So remember how we dug over 8ft down to the bottom of a solar panel? And then couldn't go back the next day because of 40 knot winds?
Well, it turns out those 40 knot winds re-filled in all the holes we had dug.
I'll start at the beginning. Friday afternoon (day 18), we got all packed up and ready to go to Castle Rock. As I mentioned last post, all the Mattracks are currently out of commission, so the PASSCAL team now has a dedicated PistenBully for our test site work. PistenBully 314 has been outfitted with metal treads, and is parked at the snowline at the Castle Rock trailhead. The metal treads work great on ice/snow (but not so much on rock), so it is parked at the trailhead to avoid wear-and-tear on the treads from driving through the gravel in town. I became fast friends with PistenBully 314.
 |
| Me and my new best friend, PistenBully 314. |
Erica, Rob, Avi, and I took a shuttle up to the PistenBully with all our
shovels and survival bags. We did the routine inspection and followed
the (very complicated) start-up procedure to get PistenBully 314 warming
up; the engine temperature has to reach 140 before driving (which took almost 10 min).
 |
| Picture from the captain's seat as we wait on PistenBully 314 to warm up. |
Finally, 314 was warm and ready to go. I drove us to the test site. Driving a PistenBully is...... different. You change the speed not with the gas pedal, but with a little
white scroll wheel on the steering wheel. And then you use the gas pedal
to keep the engine at 1500RPM. There is no brake pedal, so the PistenBully slowly creeps forward when you stop unless you put on the parking brake.
We made it to the test site with no incidents -- the metal treads were excellent for driving over the icy patches on the trail. And when we got out of the PistenBully...... we found that the solar panel holes had been completely filled in from the high winds.
 |
| These were 6-8ft deep when we left them.... |
To make things worse, we had stored some equipment in the holes -- we were worried it would blow away. Instead of blowing away, it just got totally buried in snow. So we spent the afternoon re-digging the solar panel holes and digging up our now-buried equipment.
By 1700, we had dug all three of the solar panels out again! We raised them to the surface and packed a small amount of snow around the bases so they wouldn't blow over. However, the victory was short-lived when we realized we still had 2 more panels to dig out. We will tackle those later this week....
 |
| Success!! 3 out of 5 solar panels raised!! |
On Saturday, just Avi and I went out. We dug out the sensor and one of the two plywood enclosures that house the equipment and batteries for the site. The plywood enclosure was screwed shut, but most of the screws had rotted out. We never use plywood enclosures in the field; we use the sturdy orange plastic boxes that I've shown before. Avi and I are considering replacing the plywood with spare plastic enclosures that we have back in McMurdo.
 |
| The top of the plywood enclosure (about 90cm down). |
The equipment in the plywood box included:
- 20 Lithium batteries. These are non-rechargable, and we were surprised to find these batteries at a test station, since they are consumables and the test station doesn't need to rely on extra power from Lithiums. Even though they aren't rechargable, the advantage of Lithum batteries is that they have a higher energy density than lead-acid batteries; they are lighter for the same kWh.
- 36 AGM lead-acid batteries. These batteries are rechargable, with the downside that they each weigh 75 lbs. We generally use SunXtender PVX-1290T or 1080T batteries at all our Antarctic sites.
- 1 GV-15 charge controller, which manages charging the AGM batteries from the solar panels. In the summer (when there is sunlight), the charge controller makes sure the batteries stay charged at ~13V with power from the solar panels. In the winter (no sun), the charge controller monitors the voltage of the batteries and will shut off the battery bank when it drops below a certain voltage. This is called a "Low Voltage Disconnect" (LVD), and we set it to about 11.5V. We do this to protect the health of the batteries (so they aren't damaged by being drained too low), and to protect our equipment, which usually cannot run below 11V.
- 1 Centaur datalogger. Besides the sensor, this is the central piece of equipment. The datalogger (also called a digitizer) turns the analog signal from the seismometer into a digital signal and stores it. The Centaur stores data on SD cards (other models of digitizers use different media to store data). The Centaur also connects to a GPS antenna (outside the enclosure) to record precise timing for the data.
- 1 XI-100b modem. This is one of the 2 types of modems that PASSCAL uses to telemeter limited data back to the facility in New Mexico. Telemetering seismic data would be very power-intensive (and is actually a new feature of the prototype system we will be installing at the test site later -- more on this to come!). So, we generally just send back low-resolution State-Of-Health (SOH) data. This includes data on the voltage/current of the battery bank, temperature, and GPS timing. There are ways we can get very low sample rate seismic data, by connecting to the modem from NM and requesting a small snippet of the seismic data.
We removed the datalogger and modem from the enclosure, as they were having problems sending that small snippet of seismic data, and need to be repaired. The sensor, which was buried about 5m from the enclosure, is a Horizon V1 seismometer, and needs to be shipped back to
the manufacturer to be upgraded to the newer V2, so we removed it as well.
 |
| Inside the plywood enclosure. Towards the front are the Lithium batteries, the equipment is in the top right corner, and the huge AGM batteries take up the rest of the space. |
 |
| Test site sign raised! Plus three raised solar panels! It is looking much better. |
Comments