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Laboratory for Advanced Space Systems at Illinois

CAPSat 2-way Comms Achieved!

After deployment on Oct 12, we experienced some ground station issues that delayed our making contact with CAPSat. Within a short time however, we successfully received a beacon signal from the satellite, but could not demod the signal using the GNU-radio software we had configured for the task. It appeared that the long antenna cable run from the roof to the power amp was dropping the SNR below what GNU-radio could handle.


We then took the AX100 radio out of another satellite we have in our lab and put it to good use. With hardware doing the demod, our beacon data indicated we were healthy. After a little more tweaking we established 2way comms with the radio daemon on CAPSat, and discovered that during the first week of operations (recall a CME occurred that week) the satellite was rebooting at least three times a day, filling up our logging memory way faster than we had anticipated. Eventually the memory filled completely. A shortcoming of our inherited design, is that a command script must first be placed into memory by the radio daemon before it can be executed by the command daemon. This situation effectively locked us out from commanding the satellite.


Our team persisted however, and worked up a few linux hacks that would allow us to open an existing file, shorten its length, and get a command in to delete additional files to create space for commands. Our first attempt failed and crashed the command processor completely with no way of rebooting or restarting it. Fortunately, it appears the solar flare this weekend may have helped and we were rebooted. Then at 211am this morning, we tried another hack. This time it worked, and we successfully executed a script to create file space, resync the spacecraft clock, and download some situational data.


We are now (finally) working with the science team to prepare to bring down some science data over the next week or so. They are excited to see what effect the CMEs have had on their photodetectors. As soon as we get that data, we’ll provide another update.


While nothing on CAPSat has been easy, the program has provided a number of learning opportunities for our students (and me!), the most important of which is to “never give up.” We are building a culture here that shows the benefits of discipline, rigor, documentation, and teamwork. I’m excited to be able to send some of these young engineers out into the world soon to see what else they can do with the tools NASA's USIP/Elana programs have made available to them.