And to introduce this next talk, I will first ask you another question. Has anyone here ever had the chance to send something into space? One person, two persons, three. Well, more than I expected, less than I hoped for. This next talk might be giving you a small introduction to how to do that. So, our next speaker, let's just call him INCO, has studied first in Brunswick and built hybrid graphics with the Eric, which I am proudly representing here, not an advertisement, and then moved over to Kiruna, where he studied space science and then designed CubeSat. For the next hour, he will introduce you to this topic, and I hope he will answer this one important question. How hard can it be? Audience, give a warm applause to INCO with... So, you want to build the satellite. Yeah, thanks for the introduction. As has been said, I've studied in Kiruna, and up there we have Wayne Deere's iron ore mining and space research. And I just want to give you a brief glimpse of the complexities of designing a spacecraft, especially CubeSat. So, what is a CubeSat? A CubeSat is a Pico-nanosatellite following the CubeSat center. A Pico-nanosatellite is a satellite which falls in the arbitrary weight class of 1 to 10 kilograms, and the special thing about CubeSats is inside the Pico-nanosatellite task that they are launched not only as a secondary payload, but as a containerized payload. I will later tell you what this means. And the interesting thing about CubeSats are that they provide a relatively low-entry hurdle into satellite technology. So, a short history about CubeSats. There were small satellites before, especially amateur radio satellites which acted as relay stations for amateur radio users, but most of them didn't follow any standards, so there was a lot of reinventing the wheel. With progressing miniaturization of electronic components, it was possible to shrink these small satellites which formerly had about a cubic meter, maybe in size down to just the CubeSats form factor. And, therefore, CubeSats were invented mostly as a way for students to learn how to build a full-fetched satellite without having the long delay with previous small satellite projects. But since then, CubeSats have not only been used in educational context, but also in scientific research and technology demonstrations and even as commercial applications. So, what is in the CubeSats design specifications? Most importantly, it defines the CubeSats' shape and mass, but also it defines what makes the CubeSats so easily transportable as a secondary payload. So, for example, it ensures that the launch vehicle is safe from the CubeSats, but also that the launch provider doesn't have to worry about any liabilities for not adhering to regulation. So, mostly with regards to radio communication and orbital debris. But, in general, these standards inside the CubeSats design specification with the official document you can download is just the minimum common denominator between the different launch providers of CubeSats. So, if you adhere to this standard, you will definitely be fine, but often you can hand in waiver forms which give you small exceptions to provide more volume in certain directions or something like that. So, the CubeSat envelope basically almost a 10 by 10 by 10 centimeter block. I have chosen to teach the metric system to American students. It's not really 10 centimeters in height because we have small standoffs here, but close enough. And on the edges, you have these guide rails which have a defined minimum hardness because those are important to hold the CubeSats in place and later put them into space. So, from these space units, you have different defined form factors, usually whole multiples of the base one unit, so one, two, three, four, and so on, but sometimes you also see half unit CubeSats or one and a half units. So, another standard you might encounter is the CubeSat Kit Bus PCB which follows the PC-104 standard for the shape of the PCB and the mounting holes but has a special four-row connector. And on these four-row connectors, you have common voltages, battery voltages, digital buses, general purpose IOs. And a lot of commercial CubeSat components and substance you can buy follow to this form. Of course, this is a pretty big PCB and some manufacturers have gone on to define preparatory formats for fitting more functions in this same PCB form factor with sub-words and so on. Something which you might find unusual is that the mounting holes are not really symmetric, so, yeah, you have to pay attention how to mount this thing inside your structure. And these PCBs are then stacked and the connector here is just for the electric connection. The real mechanical connection which holds the PCB inside the CubeSat structure is done via threaded rods inserted here in the edges and then the PCBs hold together with spacers. So how is the CubeSat launched? CubeSats are integrated in so-called pod dispensers. So here you can see six pod dispensers in a bigger box and these dispensers are then mounted on the upper stage of the rocket. So, for example, on the payload adapter somewhere in between or even below near the engine. And after the main payload is gone and it had a good head start, so you can't hit it anymore, these pods are opened and the CubeSats are released. Here you can see such a pod, so the most important work this pod does is it contains the CubeSat during launch, so it holds it in place and even if something breaks inside the CubeSat it will not hurt the main satellite because this is all the rocket operator cares for. So you are integrated into these pods and this is basically the last time you see your satellite. It has some access hatches to remove arms and safety plugs after integration but then it's integrated, it's shipped to launch site and you don't see it anymore. Inside this CubeSat, in this case, a three unit CubeSat is hold by rails and sitting on top of a spring loaded pusher plate and then when time comes and you're in space the box opens and the pusher plate just pushes out the satellite into space. So some words about payload safety. The CubeSats design specifications have a couple of them, so for example the payload has to be that during launch so there is no power going anywhere inside your satellite. The batteries and solar panels are physically via launch switches separated from the electronics. This means that you get no communication after integration. You also can't emit any RF frequencies or magnetic fields by accident and therefore ensure that you're a good co-passenger. Also of course because the pod has to contain your satellite you are also not allowed to have very high density of energy inside your satellite because that has the potential of getting out of the pod. Let's put it this way. This is especially important if you want to have some pressurized containers on board or if you wanted to have a kind of propulsion for example chemical propulsion this is usually not possible because of this energy limit. There are further limits for example on hazardous substances so the workers on the ground are safe from your satellite or also on volatile materials which evaporate from your satellite and might recondense on other people's satellites on their optics or something like that. So this is not allowed. So I just want to go over the most important subsystems of CubeSat which you can see here. They are mostly similar to big satellites it's just the differences that they are miniaturized and you have a much tighter integration between the different components so you will see that there are some a lot of interdependencies between these subsystems. So starting with mechanisms and structure. So a mechanism and structure is everything that holds things in place or makes things move and you have to see that mechanisms are common points of failure in space projects so it's important that if you don't want to be one of the 50% of first time satellites CubeSats, first time CubeSats which fail without doing anything significant in orbit you have to verify them and the common mechanism includes for example antenna deployment if you have deployable solar panels they can be deployed and this is usually just done by spring loading them and holding them back by a burn wire which you burn an orbit and then releases. So verification what are common verification methods for example for launch vibration the vibrations during launch are much more severe for your satellite than just the static G-loads so how do you find out what kind of vibrations you expect you could read the manual nearly any major commercial satellite launcher has a publicly available user manual so area in five, so yours and so on so you can just find it on the internet the problem is they give you a vibration profile which is meant for the main payload and you are mounted inside the pod on somewhere else on the upper stage so you would need to know the behavior of the pod and the mounting to really know what your satellite feels so it's better to just look at your CubeSat launch provider they also have documents and they specify an acceptance level of vibrations you have to withstand before or during launch so that's usually what you test for and for my mechanisms of course it's usually easy to get it working on Earth under ambient temperature and so on and so it's very important if you have a crucial mechanism that you test it under the conditions that you might actually encounter in space so for example after it has been shaken from the launch or at the temperature profiles you encounter in space so it might have different expansions and might stuck or a vacuum might be a factor and also low battery levels because if you have burn wires and you want to deploy your solar panels and you don't have enough battery how do you get more battery power because you can't deploy your solar panels so please test them also under these circumstances so next few words about thermal so there's often a question is space hot or cold? it totally depends because in space due to the lack of atmosphere heat can only be transported over conduction inside the satellite radiation inside the satellite and to the outside only radiation and due to the small thermal mass of CubeSats you can get very high temperature variations even over one orbit so from in the eclipse area inside the shadow of the Earth and then in the sun so for example the FunCubeSatellite would publish its data online it has surface temperatures from minus 20 degrees to 40 degrees just maybe over one orbit so what you get is a radiation balance between solar radiation also some reflected solar radiation from Earth also emission of thermal radiation from Earth and then of course your satellite heats up also emits thermal radiation and then you get a kind of balance or let's say a budget so what can you do? for externally usually you can just on CubeSat level change the observability and emissivity values of the surface so let's say the color of the surface for IR radiation and so on the problem is that the large contribution of the surface will be covered in solar panels because you really need this power so you can't really just make it reflective that would be not a good idea what you can do for example if you have a problem with uneven heating if you have one side of the satellite always face the sun and overheat while the other one is relatively cool you can go in something called a BBQ mode which basically means you rotate your satellite so make it crispy from all sides but internally if you have some very sensitive heat-sensitive components you might want to insulate them to keep them away from these huge temperature swings you see on the outside of the satellite so for example you can start by insulating the side panels so these most important swings are kept away from your inside but then you also have to see that the heat you generate with electronics inside or with heaters inside has to go somewhere so you need some kind of conduction path to the outside this is a very complex trade-off so how can you verify it first thing you could do would be just think about if the satellite would just be masked with a surface in orbit under certain illumination conditions would it heat up to a certain temperature or would it cool down to a certain temperature so what is the radiation really balanced temperature so it just gives you the first idea of what problems you're facing but in the end you usually do a finite analysis and try to just calculate what is the temperature difference temperature distribution inside your satellite especially because with this shadowing time and then time and sunlight you really have transient behavior you want to you want to know about and then to finally verify it you usually do a thermal vacuum test also to know if the models you did here have anything to do with reality that isn't always the case so thermal vacuum because of course if you would have convection this changes the physics a lot because this is much more prominent so you want to do it in a vacuum environment and of course you might think ok this is relatively late in the development schedule because you already need your components and maybe if then there is a major problem this gives you a lot of problems because everything else is already developed so maybe in the only stages of your development you want to test the structural model with resistor heaters as dummy loads basically for heat so to the attitude determination control subsystem the attitude is the orientation of the subsystem space you can define different frames you want to know your orientation inertial frames so non-rotating basically with regards to the stars Earth centered frame is interesting if you want to do Earth observations Sun centered frame is interesting if you want to know something about the thermal conditions or your power generation and for control what do we have to work against so we have to work against radiation pressure from the Sun we forgot some magnetic cleanliness so magnetic cleanliness basically means if you have built your satellite and launched into orbit you might not have built a satellite into it you might but that comes later but if you don't want to have a magnet in your satellite you still have some kind of magnetic field so for example because you have magnetized materials inside or just because of the currents flowing inside your satellite and this creates a talk with the Earth magnetic field and gives you a disturbance but also if you have a maybe a little bit larger CubeSat you might encounter uneven drag for example if you have a deployable solar panel or something like that so even the not very dense atmosphere might give you some kind of disturbance talk and if you would have a really big satellite or maybe have a tether or something just the changing gravity with height induces a torque trying to reorient the satellite so how do we determine our attitude in space in this way would be just use the illumination so this just measures the illumination of the Sun the solar flux on your sensor and then says okay I have a sensor on each side of my CubeSat and then I try to determine from where the Sun comes of course you always have a degree of freedom rotating around the direction where the Sun comes from because this doesn't change your reading but this gives you a reading in the Sun centered frame then you have the magnetic field where the smartphone you can use the compass to determine the way you are heading you can use a more sophisticated Sun sensor this is different from the emulation sensor in that you usually have some kind of baffle system which projects like a slit of light on the sensor and then you can determine directly an angle where this light came from so this is more accurate you can use Earth horizon sensors which basically try to detect the Earth or just the line where Earth meets space and then you get a reference in the Earth centered frame and the highest class usually are star cameras these are literally cameras looking at the stars and then from the picture they see they are looking with an algorithm in a star catalog and trying to determine which stars they have seen just by the brightness the relative positions and so on and from that you really get a good knowledge about your attitude so why would we control attitude so after deployment due to the deployment mechanism with the push-up plate you usually have some tumbling it's not perfect so if you think you can just be still and then do nothing, of course you have to store in stocks but you also get tumbling from the start then of course you might have a payload which requires pointing so your camera wants to look at Earth or things like that then you have antennas they want to be pointed to the ground station and also if you have antennas which are nearly omnidirectional but have some zeros some places where you don't really radiate anything to then if you just tumble you get just fading signals so this signal goes down and you might not be able to send a complete packet and of course if it is too excessive the antennas might actually bend and then they are behaving completely different because RF is black magic so another important thing is power collection especially if you have a deployable solar panel you really want to use it then you of course should try to orient yourself towards the sun and then you also might want to have attitude control what problems do we encounter I mean if you think about normal motion if I push something in a direction Newton says it should start to move in this direction and continue to move in this direction this is nice if you have a torque around an axis it would probably just start to tumble the problem is that if you look into the physics the motion around just arbitrary axes are usually coupled so this is a matrix that would come into play here and there are only three defined distinguishable axes in each solid body where you don't have any coupling the so-called principal axis but only even two of them the motion is stable so one of the three axes will again start to make a tumble so if you want to have a satellite which moves around a certain axis maybe because you want to have a measurement or something like that then you should think about distributing the mass inside your satellite so that it's easy for the control algorithm to control it so maybe choose a principal axis for that which is stable a couple of methods how to stabilize the satellite especially cubesat the easiest way would be passive magnetic stabilization you by choice put a magnet in your satellite which is fixed to the frame and it of course tries to orient itself like a compass needle to the earth magnetic field the problem is of course if it starts to orient itself it gains kinetic energy and basically then goes into a pendulum oscillation so you also want to have something which dissipates this movement away so you also have hysteresis rods here which have hard ferromagnetic material in each direction and inside these the movement is then dissipated of course there are limits because I mean it's easy so it has to be somehow flawed so you have interference with your attitude to termination I mean if you build a huge magnet inside your compass then it will not work anymore it's not easily changed for a fixed position over the earth because I mean if you really built this hard into your satellite then maybe you can use it to point your satellite to your ground station directly above but in any other position above earth you don't really have any wiggle room to readjust your position the accuracy is not good and of course you still have a degree of freedom it just rotates around the magnetic field line because then there is no torque applied and you might have deployment problems because let's say we have two of these in one deployment pot they are pushed out and then they are just attracted that's not good so the next step up let's say is active magnetic control we have electromagnets inside the satellite so for example air coils integrated into the kubesat panels here or maybe also magnet talker watts which are just slender slender electromagnets inside the satellite structure and yeah just by controlling the current going through it we produce our own variable magnetic field so we have a lot more degrees of freedom to control it and move the satellite around so for example in combination with the magnetic attitude determination we can use something called a B dot algorithm to just detumble the satellite so then afterwards it's just spinning around one axis that's nice but of course this as opposed to the other one uses power, power is scarce and again you have one degree of freedom so if you are let's say spinning around the magnetic field line and you want to stop that there is not much you can do so even more accurate are reaction wheels they are basically fly wheels with an electric motor and as you know actual is reaction so if we put a torque on the fly wheel the motor itself and the whole satellite it's mounted to will get a torque in the other direction so with this you can get very high pointing accuracy the problem is for example if you have a disturbance torque which always has a bias so always tends to push you let's say clockwise then you always have to apply counter torque in the same direction so you add spin to the wheel and spin to the wheels until maybe the bearings fail of course you don't want that so you need to have the way to have another type of attitude control to desaturate your wheels and of course this needs also power and needs continuous power because we would just stop power to the fly wheels then they would slow down due to friction and this would give the torque you put into them back into your satellite so the whole thing starts to spin and tumble again you usually don't want that so again this needs more power a few words about communication so to let me to enter command if you can't get data to your satellite if your satellite doesn't respond then the satellite is bust so you really want to have this thing nailed down first measure usually after you are deploying your satellite or if there was any fault and the satellite goes into a safe state it starts to transmit beacon which is just a short package burst which includes the most important telemetry values of the satellite this A helps you to locate your satellite so for example after launch you have just a flock of satellites which were released these are yours so you just try to ping each one and whichever sensor beacon might be the right one so yeah, if in case of failure you just get the most important values you need to debug the problem or at least find out what's going on so different types of antennas the easiest type of antenna are just these kind of extending rulers bent over the edge and hold down so if you burn this wire it flips up and you have a working antenna if you did everything right you have to distinguish between directive and omnidirectional antennas so these types of antennas are usually near omnidirectional so they have a monopodipole return site configurations and they are very good for let's say lower frequencies if you want to have a directive antenna you usually go to higher frequencies because there it's feasible to construct such an antenna because the same structure used for example here for this antenna would be much, much larger if you go to these frequencies here and basically here we have a patch antenna which really just is a patch helical antenna, of course here you would have another point of failure because you have to deploy this in orbit but these are the most common forms of antennas you see on CubeSats so just a few words about frequencies common CubeSat frequencies if you come from the amateur radio edge of the spectrum are 70 centimeters and 2 meter frequencies so about 430, 144 megahertz very common long time use for amateur radio purpose and the nice thing is because the frequencies are relatively low you have pretty efficient components problem is because the frequencies are so low the available bandwidth or the bandwidth you are allowed to use is relatively small so you get only about 9.6 kilobits per second while the satellite is in reach of your ground station this is only just a fraction of its orbit so you need a lot of orbits to get let's say a picture down and of course the high gain antennas for these wavelengths will get pretty big and you can't put this on your CubeSat probably so you might want to go to higher frequencies especially popular with commercial CubeSats which get some kind of licenses so usually not operated under amateur radio regulations and those get signal rates up into the megabits per second range so that's much nicer because they have more bandwidth available and if you don't need your higher data rate you want to use less power then you can also use the higher bandwidth to increase your link budget so the transmission is more reliable so just a few words about the protocol really just a few common protocols you might want to look into if you are interested in things like that would be X-25 which is an amateur radio, a packet radio protocol which is used has been used for lots of CubeSats especially in the older days if you want to take a look at the satellite communication protocol which is a little bit more advanced which is also used for big missions and big satellites you can take a look at the available documentation on CCSAS which is used for ESA missions and please note that especially if you need a good connection for example if the satellite just started tumbling you want to recover it then it's important that your protocol is able to work with a weak signaling I heard of people trying to log on with SSH on the satellite not a good idea needs hand shaking so more on regulation so of course if you want to use amateur radio frequencies you are as an amateur radio user usually allowed to use them but you should go through a frequency coordination step which just makes sure that there is no other satellite in similar orbit sending on the same frequency and then you get a lot of restrictions which vary between the restrictions based on for example are you allowed to use amateur radio if you get a government grant or is your ground station operator allowed to be paid for operating ground stations things like that but in general there is at least an exception for commands being sent to the satellite because they are allowed to be encrypted everything else under amateur radio regulations has to be clear text so it has to be readable it might be compressed that's okay as long as it's documented but commands to satellite is the only thing that is allowed to be encrypted so you can use amateur radio and what is also important is that you have a fast and permanent transmission kill switch so if your satellite goes haywire and just sends carrier on your frequency you have to be able to shut it down and fast could even mean that you need multiple ground stations in middle latitude so we get it on the let's say in half a day or so and permanent really means permanent so there has been a satellite which has been sent to transmit again that is not good so please really make it permanent so if you are not operating on the amateur radio license you have to talk to your national frequency coordination agency then you can get something like experimental permits or things like that which allow you to use similar frequencies maybe even the same range and get a little bit more to see what kind of applications you use here but please note that frequency coordination and allocation takes a lot of time so it would be bad if your satellite is built ready to launch but you don't have your allocation yet so please look into it early in the project so electrical power systems it's all about power so usually for power collection triple junction solar cells are used are pretty efficient we have maximum peak efficiency of usually 27-30% if they are lit directly and afterwards you usually have a maximum optimum power point tracker which adjusts the load the solar cell needs so that the power which is sucked out of it is optimized because otherwise you might especially with this low voltage you have on just a few cells on the keepset side you don't really get the maximum power but of course you lose some power also due to these things so as every wheel circuit it's not really 100% efficient but let's say near the earth you get about 2.3 watts per cubesat panel when they are illuminated perpendicular so if you have a satellite which is rotating then you would get a slightly varying power intake and yeah on power collection please remember to include a charging connector for testing and also for storage because it is not very nice if you would have to put your satellite under a lamp every time you want to charge it during testing so how could we increase this power collection obviously we could try to increase our solar cell area so here a few common things we commonly see so for example just wings falling out or flaps going up of course if you look at this configuration when it's stored it looks like this this might not be a nice thing if you have to recover your satellite something went wrong during early phase because of the battery drains so you might also want to include a few solar cells here on the outside but then after they deploy they are shadowed and shadow solar cells tend to become loads if you don't include extra protection circuits so please this doesn't eat up all your power and gets hot so if you have collected your power you want to store it usually so often lithium batteries are used which for just a satellite bus usually the most temperature sensitive components so you want to keep these happy usually they are coming pre-integrated with a heater so at least you don't freeze them but what kind of capacity you need so you have to supply your satellite with power throughout the eclipse period so the period in the earth's shadow but also if you have short bursts of activity so for example transmission if you have a payload you have to operate then you need just short bursts of power and this is also cared for by the buffer of the battery here the problem is if you just look at the advertisement see 10 watt hour batteries and you can get yeah it should be enough you usually are only allowed to discharge 20% of that the reason is that if you think about your phone I mean it maybe last the battery lasts a year without that much drop in capacity but in a satellite you have a charge discharge cycle maybe every 90 minutes so you really want to limit your death of discharge so you get maybe two years of battery so what about verification yet important that you really test the whole power chain as one so maybe get some kind of lamp which simulate the solar spectrum and then see if really your battery gets charged if your consumers can get the charge from the battery and so on and also make sure that the efficiency values are according to your calculations because often in the data sheets even if you are buying a satellite electrical power supply you only get one efficiency value which is really not enough so please make sure that the efficiencies that occur under your operational profile are such that you don't run out of power onboard computer so really if you look at flown onboard computer systems you see everything from really small mic controls to embedded CPUs you can find in phones sometimes onboard computers are phones but this is not so often but you can also see some FPGAs which have been flown in CubeSats and of course in space you have to deal with a different radiation environment when you find an earth and there you have two types of effects one scene event effects for example latch up on this shortly and a bit flips memory corruption this later just messes with your program this can damage your software your hardware if you don't and then you get total dose effect which don't happen instantly but accumulate over the life of your satellite usually this leads for example to increase in power consumption of your electronics so if you size your power system take this into account that you have some head space for later in your satellite's life so what are latch ups latch ups are typically a cure if your heavy iron or proton hits a CMOS device and then activates a parasitic transistor if you look at the typical CMOS device structure here there are these two transistor structures here which are not really intended to be there but just because of the structure they can be there and now we have a particle going in here creating charges and those two are activated they're basically short circuiting your supply and this is of course not good because it heats and damages the device so if you are seeing a sharp increase in power consumption then it's a good idea to just reset the circuit because this will not turn off until the power is taken off and put it back again this is for just commercial of the shelf circuits if you have a better hardened integrated circuit then you sometimes get isolated substrates so maybe it's on a sapphire or something like that and there this kind of problem is prevented but this is one of the main reasons you often get resets on your satellite just because the power supply detected the latch up and reset the whole system so this latch up protection here is often integrated into the electrical power supply if you're looking at commercially available cubes at power supplies a few other effects on electronics which you might not have heard of soldering whiskers are small really small tendrils which are forming from soldering points but they are big enough that they might bridge to another voltage potential and then create a short circuit and this is especially problematic if you use a lead free solder so that's the reason why space applications are usually exempt from using lead free soldering another thing especially for launch vibrations it's always good to have strain relief so if you want to solder a cable to your PCB think about just putting it once through and then up so you can inspect it from the top and have some kind of strain relief here so that when the vibrations kick in you are not damaging your soldering point and always of course remember you don't have any convection so if you find formulas describing how to size your lanes on your PCB to send a certain amount of current think about if it's also the same under vacuum conditions without these cooling effects because now you have to dissipate all your heat through your PCB a few things about programming unscheduled results are to be expected so if your program has any problems with that then you should rewrite it for example if you have some state which must not be lost memory obviously which also sometimes creates problems with timing synchronization so after reset if you solder it it has no idea which time it is it might not be able to perform important work send when it's over a ground station things like that so for example there was own satellite which couldn't complete a mission because it's timer reset at one point and the sequence just didn't get through and then also as I talked about earlier program code might get corrupted so it's a good idea if you have a bootloader if it's not integrated into the silicon of your processor then just have a small very compact bootloader which is unlikely to get hurt and which maybe checks itself and also the other software program prior to execution and then if you have the space maybe have several copies so you can at least reconstruct your program code afterwards and if you want to update your software in space of course there's always a risk if you have really long term mission you might want to do it so then maybe space is a little bit apart if you have different software, different code blocks which fall out of your compiler prior to linking maybe have a relinker file which spaces them apart in your memory because then you can overwrite parts of your memory without having to shift back all the things that come after it so this would make it easier to update your software in space because you just have to make delta updates instead of reprogramming the whole non-volatile memory just some miscellaneous things about orbits so available orbits are mostly dictated but what kinds of launches are available because you're only secondary satellites, there are some startups who try to build rockets just for CubeSat launches but they haven't materialized yet so they do common orbits low Earth orbit with ISS deployment, they really don't have such a long lifetime maybe a month depending on your size but they are relatively inexpensive so I've seen it starting at let's say $60,000 for this launch and then we get a little bit more expensive if you want to go in SunSynchronous orbit I will tell you a little bit about that later $100,000 but here you get more interesting illumination properties if you want to do Earth observation or if you want to optimize your thermal or power budget and then we have not so common geotransfer orbits which are the orbits that rockets inject into if you want to put a satellite on the geostationary orbit which is pretty eccentric, gets you pretty far out if you need it but much less common than the previous two so what is the drivers on your orbit selection if you can select so the distance to Earth surface for example is important if you consider the power you need to transmit your data or get commands back to the satellite, the illumination is important because all the planes have different vectors to the Sun so you have different times in the shadow of the Earth, different times in sunlight, this not only messes with your power collection but also with your thermal behavior and here you also have variations over the year because the Earth moves around the Sun, that's known so then the next thing is radiation so if you don't want to study the Van Allen belts keep out of the Van Allen belts these are in the medium Earth orbit range and if you stay there for long then you probably get just resets all the time and something which might not be as obvious is there is an implicit lifetime limit so this is not yet legislation but in general it will be probably pretty soon that every CubeSat put into space must be re-entered before 20 years of its lifetime just to reduce the amount of space debris not every CubeSat launched last year has kept this limit so we'll probably have a long lifetime in orbit but many CubeSat launch providers now require to show that the orbit you launch in is compliant with this this also is of course dependent on the type of CubeSat you have and there are currently things in development which reduces your lifetime so for example balloons which inflate or things like that so about the some synchronous orbit because I found this interesting so if you would just have a normal undisturbed orbit and you would move along an orbital plane then as the year progresses the plane wouldn't change because it's static in the inertial frame so you see the illumination conditions here you have a midnight noon orbit named after the time zones at least flying over and then this changes to a dusk dawn orbit here because it moves along the so-called terminator line between light and shadow here if you have a sun synchronous orbit you're using the the fact that the Earth is not a perfect sphere it's slightly oblated so this distribution of mass here exerts a force and tends to rotate your orbital plane and if you are going into the just the right inclination so just the right just the right angle between the equator and your orbital plane then this will rotate it such that as the Earth moves around the Sun the orbital plane rotates with it so here you can see that approximately at each time of the year the orbit is stable and then you just need to choose which which basically local time you have here on your satellite so here for example you would always have a midnight noon orbit but you could also always choose a dusk dawn orbit so this would dusk dawn orbit would mean that nearly always you are completely out of one side in sunlight this is good for power maybe not so good for thermal but that's a trade-off you have to do so it's something about CubeSat transports of course you don't only want to build your CubeSat you want to maybe keep it stored at your university or hacker space location but then at some point you have to transport it to your CubeSat launch provider and there of course it's obvious you want to prevent excess humidity particle contamination in electrical and mechanical shock but you also really have to think through your whole transport chain so for example if you want to transport your satellite in your hand luggage at the airport at the airport you might be asked to open it and this is especially bad if you have taken extensive measures to keep humidity and particles away from the satellite so I also heard stories about experiments headed to Mars which were asked to be opened at the airport so please make sure in advance that you don't get into any problems like that and of course then also after the transport you want to check for transport damage and if you can't look into your satellite anymore maybe think about that how do you can verify that there really was no damage just have a basic check so yeah I hope I could give you a small glimpse into the development and what kind of peculiarities there is in satellite and CubeSat design if you think it would be best if you look up other CubeSat projects usually they if especially if they are university projects they write papers about operation and so on and there are lots of interesting things to find here and I just want to remind you that verification is key so if you have a thing that must work then you have to test it otherwise can just think it probably won't work and if there is something a risk you take then think about a plan B so first what do you do is there any mitigation at least you can do maybe a reduced set of science measurements or things like that so yeah and this is the end of my talk I hope it was interesting for you and I think we can do Q&A now yes so thank you very much so for now the usual please line up behind the microphones while we see if we have questions from the internet I don't see our signal angel so just line up it wasn't really interesting talk by the way so oh yeah please leave the room quietly because we are still wanting to hear the questions that might occur and as we can see there are many many questions that's interesting okay we'll just start over there hello hello thanks for the talk I've heard about Intel Edison boards Hacker PCB something like that used for concert do you know about any Hacker PCBs like Raspberry Pi or Arduino clones which are which can work at the space fine well depending on how you build it it's more the question of how well it will work so as I showed you about radiation there are some things you have to design around for and so on so there was at least Arduino I know for certain that there was a mission which used Arduino at least compatible hardware as on the computer but this was also as if I remember correctly mostly done so that other people can program for the satellite so it was more used as a compatibility thing and not for any other obvious advantage in hardware architecture programming but these PCBs are not specified for such circumstances such conditions well the problems you might get with just commercial of the shelf PCBs for Raspberry Pi also are for example as I showed you these soldering whiskers because they are certainly produced without lead in their solder and there have been even full commercial satellites which failed due to soldering whiskers at least that's what they think it was so this might be a problem and then of course the whole way structures might not be ideal to mount inside a satellite but that has to really depend on the PCB I can't give you a general answer for that thank you then you have two questions from the signal angel so yes an IRC a photo is asking if there are any satellites up there that can be used freely and legally by hobbyists well if you are a licensed amateur radio user then there are some amateur radio satellites up there so then you get most of them are relay satellites so you send analog signal usually sound up there and then it just gets repeated on a different frequency down but they are also not sure if there is anyone active right now but there is also some radio satellites in the past which used some kind of message boxing technique to transmit message but as I said at the beginning you have to need an amateur radio license to use these satellites and the other question is from Handsome Pirate asking if you would recommend to use a red hardened CPU and memory well the problem with these are if it's really red hard then they cost usually a lot of money because they have small lots and so on and they are usually at least that I know of not many CubeSats which use this kind of technology so at least the consensus among the CubeSat design seems to be that you should rather design around the radiation problem than to just select hardened components because especially if you are using the CubeSat form factor because it's cheap maybe you can accommodate for a certain failure rate then you don't want to get into this just expenses with red hard components ok then we have questions here on the for you left side yes I have one comment and one question actually and the comment is if you think about orbit think latency especially if you do communication because at certain altitudes the speed of light actually is your limit for communications and it takes a while to get there and if you especially go in high orbits like geostationary orbits you have significant delays so that's from my experience with geostationary satellites but my question is also regarding orbits till what orbit do you know if GPS is available or is it available at all well there are lots of tricks I mean GPS I use on CubeSat the problem is that if you just buy a GPS receiver off the shelf there are these limits built into it usually so that you don't use it to build intercontinental ballistic missiles so they have a speed limit and while on high altitude balloons you usually get away if you find something which needs both of them violated to shut down on a satellite you violate both of them so either you need some special firmware for that or use a component which is built to meet these requirements but of course those get pretty expensive so it's definitely possible to use GPS especially on the lower orbits because GPS is more like a medium Earth orbit but even if you are above the satellite the GPS satellite orbits there are I'm not sure if I think it has been used already but the antennas of the GPS satellite try to illuminate basically the whole Earth but they have some overspill so if you look at the Earth then a GPS satellite coming from the other side you get a signal and by a trick like that you get also some GPS reception on higher orbits so it is possible it has been done but I don't know of any component you can grab for that interesting and one more thing are you familiar with the alternate project the alternate which is actually an attempt to build a global internet with CubeSats but they are not very far yet I guess but have you ever heard of that? I'm not completely sure I heard of one project which I think wanted to use I'm not sure if it was CubeSats I think they use just regular communication satellites to distribute information but I'm not sure if this is the same project I think it is currently they are using the existing satellites so just broadcast things like Wikipedia and stuff as I said if you just use let's say amateur radio frequencies the problem is also in low orbit of course the satellite just wooshes by so you maybe have a 10 minute contact window and you don't get a lot of data down this time and so if you really want to distribute a lot of information then you might have to think about how to time it and how to maybe use multiple satellites and of course transmission on the satellite is often some of the more power hungry things so if you're looking at your overall power budget this might also limit the time you can transmit at all and you need multiple tracking antennas which is also a problem I mean this of course depends on what kind of signal and if it's a very robust signal which can penetrate even noise or something like that then maybe you get away with less a less directive antenna on your ground station but yeah it's of course a tradeoff thanks okay we don't have an endless amount of time left so maybe if you have longer questions it would be nice if you could ask them afterwards and for now on this side there might be another one just wanted to ask if you have a tip or something where we can get some of the already computed data or something cool project on the CubeSat you can recommend well if you are just interested in let's say CubeSat housekeeping data then I already mentioned the FunCube project once they upload all the housekeeping data they have on the satellite so if you just want to know how just the environment is approximately on your satellite in orbit then you might take a look at their website yeah there is a slight problem with the data which is that if they don't have data for a certain time period they still give you data but it's just repeated over and over again with a new timestamp so if you want to scrape the data you might have to filter it out afterwards but at least that's where I got some just data on housekeeping okay again over here the UV pool so you told that battery discharge is limited to 20% of the capacity can there be another types of batteries which is more designed for such kind of temperature swings or I don't know ionizers I mean of course you can look at the whole range of available batteries the problem is that well CubeSats often are more volume limited than really mass limited I mean often in space you hear about mass and how much is cost to put a kilogram into orbit or something but CubeSats it's really more the problem of just putting everything into your small space so you basically have a similar problem as you have in your smartphone and that's why they both converge maybe to the same type of technology because it's so far above the energy densities of other alternative methods thank you before you can ask the next question everyone that's leaving now it would be great if you could leave through the door near the stage because there's already a queue outside and then it's not getting up wrangled and you know many people and stuff this microphone thanks for this amazing talk my question is how do you maneuver your satellite in a specific orbit once launched and another question how does the electronics react under a high vacuum condition such as capacitor wouldn't it evaporate yeah well of course you sometimes see space vacuum applications that they just coat their electrolytic capacitors so it's somehow encapsulated but of course if you have a space application you might try to get just away from these kind of capacitors the other thing about in-orbit maneuvers the problem with that is that there you get into let's say rocket propulsion territory which means you need mass mass and energy to make any kind of maneuver and as I said usually if you would just need a small engine a chemical engine might be the way to go but you are not allowed to have dangerous substances or high energy content in your satellite so these kinds of engines usually can't be used there are some projects at the moment which try to develop let's say iron engines use the power collected by the satellite to propel medium and thereby generate some thrust but even if you would think if they are brought to applications and use the amount of thrust they give you the amount of total change in velocity so-called delta v is not that much so you might be able to extend let's say your lifetime if you are in a lower orbit but it's difficult to stay on the same orbit significantly or even change the orbital plane that's very expensive so yeah it's currently not that feasible in a CubeSat to make big changes I mean there are these light sail projects going on let's see what they get at but at the moment there is no component you can use for that so you basically stick with the big satellite usually you stay on the same orbit the upper stage left you on and of course then you have all these disturbances which changes your orbit but in general you stay on the same orbit okay we are out of time thank you very much again