[SpaceProgram] Kickstarter ArduSat - Your Arduino Experiment in Space by ppl4world

[Luke Weston]

Here are my thoughts on what I've seen of this ArduSat business, based
on what I've read on their KickStarter page so far.
Apologies if this comes across as too critical... I'm trying to be
constructive and helpful and positive, it's interesting and exciting
:)

- Oh, ok, so they are actually basing the CubeSats around an existing,
well-designed, proven, tested professional CubeSat satellite bus.
That's good, it makes the whole thing feel a whole lot more credible
and serious now that I know it's not just "we're making an Arduino
based satellite!". It's basically a CubeSat with a good basic existing
satellite bus design and some custom open-hardware AVR based
electronics as a user payload.

- I had never previously heard of GOMSpace, but obviously they do look
very interesting, and they know what they're doing and they sell some
serious well-designed CubeSat and space hardware that is seriously
interesting. Potentially very interesting for several other
small-scale space-related projects and organisations.

http://gomspace.com/index.php

- Obviously the AMSAT community has a lot of proven experience with
designing and deploying satellite systems on an amateur scale, and I
would try and tap into that and get access to that base of knowledge
and experience and put it to good use, personally.

- I think some of the currently proposed sensors are inappropriate,
insufficiently thought out, or pointless, to be honest.
If I was designing this thing, these are some of the things I would
consider, particularly in terms of the sensors:

- A temperature sensor is a good idea. In fact, a couple of
temperature sensors. Choose sensors that are cheap, linear, accurate,
easy to interface to, and which require minimal additional components.
Perhaps the Microchip MCP9700 might be a good place to start in
regards to these factors.

- If you look at this GPS receiver module from Adafruit, they
specifically say that they've asked the manufacturer to tweak the
firmware to make sure that the COCOM non-proliferation firmware
restriction is implemented as "altitude AND velocity" so you can take
it to altitudes above 60,000 feet (as long as your speed does not
exceed Mach 1.5) and you should not have any problems.

http://ladyada.net/products/ultimategps/

That's just but one example of one GPS receiver that anyone can easily
source. So COCOM altitude restriction should not be a problem.

Also see:

http://www.gtop-tech.com/jsf/moduleproduct.jsf?muid=5a50acc3cd4f20749b345fe86e442ed78a6d204d&suid=b0b43a06ddc9bc4756cbd4147652af895bcb727d&puid=1529f2c5a2d16e5ccdc255258399ca4bb62c9e9b

- A CO2 sensor and an ozone sensor are pointless in vacuum. Also, if
you must have gas sensors of that type, remember that since they
contain what is essentially a heating element to heat up the thin-film
electrochemical sensor, they do draw a fairly large amount of current
and that current needs to be budgeted appropriately. Also, they will
heat up any nearby temperature sensors if they are close because they
do get warm if you're running the heater appropriately.

- The BMP085 barometric sensor is pretty pointless in vacuum, unless
you had a system like Sputnik where the barometric sensor was inside a
pressurised vessel (the "ball" chassis of Sputnik) and it would detect
depressurisation in the event of a micrometerorite strike puncturing
the shell.

- If you really wanted a barometric pressure sensor, the Freescale
MPL115A2 is much cheaper than the BMP085.

- The Single Event Upset Counter is a very good idea, it will
certainly be a cool idea to keep that included on the satellite.

- I also like the look of the visible-spectrum spectrometer, that one
looks very worthwhile too.

- A 3-axis MEMS gyroscope, 3-axis magnetometer and 3-axis MEMS
accelerometer are certainly workable in space, cheap, small,
solid-state and interesting and useful to include on the satellite.
Good idea.

- I have serious doubts that a Geiger–Müller tube will be suitable for
use in hard vacuum, although this is somewhat dependent on exactly
which style of GM you've got. GM tubes, especially "pancake" tubes and
those with thin mica windows, can "pop" their delicate windows easily
when they're exposed to changes in air pressure or significant
reductions in air pressure, for example if they are transported in an
unpressurised aircraft cargo hold, destroying the tube.

- Also, if you're flying a GM tube you'll need to be careful with the
design and filtering of its high voltage power supply, to make sure
that electromagnetic noise or spikes or transients, either on the
power supply bus or electromagnetically coupled, are not generated by
the HVPS and coupled into the rest of the electronics. I wouldn't
trust the Sparkfun Geiger counter kit in this regard to be honest.

- For the detection of energetic photons and other ionising radiation,
perhaps a solid state system based on one or more silicon PIN
photodiodes, usually intended for the detection of visible light,
might be a better choice, since they are much more robust, much
cheaper, solid state, and don't require HV. You'll need to cover them
with opaque material to keep visible light from entering, and you'll
need a high-impedence JFET preamplifier stage to amplify the charge
signal from radiation strikes on the silicon detector.

Here are some examples and references:

http://www.maxim-ic.com/app-notes/index.mvp/id/2236

https://github.com/lukeweston/PINDetector

- Vibration sensor? Sure, why not. Can't hurt.

- Visible light sensor? Sure, a good backup to the visible-spectrum
spectrometer.

- What exactly is an "EM Wave Sensor"? Some sort of broad-spectrum RF
power meter? If so, how do you "filter out" the background of the
satellite's RF telemetry transmissions? To be brutally honest here, in
the photos provided, this "EM Wave Sensor" thing looks like some cheap
crappy thing they've picked up from one of the thousand cheap
China-based eBay vendors which sells experimentation modules and
gadgets to electronics hobbyists.

Regards,
  Luke

On Sun, Jun 17, 2012 at 6:15 AM, Jerry Isdale <isdale at gmail.com> wrote:
> This kickstarter plans to build an Arduino based CubeSat for launch as part
> of NASA's CubeSat initiative ...
>
> http://www.kickstarter.com/projects/575960623/ardusat-your-arduino-experiment-in-space
>
> http://www.nasa.gov/directorates/heo/home/CubeSats_initiative.html
>
> I met some of the CubeSat folks at the Maker Faire last month.  It sounds
> like a very cool program.
>
> Jerry Isdale
> isdale at gmail.com
>
>
>
>
> _______________________________________________
> SpaceProgram mailing list
> SpaceProgram at lists.hackerspaces.org
> http://lists.hackerspaces.org/mailman/listinfo/spaceprogram
>