly in so close to each other they get a stereogram that contains 3D information. In the routine phase a scientist is required to record certain data or pictures online and the control center is required. The data is downloaded to the earth and passed on to the scientists. This is the main phase. In this picture it's a picture of an American-German mission. It was about... These were two satellites that had a laser link or a microwave link in between them. The goal was to measure the gravity of the earth and there was also a... there was also a day a lecture about the successor mission later. In this phase you have to monitor the vehicle. Everything still works as it should. You have to adjust it for new missions for new parts of the mission new women's missions and you have to upload new software for it. Something different about this another problem is that the vehicle gets older for example the battery can get weaker and you have to adjust it. If you have less power available then you have to take less data and you have to constantly monitor it and adjust accordingly. How does this monitoring work? This is part of the TCTM or data system. The idea is that the vehicle will miss different properties and will continue. For example we have the temperature of a certain part but think about it we don't have it live but we can only download it from time to time and then we will get a big amount of data. Ok This is the condition of this space ship There can be up to 20.000 very, very many data points that you want to have measured. Imagine if you measure something once in a second for several years there is a lot of data very fast, a lot of data and you can analyze it very well you can find anomalies in the data and what you do is you kind of save it in an offline database because different other part systems want to use this data. This is an example for telemetry this is a software that we use called GECCOS and you can see telemetry packages that we have received there is confirmation that a certain check sum was correct that you received a ping and that it was answered everything has time stamps and so you can understand it very well as soon as you can see the condition of the space ship you can give it a command by taking this TC command on this picture you can see some commands which have been executed but also some other which have to be executed for example in the upper part of the picture you can see the pings which were not answered but the last one was answered the operator for example prepare commands and execute them relatively quickly this is the lower part this is of course very specific for each space ship some of them are offered by the manufacturer and you have to understand what you can do usually you don't just want to do very small things atomic things but a big reaction for example telemetry test and you can do that as a flight operation procedure a bundle of things which should be executed on the space ship what is also important as I said more times you can see the ship is not always you can't always send commands and that's why you send a time command when the command has to be executed this a TC this command this is for example a TTC for a manoeuvre so for time T0 you want to execute the manoeuvre for example the the space ship that means you have to check before whether the space ship is in a certain state then you have to pre-heat then you can switch on telemetry for example you would switch on the debug mode the space ship to say that there should be more data and then switch on the the banners then it will vibrate and a lot of alarms would go off that's why you switch them off at some point you will actually get infected and at some point it has to be stopped and for the case of the case you also do a second stop so that the main thrusters are switched off and everything that you have changed is back in the old mode and this series you can load up as during a certain time where you have a blink and then automatically switch it off this maneuver thing is called a mission planning it is a little less known subsystem that is the point where you have to switch between automatic and manual control so if we want to take pictures of the satellite then we have to reserve it and this is done by the mission planning system and then you give a feedback to the scientists and so on and the telecommand operator will be able to find out but there are some small problems that you can always have you can't automate everything there is a certain amount of manual control that is still needed for example because of all of this weirdness the mission planning system is used internally to get into a conflict-free way to download the data you have to download the image before you want to download it there are two activities that have to take place in a certain order from these activities that have been requested by scientists the system makes a timeline that is given to everyone who knows what the space vehicle does here is an example the one software we use it is called Pinter and it shows on the x-axis the time and up there you can see these black and white things these are actually finstallises you can see here when the space vehicle is in the sun and when not there are planned experiments but one of them is partly planned in a finstallise and it has the idea that it is not allowed to take place in a conflict the system identifies these conflicts and gives the information to the scientist or the operator so that you can do something about it something else that you can see is something else that we talked about at the beginning you have to download the information from the experiment so you need opportunities for that and here you can see two of them these are the green lines from the blue background when the satellite sees a station and the results of the previous experiment can be downloaded ok so now we do half automated all our experiments we have a lot of scientific data but at some point everything has to end so you have to think about the end of the mission generally the mission time of a space vehicle depends on the mission target for example a special experiment and that is done at some point it can also depend on orbit if you have a space vehicle in a height of 3 to 4 kilometers then it will fall into the atmosphere within at least one year if the satellite is over 700 kilometers it will take more than 25 years until the satellite is down in a geostationary orbit you will never fall then there is something mainly for geostationary orbit the difference is the amount of fuel at some point the space vehicle can no longer stay in the position where it is so the mission has to end for geostationary satellites it takes about 15 years for such a low orbit geostationary orbit is often a few years but can often increase the lifespan if you are very careful with the fuel and only use it with thought so what do you do when the end of the mission is reached depends on orbit again at a satellite in a low orbit you hold some fuel back so that you can move around so that it falls from the orbit within 25 years and falls into the atmosphere these 25 years will be given today by the American FCC and also by the ESA you have to at least 25 years until the end of the mission so you can take leo satellites out of orbit but it is usually not only fuel geostationary satellites in this case you increase the flight about 500 km and do it in a so-called cemetery orbit nobody uses it for active satellites so you can bring them there and there they do not disturb then you can look back on his mission he spent a few years with it and hopefully everything worked well that a lot of scientific data and with that I would like to end my talk so thank you and enjoy the rest of the congress this works pretty simple you walk to a microphone so there are questions answers it is pretty simple goes to a microphone so it is really a lot of questions not for me, I liked the talk the first question goes to the internet our signal engel has twitter and ERC all the time there are questions on the internet he does not have a microphone so we do a different someone else his microphone unfortunately does not work ok, great test 1, 2, 3 if possible for example to move 4 satellites in a geostationary orbit as a communication relay so that you always had communication and why would you do that aha, that is possible and that is also done so the ISS makes the most communication with relay satellites and they are operated by NASA or ESA there is also a European data relay system that is used money is of course always an important factor if you use the system of someone else then you have to pay for it and therefore you minimize the possibility to use something like that next next question microphone 2 question on the internet how do you see the security of this protocol destruction and so on I can not give too many details because it is not my area the telemetry is typically locked so there is a lot of work so that it is with the payload with the user data they are not always locked for example the weather satellites the data from them can be received they are sent as clear text microphone 1 thank you you have shown an example of a satellite that did not work where who makes the final decision we cancel the project and who decides and in this example this satellite is already there where is it now? is it still there? two questions what is decided and what happens with the satellite stays there the I do not know the details because I have never been there but there are a lot of people who decide not only the flight director the flight director the project investigator who observes the scientific part there are more people in the organization who decide together and the other question for the TV1 you could still control the satellite that was a possibility to put it in a deeper space so that it would be illuminated I think it was in the meantime it is certainly already illuminated in the atmosphere you could use it to a certain extent but you could also reduce the orbit and worry about it you have noticed that you have a temperature time how do you find anomalies in it which method is used to find anomalies that yes there are a lot of parts and a lot of indicators that something is no longer okay you try to prove that something does not work because everything still works but if we have a average value but it gets slower then for example what you can see for example moving average in this particular example I do not know if it shows an anomaly I think that is the normal operation yes that everything worked well next question from microphone 1 you talked about commands send commands these commands are sent and interpreted from the satellite and can also send binary data so it is a kind of server you send a compiled command or a PI which the satellite manufacturer gives so the protocols are very efficient it is just checked that everything was transferred correctly and then it is executed so for example switch this part of the machine and there is just error checks check sums and so on and apart from that it is executed very directly sometimes you also have to upload the binary data for example something moves a little bit then the orientation is not correct and that is usually calculations new and then you have to upload a rotation matrix which is then stored in the on-board computer in the right place the next question from microphone 4 it is about the travel there is a lot of space and in any case there is a lot of space space garbage old satellite parts and so on space debris parts which could and damage our satellites there are some of them you also have to remove the sometimes to avoid it gets and more for example a few years ago a satellite was destroyed by the Chinese they want to destroy their own satellite and that has created a lot of individual parts small parts now you have a lot of small parts that you have to avoid instead of a big one so you find also online and the stars offer that they write a mail when the satellite is on the collision course and could you see how the further questions would be moved I can't answer that in detail but the ESA has different projects and there are also conferences which you could take part in but there is no final and good solution hopefully in a few years the next question I would like to add about this question it was talked about the captor syndrome in the Leo you also talked about the Friedhof orbit there is a second captor syndrome a little further away I'm not sure if I understood the question these Friedhof orbits are only for geostationary satellites because you can't get them down but then you take them away the question is again do we now have a new problem on geostationary satellites there are also geostationary satellites but with larger orbit it has more space so you take the density of the satellites you don't have the same problems as with Leo with Leo there were more collected faster than you could take them out of orbit and that doesn't happen on geostationary satellites and probably won't be a comment nowadays there are fewer geostationary orbits so in the long term there will probably be less and less a problem a question from the internet that you would like to know if if it makes you worry if spacex now wants to start 5000 satellites so spacex is talking about that many 5000 small satellites want to start is that a problem? I don't have details about this project but I think you talked about 4000 communication satellites in deep orbit I think they should communicate with less so should and they want a laser-based communication network and the information about it yes of course there are many satellites I don't know how high they will be if the problem will be caused but the FCC at least said that it's ok to continue let's see at the moment we can't say exactly microphone number 3 that will probably be the last question I would like to know how redundant is and antennas are the satellites built that a antenna for one frequency the tasks of an antenna of another frequency can take over for example in two scenarios if the antenna that should receive commands doesn't work you could use the telemetry antenna somehow so on the ground for example you can switch antennas for other frequencies so on the ground station can the antenna more frequencies on the satellite I don't think that it's really done but you can of course give the information in case it's very important of the construction of the base of the satellites some have completely separated then you can't route the information back and forth and on other satellites there is a communication bus where you can route the information back and forth and then you could do it that's why we can at the end of the lecture also we would like to get out of the passenger cabin