Space Tweep Society

This week @ULSF has been quieter than usual.  Looking out at our world, @PTScientists have a new blog post on rover wheels, and Alex @Csete is at the AMSAT UK Colloquium discussing Gnu Radio and OZ7SAT.

Reading about the ISS this week chills the bones.  Glad everyone is safe.

Work on the Sagittarius “plastic lifter” design study project continues in the solid modeling software.  The Constructive Solid Geometry package is presently being debugged. 

Additional work on future flight test locations has identified Floyd Bennet Field as an ideal candidate.  This location is an established R/C park, expansive, isolated, and surrounded by water.

This week @ULSF we’ll have a look into open engineering since 1962.  That was the year in which Richard Hamming published his book, “Numerical Methods for Scientists and Engineers” complete with the most interesting appendix, “N+1: The Art of Computing for Scientists and Engineers”.  Hamming’s premise for “Numerical Methods” is “the purpose of computing is insight, not numbers”, following the standard “garbage in, garbage out” caveat for data processing.  In “N+1″ Hamming develops the principle into “The open shop philosophy” via an epistemological “What do we know?”.  As in “What is the input?” and therefore what is the computation that describes the output.  Hamming wrote, “If we believe that the purpose of computing is insight, not numbers, then it follows that the [person] who is to get the insight must understand the computing”. “If he does not understand what is being done, he is very unlikely to derive much value from the computation”.

These principles extend into the more practical applications of computing that are common and familiar today.  What are the choices necessarily made by the programmer, and how were those choices implemented?  The open source software movement responds with, here is the code reflecting the choices made and available to inspection as well as alternative design and implementation.  For example in the realm of computer operating systems, is this code making the user vulnerable to resource or even identity theft.

Of course NASA has long been a leading member of the openness that has differentiated the US from most of the world throughout our brief history.  For example, the NASA Technical Reports Server contains millions of person-years of scientific and engineering knowledge and information (that statistic is simply my own guess at a conservative minimum bound).

This week NASA Nebula pushed forward in the exemplary OpenStack initiative for cloud computing, an application computing infrastructure for NASA on par with that of Google or Amazon.

This week Alex @Csete has taken more steps forward into opening up Gnu Radio, detailing the decoding of the RS0ISS message board.

The wide strong peek at 145.82 MHz is the ISS FM packet radio downlink in AX.25, shown in the neighborhood of VO-52.

I’d like to take this opportunity to admit that not since childhood have I been so close to reaching for an amateur radio operator’s license.  Apparently it’s pretty easy.  Alex is saturating my head enough that I’m starting to get some framework in mind to comprehend radio waves and their creation and propagation.  For me, RF is the weirdest area of Physics that I’m aware of.

Plus, the software defined radio is an FPGA application, like JOP that I’m also interested in for ULSF JFlight.  Although electrical engineers should feel free to jump in to help with Sagittarius.

This week @ULSF we have a cool NOAA APT catch by Alex @Csete.

This image from the North Pole was captured from Denmark.

This video shows the tracking sequence as illustrated by Alex’s GPredict software.

 ”I used GNU Radio and the USRP to receive and Gpredict … to predict the AOS/LOS times and to know where to point the [hand held] antenna during the pass.  What I did was to record the received spectrum (250kHz as seen on the video from last week) in raw format. This data is pretty much a digital representation of what was on the air at that time at 137.x MHz +/- 125 kHz (At 137 MHz the Doppler shift will be less than +/- 5 kHz). The recorded data is about 1.7 GBytes for a 15 minute pass.

“After the pass, I replayed the recorded spectrum and ran it through the channel filter, FM demodulator, audio recorder and image decoder.   It still feels like listening live the only difference being the signals don’t come from the antenna but from a recorded file. It has the advantage that I can always restart if I make a mistake during decoding and it is also very useful for experimenting with the receiver chain.

“The idea with the DX was to try to receive signals when the sat is still far away (low  elevation). Due to the FAX-like transmission, the image is transmitted line by line and the  satellite always transmits what is right below it (sub satellite point/line). It’s like a camera always pointing down to Earth and only capturing one line at a time.   So, the lower the elevation angle, the farther away will the transmitted image come from. Obviously, there is a limit to how far away this can be because the satellites are in a low Earth orbit (between 800-900 km).

“Receiving while the satellite is still at low elevations can be very easy if there is clear line of sight or very difficult if there are trees in the way. I got mixed results this weekend:
http://www.oz9aec.net/index.php/gnu-radio/gnu-radio-blog/353-more-noaa-apt-images-with-gnu-radio-ursp-and-wbx
The best accomplishment is probably the one from the North pole, though it’s rather noisy and difficult to recognize.”

This week @ULSF we’ll meet the original, broad definition of “ULSF” as looking out at the world more than looking into our own group.  Following from @ULSF we see @Odyssey_Moon wishing everyone in the US a Happy Fourth.  @ClydeSpace sees young James Tiberius coming up through the classic apprenticeship.  And @AstroTek shares @MilesOBrien always loves a good lander flight test.  @NASA_Wallops wishes us a safe Independence Day with a historical note that on this day in 1945 they launched the first Tiamat research rocket.  As always, @AronSora is tweeting a universe of space ideas.

Alex @Csete has been pointing Gnu Radio + the USRP at NOAA satellites this week, great articles at OZ9AEC.

For my own part, I’m still working on this
stack and learning OpenGL — instruments of study and work.  I’m happy to be gaining traction with OpenGL and making some (albeit minor) progress on the space
plane design study project that all of this effort is primarily
pointed at.  This week I opened “elme”, electro-mechanical simulation
software project with “Prop”.  This is (the beginning of)
a variable pitch propeller using a helicopter style control plane for
vectored thrust.  A pair of these counter rotating will be used for atmospheric flight control, but reminds me of a very similar configuration used for thrust in the
Lockheed XFV-1 project.  My grandfather worked on the propeller pitch control gear set for this project.  Makes me  warm and fuzzy to find a variable pitch propeller in the position of a favored solution.