#EngineerSpeak Hangout 2013-10-03

Mach 30 #EngineerSpeak Hangout October 03, 2013

Discussion Topic: SkyCube & Mach 30 Ground Stations

Attending: J, Jeremy, Tim, Aaron, Juli, Chris

Start: 2205

End: 2305

Minutes:

Aaron - EE in Wassenburg, CO; project lead on Mach 30 ground stations
Chris - Software Engineer in Baltimore, Mach 30’s code monkey
Jeremy - Mach 30 board member, Shepard Test Stand team lead, from Ft Wayne (ish) Indiana
Juli - Mach 30 volunteer and Jane Q. Not-an-Engineer, Albuquerque
J - President Mach 30, do a little bit of everything, Dayton OH
Tim - president of Southern Skies who KickStarted a cubesat, Southern Stars sells astronomy software for smartphones; space enthusiast which is why Southern Stars built a cubesat

Tim - it’s a cubesat with three missions: tweet from space (intended to be listened to by amateurs), takes pictures from space and sends them to the ground, (not quite intended for amateurs), inflates balloon to deorbit itself on command
Tim - this is a public outreach mission (what can 3 guys in their garage do to get into space)
Tim - on KickStarter, 2700+ backers and $117K raised

Aaron - Omni-directional UHF receive only ground station, with an original cost ~<$80 for development material costs. It could read the second harmonic of the SkyCube in close range. The design is currently being re-engineered for a 900MHz range, compatible with SkyCube.
Tim - It uses a software defined radio to read the RF on the computer?

J - this is the ground station targeted primarily at people who want to listen to the “tweets” from SkyCube
Tim - What we haven’t done is much work towards antenna and pointing. For longer distances we’ve gotten 2-3mile range with an alternative COTS antenna
J - Where are we with documentation and finalizing the design?
Aaron - the biggest problem we’re running into is the window screen material we utilized for the ground plane was quick to use but significantly increased gain. as a result, we are looking at using conductive fabric to reduce gain while targeting higher frequencies (~915MHz)
J - Have you tested with the amplifier yet?

Aaron - No, I haven’t completed assembly yet.
J - Implementation and testing still in progress? And what about documentation?
Aaron - Yes (on testing and implementation), and a lot of documentation still to be done

J - We also haven’t looked at all into kitification to see if there’s optimizations to be made for production sake

J - want to iterate that for the ~430MHz range there was a fair amount of testing done with birds flying overhead
Tim - we’re scheduled for launch on Nov 8. If everything goes well, we could be in orbit transmitting mid Jan, but it could easily be delayed months (such as summer ‘14)
J - The biggest difficulty is the limitation of resources, where the majority of resources for the ground station are also working on the Shepard Test Stand, which is longer in the making. That being said, if there are people on the Southern Stars team that may be able to lend expertise and cycles, that could greatly help development speed

Aaron - a different approach to the ground station’s antenna. instead of an omnidirectional antenna, it will be a directional antenna that requires aiming the antenna at the transmission source. Originally designed for UHV, but can be adapted for other ranges. The project came from a class project for an azimuth elevation mount.
Tim - what’s the motor control mechanism?

Aaron - Azimuth is a standard DC motor with a gear trane for azimuth, max RPM @ 4per minute, using servos with stainless gears for elevation and bearings to bare the weight of the antenna assembly.
Aaron - utilizes magnetometer to determine north/south and an accelerometer to cross-check directionality to keep high accuracy

The Arduino is programmed to take in serial data via USB. It utilizes a standard protocol for elevation / azimuth

Tim - Given that gov’t funding may prevent usage of US based ground stations, currently the only alternative potentially available is SABRE in Australia

Aaron - that won’t provide a lot of coverage, but a couple units of GS002 easily enable communications

J - less likely that MC3 will close up, but possible that accessibility could be decreased

Tim - again, my real interest is in getting something inexpensive and easy to use. GS001 would be great for Southern Stars usage. As such, I’d recommend the focus be on GS001
The Sky Cube has a fallback mechanism where it does something that J will put HERE
J - From a process standpoint, where are we? What’s been done and what needs to be done? it seems like we’re on our way to a 3rd prototype for the omnidirectional GS001
J - Shift the 3rd prototype to the 900MHz range

Tim - here’s another thing we can likely help with: because we use the same software defined USB radio dongle, we could share with you the comms protocol, either the binary or maybe the source. We could probably take on a lot of the software side of the radio
J - I think we should just get a working prototype utilizing an amp and the upgraded ground plane, documented, and listen to some signals with the Southern Stars software
J - If Southern Stars provides software and Aaron does most of the hardware development to prototype, we can then take the lessons learned from prototype 3 to look at kittification and design analysis. After prototype 3 is complete, then we can look again at resources.
ACTION: Aaron - Work on the 3rd prototype of GS001 for SkyCube while Shepard is still in requirements mode.
J - If we need to in the event of issues due to Gov’t shutdown, lets focus entirely on GS002

Tim - SABRE is the immediate fallback, but having GS002 available would also be good