In the last few days, from August 10th - 13th, there have been four brief periods when communications with the Saipan station have resumed. This post explains what we have learned from the existence and the contents of those communications.
First let's look at the timing and duration of these periods, speaking in local Saipan time:
- Friday, August 10th, 7:18 am - 7:42 am (5 records)
- Saturday, August 11th, 1:30 pm - 4:48 pm (34 records)
- Sunday, August 12th, 11:24 am - 11:30 am (2 records)
- Monday, August 13th, 9:42 am - 1:54 pm (33 records)
The record counts I've listed are from the 6-minute data table.
First of all, note that every record in a data table is given a sequential record number. This makes it possible to identify cases where records are (or are not) consecutive. Because of this we can say with high probability that
the station's datalogger was completely non-functional from the period from July 19th to August 9th (with times in UTC). There is no chance that this could be yet another communications-only failure, with little impact otherwise to station operations.
The pattern of communications is somewhat consistent with the explanation that, following a severe power loss that to some extent drained the station's rechargeable batteries, the station may be recharging itself and may briefly resume operations during daylight hours. However there is still no explanation for the initial power loss, or for the previous power drops (May 19th - June 4th, June 26th - July 5th) seen in the data record.
Perhaps worse, this pattern suggests that the intermittent voltage drop may not be over. Normally if a short-circuit is repaired we would expect to see better and longer "ontimes" with each passing day. Instead we start with a brief uptime in the early morning (followed by silence during that day's prime daylight hours). We also see a stronger performance Saturday followed by a weaker performance Sunday. Monday's communications are longer but they describe power levels that are getting lower throughout the morning and early afternoon. And on Tuesday, which has already ended in Saipan, there was no resumption of communications at all.
Another problem is that many of the station's instruments are now malfunctioning. This may be due to electrical problems (an artifact of running them at very low levels) or their calibration files and settings may have become corrupted, leading them to produce reports in a format that the datalogger program was not designed to parse. A brief rundown of the state of station instruments follows:
The standalone air temperature sensor, barometer, anemometer and electronic compass all appear to be working normally. These are all analog instruments and do not depend on serial communications in any way.
Both light sensors are damaged. The surface light sensor continues to produce serial reports of some kind (as evidenced by that sensor's instrument "counts" in the logger) but these reports are apparently filled only with zeroes, day or night, including for temperature and voltage. The underwater light sensor has been offline since last October and this has not changed.
The Deep CTD (Teledyne) seems to be at least partially operational. Its conductivity and temperature readings seem reasonable, although its depth reading show an odd 30-cm shift in the past few days and may indicate a problem.
The PacIOOS CTD was producing data reports on Friday and Saturday but since that time its output has been in a format that was unrecognized by the datalogger programming. It produced a full "status" report (in response to hourly prompting by the datalogger) on August 11th, 2012, at 4:02 UTC. This report's contents were as follows:
- Year: 2012
- Month: 8
- Day: 11
- Hour: 4
- Minute: 2
- Second: 56
- Serial Num: 1606481
- Num Events: 15
- Volts Main: 7.3
- Volts Lith: 8
- Curr Main: 61.3
- Curr Pump: 283.4
- Curr Ext: 286.8
- Mem Bytes: 1082107
- Samples: 56953
- Sample Free: 3406107
- Sample Len: 19
- Headers: 4
The Vaisala WXT, like the surface light sensor, is apparently producing reports but as recorded by the datalogger these reports are all zeroes.
It is possible that there has been damage to the datalogger, memory unit, serial port units, radio or cellular modem, although so far there is no sign of such damage.
The main problem at this point is not the instrument failures but that of isolating the cause of these voltage drops. It seems like there have been voltage drops since mid-May, that a severe voltage drop has rendered the station non-functional for three weeks, and that this may be an intermittent problem that is still ongoing. If we knew or suspected the cause of the power issues then it would simply be a matter of replacing the station instruments with the spares in storage at CRM. However our first focus must be on diagnosing the underlying cause of the power losses and then repairing it.
Mike J+
