KSP Community CubeSat

[cpast]

those answer are wrong.

GPS home system, low time ago, they had a restriction of 10 m on accuracy, that restriction now is out.

Thats it!

There is no more lock.

http://www.nasa.gov/centers/ames/engineering/projects/phonesat2.html#.U8f0kvmSzwA

This answer is wrong. That's an entirely separate thing to height/speed restrictions. Selective Availability was a system to prevent non-military receivers from having too much accuracy. Altitude/speed restrictions are to prevent use as missile guidance system. Note that exemptions can be made (e.g. Copenhagen Suborbitals got one), but they are not made for just anyone.

[AngelLestat]

You know how GPS system works??

You just need to know the time, position of each satellite, then with an antenna you recieve signals of 3 or more satellites, using Einstein formules, you calculate your position and altiture.

Then speed and other values are derivative of multiple measures.

Anyone with electronic knowledge and software can develpe their own gps without restrictions.

If someone can develope a intercontinental missiles, then it can develope their own gps!!

For that reason after some time, the only restriction (10 m on accuracy, there was not altitude restriction) was eliminate from commercial devices.

[PakledHostage]

You know how GPS system works??

You just need to know the time, position of each satellite, then with an antenna you recieve signals of 3 or more satellites, using Einstein formules, you calculate your position and altiture.

Then speed and other values are derivative of multiple measures.

Anyone with electronic knowledge and software can develpe their own gps without restrictions.

If someone can develope a intercontinental missiles, then it can develope their own gps!!

For that reason after some time, the only restriction (10 m on accuracy, there was not altitude restriction) was eliminate from commercial devices.

The article you cited in your earlier post describes how NASA has developed a phonesat using phone hardware including GPS. It does not say how or even if the GPS hardware was used and whether or not it was unlocked. Likewise, GPS signals are encrypted. Developing your own GPS receiver is far from trivial. It can be done (as evidenced by people who have sucessfully developed GPS spoofing and jamming devices), but that doesn't mean it can be done readily.

The restrictions that others here are describing are arms trafficking restrictions that GPS hardware must comply with. Depending on the age of the GPS hardware in question, it will likely either comply with COCOM export restrictions or the Waasenaar Arrangement. The Waasenaar requirements are newer and remove the altitude restriction but retain the velocity restriction (albeit a slightly higher velocity restriction than COCOM).

- GPSs meeting the COCOM restrictions won't work above 18000 m altitude or 515 m/s.

- GPSs meeting the Waasenaar arrangement restrictions won't work above 600 m/s but have no altitude restrictions.

Edited July 17, 2014 by PakledHostage
Revised to respond to more recent post

[dharak1]

A phone battery does not have as much insulation as a cubesat battery. It also doesn't have a thermometer to check temperature. We wouldn't want to cheap out on a battery and have it break part way through the mission. They aren't very expensive either. Only about 2 grand

[K^2]

Fortunately, it's relatively easy to obtain an unlocked GPS unit.

So like I said, the only real advantage of a phonesat is easy access to camera, and Sky have demonstrated why even that can misfire against us.

Might as well just build all the electronics/software from scratch. Neither needs to be all that complicated. In fact, the simpler, the less the chance that something goes wrong, under the circumstance.

[dharak1]

What kind of off the shelf components could we use? How long would something like a Rpi last in hard vacuum? Has there been a PiSat yet? That would be something new and would help keep cost down for our primary mission.

[christok]

Man, that was a lot of reading for such a young thread.

My idea is basically to spec a communications-grade radio transmitter capable of 80W (plus some overhead for the sake of reliability) so that we can also use it to drive the ion engine.

I love that so much. Pity it's just too ambitious for now.

No matter what we build it can't have anything on the outside. It has to fit inside the little deployment bay on the spacecraft. They bay is built for cubes exactly 10x10x10cm. I wasn't aware that the tether would need a weight at the end as well. It probably wouldn't need to be as heavy as the mars direct type centrifuge it still has a penalty on what equipment we can bring. The tether type of mission needs a 2U cubesat.

There just has to be a way to combine this with a biological experiment within the available mass/volume. There isn't much research on partial-gravity biology so it would be Real Science (33 points? I never really paid attention) if we pull it off. In case it isn't obvious, I'll contribute some cash at the very least.

I'm worried about the containers being suggested for biological experiments. Being able to withstand the pressure difference isn't my concern, but rather at what rate they leak air and how that number will stand up to vacuum exposure, extreme UV radiation and large temperature fluctuations.

[K^2]

What kind of off the shelf components could we use? How long would something like a Rpi last in hard vacuum? Has there been a PiSat yet? That would be something new and would help keep cost down for our primary mission.

Just matter of luck and Solar activity. It takes one gamma through the wrong part of the chip, and it's out. Tends to be matter of weeks, if not days. But it could all end a lot sooner, so it'd be a risk. And yeah, I think I've heard of a cubesat with a Raspberry Pi before. At least, in planning.

[B787_300]

hey K^2 did you see my post #521?

[AngelLestat]

Developing your own GPS receiver is far from trivial

http://www.extremetech.com/extreme/98063-how-to-build-your-own-gps-receiver

http://lifehacker.com/build-your-own-gps-car-tracking-system-1476721470

You know what else is not trivial? Try to interconnect different devices without future problems and develop their software to work all in synchrony in plattaforms that not everybody knows.

- GPSs meeting the COCOM restrictions won't work above 18000 m altitude or 515 m/s.

- GPSs meeting the Waasenaar arrangement restrictions won't work above 600 m/s but have no altitude restrictions.

Ok, I dint know that, but in the gps wiki page said:

These limits only apply to units exported from (or which have components exported from) the USA – there is a growing trade in various components, including GPS units, supplied by other countries, which are expressly sold as ITAR-free.

A phone battery does not have as much insulation as a cubesat battery. It also doesn't have a thermometer to check temperature. We wouldn't want to cheap out on a battery and have it break part way through the mission. They aren't very expensive either. Only about 2 grand

Only 2 grands? ah ok. give me 4.. XD (try to noy use acronyms, not everybody here knows english so well)

Its ok to get funds to accomplish our objetives, but drop away the money that we can gather in silly things that we dont really need (or you plan a 4 years mission?) is an insult to the people who gives us money.

Why you can not shield or insultate the whole smartphone?

The 3 phonesats 1.0 cost $3500 each, and the phonesats 2.0 cost $7000 (the whole satellite).

If you try to achieve the same functionality with regular cubesats components you end with $30000 each.

The lifetime was 1 year, when it start to reboot it self (occasionally) after several solar flares.

I dont have any info of any shield used on these phones.

Five phonestats were already sent to space by NASA, strand-1 mission would test the smartphone use with fully understanding. It would have extra computers and sensors to corraborate data with the smartphone sensors.

Many other missions are comming, these missions would give us a lot of info to make a good choice in this matter.

Is a huge money difference that we are talking about. And test already done seems promissings.

Fortunately, it's relatively easy to obtain an unlocked GPS unit.

So like I said, the only real advantage of a phonesat is easy access to camera, and Sky have demonstrated why even that can misfire against us.

Might as well just build all the electronics/software from scratch. Neither needs to be all that complicated. In fact, the simpler, the less the chance that something goes wrong, under the circumstance.

He dint prove it.

It all depends on our lifespan mission expectatives. How evidence show, none of the already phonesats launched had problems in their lifetime, only 1 after 1 year of use.

They had also bluetooth, that can be used to connect with other devices.

And you are underestimating the time that it takes develop all the software that you would need.

There is a lot of research to be done even with the low requirements missions, if you need to add the construction and software development, then it would take several years to finish the project, so it would be abandoned.

I can help in research, some software development, maybe a dynamic webpage where everyone can see the progress of the mission, or maybe to command the cubesat from there. But we need to try choose a short lifetime mission to cut expenses and mission budget.

[K^2]

Why you can not shield or insultate the whole smartphone?

It takes ten meters of water to provide same kind of radiation protection that our atmosphere gives us. You don't need that much, but reasonably, you need a few inches of lead to make a significant difference. Good luck.

And you are underestimating the time that it takes develop all the software that you would need.

Having written code for MCUs, having participated in robotics competitions, having written computational code for superclusters, and having a software engineer job lined up, I'll take my chances with the software.

[AngelLestat]

It takes ten meters of water to provide same kind of radiation protection that our atmosphere gives us. You don't need that much, but reasonably, you need a few inches of lead to make a significant difference. Good luck.

dharak1´s point was that the cubesat regular batteries are already insulated.. This mean ten meters of water too? Please...

Having written code for MCUs, having participated in robotics competitions, having written computational code for superclusters, and having a software engineer job lined up, I'll take my chances with the software.

I work making software.

And I tell you, the time that it would take to develope each piece of software to control all, is a lot.

But if you want to do this project alone, why you did a topic about that?

If you are the only with experience in MCU then is all on you.

The main advice that NASA give us in the smartphone use, is the money and time that you can save in software development.

[K^2]

AngelLestat, this project needs low level localization and navs code. Compared to that, writing a few drivers for the sensors and servos is child's play. We will find a team of capable people. Don't worry about that. But even if I would have to write software myself from scratch in my free time, it's a matter of a few months to get the framework ready. It will take longer to get all of the necessary clearances, find quality hardware, and begin construction.

As for batteries, they don't need radiation protection as much as processor and memory do. Battery will degrade from radiation, but it will do so gradually. It's not something that will just randomly quit on you after a random time interval. Battery's temperature needs to be regulated, however. That might be where the talk of insulation comes from. That has nothing to do with radiation. Just the fact that you are working in a vacuum with a short day/night cycle.

[Mr Shifty]

It takes ten meters of water to provide same kind of radiation protection that our atmosphere gives us. You don't need that much, but reasonably, you need a few inches of lead to make a significant difference. Good luck.

Water and lead serve two different purposes wrt radiation shielding. I gather that space radiation is typically charged particles (protons). I'm not sure how significant it is in LEO. Regardless, electronics don't really care all that much about energetic photons; it's more the nucleon sized particles that can screw up memory cells and cause latch-up in logic circuits. (I am an electronics designer at a high-rad facility.) Likewise camera CCDs sustain significant damage when exposed to a neutral or beta (or presumably proton) flux.

Another issue that I haven't seen brought up here yet is the materials requirements for vacuum. Pre-launch testing for CubeSats includes vacuum testing for outgassing. Launch provider requirements for outgassing probably vary (and NASA's are somewhat opaque.) But I know they desire to control it to avoid cross-contamination of payloads. Our outgassing controls on our high-vacuum (tokamak) chamber here at work specify no plastics, no rubber, no fiberglass, no lead-based solder, no liquid or emulsified lubricants. We pretty much use metals and ceramics and graphite only. But our requirements (quickly draw and reliably sustain high vacuum) are different than those of launch providers.

Edited July 17, 2014 by Mr Shifty

[Rakaydos]

It takes ten meters of water to provide same kind of radiation protection that our atmosphere gives us. You don't need that much, but reasonably, you need a few inches of lead to make a significant difference. Good luck.

Out of curiosity, how good is titanium, tugstin, or another "heat shield" grade metal as radiation shielding? perhaps a more adventerous cubesat could have a single mass penalty do double duty?

If alpha or beta rays are the problem, then for a design that uses an ion drive, can the magets for the drive remain powered even outside operation, and use that for shielding? As I recall, the range of the magnetic field is usually a problem for that approach, but a cubesat is a tiny target.

Edited July 17, 2014 by Rakaydos

[Mazon Del]

Robotics Engineer here. Writing drivers for servos is laughably easy. For sensors, that is up to the sensor package you choose and the interface. Most sensors you have the ability to purchase with a variety of connection methods I2C, USB, Bluetooth, etc.

Personally, I am in favor of having one of those "jungle in a jars". There was that one that keeps getting brought up on Reddit where the guy stuck several plants into a jar, topped it off with water, sealed the top, and it has been a viable ecosystem for like 30+ years.

We could construct a triple cubesat where all the gear to run it (orientation, power, etc) was held on one of the ends, and the remaining 2 are a single enclosure. Once in orbit, a single panel could rotate back out of the way to allow for sunlight through a (likely heavily) filtered 'window'. For science there could be humidity sensors, thermometers, oxygen content, etc. But most importantly a camera, either for a semi-live cam setup or just the occasional picture. Depends on what we can get as far as radio communication (depending on how into it they are NASA may be interested in occasionally lending some comms time. They have done it for things like the FIRST competition kickoffs).

Now, if we want to add more to the science, we can add an accelerometer and spin the system about its long axis. Put the plant at say 1.5Gs or even 2.0 Let it sit for several days or a week and every now and then slow the rotation a bit. 1.75...1.5...etc and record measurements from the various sensors.

If you have a control on Earth (basically a copy of the habitat, admittedly it wouldn't be perfect cause plants) you might be able to draw some conclusions about the plants. Maybe the data shows that plants tend to grow/live better at 0.8Gs than the do at 1 or 0.7.

Imagine having a 'live' cam up that occasionally shows a view from the inside of a mini-greenhouse in orbit with the (possibly [like blurry) Earth in the background.

[K^2]

Water and lead serve two different purposes wrt radiation shielding.

Not really. At relevant energies, it's just about having electrons to scatter from. Be it charged particles, beta or proton radiation, or gamma radiation. Now, in terms of neutron radiation shielding, yes, things are different. But neutron radiation isn't as significant.

Until you get into heavier elements, electron density is basically proportional to mass density. So you get same protection from equal weights of water and air. About 1atm worth. Lead ends up being a bit worse, because it has more neutrons in the nuclei. But it's pretty close. It does, however, provide better neutron shielding. High density makes it more compact as well, which is why it's a common material for shielding.

Out of curiosity, how good is titanium, tugstin, or another "heat shield" grade metal as radiation shielding?

Just as above. Because density is lower, you need a bit thicker layer. But weight of lead shielding or titanium shielding will be about the same. And you can dual-purpose your heat shield as radiation shield, yes.

There are some interesting differences at lower energies, but these tend to be absorbed even by the thin skin of the sat and don't cause as many problems. It's the rare, but very energetic particles that usually screw things up.

Personally, I am in favor of having one of those "jungle in a jars". [...] Now, if we want to add more to the science, we can add an accelerometer and spin the system about its long axis.

A few people suggested an inflatable biosphere. I'm worried that it might be a bit too prone to failures. However, a jar should be easy enough. Even with magnetotorquer and a gyro for attitude control, most of the space in the 1U frame can be left empty. That can easily have a jar with some plants in there. Maybe even some plankton or similar in a liquid solution.

I really like the idea of setting up artificial gravity in there. I'm pretty sure it'd have to be much less than 1G, but that only makes it more interesting. I don't think anyone has done any studies on plants in low gravity. Unless there has been some centrifuge experiments on ISS that I'm not familiar with. (I'm half-expecting someone to jump in with, "But there have been!" link right about now.)

Anyways, that's pretty doable, and there could be some interesting things to do with it.

Inflatable might still be viable with better funding, but how about "life in a jar" for basic? It's something that can be done on the target "under $10k" budget, and it might have some value as an actual research project.

[Rakaydos]

Not really. At relevant energies, it's just about having electrons to scatter from. Be it charged particles, beta or proton radiation, or gamma radiation. Now, in terms of neutron radiation shielding, yes, things are different. But neutron radiation isn't as significant.

Until you get into heavier elements, electron density is basically proportional to mass density. So you get same protection from equal weights of water and air. About 1atm worth. Lead ends up being a bit worse, because it has more neutrons in the nuclei. But it's pretty close. It does, however, provide better neutron shielding. High density makes it more compact as well, which is why it's a common material for shielding.

Just as above. Because density is lower, you need a bit thicker layer. But weight of lead shielding or titanium shielding will be about the same. And you can dual-purpose your heat shield as radiation shield, yes.

There are some interesting differences at lower energies, but these tend to be absorbed even by the thin skin of the sat and don't cause as many problems. It's the rare, but very energetic particles that usually screw things up.

Excuse me if I'm leaping on a slip of the toungue, but if alpha and beta radiation (energetic particles) are more of a concern than gamma rays (Ionizing EM radiation), would maintaining an active magnetic field on a drive make electronics more reliable?

Would the field strength required even be reasonable as a solar powered drive system? (I know I'm going afield of the current topic- I'm still working on the "advanced mission" in another topic, and would love your input)

A few people suggested an inflatable biosphere. I'm worried that it might be a bit too prone to failures. However, a jar should be easy enough. Even with magnetotorquer and a gyro for attitude control, most of the space in the 1U frame can be left empty. That can easily have a jar with some plants in there. Maybe even some plankton or similar in a liquid solution.

I really like the idea of setting up artificial gravity in there. I'm pretty sure it'd have to be much less than 1G, but that only makes it more interesting. I don't think anyone has done any studies on plants in low gravity. Unless there has been some centrifuge experiments on ISS that I'm not familiar with. (I'm half-expecting someone to jump in with, "But there have been!" link right about now.)

Anyways, that's pretty doable, and there could be some interesting things to do with it.

Inflatable might still be viable with better funding, but how about "life in a jar" for basic? It's something that can be done on the target "under $10k" budget, and it might have some value as an actual research project.

What about combining this idea (the gravity jar) with the tether centerfuge idea? the biosphere would be in (or expand from) 1 cube, and the cable connecting it to the other cube would relay camera and sensor data from the hardware in the second cube.

[Mazon Del]

I believe that NASA has attempted to do centrifuge experiments, upon a bit of research I find this. http://en.wikipedia.org/wiki/Centrifuge_Accommodations_Module

They were going to have a module in the ISS that had a centrifuge for such experiments, but it was cancelled before delivery. Amusingly enough, they had the same G spectrum as what I listed, 0-2Gs. Technically 0.01, but whose counting decimals?

If we wanted to, we could possibly do (at higher funding levels) a mix. With a 3U, we could have one end be the life in a jar, the other could be an experimental inflatable module.

As an interesting thought, one additional test we could do is after a certain point for either system, release the atmosphere from one of the modules, but keep the camera running to see how plant matter "decays" in the vacuum of space. Obviously it wouldn't be normal decay, but exposure to the vacuum could have some interesting effects. If we were to do this, I think an interesting addition would be to have a material like untreated leather be at one end of the module to see what happens to it.

[Mazon Del]

Excuse the double post, but if we went along the lines of the life in a jar, we may want to consult with Mary Musgrave. http://today.uconn.edu/blog/2009/08/the-effects-of-gravity-on-plant-growth-and-development/

She has been doing research on plants in varying gravity levels for over two decades.

[dharak1]

I like the idea of life in a jar. The jar couldn't be very big but we could probably put a bit of plants and stuff in there.

[AngelLestat]

AngelLestat, this project needs low level localization and navs code. Compared to that, writing a few drivers for the sensors and servos is child's play. We will find a team of capable people. Don't worry about that. But even if I would have to write software myself from scratch in my free time, it's a matter of a few months to get the framework ready. It will take longer to get all of the necessary clearances, find quality hardware, and begin construction.

I help to my brother once to make an assembler code to measure and storage wind speed data from an anemometer. At the begining all seems simple, we made the code, we test it, it works. Then we install the devide for 2 month in the study location. When we look in the data later, we notice that the data was discrete with jumps between values.

It was something that we dint have into account in the code development.

Similar things like this happen all the time in all kind of projects. Use already test it software saves time and reduce the chance of failures.

A temperature sensor may not be complicate. But a CCD integration, accelerometer or other kinds of devices may not be so easier to code the current plugin.

I find some software in internet for some cubesats cpu. But there are few, and they work only with their special hardware.

We are not a whole university with lot of students, each working hard in their specialty with one goal and teachers as guide.

You know me, I am an optimistic. But we need to stop make this project harder than already is.

As for batteries, they don't need radiation protection as much as processor and memory do. Battery will degrade from radiation, but it will do so gradually. It's not something that will just randomly quit on you after a random time interval. Battery's temperature needs to be regulated, however. That might be where the talk of insulation comes from. That has nothing to do with radiation. Just the fact that you are working in a vacuum with a short day/night cycle.

We can measure the cellphone temperature battery using the temperature sensor already located in the smartphone (if it has), if the battery warm, the phone would warm too.

But if this happen, it will not matter what kind of battery we use, there is nothing that we can do about it.

So what is your idea? What do you propose as mission? I know that you really want to leave the earth influence to go somewhere. But think about it. That is way far of our limits. If the launching cost drops significantly, then cubesats parts cost would follow too. Then that possibility may be taken (of course with a high chance of failure, Either way, it's going to be one hell of a ride)

Another issue that I haven't seen brought up here yet is the materials requirements for vacuum. Pre-launch testing for CubeSats includes vacuum testing for outgassing. Launch provider requirements for outgassing probably vary (and NASA's are somewhat opaque.) But I know they desire to control it to avoid cross-contamination of payloads. Our outgassing controls on our high-vacuum (tokamak) chamber here at work specify no plastics, no rubber, no fiberglass, no lead-based solder, no liquid or emulsified lubricants. We pretty much use metals and ceramics and graphite only. But our requirements (quickly draw and reliably sustain high vacuum) are different than those of launch providers.

I have understand that any cubesat before launch it needs to be inspected by a specialized center. I guess they had vaccum test and other things. I dont know would be the cost (if it has).

Out of curiosity, how good is titanium, tugstin, or another "heat shield" grade metal as radiation shielding? perhaps a more adventerous cubesat could have a single mass penalty do double duty?

If alpha or beta rays are the problem, then for a design that uses an ion drive, can the magets for the drive remain powered even outside operation, and use that for shielding? As I recall, the range of the magnetic field is usually a problem for that approach, but a cubesat is a tiny target.

About shielding, the only that comes to my mind is these CNT sheets that are used to shield against magnetic interference. Something that is not needed in these circustances.

http://www.raytheon.com/newsroom/technology_today/2012_i1/nano.html

Excuse the double post, but if we went along the lines of the life in a jar, we may want to consult with Mary Musgrave. http://today.uconn.edu/blog/2009/08/the-effects-of-gravity-on-plant-growth-and-development/

.

Any approach that we want fallow, it will be highly recomend to talk with people who highly knows these stuff first.

I am not against this idea, but we need to avoid use any kind of inflatable device. The risk of lose pressure due to a fail in the sealed or being hole by a micro debris is high.

Composite Fabrics that Nasa use are not easy to get.

But if you said a tether that sepate a 2U cubesats in 2, to spin and give low gravity, then it can be done. (in fact it was done before, was called "SporeSat, 3U CubeSat")

---------------------------------------------------------------------------------------------------------

Look the price of the CPU without memory or any other needed device:

http://www.cubesatshop.com/index.php?option=com_virtuemart&Itemid=75

The prices goes from 5000 euros to 45000 euros. The one of 45000 has similar capabilities of any smartphone, it can have 2 camera and some sensors.

Sorry, but I need to insist. Smartphones are the way to go. We can ask for recomendations to experience people to decide.

Edited July 18, 2014 by AngelLestat

[Nicholander]

I still think proper computer systems and such are better then a Smartphone. As K^2 said, the only real advantage they give is that they have a camera. And there's also a lot more drawbacks.

I also like the idea of doing the "All in one" mission, with the gravity centrifuge, "Jungle in a jar", electrodynamic tethered propulsion, and pressurized inflatable. Though that will have to be a stretch goal.

Edited July 18, 2014 by Nicholander

[dharak1]

If we aren't using parts specifically for cubesats we should use something easy to develop for. My personal pick would be the raspberry pi compute. http://www.raspberrypi.org/raspberry-pi-compute-module-new-product/ it's pretty compact and dependable. I'm sure we could do it with something like a Picaxe chip but then we would need to do lots of coding and such ourselves. The pi compute is pretty much a little computer. I don't know about its power consumption though.

[K^2]

Excuse me if I'm leaping on a slip of the toungue, but if alpha and beta radiation (energetic particles) are more of a concern than gamma rays (Ionizing EM radiation), would maintaining an active magnetic field on a drive make electronics more reliable?

Would the field strength required even be reasonable as a solar powered drive system? (I know I'm going afield of the current topic- I'm still working on the "advanced mission" in another topic, and would love your input)

With ionizing radiation, the only thing that matters is center of mass energy. Not the type of particle that delivers it. Granted, at moderate energies, a proton will deliver higher CoM energy in collision with an electron simply due to its mass. So that could be a factor. The other thing is that there might be more charged particles than energetic photons coming in from the Sun. But otherwise, the two types of radiation are the same.

Looking at some info on Wikipedia, it looks like most dangerous radiation is going to come from Solar Particle Events, which results in up to 10MeV proton bursts. That's heavy ionizing radiation, but the protons themselves are going to be strictly classical due to their mass, traveling at roughly 1% c. If you try to deflect these with a mag field, cyclotron radius formula applies. p = Bqr. At 1 kGauss, that's over 30cm turning radius. I'm having hard time picturing a stronger field around a cubesat.

So no, I don't think magnetic shielding is viable.

What about combining this idea (the gravity jar) with the tether centerfuge idea? the biosphere would be in (or expand from) 1 cube, and the cable connecting it to the other cube would relay camera and sensor data from the hardware in the second cube.

Tethered centrifuge is significantly more complicated to pull off in terms of attitude control. I also can't picture it anything other than a 2U mission. That could be a budget+ option. But for base, I'd go with a jar fixed within the body of a 1U, with about half of the volume taken by a 10x10x5 pill box jar, and the other half with electronics and attitude control hardware. Sensors can go into corners around the jar as well. Solar panels can then probably go on the sides. Back wall would be open, allowing sun light. Two cameras can be installed on the board, one pointing forward, the other back through the jar.

If we want to generate up to about 1m/s² of artificial gravity in the jar, we can just spin the whole sat at roughly 30RPM. Spinning much faster than that would make it difficult to track rotation with horizon sensors. And I doubt we can completely avoid axis tumbling or some excess torques. Hopefully, however, the whole thing can be corrected with magnetotorquer.

How does that sound for basic mission? Because this we can probably put together on minimum budget.

I know bugger all about biology, however. I know people have made some completely enclosed mini-biospheres with some algae and plancton. But I've got no clue what one would need to set this up. I can add anything we need to control temperature and lighting to the shopping list. As well as a Geiger counter. But I'd need someone to tell me exactly what the parameters should be.

Anyone here has a green thumb and/or some biology know-how?