A busy day in the Wasatch Back valley! Day was overcast to mostly cloudy, with a stiff southerly breeze, and cooler than in the last few days. There is no IOP planned for tomorrow with the next IOP possibility on Thursday into Friday.
ISS1 – Profiler status this morning: @ 1021 100m: 4.46A @ 50V & 1.833A @ 32V, and @0930 150m rass: 3.70A @ 50V & 1.881 A @ 32 V. There were several things of note today from the ISS1 site.
First, I noticed a few days ago that the histogram of signal to noise ratio (SNR) for channel 0 (red) was higher in the xplotmapr Diagnostics plot. I theorized that this was due to channel 0’s antenna panel receiving more morning sunlight, thereby melting off the frost layer faster than on the other channels’ antennas. Today I noticed on the profiler’s Display screen that the SNR for the red channel was higher than the other channels when an interfering signal was being picked up (see image below). This is likely due to the orientation of the antennas, clutter fence, the speaker surrounds, and the direction the interfering signal is coming from. This additional signal strength may be contributing to the higher SNR levels in the distribution seen in the Diagnostics window.
Next, when the RASS mode started there was no sound coming out of the speakers. I did not see a signal LED light up on the audio power amplifier so it looked as if the amplifier was not generating an output signal. I started by disconnecting the speakers from the terminal block and power cycling the amplifier. While disconnecting the speakers from the terminal block I noted that the speakers were connected in parallel, which presents a lower impedance to the output of the audio amplifier, which causes higher currents from the amplifier that could potentially damage the output stage(s) and/or trip the internal over-current/over-temperature protection circuity that the amplifier has built in, per its datasheet. I do think one of the protection circuits was triggering, most likely the over-temperature protection, as a result of the speakers being wired in series. To present a higher impedance to the amplifier's output, I rewired the speakers to be in series and the ran the RASS mode. The system for a couple of minutes before the audio stopped working again. I now suspected that one of the two output stages of the amplifier may beginning to fail, which could be tripping the protection circuitry. I enabled the audio amplifier’s “Y” Input Switch so that the input signal is sent to both channels of the amplifier. I also switched the amplifier’s output from Bridged Mode to Dual and connected the series-wired speakers to the channel 1 output terminals. As a result, I had to increase the output level of the power amplifier to get the same volume out, but the system is now running using only channel 1 of the audio amplifier. I measured the AC voltage coming out of the amplifier at the terminal block with a multimeter to be 11.4 VAC across the four speakers wired in series, with each speaker is seeing ~2.85 VAC across its terminals. Below are some pictures of how the speakers are wired at the terminal block, the settings and LED display on the power amplifier, as well as a few action shots of me taken by Jacquie.
Jacquie took some pictures of the snow conditions around the array while the system was stopped. It looks like all the frame and cabling on the frame are free from the snow and ice and that it will be possible to simply raise the array to remove the RFE troughs and much of the cabling.
ISS2 – Fortunately, there were no issues at the ISS2 site today. Bill was working on the lidar laptop, trying to free up some disc space, but otherwise nothing to report.
ISFS – While I was debugging the RASS, Isabel informed Jacquie that the ISS1 DSM was no longer responding on the network. The problem was traced to a bad Ethernet connection. See Jacquie’s blog post in the ISFS wiki for more details.
Soundings – A stiff southerly breeze during the sounding again today. I was able to drain 10 cubic feet of helium out of a tank that had previously been flagged as empty. All the empty tanks on the right side of the trailer are now truly 100% empty. We will continue to check the other cylinders on the left hand side of the trailer for residual amounts of helium.
Finally, I gave my Introduction to CubeSat presentation at a Wasatch High School engineering class for ~25 students as an outreach activity (why should the scientist have all the fun?!?!?)