Now Ye're Talking - to the team for Ireland's first satellite, EIRSAT-1

enda1 wrote: »

Which university departments/faculties are getting involved?
I presume astrophysics, mechanical, computer, electrical etc.?
Yes, we have a great diverse team, mechanical engineers, electronics engineers, astrophysicists, detector physicists, software engineers, mathematicians, aerospace engineers, space scientists etc. UCD is the lead university, with Queens university Belfast as partner. We've had students from UCD, QUB, TCD and La Mancha in Spain, working on the project so far...

Where is the technology being built? Like the physical gamma ray detector etc.?
The gamma-ray detector is being built in UCD Space Science group, in the School of Physics.
The EnBio module is being built in EnBio and in UCD School of Mechanical & Materials engineering. They are all being built by students.

When is launch date and is it from French Guyana?
We don't have a launch date yet, possibly late 2019/early 2020. The satellite will go up to the ISS and be 'released' into space from there.


Good luck!

Thanks Enda.

Haughey Was Framed wrote: »

Sounds amazing! So many questions!

How long will the satellite be in orbit for?
How is it powered?
You mentioned it's being launched from the ISS - how does that work? Is someone throwing it out a window?

Good questions!

The satellite will be in orbit for about a year. We've done simulations that vary from about 9 months to possibly up to 2 years. Why so uncertain? At the relatively low altitude of 400km, there's still enough atmosphere to cause a significant aerodynamic drag which slows the spacecraft down and eventually causes it to de-orbit. The amount of drag is dependent on solar activity amongst other things so it can be difficult to say for sure. We make a best estimate based on the past solar activity during a similar phase in the solar cycle.

The satellite will be powered by solar panels. It will have solar panels covering the 4 larger sides. It's a lot easier on such a small satellite to have panels that sometimes face away from the Sun than it is to include the necessary systems to make sure the panels point straight at the Sun. The satellite will also have a battery so it can remain fully operational when it is eclipsed by the Earth.

The launch from the ISS is about as close as you can get to throwing it out the window in space. It will be loaded into a CubeSat deployer with a number of other satellites. The deployer is basically a tube with a big spring at the bottom and a remote controlled lid. So it's kind of like a Jack-in-the-box or even a Pez dispenser. The Japanese module on the ISS (Kibo) has a small airlock for experiments. The deployer will be taken outside through the Kibo airlock and a robotic arm will pick it up and point it away from the station and then the lid will open and all the satellites will be "launched". We need to include some very small springs in the end of EIRSAT-1 to push it away from the other satellites that it will be launched with.

Thanks!

Gloomtastic! wrote: »

How much will the project cost and where do you get funding for something like this?
Hi there!

We estimate the cost of the mission to be about €1.5M over 3 years - this will be spent on supporting studentships, internships and of course materials and much more.

How many points did you get in your leaving?
The EIRSAT-1 team members have achieved a wide range of points in the Leaving Cert. Here are two team members backgrounds:

David Murphy, System Engineer -455, but that was before bonus maths points.
Lána: I got 560 points in 2013 - lucky enough to get into the UCD Science undergraduate course! Whilst most people think that you need to be a genius to be in astrophysics, I think our team represents a wide range of abilities and we all work to our own strengths.

Do you like watching sci-fi movies/programmes?
Yes, we love Sci-fi - doesn't everyone? The EIRSAT-1 team are serious sci-fi movie/programme fans.

If yes, which is your favourite?
David Murphy: Wow, that is very difficult to answer! There’s so many good ones! I’m just going to have to post a list of some of the ones that I love. 2001: A Space Odyssey, Moon, Gattaca, The Fifth Element, Sunshine, Blade Runner, The Martian, Interstellar. I could go on for a lot longer. On TV, I really enjoyed The Expanse, though it’s not as good as the books. I appreciate how they always go to a good effort to get the physics right.
Lána Salmon: I'll have to agree with David, and add the new Star Trek movies! Although it's not really sci-fi, BBC documentaries like Wonders of the Solar System were my gateway into physics.

Also, do you shout at the telly when they suggest doing something you know is not physically possible?
David Murphy: Yep, I’m very guilty of this. Though I have learned lately to try and leave it go, you can enjoy it a lot more that way. Sometimes they have to introduce one big inaccurate concept to make the story work - that’s what makes it fiction, right? But it still really annoys me when there was an easy way to get the science right without effecting the story.
Lána : I think physicists/engineers love talking about whether what happens in a movie/tv programme is physically possible. Don't get us started about Interstellar!

Good luck to you and your team, hope it’s a great success!!!

Thanks so much!

frozenfrozen wrote: »

any pictures of renders or anything so far so we can see what it looks like?

We don't have any photo-realistic renders yet, but hopefully this gives you some idea. To give you a sense of scale, it's 22.7cm tall! The antennae that you see sticking out at the bottom will be stowed for launch and we'll deploy them 30 mins after leaving the space station.

frozenfrozen wrote: »

how are you going to be communicating with it, is it 1 way or 2 way communication and what kind of security is there for accessing the information gathered by the satellite? Is there a constant stream of data or is a period of time sent in bursts?

We're hoping to communicate using amateur radio. We don't have a frequency allocation yet, but the Irish Radio Transmitters Society and the International Amateur Radio Union as well as ComReg have been very helpful to us so far. It's two-way, we'll use 9600bps downlink on UHF and 1200bps uplink on VHF. That's not a very fast connection! And to make matters worse, it will only be in range of our ground-station at UCD for an average of 6.5 minutes per day! So we have think really hard about what data we want to get down to the ground. In terms of security, it's not allowed to encrypt broadcasts on the amateur band except for satellite control commands. So all the data coming down will be wide open for anyone with the equipment to listen and we definitely encourage that! But we can prevent other people from controlling the spacecraft.

frozenfrozen wrote: »

How much power does it consume, and is it powered by solar panels or a nuclear battery? and do you have any way of moving it in case it was going to crash into something else?

It has a bunch of solar panels that you can see as the blue sections on the picture. You wouldn't believe the hoops that need to be jumped through to certify a lithium battery as safe enough to be allowed onto the space station, so anything nuclear would be right out! The spacecraft runs off 2 watts on average, more when we're transmitting but we spend most of the time not transmitting. Because of power conversion efficiencies and the time we spend in the Earth's shadow, we need to be generating an average of 3.7 watts when we're in sunlight.

We have attitude control but no orbital control. So we can control where it points but not where it goes. So basically, we can't prevent it from hitting anything, but that's really unlikely anyway.

frozenfrozen wrote: »

how many years will it stay up there and is there any way to get rid of it when you are done with it?

About a year. See the response to 'Haughey Was Framed' above for why we say about.

frozenfrozen wrote: »

sorry for all the questions feel free to give short answers or skip any of them so you don't have to spend ages answering just me

No problem! We're very happy to talk about all things EIRSAT-1! Thanks!

Nate--IRL-- wrote: »

Great thread and great project! Lots of questions...

Is attitude control just to keep the sat from spinning endlessly or it is required to point the instruments in particular directions?

Is it a gyro within?

We're actually going to spin the spacecraft around the long axis on purpose to help stabilise it, but you're right in that what we're trying to avoid is 'tumbling' where the spin is a bit unpredictable.

It's a bit of a balancing act to keep the different subsystems happy in terms of where the spacecraft should point. The Gamma-ray module (GMOD) is at +Z end of the spacecraft (the top in the picture I posted a while ago). That makes this end of the spacecraft the most sensitive to gamma-rays. It can also detect gamma-rays that come through the other end, it's just not as sensitive because some of them get absorbed. Since the gamma-rays (at least the ones we're most interested in) come from space, it makes sense to have the top pointed away from Earth at all times. We call that zenith pointing.

The Enbio module (EMOD) wants to heat up samples using the Sun to see how hot they get and how fast they cool when we go into the Earth's shadow. So for EMOD pointing directly at the Sun is best. But there's a problem there, if we point the top at the Sun, the solar panels which are on the side never see the Sun. It turns out that a good compromise between both EMOD and the solar panels getting the Sun they want is to do zenith pointing and that's great for GMOD. So that's what we're trying to do with the attitude control.

We debated using gyros, but in the end we kept coming back to our first idea which is magnetorquers. These are basically electromagnets and when they're energised they can provide a torque against the Earth's magnetic field causing the spacecraft to rotate.

Nate--IRL-- wrote: »

Can we get a bit of technical detail on the internals, such as the computers controlling the Sat? Are they linux based etc. Does they have to be hardened/shielded for cosmic rays/ solar flares etc? Or have you stuck a few Raspberry Pis together in a box ?

Sure!

We're building a lot of the stuff ourselves - all the electronics and detector assemblies for GMOD and EMOD, the antennae and its deployment system, the structure and all the activation and separation stuff that goes along with that. But we are buying some of the systems off the shelf, such as the Onboard Computer (OBC).

The OBC is supplied by a Scottish company called Clyde Space who specialise in CubeSats. It uses a MicroSemi Smart Fusion 2 System on Chip (SoC). The SoC provides a real CPU and an FPGA which is also used to synthesise another CPU, but the main purpose of the FPGA fabric is to synthesise all the various different hardware interfaces we need. Those are nothing exotic, they're what you might find on a Raspberry Pi (i2c, SPI, TTL UART, etc.), we just need a lot of them. The Smart Fusion 2 was chosen because it's fairly radiation tolerant. It's also got magnetoresistive RAM which is non-volatile and radiation immune, Error Detecting and Correcting storage and other stuff like a hardware watchdog. So basically, a lot of protections against radiation.

We did explore rolling our own using a Raspberry Pi compute module with a radiation-hardened micro-controller to act as a controller/bootloader. But the Clyde Space OBC seemed like the safer option for our first satellite.

The OBC will run a RealTime Operating System. I think it has a custom kernel, so technically not Linux, but not entirely different.

Nate--IRL-- wrote: »

How did you go about designing the Sat? Have you had a few prototypes built already? How do you test for how it will perform in Zero-G and a vacuum?

We knew it would have to be a CubeSat to stand any chance of us being able to procure a launch for it.

We basically started by asking ourselves "Okay, so what's it going to do?" The obvious thing to us, since we've been working on new types of gamma-ray detectors for ESA for a few years now, is that it should detect gamma-rays. Specifically, it should detect Gamma-Ray Bursts (GRBs) since that's a topic that we're really interested in as astrophysicists. Then we tried to figure out how small we could make our gamma-ray detector based on the previous prototype detectors that we'd built and some new technology that we knew was coming down the line.

CubeSats come in a fixed number of configurations - usually 1U, 1.5U, 2U, 3U, 6U and sometimes bigger, where a U is the base unit which has a size of 10cm x 10cm x 11.35cm and a mass of 1.33kg. Our detector takes up about half a U in volume so a 2U CubeSat made sense once we factored in the other systems that would have to be onboard.

We also approached Enbio about turning their thermal management coatings into a student experiment since we have a good relationship with them and we thought it could be done without taking up too much space on the satellite.

That's basically how we arrived at the general idea and the basic design. After that it was a lot of iterating over a whole bunch of different requirements and tradeoffs, and seeing what systems were available to us.

As you've probably guessed, we can't really test in zero-g. For tests of the attitude control, we can place the spacecraft on very low-friction bearings and make sure that the spacecraft can turn. Unfortunately that's only one axis at a time, but it's enough to make sure that the actuators work. Vacuum is a lot easier, and we won't just test vacuum, we'll also test temperature extremes. That's done using a thermal-vac chamber that can expose the spacecraft to vacuum and heat it up or cool it down. We'll test going from hot to cold to hot to cold very quickly to make sure EIRSAT-1 can withstand it. We'll also shake the crap out of it to simulate launch and make sure it doesn't fall apart.

Nate--IRL-- wrote: »

What is the most difficult aspect of the design/build (I imagine weight) ? What is the design brief/specifications that you have to meet? Weight, performance etc...

Nate

The main design brief/specification that we have to conform to is the CubeSat Design Specification published by California Polytechnic. ESA have actually given us a custom specification, but I can't share that and it doesn't diverge too much from the one I linked. Weight turned out to not be too much of a problem. The CubeSat spec is well thought out so when you design something to fit in say 2U like EIRSAT-1, it ends up being around about the correct weight. So we didn't struggle with that at all.

The most difficult aspect was trying to balance attitude control, power generation, and mission lifetime. We wanted good attitude control because we wanted to be able to accurately point the spacecraft to make it the most sensitive to gamma-rays and to accurately know where EMOD was facing and how much solar energy it was receiving. That implies we should use reaction wheels (gyros) which are better than magnetorquers, but reaction wheels are very power hungry, we'd need maybe an additional 3 watts of power. We couldn't generate enough power for the spacecraft using the solar panels we had so we'd have to add more and they'd have to be deployable because there was no space left on the surface of the spacecraft. Deployables are risky so you always want to avoid them if possible and they increase the surface area of the spacecraft which increases drag which causes de-orbit to happen much sooner, completely killing your mission lifetime.

In the end it took a lot of going back to the drawing board, running a lot of simulations, and getting some good numbers on what sort of performance hits the instruments could take (by not having the absolute optimal attitude) in order to end up with a feasible mission.

Thanks for the questions!

-David

TheChizler wrote: »

I work for Microsemi and use the SmartFusion2 every day so I'm getting a massive kick out of reading this! We interact with it's designers occasionally and they'd be delighted to hear about a specific Irish space application. I'll definitely be following this with great interest.

That's cool!

TheChizler wrote: »

Just wondering how you got started with this process at all, did your existing work with the ESA help get a foot in the door or did you have to start at the same point in the application process as everyone else?

We were the same boat as the all the other teams and applied to the Fly Your Satellite! Program with a detailed proposal back in March. Our previous work with ESA didn't give us any foot in the door, or any special treatment - the ESA experts and the Fly Your Satellite team told us they were impressed with the educational nature of the mission and the cross-border collaboration between the Universities.

We were lucky to be one of the teams chosen to attend the Selection Workshop in the ESA European Space Research and Technology Centre, where the team were grilled by ESA experts and took part in training workshops. From this workshop, 6 teams (including EIRSAT-1) were chosen to take part in the program. Ireland has strong links with ESA already but we hope to strengthen those links further!

TheChizler wrote: »

Will they accept slideware for the idea or do you need to have a working prototype of your proposed scientific instrumentation?

Good question - the Fly Your Satellite! proposal described both the past work of the team but also outlined the designs for payloads which we had not built prototypes for. UCD and QUB are very experienced in CubeSat development, so I think the FYS team could see our experience. We have had more experience with some subsystems before - for example Gamma-ray detectors have been designed, built and tested in the UCD Space Science and Advanced materials lab previously. These detectors are similar to what is proposed for GMOD, the Gamma-ray module on board EIRSAT-1.

The proposal defined the designs and capabilities of the team. Now in CDR, we have to prove that these designs make sense - why did we choose one component over another? Have we tested any prototypes and what were the results? If there is no prototype yet, how will we go about building and testing them, and what is the timeline for all of these activities?

TheChizler wrote: »

How easy was it you get the Universities on board? I presume they have to commit to supporting the project until the expected lifetime of the sat before the ESA will even talk to you.

The universities are hugely supportive of the project, as it connects our activities in space-related research and teaching very strongly across Science and Engineering. We submitted a proposal in response to an open call from ESA for the 'Fly your Satellite' competition for university teams to build and launch a Cubesat. We didn't really expect to be selected! UCD will now sign up to an agreement with ESA, that will set out the ground rules regarding IP, adherence to ESA processes etc. While UCD and QUB are providing some support in the form of students and access to labs etc., the bulk of the funding is still being sought.

TheChizler wrote: »

How far along are you in the Critical Design Review stage, can you speak about what some of the deliverables are before you can be confident you'll be accepted for launch?

So currently we have submitted version 1.0 of the CDR, which has been reviewed by the Fly Your Satellite team. We have received their feedback and currently have a week to implement their suggested changes/additions. Once version 1.1 gets sent to them, the CDR Data pack will be reviewed by ESA experts. The experts will issue Review Item Discrepancies (RIDs), which are suggested changes and additions. The team will then visit the ESA European Space Research and Technology Centre in December.

There are a number of subsequent reviews to pass through if we successfully pass through CDR in December. There are 4 phases - we are currently in the first stage, Design. The next stage is building the satellite, including prototypes. This includes Ambient and Environmental Test Campaigns, where prototypes of the satellite will be tested both in our own facilities and in facilities which better model the space environment. Each of these test campaigns are accompanied by documentation which will also be reviewed.

The next stages are Launching and Operating your satellite. There are the Flight Readiness and Flight Acceptance reviews. The teams are also monitored whilst the satellite is in orbit to ensure operations are going smoothly.

TheChizler wrote: »

Will there be many redundant systems on board or do space and power constraints remove that possibility? If one subsystem stopped working in the harsh conditions of space would there be any hope of salvage? Of course it depends on the system.

As you can imagine, with dimensions 20cmx10cmx10cm, we are pretty tight for space! I think you're starting to think like an EIRSAT-1 team member - the 'ifs' of missions are really important, and we do have to put procedures in place as backups. As with any mission there are risks, but we keep a record of these risks and implement strategies to mitigate these risks throughout the mission.

TheChizler wrote: »

Thanks for doing this AMA!

Thanks for all your questions!