This week @ULSF
John Pritchard
Hi,
I've been doing commercial work. Anyone else have anything?
John
Joshua
John Pritchard
I am in red numbers because few conferences this month. Nothing else.Joshua
(lol - guess you planned it that way)
Thinking about something about learning by experience (walking, running, model building) versus learning in the abstract (pure math)
- Learning in the abstract is tedious when your perspective and interests are practical
- Too much abstraction can make connecting the practical dots hard to do, indeed it is the matter of a great deal of professional research, for example the subject of aerodynamics could be described as the practice of a branch of thermodynamics
Joshua
Alex Csete
video streams and muxing them together into a single MPEG-TS transport
stream. I'm collecting useful shortcuts here:
http://wiki.oz9aec.net/index.php/Gstreamer_Cheatsheet
On Sun, Jun 20, 2010 at 1:01 AM, John Pritchard <j...@ulsf.net> wrote:
>
Joshua
Alex Csete
quite good and works well for experimentation.
I haven't followed much on what's going on in GENSO. Do you mean the
network is no longer operational or that it has never become fully
operational?
Alex
> --
> http://groups.google.com/group/ultra-light-space-flight?hl=en
>
John Pritchard
I am in red numbers because people fails.
oh, sorry to hear that
To much maths are no good.
i guess it's regularly linking the abstract with the experiential that's important. the useful bit may be noting that feeding the brain what it wants which produces a cyclic study habit between many different subjects is actually necessary.
John Pritchard
Another interesting post from Twitter @AronSora
John Pritchard
http://spacetweepsociety.org/blogs/jdpsyntelos/ultralight-spaceflight-math-movies
Alex Csete
http://www.oz9aec.net/index.php/gnu-radio/gnu-radio-blog/344-a-weekend-with-gstreamer
You are welcome to corss-post it on the spacetweep blog in whole or in
part as you see fit (just link back to the article).
If you need the html source let me know.
On Sun, Jun 20, 2010 at 8:18 PM, John Pritchard <j...@ulsf.net> wrote:
> ok, so this is what i came up with..
> http://spacetweepsociety.org/blogs/jdpsyntelos/ultralight-spaceflight-math-movies
>
>
> --
> http://groups.google.com/group/ultra-light-space-flight?hl=en
>
Joshua
Best,
John Pritchard
GENSO will be operative at the end of the nxt year, I guess.
Best,Joshua
Did you go to their conference?
They don't seem to publish any technical info or software?
Is it some kind of commercial model?
Alex Csete
That was indeed one of the reasons why I didn't care much about it.
Managed as a typical space program, it will take them anywhere between
5-10 years to specify, design, implement, validate, ... and whatever
else they need to do before they feel they can release it publicly. In
the mean time, technology evolves exponentially. Already when I first
heard about it (3 or 4 years ago?) and even saw technical specs I
didn't consider it to be useful for anything else than university
cubesats.
John Pritchard
So what's needed for the N-Prize mission? I imagine extensible elements of any mission (swapping power, antenna and frequency).
Yes? Should we do something for it?
Joshua
Alex Csete
even for multi million $ missions.
I think the important thing is to place ground stations so that they
cover the first orbits after launch when the satellite is expected to
begin transmission.
For low data rates / small comlink, we can consider designing a
portable ground station pack that can be distributed according to the
desired coverage during LEOP. I have already looked at such setup for
hamradio I found that we can get very cheap motorised Az/El telescope
mounts such as the DS2000 which can take up to 4kg antenna and costs
~220€.
I don't remember if there are any particular requirements for the N
Prize in terms of what transmission is required. If there are no
requirements we can make *very* simple. A simple, traditional, morse
code transmitter! This would be very low rate telemetry (few bits per
second) but it would be extremely easy to receive and decode. The
problem of ground station coverage would be reduced to finding
individuals along the anticipated trajectory who would be willing to
help.
Alex
> --
> http://groups.google.com/group/ultra-light-space-flight?hl=en
>
Joshua
John Pritchard
Well, aside from some small possibilities among close friends, there's also the Space Tweeps and our ULSF readers -- among which there are better possibilities.. especially if what they need to buy and build can be applied to other similar projects(?) (with variation?)
ps http://ulsf.googlecode.com/svn/readers/GeoMapReport-20100513-20100612-1004x628.png
pps ((If it didn't require a HAM license, it would be more fun, but I guess this isn't practical. I've learned why many projects use the 2.4GHz/12.2cm band.. it's a clear window through atmospheric absorption. but you probably knew that.))
ppps ((One meter dishes seem to have good economy, but i see that the winegard 1m weighs 10kg))
John Pritchard
- http://ben.davies.net/Equatorial%20Mount.htm
- http://www.bbastrodesigns.com/BBAstroDesigns.html#Computer_Operated_Telescopes
Joshua
John Pritchard
Hi,Looks like interesting but today I have listened a brilliant idea from Juan Martinez (in Majorca). He states that we only need one ground station (the same used in the launch) to monitor each orbit. We only have to launch in the Equator like KOUROU or from a trip in a boat near to the Equator. Great!Best,Joshua
Yes, that sounds very interesting!
ps. I've always wondered if a mostly submerged cylinder would be a stable platform (reduced wave action) -- perhaps the length of the column filters out the effects of waves with shorter amplitudes
Alex Csete
I think the popularity of 2,4 GHz is because it has become cheap,
though I do not know of so many space projects who have used it. (Or
maybe you mean 2.0/2.2 GHz used by space agency missions? That's a
whole different story)
There is a catch though with using cheap 2.4GHz equipment for space
comms... The Doppler shift to/from LEO is very high at 2.4GHz and ISM
equipment not designed for that will most likely not be able to lock
on.
> --
> http://groups.google.com/group/ultra-light-space-flight?hl=en
>
John Pritchard
License is only required if the station wants to transmit.
yea, or if a hamr is reqd the antenna can be remote operated
I think the popularity of 2,4 GHz is because it has become cheap,
though I do not know of so many space projects who have used it. (Or
maybe you mean 2.0/2.2 GHz used by space agency missions? That's a
whole different story)
There is a catch though with using cheap 2.4GHz equipment for space
comms... The Doppler shift to/from LEO is very high at 2.4GHz and ISM
equipment not designed for that will most likely not be able to lock
on.
oh, i don't know about cdma and friends and how they're implemented.. just learned a spot about absorption spectra
John Pritchard
I think the popularity of 2,4 GHz is because it has become cheap,
though I do not know of so many space projects who have used it. (Or
maybe you mean 2.0/2.2 GHz used by space agency missions? That's a
whole different story)
There is a catch though with using cheap 2.4GHz equipment for space
comms... The Doppler shift to/from LEO is very high at 2.4GHz and ISM
equipment not designed for that will most likely not be able to lock
on.
oh, i don't know about cdma and friends and how they're implemented.. just learned a spot about absorption spectra
mixed my numbers from memory.. was thinking of this
which is pointing to a ~58GHz window, better for ranging and worse for tuning radios during a satellite passes
(oh well)
John Pritchard
that's a nice graph but the labeling is odd.. the vertical axis is transmission, not attenuation
so the meaning is inverted, and the domain of interest is not there
Alex Csete
As a rule of thumb one can assume that between 1 and 10 GHz the
atmospheric effects will be less than a few dB so it is not critical
if one leaves ~10 dB or more margin in the link budget.
Note that attenuation is only one of several signal degrading effects.
Molecules and electrons in the atmosphere also induce group delay,
depolarise the beam, etc... which one has influence on the signal
depends on what properties carry the information: amplitude, frequency
or phase. This is why Wifi and other terrestrial stuff becomes
unsuitable. In order to achieve high symbol rate/bandwidth many
standards use both amplitude and phase to carry the information and
will be more sensitive to atmospheric effects.
This book has been a good reference for me on this topic and also
includes the models that can be used for quantitative assessment:
http://www.amazon.co.uk/Satellite-Communications-Systems-Engineering-Atmospheric/dp/0470725273
you can look at the TOC to get an idea about the effects
> --
> http://groups.google.com/group/ultra-light-space-flight?hl=en
>
tobias krieger
http://www.igep-platform.com/index.php?option=com_content&view=article&id=91&Itemid=95
could be adjusted to transfer data.
-Tobias
> Date: Thu, 24 Jun 2010 11:12:19 +0200
> Subject: Re: This week @ULSF
> From: a...@ulsf.net
> To: ultra-light-...@googlegroups.com
> http://groups.google.com/group/ultra-light-space-flight?hl=en
Hotmail: Powerful Free email with security by Microsoft. Get it now.
Joshua
Alex Csete
Presumably, the baseband signal processing is built into the main
computer board which might be similar to their beableboard derivative:
http://www.igep-platform.com/index.php?option=com_content&view=article&id=46&Itemid=55
On Thu, Jun 24, 2010 at 11:31 AM, tobias krieger
<tobio...@hotmail.com> wrote:
> --
> http://groups.google.com/group/ultra-light-space-flight?hl=en
>
John Pritchard
The image didn't get through but I can imagine what it shows ;-)
hm.. unfortunate (that gmail html content is strictly truncated to text content)
As a rule of thumb one can assume that between 1 and 10 GHz the
atmospheric effects will be less than a few dB so it is not critical
if one leaves ~10 dB or more margin in the link budget.
Note that attenuation is only one of several signal degrading effects.
Molecules and electrons in the atmosphere also induce group delay,
depolarise the beam, etc... which one has influence on the signal
depends on what properties carry the information: amplitude, frequency
or phase. This is why Wifi and other terrestrial stuff becomes
unsuitable. In order to achieve high symbol rate/bandwidth many
standards use both amplitude and phase to carry the information and
will be more sensitive to atmospheric effects.
This book has been a good reference for me on this topic and also
includes the models that can be used for quantitative assessment:
http://www.amazon.co.uk/Satellite-Communications-Systems-Engineering-Atmospheric/dp/0470725273
you can look at the TOC to get an idea about the effects
Many thanks for the info..
I'm also wondering if picosar / patch ants could be wrapped around airframe shapes like a cylinder for flight control inputs
Alex Csete
> ...
> I'm also wondering if picosar / patch ants could be wrapped around airframe
> shapes like a cylinder for flight control inputs
Yes, it's possible, but it depends what the objectives are.
The goal with planar arrangement of phased patch elements is to
increase the gain/directivity by creating constructive interference in
the desired direction. Therefore, they have to face the same
direction.
If you mount them so they point in different direction then you will
not get a gain in one particular direction. If you mount them all the
way around a cylinder you will more or less reproduce an isotropic
radiator :)
Also note that "gain" in antennas is not active gain like in an
amplifier - it is just an expression of how much you gain in one
direction compared to an isotropic radiator.
John Pritchard
many thanks for the info and explanations..
for my "sagittarius rev zero" (commercial model airplane) project i'd dream of having a forward looking hemispherical radar coverage for ten meters. in flight obstacle avoidance only needs (more) lower resolution data, while take off and landing can use (less) higher resolution data.
if this can be done for a couple milliwatts @ 5V then it would be the kind of thing that could fit into the kind of power budget needed (design target is 4 AA batteries with half that assigned to propulsion)
the attraction of radar is no moving parts, fast response, and broad coverage -- if it could detect a bird or a ball in flight within ten meters, i'd be very happy. :)
the craft shape will be some kind of blended wing body -- i.e. it will have a nose with a little flexibility in geometry although not much.
communication is the last priority. maybe some micro wifi would fit.
this project is in such extremely early design stages that there's really only so many feasibility questions
Alex Csete
http://www.uk.amsat.org/content/view/713/284/
Presentations are usually streamed on the web.
PS: I'll be there talking about GNU Radio
> --
> http://groups.google.com/group/ultra-light-space-flight?hl=en
>
John Pritchard
Presentations are usually streamed on the web.
PS: I'll be there talking about GNU Radio
That's cool. Will you discuss the transponder mode?
Alex Csete
I'm not sure I understand what you mean with "transponder mode" ...
GNU Radio is a library of signal processing blocks and a framework for
putting the blocks together into whatever one wishes to do, so it
doesn't have a transponder (or any other) mode.
John Pritchard
sat application mode.. i don't really understand the SDR, and how it would operate in a ranging transponder.. if there's a digital process involved and the relation between ranging operation and the transponder process
Alex Csete
Ah ok... Think of a radio (hardware) as a handful of parts (resistors,
capacitors, transistors, ...) that are mounted on a PCB to perform the
radio function. That function can be receiver, transmitter,
transponder, .... the same parts wired together in different ways to
perform the different functions.
SDR means nothing more than that we replace some of the hardware
functions with software - usually the processing performed at low
frequency / baseband. The advantage is flexibility. For example if you
want to build a radio than can do both FM and AM, in hardware you
would have to create two different circuits to perform the two
functions. Two circuits cost twice as much as one circuit. You also
have to do that in SW but the additional "circuit" only costs a few
extra kilobytes :)
To get back to your original question, yes, I will talk about
satellite applications. The key advantages of GNU Radio and USRP in
this area are the full duplex operation on two channels simultaneously
(meaning 2 TX + 2 RX at the same time) and the wide bandwidth (2 MHz
for each of the 2 TX and 2 RX channels).
I will probably not talk about ranging since there is not much
SDR-specific about that.
I hope I will have time to talk about Doppler tuning and automatic
tracking, in that are GNU Radio and USRP have clear advantages due to
the wide bandwidth and software defined tuning and filtering.
John Pritchard
yes, thanks.. this is the shape of what i've understood.. the bit that pauses my thought process is the usual rough estimation of software defined transponding for ranging which leads me to believe that the time spent in the digital + software receipt and retransmit process is significant to ranging error.. i think this is a central issue, even if not a problem.. that time can be described as a uniform systemic error, and even in this case would need to be measured to an extraordinary precision..
Alex Csete
> yes, thanks.. this is the shape of what i've understood.. the bit that
> pauses my thought process is the usual rough estimation of software defined
> transponding for ranging which leads me to believe that the time spent in
> the digital + software receipt and retransmit process is significant to
> ranging error.. i think this is a central issue, even if not a problem..
> that time can be described as a uniform systemic error, and even in this
> case would need to be measured to an extraordinary precision..
>
> i think that ranging and communication in one package makes the subject
> especially compelling..
>
The required onboard functionality for ranging is a simple "bent pipe"
- no onboard processing required.
I think for ranging we can use an independent subcarrier that omits
going through the software. If that is unfeasible for some reason, the
SDR can be designed so that the ranging signal is returned
independently of the other processings and the return latency is
constant.
Alex Csete
Picture in picture compositing in gstreamer with examples ranging from
simple concepts to the more complex "Live from Pluto" video wall:
http://www.oz9aec.net/index.php/gstreamer/347-more-gstreamer-tips-picture-in-picture-compositing
Simple time-lapse videos with gstreamer and ffmpeg:
http://www.oz9aec.net/index.php/gstreamer/346-simple-time-lapse-video-with-gtreamer-and-ffmpeg
Note the image quality - it was recorded using a $100 QuickCam Vision
Pro 9000 UVC webcam from Logitech. I can't wait to try the new "HD
Webcam" series from Logitech coming out in a few months.
Joshua
John Pritchard
Yea, sweet++ :)
This week moon-20 & josh & juan & google and the world taught me about DDS files.. on the plan for fv3 (java GL).
Completed a port of the http://unbboolean.sfn.net/ package "j3dbool" Constructive Solid Geometry primitives to fv3.
And wondering what the moon-20 team will be doing with their requirements and specs online. Made me think about momentum wheels as for model rockets (the extremity of low mass), and found a couple interesting papers on "scissored pairs" that's interesting..
- http://www.spacecraftresearch.com/files/Scissored_Pair_note_web.pdf
- http://www.aoe.vt.edu/~cdhall/papers/AAS03-558.pdf
- http://www.st.com/stonline/products/applications/blocks/motor/mc009.shtml
- http://homepages.which.net/~paul.hills/SpeedControl/SpeedControllersBody.html
- Electric Motors
for Model Aircraft
http://www.epanorama.net/links/motorcontrol.html
- http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2125¶m=en026745
- http://open-bldc.org/wiki/Developing
- http://www.mikrokopter.de/ucwiki/en/BrushlessCtrl
And of course studying my physics books, wondering how i'm going to do electrical design (wonder if i can cheat electric http://www.staticfreesoft.com/ to do it, as it's free, it's java (model programming paradigm), it's 3d, and it includes cool simulation tools), needing to do lots more things like dive into the ajile web materials.
tobias krieger
So, I got last week all stuff I've ordered, my arduino, some servos, a 500mW green laser diode,....I already played a little around - arduino programming seems simple, and since some little test programms worked right away (on both, my mac and my dell), hence I'm in a quiet positive mood.
Headed yesterday to San Diego, CA, where I'm for the next two weeks. I've here a training with BMS (Broadcast Microwave Systems), since we (the company I'm working for) have some 18", 34" and a 72" inch auto-tracker systems for our UAV's.
Anyone close to SanDiego?
See ya,
Tobias
From: j...@ulsf.net
Date: Sun, 27 Jun 2010 11:39:59 -0400
Subject: Re: This week @ULSF
http://groups.google.com/group/ultra-light-space-flight?hl=en
Hotmail: Trusted email with Microsoft’s powerful SPAM protection. Sign up now.
tobias krieger
Hi John,
you can try also linear technology: http://www.linear.com/designtools/software/. I'm working with ltspice, bodecad and scad3.
For PCB I guess, eagle http://www.cadsoftusa.com/index.htm.en is known to everone, or? 5.1 is now out.
-Tobias
From: j...@ulsf.net
Date: Sun, 27 Jun 2010 11:39:59 -0400
Subject: Re: This week @ULSF
To: ultra-light-...@googlegroups.com
http://groups.google.com/group/ultra-light-space-flight?hl=en
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Joshua
John Pritchard
Thanks for all the info and updates...
John Pritchard
Tough constraints at home today, but got this published..
http://spacetweepsociety.org/blogs/jdpsyntelos/ultralight-spaceflight-gangs-all-here
Looking for more info about Moon 2.0.. for example, are you all in Barcelona?
Joshua
Best,
Joshua
John Pritchard
About Moon2.0, Juan is from Majorca and I am from Barcelona but wikisat team is around the world. Austria, Denmark, Spain and USA.
Best,
Joshua
Yes of course, but I think there is a large group in Barcelona aside from us here and Juan, no?
Joshua
http://www.youtube.com/watch?v=9AJf5bgJZPI
Sorry Alex, I need time to update your picture.
My best,
Joshua
John Pritchard
Yes, take a look to this video presentation of the group:
http://www.youtube.com/watch?v=9AJf5bgJZPI
Sorry Alex, I need time to update your picture.
My best,
Joshua
ok, thanks