Version 24 (J. Simmons, 10/16/2018 05:17 am)

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h1. History
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The Ground Sphere projects have a rich history at Mach 30, starting with a question from Mach 30 contributor Aaron Harper leading all the way to the current generation Ground Sphere intended for receiving images from NOAA weather satellites.
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h2. Mk 1
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h3. The Inspiration
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The first Ground Sphere project did not go by the name Ground Sphere, it was simply referred to as "GS-001":https://opendesignengine.net/projects/gs-001/.  GS-001 wasn't even a formal Mach 30 project.  Instead it was the physical answer to a question posed by Mach 30 volunteer Aaron Harper, _"How low can we get the cost down to and reliably receive radio signals from space?"_  
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Like all good makers, Aaron sought to answer the question quite practically, by building one with the goals of low cost and simple operations.  As you will see, the success of this early work had a profound impact on Mach 30 and influenced future project development.  Today we refer to GS-001 as Ground Sphere Mk 1 due to its relationship to the first project to bear the name Ground Sphere.
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h3. Revision 1
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_January 2013 - April 2013_
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The earliest documentation for a Ground Sphere related project dates to January 2013 when Aaron Harper started the "GS-001":https://opendesignengine.net/projects/gs-001 project.  Aaron chose to have this ground station receive signals from "Amateur Radio Satellites":http://www.amsat.org/ (or Ham radio satellites).  As a Ham radio operator, Aaron was familiar with their operation and availability of opportunities to receive their signals.  Ham radio satellites operate as "Ham radio repeaters":https://en.wikipedia.org/wiki/Amateur_radio_repeater in the sky.  Observers of Ham radio satellites can listen to Ham radio operators communicating with each other across vast distances.
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As part of his goal to have simple operations, Aaron elected to use an omni-directional antenna.  This choice meant that users would not have to track the satellite as it flies overhead, something that is required with higher gain, directional antennas.  After reviewing several options, Aaron selected an "egg-beater antenna design":http://on6wg.pagesperso-orange.fr/Page%201.html.  He tied this antenna to a "Software Defined Radio":https://en.wikipedia.org/wiki/Software-defined_radio "TV Tuner USB Dongle":http://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/.  These dongles are cheap and are often used by makers for similar applications.  
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So, how did Aaron's experiment turn out?  See for yourself in the video below.  By "Yuri's Night":https://yurisnight.net/ of 2013 Aaron had built and tested GS-001 for under $200.  Check out the blog post "Ground Station part 1":http://mach30.org/2013/05/16/ground-station-part-1 for Aaron's complete story of GS-001.
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h3. Revision 2
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_May 2013 - July 2013_
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After the success of the first revision of Ground Sphere Mk 1, Mach 30 decided to include Ground Sphere (at this point, referred to simply as the Mach 30 ground station) in its booth at the 2013 "NewSpace":https://newspace.spacefrontier.org/ conference.  This decision posed some challenges as the first revision was not intended for transport, let alone shipping.  Its aerials were permanently mounted in place, making the shipping dimensions unmanageable and exposing the aerials to potential crushing if other packages were stacked on top of Ground Sphere's box.  
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Aaron made a second revision to the Mk 1 design to address these issues.  Instead of directly soldering the aerials to the rest of the antenna, Aaron added screw terminals to the outside of the Ground Sphere structure.  The aerials could then be packaged flat in a box and attached (or detached) with a screw driver.  This design choice remains integral to Ground Sphere and has been used in all versions since the spring of 2013.
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|Ground Sphere Mk1 R2|
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NewSpace 2013 was a great event for Mach 30 in general, but it was an amazing event for Ground Sphere.  It turns out "SkyeCube":http://www.southernstars.com/skycube/, a CubeSat Kickstarted by "Southern Stars":http://www.southernstars.com/, was on exhibit two booths down from Mach 30.  Like Mach 30, Southern Stars had their hardware on display in their booth.  It did not take long for Mach 30's representative (J. Simmons) and Southern Stars' representative (Tim DeBenedictis) to realize Southern Stars had a satellite and Mach 30 had a ground station, and that clearly they should see if the two hardware projects could talk to each other. Within an hour Tim and J. were sending messages from the SkyCube engineering model on one end of the exhibit hall to the Mach 30 ground station at the other end. J. and Tim capped off the day by using the two projects to run an impromptu demo during a panel Tim was on later that afternoon.  
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|Mach 30's NewSpace 2013 Booth|
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You can see more details about Ground Sphere at NewSpace 2013 on "Google+":https://plus.google.com/+JSimmons/posts/QhnWbyVsNsC and the "Mach 30 blog":http://mach30.org/2013/08/03/new-space-2013-wrap-up/
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h2. Mk 2
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Shortly after NewSpace, Mach 30 and Southern Stars began discussing how they could expand on the joint success from the impromptu demo.  The conversation quickly turned to one of the backer rewards for SkyCube, a small ground station for backers to pick up "space tweets" broadcast from the CubeSat.  Mach 30 and Southern Stars agreed to work together to revise the Mk 1 ground station into this backer reward.  This decision would drive Mach 30 hardware development for the next twelve months and lead to the development of Ground Sphere Mk 2.
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|Ground Sphere Mk 2|
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h3. Companion to SkyCube... Ground Sphere of Course
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_September 2013 - December 2013_
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Capturing signals from SkyCube and then decoding them into the "space tweets" had a significant impact on the Mach 30 ground station project, starting with earning it the name Ground Sphere (as in the on Earth companion to SkyCube.. get it?  Ground Sphere - you can thank Mach 30 president J. Simmons for that bit of punnery).  All jokes aside, receiving signals from SkyCube required some significant changes to the Mk 1 design.  First, CubeSats have far less power than traditional satellites, making it much harder to pick up the signal.  Imagine trying to hear someone whispering from across a room, it is going to be harder to hear them, and if they cannot speak up, you need to do something on your end (cup your ears, get a microphone and try to turn up the sound from it, etc).  The same idea holds true with receiving satellite signals.  If the satellite cannot broadcast any stronger, the ground station has to make up for the difference in signal strength.  For Ground Sphere, this meant adding amplification to the communications circuit.
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SkyCube also operated on a different frequency than Ham radio satellites (specifically 915 MHz vs around 430 MHz).  Due to the nature of the physics for radio waves, this meant the dimensions of the Ground Sphere antenna had to be changed.  Specifically, it had to be shrunk significantly.  For those wondering how the SkyCube and Ground Sphere at New Space managed to work, the answer involves both a little bit of luck and the simple fact that communicating across a hundred feet while standing still is *very* different from communicating over hundreds of miles when one of the parties is moving at nearly 25 times the speed of sound.
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All of these details, and many more, were the focus of Mach 30's project team over the fall of 2013.  You can read up on all of the details of this work on the "Ground Sphere Mk 2 wiki":https://opendesignengine.net/projects/groundsphere/wiki.
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h3. Building Mk 2 
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_January 2014 - May 2014_
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By the beginning of 2014, the Mach 30 project team was turning its attention toward building Ground Sphere prototypes.  Building the egg-beater antenna at the smaller scale required to receive signals from SkyCube proved challenging.  Some of the techniques from Mk 1 did not translate well, especially where the ground plane (that mesh disk below the aerials) was concerned.  Compare the images of two prototypes below.  In the first prototype the ground plane is highly irregular and wavy.  As the name implies, a ground *plane* needs to be _flat_.  The ultimate solution came from a Mach 30 volunteer with a background in crafting.  She found plastic mesh disks in sizes very close to the Ground Sphere Mk 2 ground plane, so she sandwiched conductive mesh of the ground plane between two of the plastic disks (after cutting them down to the specific size needed for Ground Sphere) giving the final design seen on the right.  It was one of the most innovative design details to come out of the Mk 2 work.
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|First Mk 2 Prototype|Final Mk 2 Prototype|
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Not all ideas work out as well.  And Mach 30 is not ashamed to admit when it makes a mistake, even when it results in a little bit of fire.  We were looking for a way to physically secure the electronics inside the base of the Ground Sphere unit to protect them during transport (both shipping if needed and when users moved Ground Sphere from point A to point B).  One idea we were quite fond of (at first) was to create a foam insert to hold the electronics in made from expanding insulation foam (the fire resistant kind of course).  At some point during the process, one of the team members asked if the fire resistance had been tested under the circumstances we would be applying the foam to.  The short answer was "not yet", and testing the foam bumped up in priority.  The results were rather dramatic as can be seen in the image below.  You can read the full test report in this Mach 30 "blog post":http://mach30.org/2014/06/03/testing-for-catastrophic-capacitor-failure.
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|Mk 2 Fire Test Results| 
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h3. Testing and SkyCube
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_June 2014 - September 2014_
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When the first Mk 1 prototype was completed, testing was a simple as waiting for the next time a Ham radio satellite would be flying overhead and tuning to the correct frequency.  This approach was unfortunately not an option for Mk 2.  There were two key reasons why this approach would not work.  First, SkyCube was not in orbit yet, and second, its mission was set for a maximum of 90 days.  So, even if Mach 30 waited until SkyCube was in orbit, by the time testing would be complete the mission would be over and the backers would not be able to use Ground Sphere to receive signals from SkyCube.
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Instead, Mach 30 developed a set of "verification procedures":https://opendesignengine.net/projects/groundsphere/wiki/Testing including a "series of tests":https://opendesignengine.net/projects/groundsphere/wiki/Test_112_Instructions which progressively demonstrated Ground Sphere's capabilities (from the lab to field tests).  Below are some images from the testing done for Ground Sphere.
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|Testing Signal Strength from 1 m|
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|Testing Signal Reception from Orbit|
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As it turned out, the timing of the final round of tests did overlap with the deployment of SkyCube from the International Space Station.  So, our final round of testing did include attempts to receive signals from SkyCube while in orbit after all.  Unfortunately, SkyCube experienced a system failure after deployment scrubbing the mission.  Only a couple of telemetry "pings" from SkyCube were ever received by anyone (read the "full mission debrief from Southern Stars":https://www.kickstarter.com/projects/880837561/skycube-the-first-satellite-launched-by-you/posts/985395 for more details).  With the target mission over, and no other open missions operating at 915 MHz, Mach 30 closed out the Mk 2 project and returned to its propulsion related projects.
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h2. Mk 3
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h3. Mach 30 Happy Hours - Taking Ground Sphere Back Off the Shelf
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Ground Sphere spent about a year sitting on the shelf, so to speak.  By the fall of 2015, Ground Sphere was being discussed again as Mach 30 reviewed the market impact of its projects.  By the beginning of 2016, Ground Sphere would be front and center at Mach 30, having been chosen as the 2016 project.
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_October 2015 - December 2015_
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Mach 30 has long been interested in expanding its educational programming and increasing its revenue opportunities through open source spaceflight hardware kits.  Starting in October of 2015, an informal group, led by Mach 30 vice president Greg Moran, began meeting to discuss what projects had the greatest market potential for both educational work and business potential.  Ground Sphere's name kept coming up at these gatherings leading to the creation of a "market research prep document":https://docs.google.com/document/d/1zD4iFEEZ5kK3qsgPsLTkpYedvtxqU8P2unvGA2QpNHQ/pub.  Based on these meetings and this document, it became clear Ground Sphere had the greatest potential reach of Mach 30's projects.  This potential would become a critical factor in the development of Mach 30's 2016 annual plan.
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h3. Mach 30 IPT Development of Ground Sphere Mk 3
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_January 2016 - Present_
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Each January, Mach 30 prepares its annual plan during a day long board meeting called Perigee.  At the 2016 Perigee meeting the board made two critical decisions impacting Ground Sphere.  First, the purely technical team managing Ground Sphere's development would be replaced with an Integrated Product Team (IPT) made up of business, marketing, legal, and technical team members to ensure all aspects of Ground Sphere are addressed throughout the project's lifetime and in sync with each other.  Second, as mentioned, Ground Sphere was selected as the focus project for 2016.    
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If you will recall, Ground Sphere started off as a quick physical study to answer Aaron Harper's questions about the affordability and ease of use of potential ground station hardware.  Working quickly let Aaron demonstrate important results, but it left gaps in the documentation.  So, the first tasks of the newly formed Ground Sphere IPT have focused on filling in some of the documentation, especially where the engineering math related to radio communications is involved.  This is an area of spacecraft engineering that is not as accessible as Mach 30 would like to see it.  Additionally, Mach 30 found a "blog post proposing an even lower cost to entry":http://blog.nobugware.com/post/2015/listening_to_satellites_for_30_dollars/ into satellite communications than Aaron saw in the Mk 1 prototypes.  Naturally, the IPT has also been investigating this claim to see what we can learn from it.  Check out the video below and the rest of the project wiki for more details about the IPT's progress so far.
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